NEET Class 9 Biology

Chapter 6 Natural Resources Introduction

A natural resource is something that is found in nature and can be used by people. Earth’s natural resources include light, air, water, plants, animals, soil, stone, minerals, and fossil fuels. People need natural resources to stay alive. They also use them to make their lives better.

These resources can be of two types:

Natural resources: Natural resources refer to all the natural things on our earth, such as soil, air, water, minerals, coal, sunlight etc. Human beings use these directly or indirectly for survival and welfare.

Read And Learn More: NEET Class 9 Biology Notes

Artifiial resources: The resources, which have been developed by human beings, are called artifiial resources. For example, biogas, thermal electricity, plastics etc. are man-made resources.

• Every place on Earth has its own unique group of natural resources. Some countries have lots of oil or diamonds.
• Others have rich soil and thick forests but few minerals. The wealthiest countries are usually the ones with the greatest amount or variety of natural resources. They are wealthy because they can sell their resources to other countries that need them.

Types Of Natural Resources

On the basis of availability, natural resources are classified into two types:

Inexhaustible resources: The resources that are present in unlimited quantity in nature are called inexhaustible resources. They are not likely to be exhausted by human activities. For example: Air, water, solar rays, etc.

Exhaustible resources: The resources that are present in limited quantity in nature are called exhaustible resources. They are likely to be exhausted by human activities. For example, coal, petroleum, plants, animals etc.

Exhaustible resources are further classified into two types.

Renewable resources: Exhaustible resources that can replenish themselves by quick recycling and replacement within a reasonable time are known as renewable resources. For example, living beings reproduce and can thus replace the killed individuals.

However, if the consumption of these resources exceeds the rate of regeneration, it may also get totally exhausted. A few more examples: Soil, forests, wildlife, vegetation, etc.

Non-renewable resources: The resource that cannot be replaced by recycling and replacement is known as nonrenewable resources. Its increased consumption will result in quicker exhaustion.

Examples: Coal, petroleum, minerals like copper, iron etc.

The Renewable resources, if not managed properly can become non-renewable

Question 1. Is plastic a natural resource?
Answer: No, Plastic is an artificial (man-made) resource.

Question 2. Is forest an exhaustible non-renewable resource?
Answer: No. Forest is an exhaustible renewable resource. Its availability can be enhanced by increasing replenishment

Why is life possible on earth only?

• Earth is the only planet on which life exists. It consists of three components Lithosphere (Land), Hydrosphere (Water), and Atmosphere (Air).
• Life originated and evolved because of this unique combination of the three components and was ideal and favourable for life. The life-supporting zone of the earth where the atmosphere, hydrosphere and lithosphere meet, interact and make life possible, is known as the biosphere.
• The lithosphere, hydrosphere and atmosphere are non-living components of the environment and are known as abiotic. The biotic or living components include plants, animals and microbes living on earth.
• A constant interaction between the abiotic and biotic components of the biosphere results in the transfer of food and energy, which makes it a dynamic but stable system. The biosphere is the biggest biological system. It consists of smaller functional units known as Ecosystems or Ecological systems.

Let us study some abiotic components in detail in order to understand their role in sustaining life on Earth.

The Breath Of Life Air

• Air is an inexhaustible natural resource. It is essential for the survival of all the living organisms on Earth. It is found everywhere.
• It is a mixture of different gases, which we cannot see. It is also necessary for all living organisms because they breathe in air.
• Hence, air is called the breath of life as life cannot exist without air.
• The major components of air are nitrogen and oxygen while minor components are carbon dioxide, water vapour, Argon, and traces of Helium, neon, krypton, ozone etc.

In planets Venus and Mars, where no life is known to exist, the major component of the atmosphere is found to be carbon dioxide (95-97%)

Connecting Topic

Atmosphere

The envelope of air that surrounds the Earth is called the atmosphere. Air is dense below near the surface of the earth. It becomes progressively rare with height. The height to which the atmosphere extends is 500 km.

Atmosphere is divisible into four layers.

1. Troposphere: It is the lower part of the atmosphere which extends up to a height of 8-16 km. It is the most active region, which contains about 18% of the total mass of air. All the dramatic events of the weather such as air movements, water vapours, cloud formation and dust particles are restricted to it.
2. Stratosphere: It is found above the troposphere up to a height of 30-50 km. This zone is rich in ozone. Hence, it is also known as the ozone layer or ozoneosphere.
   • In the ozoneosphere, oxygen in the presence of sunlight is converted to ozone by photochemical dissolution. It completely absorbs short wave rays like ultraviolet rays, X-rays, and gamma rays. The stratosphere is free from clouds. Aeroplanes usually fly in this zone.
3. Mesosphere: It is found above the stratosphere and extends up to a height of 100 km.
4. Thermosphere: The atmosphere, between 100 to 500 km, is called thermosphere. There is a progressive increase in temperature in this region.
   • This high temperature and high energy radiations cause ionization of gases. This layer of ionized particles is known as the ionosphere. The ionosphere is radio-reflective and is important for telecommunication on Earth.

Importance of Air

1. Air contains oxygen which is essential for life. It is absolutely necessary for respiration. It is also a supporter of combustion. In nature, oxygen dissolves in water. The dissolved oxygen keeps the water fresh and is a source of respiration for aquatic life.
2. Carbon dioxide is necessary for the production of food. It is the raw material for the photosynthesis of plants. During photosynthesis, plants absorb carbon dioxide and water vapour from the air and convert it into carbohydrates in the presence of sunlight and chlorophyll.
3. Carbon dioxide is a greenhouse gas and traps infrared radiation.
4. The atmosphere condenses water vapours to produce rain. Rain is the source of all fresh water on land.
5. The movement of air determines the climate of different places.
6. The atmosphere filters high energy rays and UV rays, thereby protecting the Earth from their harmful effects.

In The Lab

Let us perform an activity to prove that air is used in burning.

Take a candle and place it in a tray of water. Light the candle and cover it with a jar

What did you observe?

The candle stops burning in a short while. This is because all the oxygen present inside the jar is used up. Water goes up the jar to take the place of the air that has been used.

Question 1. Which of these candles will burn the longest?
Answer: (3) The candle under the biggest container will burn the longest as it has the most air in it.

Role of Atmosphere in Climate Control:

• The position of the Earth in the solar system and its distance from the Sun helps in maintaining the temperature of the Earth and thus supports life
• The atmosphere acts as a blanket for Earth’s surface. It keeps the Earth’s temperature fairly constant during the time and even during the course of the whole year. You must be wondering how. Air is a bad conductor of heat.
• During the day time, it resists the heat from entering the Earth and at night, it does not allow the heat to escape from the Earth.
• Thus, the atmosphere does not allow a sudden increase in temperature during the day and a sudden decrease in temperature at night. This helps to maintain a moderate temperature, which is essential for life.

Movement of Air: Winds

• You all must have felt the presence of air although you can not see it. You can see the movement of leaves of plants and trees.
• How it happen so? It is due to the moving air. The horizontal movement of air over the surface of Earth is called wind.
• Let us now understand how wind is formed. Wind is formed as a result of the uneven heating of the atmosphere (Earth’s surface).
• A portion of the solar rays that reach the Earth’s surface is radiated back into the atmosphere. This heats up the atmosphere.
• The extent of this heating varies across land and water. During the day, solar radiation heats up the land surface. This causes the air over the land surface to heat up. The hot air expands and rises upwards. This vertical movement of air is known as convection current. This creates a low-pressure area over the land surface.

• Solar radiation takes a longer time to heat up water as compared to land. Therefore, during the daytime, when the air over the land surface is heated up, the air over the water surface is relatively cooler.
• This creates a high-pressure area over the water surface. When the hot air over the land surface rises up, it creates a vacant space. This space in the low-pressure area (over the land) is occupied by the air present in the high-pressure area (over the water).

Thus, the air over the water surface starts blowing towards the land surface during the day.

• During the night, this situation gets reversed. The land surface cools down much faster as compared to the water surface.
• Therefore, the air over land is cooler in comparison to the air over water. A high-pressure area is thus created over the land surface and a low-pressure area prevails over the water surface. This causes the wind to blow from the land surface towards the water surface during the night.

Characteristics of Wind :

• The wind blows from a high-pressure area to a low-pressure area.
• A region with a high temperature has low pressure as hot air moves up, thereby creating a vacant space in that area.
• During the day, wind blows from sea to land and is known as a sea breeze.
• During the night, wind blows from land to sea and is known as the land breeze.

The other factors that influence the formation of winds are the rotation of the Earth and the presence of mountain ranges.

Importance of winds:

Wind helps in the formation of clouds and brings rain.

Cloud formation: When the air over the land and water body heats up, a large amount of water evaporates from various water bodies as water vapour rises along with the air. A part of this water vapour also reaches the atmosphere through transpiration and respiration.

• When this heated air rises, it expands and cools and starts condensing forming water droplets. The formation of water droplets leads to the formation of clouds. Gradually, the millions of tiny water droplets in the clouds keep growing in size.
• When these drops become so large that they can no longer be held in the clouds, they fall down as rain. Thus, during precipitation, water vapour forms raindrops. At lower temperatures, rain freezes and precipitates as snow, hail, or sleet.

Air Pollution

• You all must have seen traffic policemen wearing a mask or people covering their noses with handkerchiefs at traffic signals. Why?
• It is because of heavy smoke emanating from the automobiles, which makes breathing difficult at busy traffic intersections.
• Air pollution is the addition of unwanted substances into the atmosphere that has an adverse effect on organisms and the environment.

Sources of air pollution:

All human activities from cooking at home to the working of industries contribute to air pollution.

The sources of air pollution can be divided into two categories.

1. Natural sources-
   1. Forest fire
   2. Dust storm
   3. Pollen grains from flowers.
   4. Smoking volcanoes
2. Man-made sources-
   1. Burning of fossil fuels in industries, vehicles and thermal power plants.
   2. Emissions from industries.
   3. Vegetable oils, kerosene, and coal as household fuels
   4. Pesticide residues in air
   5. Sewers and domestic drains emanating foul smell
   6. Deforestation (cutting down of trees)

Important fact:  Pollution by natural sources is much less in comparison to man-made pollution.

Air Pollutants:

The agents that pollute the environment are called pollutants. Major air pollutants are :

1. Carbon dioxide (CO₂): It is mainly produced during the combustion of fuel in factories, power stations, households etc.

Effects:

1. It increases the atmospheric temperature due to the greenhouse effect.
2. It reduces the productivity of marine ecosystems. It is because, the water in the oceans becomes more acidic due to increased concentration of CO₂ in the air, which then gets dissolved in the water.
3. The increased temperature of the Earth causes the melting of continental and mountain glaciers. This in turn would cause flooding of coastal areas of some countries. This process is known as global warming.

2. Sulphur dioxide (SO₂): It is produced by the burning of coal in powerhouses and vehicles.

Effects:

1. In plants, it causes chlorosis (yellowing of leaves) and necrosis.
2. In humans, it causes, irritation in the eyes and injury to the respiratory tract leading to diseases like asthma and bronchitis.
3. SO₂ is also responsible for discolouration and deterioration of buildings.
4. It causes acid rain. The high concentration of sulphur dioxide in the atmosphere dissolves in raindrops to form sulphuric acid which causes acid rain.

3. Carbon monoxide (CO): It is produced as a result of incomplete combustion of fossil fuels like coal and petroleum. Carbon monoxide is more dangerous than CO₂. It is a poisonous gas, which causes major respiratory diseases. When carbon monoxide is inhaled, it reaches the bloodstream. Due to its high affinity for (200 times more than CO₂) haemoglobin, it replaces oxygen.

Effects:

It causes giddiness, and headache and interferes with the normal functioning of the heart.

4. Nitrogen oxides (NO): Oxides of nitrogen such as nitric oxide (NO), nitrous oxide (NO₂), and nitrogen dioxide (NO₂) are produced from thermal power stations, automobiles, industries and aircraft due to the burning of coal and petroleum.

Effects:

1. It reduces the oxygen-carrying capacity of blood.
2. It may also cause irritation in the eyes and lungs, and skin cancer in human beings.
3. Acid rain damages materials (metals and stones).

Smog: It is a dark brown smoky mist that occurs in cold weather. It is a mixture of smoke, dust particles and small drops of fog. It is a visible indicator of air pollution.

Effects:

1. It causes necrosis and develops a white coating on the leaves of the plants.
2. In humans, it may cause asthma and allergies. It is highly suffocating.

Aerosol spray propellants: These are suspended fine particles in the air. It contains chlorofloro carbons (CFCs) and florocarbons.

Effects:

It causes depletion of the ozone layer and thereby, the exposure of humans to the harmful effects of UV rays of the Sun.

Water A Precious Resource

Like air, water is another inexhaustible natural resource, which is essential for all living beings. It covers about three-quarters of Earth’s crust. Life is impossible without water.

Note: Water exists in three states: Solid (Snow, hail and ice), liquid (Water) and gas (Water vapour).

You must be surprised to know that only 3% of the total water resources of the world consist of fresh water, found in rivers, lakes, streams and ponds. The rest 97% is found in oceans, which is unusable.

Terrestrial life cannot use seawater, because their bodies cannot tolerate high salt contents of seawater and also cannot eliminate the salts from the body.

Sources of Water:

1. Rain: Rainwater is considered to be the purest form of natural water free from impurities. Now, you must be wondering, why it is so. The water from the sea and rivers gets evaporated during the day time due to the heat of the Sun.
   • As a result, impurities are left behind and water gets evaporated. When water vapours go high up in the air they condense to form clouds. Then these water drops come down to Earth as rain.
2. Well: The rainwater seeps through the soil and goes down. On digging the well, this underground water is available to us.
   • However, this water is not pure and contains impurities such as bacteria, suspended particles and other micro-organisms.
3. Spring: Springs are formed by the percolation of rainwater into the soil. It supplies water to wells and lakes.
4. River: Rivers are formed by the melting of snow on the mountains and from the rainwater. It is also not pure and is unfit for drinking.
5. Sea: The sea is the largest natural source of water. However, it is the most impure source of water as all the impurities dissolved in rivers are carried into the sea.

Importance of Water:

1. Water plays an important role in the metabolic reactions taking place within the body.
2. It acts as a universal solvent, thus providing a medium for chemical reactions to take place.
3. Water helps in the transportation of substances such as food from one part of the body to another in a dissolved form.
4. Turgidity is maintained by water in living structures.
5. Water prevents sudden changes in the temperature of living beings. Excessive heating is checked by evaporation of water in transpiration and perspiration.
6. Metabolic wastes are separated from the blood in the solution form with the help of water.

Question 1. There is an abundance of water on our Planet Earth. But then why do we talk of water shortage in future?
Answer: We talk of water shortage because only a small fraction of water is fit for consumption. Most of the water that exists on Earth is in seas and oceans, which is highly salty and unfit for drinking.

Water Pollution

Water pollution is the addition of undesirable substances in water bodies that have an adverse effect on organisms and their surrounding environment.

Sources of Water Pollution: It could be due to natural or man-made activities.

1. Natural sources of water pollution:
   1. Soil erosion
   2. Decaying organic matter
   3. Leaking of minerals from rocks
2. Man-made sources of water pollution:
   1. Domestic sewage is discharged into rivers from areas located on its banks. Sewage contains organic matter and several pathogens that can cause diseases in animals and humans.
   2. Industrial effluents containing a high concentration of heavy metals, toxic chemicals, acids, oils, grease etc. All of these are harmful to aquatic life and also make the water unfit for drinking.
   3. Fertilizers added to crop fields also lead to water pollution. A small part of fertilizers leach down to pollute the ground
   4. water while a large part of it passes down to water bodies through rainwater.
   5. Pesticides sprayed over crops are passed into water bodies during rains. It has an adverse effect on aquatic organisms.
   6. Oils from refineries, and automobile workshops pollute water thereby killing aquatic life and affecting the growth of phytoplankton.
   7. The passage of hot water from thermal plants changes the temperature of the water source. As a result, the content of oxygen decreases. Reduced oxygen content kills the aquatic animals and reduces the decomposition rate of organic matter, which, therefore accumulates.

Effects of Water Pollution

1. The toxic materials in water cause serious water-borne diseases like cholera, typhoid, jaundice and hepatitis in humans.
2. The presence of acids and alkalies in water destroys microorganisms, thereby disturbing the self-purification process in rivers.
3. Polluted water causes the spread of epidemics like cholera, tuberculosis, jaundice, and typhoid in human beings.
4. The usage of polluted water for irrigation of agricultural fields damages crops severely. This in turn reduces agricultural productivity.
5. Heavily polluted water affects the fertility of the soil and kills soil microorganisms.
6. Contamination of seawater due to oil spilling causes ecological disasters which result in the death of aquatic organisms including fish.
7. Water pollution affects the fish and other aquatic life

Biomagnification:

• To protect the crops from several diseases and pests, a large number of pesticides are used. These pesticides reach the soil and are absorbed by plants with water and minerals from the soil.
• Due to rain, these chemicals can also enter water sources and into the bodies of aquatic plants and animals. As a result, chemicals enter the food chain. Since these chemicals cannot be decomposed, they keep on accumulating at each trophic level.
• The maximum concentration is accumulated at the top carnivore’s level. This increase in the concentration of pollutants or harmful chemicals with an increase in the trophic level is called biological magnification.
• For example, high DDT concentrations were found in a pond. The producers (phytoplankton) were found to have 0.04 ppm concentration of DDT. Since many types of phytoplankton were eaten by zooplankton (consumers), the concentration of DDT in the bodies of zooplankton was found to be 0.23 ppm.
• Small fish that feed on zooplankton accumulate more DDT in their body. Thus, large fish (top carnivores) that feed on several small fish have the highest concentration of DDT

Soil

• Soil is the uppermost layer of the land, which supports plant life and contains numerous living organisms and their remains.
• It is a complex mixture of mineral particles formed from rocks, humus, wind, water, mineral salts, and living organisms like earthworms, insects, bacteria and fungi.

Important term: Humus is a brown or black organic substance formed from decaying plant remains or animal matter.

• It determines the fertility of the soil. It is porous in nature and increases the ability of soil to retain water.
• Soil is a renewable as well as non-renewable natural resource. Its productivity can be maintained with fertilizers and manures rich in humus.
• Hence, it is a renewable natural resource. On the contrary, if the soil has been removed from a certain place by erosion, it may take hundreds and thousands of years to form new soil. Hence, soil is also considered a non-renewable resource.

Question 1. How can you alter the nutrient and humus content of soil to support plant life?
Answer: The nutrient and humus content of the soil can be increased by using manures and fertilizers. Manures are naturally decomposed organic materials that increase soil fertility. Fertilizers are either natural or chemical in nature and add essential nutrients to the soil.

The use of fertilizers is a common practice in agriculture.

Soil Formation

Soil is formed from parent rock material over millions of years by a process of weathering. The process of formation of soil is called pedogenesis. What is weathering? Weathering is the process of breaking down rock present on the surface of the Earth into fine particles.

Weathering occurs through two main processes:

1. Physical weathering is caused by physical means like atmospheric changes (heating, cooling, wetting-drying etc.).
2. Biological weathering involves the breaking down of rocks by the action of living organisms.

Let us discuss some of the processes in detail.

1. Sun: During the day, sunlight heats up the rocks on the Earth’s surface and during the night, it cools them down. Rocks expand when heated and contract when cooled down. This repeated heating and cooling of rocks causes them to break down into smaller particles.
2. Water: It causes weathering of rocks by following methods:
   • Water enters the rocks through the cracks in them and freezes at low temperatures. This expands and contracts the rocks, which results in the breaking down of the rocks.
   • Sometimes, water flows along rocks. The flow of water along the rocks creates friction between water and rocks, which results in the weathering of rocks. This leads to the formation of soil. The soil thus formed may flow along with the water and get deposited elsewhere.
   • Continuous beating of rocks by rain and hail, and wave action on shores causes the breaking down of rock particles into fiery particles through their abrasive effects.
3. Wind: Wind has an abrasive action due to the presence of dust and fine sand particles in it. Strong winds erode the rock surfaces by rubbing and striking its abrasive particles against the rock surface. Sometimes the eroded particles are carried by wind to distant places. As wind speed decreases, the wind-borne particles settle down and form soil.
4. Frost: Rainwater seeping into rock crevices and cracks may get trapped in it. In winter, this water freezes to ice. The ice expands producing a lateral pressure sufficient to break all rocks.
5. Living organisms: Weathering by living organisms is known as biological weathering. Certain life forms, like lichens, grow on rock surfaces. They secrete acids which corrode the rocky surface and produce fine particles. Then, in these fie soil particles other organisms like microbes; insects etc. grow and die, building more soil.

Sometimes, mosses grow over these crevices. They cause the deepening of crevices and the building up of more soil in them.

Deeper crevices form cracks. Roots further weather the rocks and produce soil.

In The Lab:

• We find soil all around us. What is the composition of soil? Let us perform an experiment to find out the major components of soil.
• Dig a pit in a suitable area using a spade. Collect a sample of soil from this pit and mix it with water in a glass jar. Stir well and then allow the contents to settle. Observe the contents.

Results: The bottom of the jar has a layer of coarse sand. Then you would find a layer of sand. Then there is a layer of silt.

Clay lies above the silt. Above clay, you would find clay as well as mineral salts. Humus flats over the top of turbid water. dead matter water.

Soil, thus formed, contains the following components:

1. Soil particles like sand, silt, clay, gravel etc.
2. Humus, is an organic matter formed by the decomposition of dead organisms.
3. Air
4. Water
5. Soil organisms.

Different soils have different amounts of stone, sand, clay and plant and animal matter. For example, soil taken from the beach has more sand than clay. Garden soil is rich in plant and animal matter

A fertile soil contains a mixture of all different-sized particles. The fertility of soil depends on:

1. Presence of humus and nutrients.
2. The capacity of soil to retain water and air.

Importance of Soil

1. Soil anchors the terrestrial plants.
2. It provides water and minerals to the plants.
3. Soil is a home for a number of soil organisms. Many of them are involved in the decomposition of dead organic matter and the release of minerals bound in it.
4. Some bacteria and cyanobacteria in soil take part in nitrogen fixation.
5. Soil provides water for various human needs and irrigation.

Question 1. The fertility of the soil is threatened due to various actions of humans. Can you explain one activity that destroys the soil?
Answer: Most fertilizers and pesticides are made of chemicals. Excessive use of fertilizers and chemicals can kill the natural microorganisms present in soil.

• It also affects earthworms, which help in the conversion of organic matter into humus. If the use of fertilizers and pesticides is not controlled, then the soil may lose its fertility and no longer be able to sustain life.
• This change in soil fertility, brought about by the addition of harmful substances that affect the useful components present in the soil, is called soil pollution.

Experiment 1

Soil contains Air. Put a can of soil in a basin of water as shown in the figure.

What did you observe?

You will find air bubbles coming out of the soil. This shows that the soil contains air.

What is the importance of air in the soil? The roots of the plants grow in the soil. Since they are living parts of plants they need air to breathe. The animals that live in the soil also need air to breathe hence, to support them, air is found in the spaces between the soil particles.

Experiment 2:

Air contains Water. Take a tin of soil. Put it in a clear plastic bag and tie the bag tight. Leave the bag with soil for a few hours.

What did you observe?

• You will find water droplets in the bag. The water could have only come from the soil. The water in the soil evaporates into the air and then condenses as water droplets. Thus, this experiment proves that soil contains water.
• What is the importance of water in the soil? Plants need water for photosynthesis and to stiffen them, so as to stand upright.
• The root hairs of the plant absorb water from the soil.
• As you know, plants need nutrients from the soil to grow strong and healthy. So, plants take up nutrients in the dissolved form. Water is needed to dissolve the nutrients.

Soil Erosion

• During summers, you all might have noticed, blowing wind carrying sand and soil particles from one place to another. Similarly, flowing water carries some amount of soil along with it. What this process is known as? It is commonly known as soil erosion.
• Soil erosion is the removal of topsoil by wind and water. Wind and water are the key agencies which cause the weathering of rocks and carry the fie particles to other places for the formation of soil.
• However, as we all know, the topsoil contains humus and mineral salts, which are vital for the growth of plants. So, the removal of topsoil by water and wind leaves the underneath subsoil and rocky base exposed.

Thus, erosion causes a significant loss of humus and nutrients and hence, decreases the fertility of soil.

Causes of Soil Erosion:

There are several causes of soil erosion, which can be divided into two categories.

1. Natural causes: It involves natural agents like wind and water.
   • High wind velocity over lands, that have no vegetation, carries away the loose topsoil.
   • Pouring raindrops, over areas with no or very little vegetation, also carries away the topsoil.
2. Man-made causes: Besides natural agents, there are certain man-made activities, which cause soil erosion. For example:
   • Deforestation: It is the cutting or removal of trees or other vegetation for timber or for farming purposes. The roots of plants hold soil particles together.
     • In the absence of plants, the top layer of soil is easily removed by the action of high-speed winds or water flow, thereby increasing the chances of soil erosion. Also, deforestation leads to desertification.
     • In the absence of trees, soil erosion occurs more rapidly exposing the lower hard and rocky layer. As a result, soil loses humus and becomes less fertile.
     • Hence, fertile land, which acts as a source of living for farmers, gets converted into a desert. This process is known as desertification of land.
   • Overgrazing: Overgrazing by flicks of cattle, buffaloes, goats and sheep leaves very little plant cover on the soil. The hooves of the animals make the soil dry, which reduces its porosity and percolation.
   • Improper agricultural practices: Improper tillage and burning of stubble of weeds reduces the water-holding capacity of the soil. As a result, soil becomes dry and hence, can be easily blown away as dust.
   • Heavy rainfall and strong winds: Uncovered soil is eroded quickly by heavy rain and strong winds.
   • Slope: A run of water passing along the slope gathers speed and develops high cutting and carrying capacity.

Effects of Soil Erosion:

1. Soil erosion reduces the fertility of the soil.
2. It leads to landsliding.
3. Soil erosion exposes the lower hard and rocky layer. As a result, the fertile land gets converted into a desert. This process is known as desertification of land.
4. It leads to flash floods. The roots of plants hold soil particles together. In the absence of plants, the seeping of water is reduced and thus the groundwater does not get replenished. This could then cause floods.

Control of Soil Erosion:

As we have learnt, soil loses its fertility due to erosion. So it is necessary to conserve soil. What is soil conservation? Soil conservation means checking soil erosion and improving soil fertility by adopting various methods.

1. Deforestation should be stopped and more and more plants/trees should be planted. Plantation of more trees and vegetation reduces soil erosion by both water and wind.
2. Contour Bunding should be adopted. To reduce the effect of strong winds in the fields, the boundaries of the fields should be planted with trees in two or three rows.
3. Wind erosion is reduced if rows of trees and shrubs are planted at right angles to the prevailing direction of the wind.
4. Contour ploughing should be done. Ploughing at right angles to the slope allows the furrows to trap water and check erosion by rainwater.
5. There should be a control on grazing. Grazing should be allowed only in areas meant for it and not on agricultural land.
6. Adopt a terracing office. In this, the slope is divided into a number of fields for slowing down the flow of water.
7. On the sloping areas in hills, strip cropping should be practised. Strip cropping means the planting of crops in rows or strips to check the flow of water. This reduces the steepness of the slopes and checks the soil erosion.

Biogeochemical Cycles

The cyclic flow of nutrients between the non-living environment (soil, air and water) and the living organisms is called the biogeochemical cycle.

They are called biogeochemicals as they are obtained from Earth. Nutrients are generally derived from the abiotic surroundings to which they finally return by way of the decomposition of dead organisms or waste matter. This maintains a constant recycling of nutrients. The nutrients are never lost from the ecosystems

In the biosphere the nutrients exist in two states :

1. Reservoir pool: It is the pool/storehouse of nutrients from which the nutrients are slowly transferred to the cycling pool.
2. Cycling pool: It is the pool of nutrients which is repeatedly exchanged between the biotic and abiotic components of the biosphere.

Importance of Biogeochemical Cycles:

1. The minerals such as carbon, nitrogen, carbon and hydrogen cycle through living and non-living components of the biosphere.
2. The amount of various materials cycling through the biosphere remains more or less constant.

Let us discuss the events of the biogeochemical cycle from the following examples:

Carbon Cycle:

The cyclic flow of carbon in the biosphere between its abiotic (soil, air and water) and biotic (plants and animals) components is called the carbon cycle.

In the abiotic environment, carbon is present in four forms:

1. As CO₂ in the atmosphere.
2. As dissolved CO₂ or carbonic acid and bicarbonates in water (oceans).
3. Fossil fuels such as coal, petroleum and natural gas
4. As carbonates in the rocks

The carbon cycle comprises the following processes: The basic movement of carbon is from the atmosphere.

Photosynthesis: Terrestrial and aquatic plants utilize CO₂ for photosynthesis. During photosynthesis, the inorganic form of carbon is converted into organic matter in the presence of sunlight and chlorophyll. The CO2 is thus found and assimilated by plants.

Passage to other organisms: CO₂ found by plants becomes available to herbivores as organic food. From herbivores, it passes to carnivores. The animals use these carbon compounds in the synthesis of their own organic substances.

Fossil fuels: At times, large-scale upheavals (an upward displacement of part of the Earth’s crust) trap a large number of organisms inside Earth. The heat, pressure and chemical changes convert them into fossil fuels like coal, petroleum and gas.

Carbon dioxide is returned to the biosphere in five ways:

1. Respiration: It is a metabolic process reverse of photosynthesis. During the process, the food is oxidized to liberate energy from CO₂ and water. Thus, CO₂ is produced, which passes back into the environment.
2. Decomposition: After the death of plants and animals, the decomposers (such as bacteria and fungi) break down the remaining dead organic matter and release the leftover carbon back into the atmosphere.
3. Combustion: Fossil fuels such as coal, petroleum and natural gas on burning release CO₂ and carbon monoxide into the atmosphere. Fossil fuel is a product of the complete or partial decomposition of plants and animals as a result of exposure to heat and pressure in the Earth’s crust over millions of years ago.
4. Weathering of rocks: Weathering of carbonate-containing rocks releases CO₂ into the air. It occurs through the action of soil microorganisms, plant roots and acid rain.
5. Volcanic eruptions: Volcanic eruptions also release carbon dioxide into the atmosphere.

Question 1. Animals continuously take in oxygen and give out carbon dioxide. Oxygen is used for burning also. How is that quantity (percentage) not decrease in the atmosphere?
Answer: Plants and animals exchange the gases- oxygen and carbon dioxide with their surroundings all the time. Animals take in oxygen and give off carbon dioxide when they breathe. When green plants make food during the day, they remove carbon dioxide from the air and give oxygen to it. The amounts of oxygen and carbon dioxide in the air are kept more or less the same all the time because of breathing and photosynthesis.

Nitrogen Cycle

• The nitrogen cycle is a cyclic process that involves the conversion of elemental nitrogen of the atmosphere into simple molecules that enter living beings forming complex molecules. Then these complex molecules are broken down to release nitrogen back into the atmosphere.
• Earth’s atmosphere has about 78% of nitrogen gas. It forms essential constituents of all living organisms and is essential for many biological processes. It is present in all amino acids, nucleic acids and vitamins.

Broadly, the nitrogen cycle in the biosphere involves fie main steps:

Atmospheric nitrogen → Nitrogen fixation → Nitrogen assimilation →Ammonifiation → Nitrification → Denitrification

Plants cannot absorb nitrogen directly from the atmosphere. So, how is atmospheric nitrogen then utilized by plants? It is through nitrogen fixation.

1. Nitrogen fixation: It is the process of converting atmospheric nitrogen into usable forms like nitrates. It is of three types:
   • Biological nitrogen fixation: Certain bacteria and blue-green algae can fi atmospheric nitrogen directly into ammonia that combines with organic acids to form amino acids.
     The nitrogen-fixing bacteria can be –
     • Free-living, like Azotobacter and Clostridium
     • Symbiotic bacteria like Rhizobium that occur in the roots nodules of legume roots like peas and beans.
   • Atmospheric nitrogen fixation: During lightning and thunder, the high temperature and pressure in the air convert atmospheric nitrogen into oxides of nitrogen that can dissolve in water to produce nitric and nitrous acids. The nitrogen oxide then dissolves in rainwater and passes down as nitrites and nitrates.
   • Industrial nitrogen fixation: In this, nitrogen is made to combine with hydrogen under high temperature and pressure to form ammonia. Ammonia is then converted to urea. Urea is less toxic than ammonia.
2. Nitrogen assimilation: This process is carried out by plants. Plants cannot absorb nitrogen in its elemental form. It has to be first converted into nitrates for the use of plants by the process of nitrogen fixation. The atmospheric nitrogen after nitrogen fiation gets converted into nitrates which are then absorbed by plants.
   • Nitrate first changes into an ammonium state. Ammonium ions combine with organic acids to form amino acids. Amino acids give rise to proteins and nucleotides, which in turn produce nucleic acids.
     Animals take organic nitrogen directly or indirectly from plants.
3. Ammonifiation: It is the process of conversion of complex organic compounds like proteins into ammonia, in the presence of ammonifying bacteria or putrefying bacteria.
   • Part of the plant proteins are broken down into nitrogenous animal proteins. In the animal body, the plant proteins are consumed and are broken down into nitrogenous wastes like urea, and ammonia.
   • Nitrogenous wastes are then excreted out which are then acted upon by decomposing bacteria for decomposition.
   • Proteins → Amino acids → Organic acids + Ammonia
4. Nitrification: It is the process of conversion of ammonia into nitrites and nitrates. Nitrification is brought about by nitrifying bacteria such as Nitrosomonas and Nitrobacter.
   1. Nitrosomonas oxidizes ammonia to nitrite.
      2NH 3 + 3O2 → 2NO2– + 2H+ + 2H2O
   2. Nitrobacter oxidizes nitrite further to nitrate.
      2NO2– + O2 → 2NO3– + Energy
      Nitrates are now available for plant absorption and assimilation.
5. Denitrification: It is the process of conversion of nitrate salts present in the soil and water to gaseous nitrogen which escapes into the atmosphere. It takes place with the help of bacteria called Pseudomonas present in water-logged soils.

Denitrification reduces soil fertility

Oxygen Cycle

• The cyclic flow of oxygen in biosphere between its abiotic (soil, air and water) and biotic (plants and animals) components is called the oxygen cycle.
• Oxygen forms about 21% of the atmospheric gases. About 0.7% of oxygen is found dissolved in water while most of the oxygen occurs in a combined state as oxides of metals, carbonate, sulphate, nitrate and other compounds. Oxygen also occurs in gases like CO₂, SO₂ and NO₂.

The oxygen cycle comprises the following processes:

The common storehouse of oxygen is the atmosphere.

1. Respiration: All living organisms like plants, animals and decomposers, take atmospheric oxygen and utilize it for respiration. During respiration, oxygen is used for the oxidation of glucose. Carbon dioxide and water are formed while an enormous amount of energy is released.
   Glucose + Oxygen → Carbon dioxide + Water + Energy
2. Combustion: Burning of fossil fuels in homes, industry and automobiles utilizes oxygen and releases
3. CO₂ in the atmosphere.
4. Atmospheric fixation of nitrogen: In the presence of lightning and other high-energy sources, atmospheric nitrogen combines with atmospheric oxygen to produce nitrogen oxides.
5. Decomposition and decay: Oxygen is utilized in the decay and decomposition of dead organisms.

On the contrary, oxygen is returned to the biosphere by the process of photosynthesis. In fact, green plants are a major source of oxygen in the atmosphere. During photosynthesis, plants take in carbon dioxide along with water and release oxygen as a byproduct.

• The part of the atmosphere which is rich in ozone is called the ozone layer or ozonosphere.
• The high-energy ultraviolet radiations split ozone into molecular and atomic oxygen with a large amount of heat. This heat is used in warming the stratosphere. Ozone is reformed as atomic oxygen as ozone is highly reactive.
• Farman et al, in 1985, found that the ozone hole is more prominent over the region of Antarctica.

Ozone Depletion: Ozone depletion is the reduction in the concentration of the ozone layer. It is formed due to an increased concentration of ozone-depleting substances such as chlorofluorocarbons, chlorine, methyl bromide, nitrogen oxides etc. in the atmosphere.

• Chlorine is mainly released from chlorofluorocarbons (CFCs) widely used as refrigerants. The CFCs travel from the troposphere to the stratosphere, where they release chlorine atoms by the action of UV rays on them.
• The release of Chlorine atoms causes the conversion of ozone into molecular oxygen. One atom of chlorine can destroy around 10,000 molecules of ozone and cause ozone depletion.

Effects of ozone hole: The formation of the ozone hole will result in an increased concentration of UV-B radiations on the Earth’s surface. UV-B damages DNA and activates the process of skin ageing. It also causes skin darkening and skin cancer. High levels of UV-B cause corneal cataracts in human beings. It is also harmful to crops and animals.

Water Cycle (Also Known as Hydrological Cycle)

• The water cycle is the cyclic process of water between various components of the biosphere especially the evaporation of water from the sea, falling on land and then flwing back into sea by rivers.
• Water is not evenly distributed throughout the surface of the Earth. A major percentage of the total water on the Earth is chemically bound to rocks and does not cycle. Out of the remaining, nearly 97.3% is in the oceans and 2.1% exists as polar ice caps.
• Thus only 0.6% is present as fresh water (in the form of atmospheric water vapors, ground and soil water). The ice caps and the water deep in the oceans form the reservoir.

There are two overlapping water cycles operating in nature.

1. Global water cycle: It does not involve life. It involves three main processes that keep on alternating with each other.
   • Evaporation/Vapourisation: It is the process of converting liquid water into a vapour state. Water molecules change into water vapour and move into the atmosphere by the process of evaporation. Water evaporates from water bodies like seas, oceans, rivers and lakes.
   • Condensation: The process by which water vapour rises up, cools down in the higher atmosphere, and forms clouds is called condensation. Water vapours being lighter, rise in the air and cool down when the air becomes rarified. Cooling of water vapours produces tiny droplets around dust particles. The condensed water vapours form clouds.
   • Precipitation: As condensation proceeds, water vapour changes into water droplets. When enough water droplets accumulate, they fall down as rain. This process is called precipitation. The clouds precipitate to produce rain or snow in very cold areas. Rain is the source of all fresh water.
   • Infiltration and runoff: A part of rain falling on land percolates into the soil to replenish soil water and groundwater. The process of rainwater thus entering the soil is known as infiltration. The rest of the rainwater flows over the land surface as runoff.
     • When rainwater flows over the surface of land before entering the water bodies, it is called surface runoff. It forms lakes, streams, or ponds.
     • Springs and streams give rise to rivers. Rivers ultimately pass water into the sea. The global water cycle is in a steady state as total precipitation is balanced by total evaporation.
2. Biological water cycle: It involves the entry of water into living beings and then returning back to the environment.

Underground water acts as a starting point.

Utilisation of water by living organisms:

1. Aquatic animals take water from their surroundings.
2. Terrestrial plants absorb water from the soil through their roots.
3. Terrestrial animals obtain water directly from different water bodies or indirectly from the plants they consume.

Production of water by living organisms:

1. Plants lose water to the atmosphere through transpiration in the vapour form.
2. Animals lose a lot of water in vapours in their breathing and liquid forms in urine and perspiration.
3. Water returns to the atmosphere after the death and decay of plants and animals.

Water vapour results in the formation of clouds; clouds precipitate to produce rain, which then enters the global water cycle. Thus, there is always an exchange of water between the global water cycle and the biological water cycle.

Chapter 5 Improvement In Food Resources Introduction

All living organisms require food for survival. Food is a basic need for the existence of life on earth. It provides energy for doing work, and materials for growth, repair, development, and health. You must have heard people discussing the methods to improve ways of crop production.

• But, why do we require devising methods to improve the production of crops? It is because our country is overpopulated and supports around one billion people. Therefore, in order to feed such a large population, we need to produce several million tonnes of grains every year along with higher requirements of milk, eggs, and meat.
• Therefore, we need to increase the production of both plant and animal products. Do you know, to produce such a huge amount of food we need a large area of land under cultivation? However, this is not possible as our land availability is limited. India is already intensively cultivated.
• So, what now? The only possibility is to increase the production efficiency of both plants and animals. We can increase the production by the development and use of improved varieties with high yield and better agricultural practices Improved agricultural practices have increased the production of about 400 million tonnes of plant food products and about 90 million tonnes of animal food products.

Read And Learn More: NEET Class 9 Biology Notes

Also, it has resulted in a variety of “revolutions” which made India self-reliant.

These revolutions include:

Agriculture

The term “agriculture” is derived from two Latin words Agger-field and cultural-cultivation. Thus, agriculture is the branch of science that deals with the mass production of plants and animals useful to human beings.

It involves the study of:

1. New methods of food production
2. How new and better varieties of crops can be grown
3. How animals like cows and hens can be reared well and made to give more milk or better quality eggs…etc.

All these new methods that scientists develop come under agricultural practices. We need vegetables, fruits, cereals, pulses, etc. as food. For our clothes, we need the fire of plants or animals. We get all these foods and fires by farming or agriculture.

Dependence Of Humans On Plants And Animals

• Humans are dependent on plants and animals for food. Most of our food items are either plant products such as grains, vegetables, and fruits or animal products like milk, egg, mutton, chicken, etc.
• We eat various parts of the plant as food. For example, grains of rice and wheat are seeds; radishes and carrots are roots; potatoes and ginger are stems. We also eat leaves and stems of spinach and plenty of fruits.

Crop:

• A Crop is a plant grown in the fields on a large scale to obtain food. For example, if all the plants of rice are grown in the field, then it is called a rice crop.
• Similarly, if all the plants of wheat are grown, then it is called a wheat crop. Crops are cultivated by humans for food, fodder, and other materials.

Let us discuss some important types of crops:

Types of Crops

Different crops are grown in different seasons. Have you ever thought why? This is because each crop requires a different climatic condition, temperature range, and photoperiod for its growth and to carry out its life cycle. Therefore, some crops are grown in the rainy season while others are grown during winter.

Based on the seasons of cultivation, crops are classified into two categories:

• Kharif crops: The crops that are grown in the rainy season (or kharif season) are known as Kharif crops. These crops are cultivated between the months of June and October.
  Examples of Kharif crops include paddy, maize, cotton, green gram, soybean, pigeon pea, and black gram.
• Rabi crops: The crops that are grown in the winter season (or Rabi season) are known as Rabi crops. These crops are cultivated between the months of November and April.

Examples of Rabi crops include wheat, barley, gram, peas, mustard, and linseed. Such seasonal cultivation of crops assures maximum productivity of crops.

Question 1. Kharif crops are more susceptible to infestation by pests than the Rabi crops. Why?
Answer: Kharif crops are grown in the rainy season. Hence, these crops are more susceptible to infestation by pests as humid and warm conditions at that time are favorable for infestation.

Also, the yield of a crop can be increased by adopting a number of improved agricultural activities, which include three scientific approaches.

1. Crop variety improvement
2. Crop production improvement
3. Crop protection management

These activities can be understood by following practices involved in farming.

The practices involved in farming can be divided into the following three stages:

1. Choosing appropriate seeds for planting
2. Nurturing the crop plant
3. Protecting the growing crops and minimizing the loss of harvested plants Firstly, let us discuss the Crop variety improvement methods

1. Crop Variety Improvement Methods

• The high yield from the crops is directly related to the inputs and the agricultural practices that the farmers adopt. The higher the inputs, more is the yield.
• But before, going into the details of various methods of crop variety improvement, let us understand the need for crop variety improvement.

The various aspects for which crop variety improvement is carried out are as follows:

1. To obtain a higher yield of crop
2. To enhance the desirable quality of food items: Improvements are aimed at maintaining the quality of crop plants (nutritional factors). Improving crop quality is done in the following parts of plants:
   1. Protein quality in pulses
   2. Oil quality in seeds
   3. Preserving quality in fruits to reduce loss by spoilage
3. To produce crop variety that is resistant to biotic and abiotic factors :
   1. Abiotic Stress: The problems caused by non-living factors are termed abiotic stress. The produced plants, which can resist them, are called abiotic stress-resistant plants
      Some abiotic stress-resistant plants produced are
      1. Drought resistant
      2. Salinity resistant
      3. Flood (water-logging) resistant
      4. Heat/cold/frost resistant
         Therefore, producing plants, that can resist the attack by pathogens, is beneficial.
   2. Biotic Stress: Plants are attacked by insects, nematodes, and other disease-causing microbes, which can decrease the yield.
   3. The problems caused by living factors are termed biotic stress. The plants, that can resist them, are called biotic stress-resistant plants. Biotic stress-resistant plants are also called disease-resistant plants.
4. To change the maturity duration of crops: By growing a plant that grows and yields faster, the crop cycle is reduced to increase profits. This reduces the cost that a farmer incurs during crop production. Thus, the shorter the duration of crops, the more economical the variety.
5. ActivityUniform maturity allows the farmer to harvest crops together. Let us discuss, how? Take a handful of beans and sow them in the soil. Water the soil regularly and allow the beans to grow. You will observe that all plants do not grow together. Some grow faster while others grow much later.
6. Imagine this problem in a vast farmland. If a farmer sows seeds and they do not grow uniformly, then they would not mature uniformly and thus he would not be able to harvest the yield at the same time. Therefore, it is necessary to germinate seeds that require similar conditions for sowing and maturity at the same time.
   • To induce desirable agronomic traits: Tall branching plants are beneficial for plants whose leaves are to be utilized. For example, fodder crops that are grown to feed farm animals. Short plants are beneficial in cereals so that nutrients are not consumed by plants to grow taller.
   • To develop plant varieties with wider adaptability: India is a country with varied regions. Certain regions are very fertile while others are dry with very low rainfall.
   • Hence, all crop plants cannot grow in all regions. Therefore, crop plants that produce high yields in all regions with different conditions need to be produced.

Methods of Crop Variety Improvement

1. A farmer grows two varieties of rice, one which produces nutritionally rich grains during the monsoon season and the other which produces nutritionally poor grains in all seasons. He wonders if he could grow nutritionally rich grains in all seasons. Is it possible for him to do so?

• Hybridization is the method by which two characteristics present in different organisms can be brought together into one organism.
• A hybrid plant produced from two varieties will have characteristics from both the parent plants. Therefore, the farmer will be able to produce nutritionally rich grains, which can be cultivated throughout the year.

Steps to be followed to obtain an improved variety of crops are:

1. Choice of parental plants: Select two existing varieties of plants having different desirable characteristics; say for example, one having higher yield and the other having more resistance to diseases.
2. Cross-breeding of selected parental plants: This produces a new variety, which has characteristics of both parents. The process of crossing plants of two varieties having different traits to produce a hybrid having good traits of both is called hybridization.

2. Introduction: It is the oldest method of crop improvement. It involves taking a new variety of a plant from an area where it grows naturally to a region where it does not occur before. The initial introduction of new varieties is carried out in those areas which have similar climatic and soil conditions. Slowly, the area is allowed to spread as the variety gets acclimatized to other conditions.

3. Artificial Selection: It involves picking up of plants with better traits for further multiplication. The selection operating for long time spans can give rise to varieties different from the starting generation. For example, cabbage, cauliflower, and broccoli have been obtained through artificial selection from wild cabbage.

4. Recombinant DNA technology: Genes are responsible for the features present in an organism. Therefore, another method to grow plants with the desired characteristics is to incorporate genes responsible for that character into plants. This method will result in the production of genetically modified plants. Thus, recombinant DNA technology transfers genes from one organism to another so as to modify the latter.

For example: Bt cotton is a genetically modified crop, which carries bacterial genes that protect the crop from insects.

By now, about 200 genetically modified crop varieties have been produced.

Crop Production Improvement

It involves controlling the various aspects of crop production so as to obtain the maximum quality yield. It has three components:

1. Nutrient management
2. Irrigation
3. Cropping patterns

Let us discuss each of these components in detail.

1. Nutrient Management

Have you ever observed a plant growing in your garden? Have you ever thought about the sources from which a plant obtains nutrition? The plants absorb the nutrients and inorganic raw materials from their surroundings and utilize the same building up their organic matter. The main sources of nutrients for plants are air, soil, and water. In total, there are sixteen nutrients required by plants.

1. Out of these, two nutrients (Carbon and Oxygen) are obtained from air.
2. Hydrogen is obtained from water.
   These three elements – Carbon, Oxygen, and Hydrogen are called non-essential elements as they are not obtained from the soil.
3. The remaining thirteen nutrients are obtained from soil with the help of roots. They are called mineral nutrients or essential nutrients.

Maze in 1915 divided essential plant nutrients into two categories-

1. Micronutrients: Nutrients required in small quantities are called micronutrients.
2. Macronutrients: Nutrients required in larger quantities are called macronutrients. Nutrients are essential elements, which are used by plants in large quantities.

Mineral Replenishment

• Plants require essential elements for the growth and development of the body. When nutrients are not available to plants, physiological activity, such as growth, reproduction, and vulnerability to diseases, increases. Providing the proper quantity of nutrients to plants ensures proper growth.
• Sanjana germinated a few gram seeds in two different pots. She observed that some of the plants in pot A showed weak growth while the plants in pot B grew vigorously.
• Can you guess, why such variation is seen? One of the reasons for such variations could be a lack of certain nutrients. Lack of nutrients makes the soil infertile. So, unless the depleted plant nutrients are put back into the soil from time to time the growth of crops would be poor.
• But what are the ways by which nutrients can be added to soil? Soil can be replenished and the lost nutrients can be retrieved by adding manures and fertilizers. Let us learn about them.

Manures and Fertilizers

1. Manure: Manure is a natural fertilizer. It is prepared by the decomposition of plant and animal waste.

Composition of Manure

Manure is a source of many plant nutrients. It is composed of organic matter and minerals. Ammonia, nitrate, organic substances, etc. are predominant organic matters found in manures. Manures are mostly composed of micronutrients such as zinc, manganese, copper, magnesium, sodium, etc.

Types of manures

Based on the kind of biological material used, manures can be classified as:

1. Farmyard manure: Farmyard manure is formed from decomposed cattle dung (excreta) and urine, leftover fodder (cattle feed), and litter (bedding provided to cattle on the farm). These waste materials are collected daily from cattle sheds and stored in a pit for decomposition by micro-organisms (bacteria and fungi).
2. Compost: Compost is manure made from vegetable and animal refuse collected from domestic waste, straw, and weeds, etc., dumped in a deep pit to decompose. During the process, microbes decompose the animal and plant waste and convert it into inorganic materials. These inorganic materials are excellent nutrients for plants.

Composting: is a biological process of converting dead organic matter into rich humus. It takes about 3 to 6 months for decomposition of organic refuse.

Vermicompost: is compost broken down by earthworms. Earthworms can consume practically all kinds of organic matter. This organic matter undergoes biochemical changes in the intestines of earthworms. Hence, earthworm converts matter into rich humus, thereby enriching the soil with nutrients.

• Earthworm used in vermicomposting is Dichogaster bolani and Drawida Willis.
• The process of composting ensures the continuance of the fertility cycle.

3. Green Manure: Green manure is formed inside soil from young green crop plants plowed back into soil. The crops plowed are generally quick-growing legume crops that are mulched by plowing them back into the field in the tender stage only. Examples of green manure are Sunn hemp, Cluster bean, Cowpea, Lentil, etc.

Advantages of manure

1. It enriches the soil with organic material called humus to the soil.
2. It increases the water-holding capacity of soil.
3. It aerates the soil by making it porous.
4. It helps in the growth of microorganisms. The organic matter of manures provides food for the soil organisms which helps in making nutrients available to plants.
5. It improves the soil texture.
6. It increases the crop production.

Disadvantages of manure

1. Manures are bulky with low nutrient content.
2. They are inconvenient to handle, store, and transport.
3. Manures are not nutrient-specific. Hence, it is not very useful when a particular nutrient is required in the soil for a particular crop.
4. The nutrients of manures are released slowly, not keeping pace with the high and rapid demand for nutrients by crops. So far, we have seen how natural materials are used as sources of nutrition for plants. Let us now discuss synthetic nutrients that are available to plants.

2. Fertilizers: What if plant nutrients are required in large quantities? Are there any synthetic nutrients available? Fertilizers are plant nutrients, which are commercially available.

• They can be organic or inorganic in nature. They ensure healthy growth and development in plants by providing them with nitrogen, phosphorus, potassium, etc.
• However, the addition of fertilizers to soil requires special guidelines to be followed such as dosage, time, post-addition precautions, etc. Fertilizers should not be applied directly to soil if the crop is standing. This is because, then it would bring about withering of crops due to the development of high osmotic concentrations around plants.
• Let us now discuss how composting is better than manufacturing fertilizers. Are there any advantages (or disadvantages) associated with the use of fertilizers in comparison to manures? Yes, there are.

Advantages of fertilizers

1. They are mostly inorganic compounds, which can readily dissolve in water. They are easily available for plants.
2. They are a good source of nitrogen, phosphorus, and potassium. However, they are good only for short-term use.
3. They are nutrient-specific.
4. They are compact and easy to store and transport.
5. They are required in very small amounts.

Disadvantages of fertilizers

1. They get washed away because of irrigation. Hence, they are a cause of water pollution.
2. Continuous use of fertilizers causes harm to useful or symbiotic microorganisms living in soil.
3. They can also result in the reduction of soil fertility.
4. They cannot replenish the organic matter of the soil.
5. They are quite expensive.
6. They have only short-term benefit

Therefore, to get an optimum yield, it is necessary to use a balanced combination of manures and fertilizers.

In the Lab

Let us perform an activity to find out how fertilizers and manures affect the growth of plants. Take some healthy gram seeds and allow them to germinate in a pot

Then take three empty jars and label them as A, B, and C. In jar A, add a small amount of soil mixed with green manure.

In jar B, add a similar amount of soil but mixed with urea, a fertilizer.

In jar C, add a similar amount of soil without any manure or fertilizer.

Now water all these vessels bearing soil.

Now from the pot, select three equal-sized seedlings and plant them in jars A, B, and C. Keep the vessel in a safe and lighted place.

Water them regularly and observe their growth.

What did you observe after a few weeks?

You can observe that seedlings develop into small plantlets in all three jars after a few days. However, their growth varies in all the three. Jar B showed maximum growth while jar C showed the least growth.

Plantlets in jar B showed the maximum growth because urea is readily soluble in water and is quick-acting. When it is supplied to the soil, nitrogen is rapidly changed into ammonia. Later seeds use this ammonia for their growth and development. The plantlets in jar A also show growth but less as compared to jar B.

The growth of plantlets in jar C is the least because the soil is infertile as it lacks certain essential soil nutrients.

Question 1. Which one of the following crops would require a minimum quantity of NPK or urea for its proper growth and development?
Answer: The pea plant would require a minimum quantity of NPK or urea as they are leguminous plants and have the ability to fix atmospheric nitrogen themselves.

Question 2. Why is organic matter important for crop production?
Answer: Organic matter forms humus. Humus makes the soil fertile.

Importance of organic matter

1. It improves soil structure by forming soil crumbs
2. It increases the water-holding capacity of the soil.
3. It improves the aeration of the soil.
4. Decaying organic matter improves the growth of crop plants.

Is there any other method of providing nutrients to plants? Yes, Organic Farming.

Organic Farming: Organic farming is the practice of raising crops through the limited use of chemicals such as fertilizers, pesticides, herbicides, genetically modified organisms, etc. Sometimes they are not used at all. This method utilizes farm wastes such as excreta, a healthy cropping system (mixed cropping, intercropping, and crop rotation), the use of bio-pesticides such as neem and turmeric leaves mixed with stored gains, etc.

Advantages of Organic Farming

1. It does not cause pollution of crop plants, soil, air, and water.
2. It helps in recycling of waste materials.
3. The food obtained from organic farming is free from pesticides and chemicals.
4. It maintains the health of the soil.
5. It keeps insects, pests, and weeds under check.

2. Irrigation

Water is essential for the growth of plants. Plants obtain water from soil and soil obtains water from rain. However, sufficient rain is not always there. It is, therefore, necessary to supply water to crop plants in the fields, periodically. The process of supplying water to crops in the fields is called irrigation. The various sources of irrigation are wells, canals, rivers, dams, ponds, and lakes.

Importance of irrigation

1. It makes the soil soft which plowing easier.
2. It provides moisture for the germination of seeds as seeds do not germinate in dry soils.
3. Irrigation water helps in the absorption of nutrient elements by plants from the soil. The water dissolves the nutrients present in the soil to form a solution, which is then absorbed by the roots for the development of plants.
4. Irrigation is essential for the growth and elongation of the roots of crop plants as the roots of crop plants fail to develop and elongate in dry soil.

The crop is irrigated according to its requirements and soil characteristics. Irrigation is essential during the seedling, flowering, and grain-filling stages of the crop. Rice crop needs standing water.

The irrigation of crop plants depends on the following two factors:

Nature of crop plants: Water requirements of different crops are different during various stages of growth. Some plants require more water, while others require less. For example, paddy crop is transplanted in standing water and requires continuous water supply while crops like wheat and maize require less water.

Nature of soil: The crops grown in sandy soil need irrigation more frequently than crops grown in clayey soil. This is because; clayey soil has good water-retaining capacity and thus needs irrigation less frequently. Sandy soil, on the other hand, is highly porous with poor water retaining capacity. Thus, crops grown in sandy soil need more frequent irrigation.

Irrigation Systems

There are a number of irrigation systems in India depending on the availability of water resources and the requirement of water by crops. The various sources of irrigation are wells, canals, rivers, dams, ponds, and lakes.

Based on water resources, the various irrigation systems are as follows:

1. Tanks: Tanks are small storage reservoirs, which catch and store the runoff of smaller catchment areas. Small dams are built below the higher elevation of catchment areas. The outflows are regulated according to the water availability.
2. Canal system: In this system, human-made canals receive water from rivers, storage lakes, dams, etc. The main canal passes into a branch canal, which in turn divides into distributaries. The distributaries ultimately supply water to the individual fields or groups of fields. Each field or group of files is given water by rotation.
3. Wells: Wells are shafts sunk into the ground that reach the water table and are used to draw water. They are of two types:
   1. Dug wells: They are deep pits with the bottom reaching below the groundwater table. The water from the shallow strata slowly accumulates in the pits. The water is lifted by bullock-operated devices as well as pumps.
   2. Tube wells: They are deep bores used for pumping out water. The water is lifted by diesel or electricity or steam-operated pumps.
4. River lift system: In this system, water is directly drawn from the rivers for supplementing irrigation in the areas near to rivers. This type of system is more useful in areas where canal flow is insufficient or irregular due to inadequate water release.
5. River valley system: In riverine valleys with heavy rains, the slopes and valleys remain wet for a long duration to grow perennial crops like coconut, rubber, and tapioca.
6. Drip system: In this method, water is delivered at or near the roots of the plant drop by drop. Water is passed through plastic pipes that have holes in it. These plastic pipes are then laid along the rows of crops. It is the most efficient method of irrigation as there is no wastage of water at all.
7. Sprinkler system: This system supplies water to plants in the form of rain. The water is supplied using pipes to one or more central locations within the file. When water is allowed to flow under high pressure with the help of a pump, it gets sprinkled on the crops

Question 1. In a village, there is low rainfall throughout the year. What measure will you suggest to the farmers for better cropping?
Answer: Farmers should enrich the soil with humus. Humus increases the water-holding capacity of soil.

Farmers should use drought-resistant and early-maturing varieties of crops.

3. Cropping Patterns

Cropping patterns are models of raising crops that help in obtaining maximum benefits from a single piece of land. These patterns reduce the risk of crop failure, disease, and infestation.

The common types of cropping patterns are:

1. Crop Rotation: Have you ever been to a village? Farmers plant wheat crops during the month of November and harvest them in March and April. Similarly, rice crop is planted in June-July and harvested in October and November. The land that lies fallow in between these two cereal crops is used by the farmers for sowing a leguminous crop at this time.

• A leguminous crop does not take as long as wheat or rice to grow. So, by the time the farmer has to plant the cereal crops (rice, wheat, etc.) the pulse is ready to be harvested. Have you ever thought about why it is done so? What this type of method is known as? The practice of growing two or more varieties of crops on the same field in a sequential season is known as crop rotation.
• Generally, a leguminous crop like pulses, beans, and peas, is rotated with a non-leguminous crop such as wheat, maize, etc. Leguminous crops harbor nitrogen-fixing bacteria in nodules of their roots. These bacteria convert free nitrogen from the atmosphere into usable form.
• Thus, after the leguminous crop is harvested, the soil is left fertile for other crops. In this way, rotating different crops (leguminous and non-leguminous crops) in the same field replenishes the soil with nitrogen naturally and thereby increases crop production.

Advantages of crop rotation:

1. It improves the fertility of the soil and hence brings about an increase in food production.
2. It helps in weed control.
3. It protects crops from diseases.
4. It reduces the dependence on fertilizers.
5. It results in the optimum utilization of nutrients as different crops obtain nutrients from different layers of soil.

Question 1. How do crop rotations save a lot of nitrogenous fertilizer?
Answer: Growing a leguminous crop, during the rotation fixes atmospheric nitrogen with the help of their nitrogen-fixing bacteria. This reduces the need to add fertilizer to the soil.

Question 2. How does crop rotation restore the fertility of the soil and give better yield?
Answer: The practice of growing two or more varieties of crops on the same field in a sequential season is known as crop rotation. Generally, a leguminous crop like pulses, beans, and peas, is rotated with a non-leguminous crop such as wheat, maize, etc. The pulse crop uses different nutrients from the soil.

• It fixes the nitrogen from the air and makes the soil richer in nitrogen and thereby more fertile. This way the next cereal crop gives a better yield.
• If we do not practice crop rotation by growing different crops on a piece of land, but continue to grow the same crop, year after year, they will keep on using the same nutrients from the soil till all the nutrients in the soil get used up.
• The newly grown plants get poor nourishment from the soil and grow up to be weak and of bad quality. When plants are weak the insects can easily attack them and destroy them. Thus, crop rotation restores the fertility of the soil and gives better yield.

2. Multiple cropping: Multiple cropping is the growing of two or more crops one after another in the same field. It is of two types:

1. Mixed Cropping: It is the technique of growing two or more different crops simultaneously on the same field. The farmers mix the seeds of two crops and sow in the field. It is like insurance against crop failure due to abnormal weather conditions and attacks of pests and pathogens.

For example:

• Maize + Urad bean
• Soybean + Pigeon pea
• Wheat + Chickpea
• Wheat + Mustard
• Barley + Gram

There are certain criteria that farmers follow while selecting different crops for mixed cropping.

Some of these are discussed below:

1. The crops should not have the same root pattern. If one crop is deep-rooted, the other should have shallow roots.
2. Both crops should have different water and nutrient requirements. If one crop plant requires a higher amount of water and nutrients, the other should require a lesser amount.
3. Both crops should have different maturity times. If one is a long long-duration crop, the other should be of short duration or early maturity.
4. The crops should have different growth habits. They should have a different structure of leaves, stems, branching patterns of stem, and flowers. If one plant is tall, the other should be dwarf.
5. Always select the crops such that the products and waste materials of one crop stimulate the growth of the other crop. For example, if a wheat crop is grown along with a leguminous crop, then the usage of nitrogen from the soil by a wheat plant is compensated by the addition of nitrogen in the soil by the nitrogen-fixing legume. This in turn increases the soil fertility and ultimately the yield of the crop.

Need of following above criteria:

• All these criteria ensure that the component crops do not compete with each other for any of their requirement.
• It ensures that in case one crop fails, the other crop continues to flourish and cover the risk of the complete failure of one crop.

Advantages of mixed cropping:

1. It reduces the risk of total crop failure.
2. It increases the yield of crops due to the complementary effect of component crops.
3. It tends to harvest a variety of produce such as pulses, cereals, vegetables, etc.
4. It improves the fertility of soil and reduces the requirement for fertilizers.
5. It helps in the optimum utilization of the soil.
6. It reduces the chances of pest infestation.
7. It enhances the optimum utilization of nutrients as they are absorbed from different layers of the soil.

Disadvantages of mixed cropping:

1. The seeds of two crops are mixed and there is no set pattern of rows of crops. As a result, harvesting and threshing of crops separately is not easy.
2. Farmers face difficulty in spraying pesticides and applying fertilizers to individual crops.

2. Intercropping: It is the practice of growing two or more crops simultaneously in the same fild in a definite row pattern. This technique enhances the productivity per unit area. The crops selected have different nutrient requirements and different sowing and harvesting dates.

For example:

1. Soybean + Maize
2. Bajra + Lobia

Advantages of intercropping:

1. It increases the productivity per unit area.
2. It saves time and labor of the farmer.
3. It makes better use of natural resources of sunlight, land, and water.
4. Since the seeds of different crops can be sown separately, so specific fertilizers required for each crop can be added.
5. The produce of each crop can be harvested, threshed, and marketed separately.
6. This method keeps a check on soil erosion.

Question 1. A farmer cultivated soybeans in the field of Maize in well-planned rows. Explain the method of cultivation
Answer: Intercropping. Intercropping is the practice of growing two or more crops simultaneously in the same field in a definite row pattern. This technique enhances the productivity per unit area.

Crop Protection Management

Crops are affected by pests and a large number of weeds in fields. Uncontrolled growth of weeds and pests reduces productivity. Also, after harvesting, the produce is still in danger of getting spoilt by various biotic and abiotic factors. Therefore, these factors must be controlled to prevent loss. Crop protection management involves the protection of crops from their pests, pathogens, and weeds.

Let us first learn about the factors that affect crop plants and the measures used to control them.

1. When you sow a food crop in the field, you must have noticed the growth of certain other plants along with major cultivated crops. What are these? These undesirable plants that grow in cultivated fields along with the crop plants are called weeds.
   They compete with the crop plant for nutrients, light, and space. As a result, the crop plant gets lesser nutrients, light, and space. This also reduces the productivity of crop plants. Xanthium (gokhroo), Parthenium (gajar ghas), and Cyperus rotundus (motha) are some examples of weeds.
2. Pests are organisms like rats, insects, mites, fungi etc. that damage or destroy cultivated plants or plant products and make them unfit for human consumption. They destroy crops by the following methods:
   • Sucking the cellular sap from various parts of the plant example. aphids, leaf hoppers, bugs.
   • Cutting the roots, stem, and leaves of plants example. Locusts, hoppers, caterpillars, etc.
   • Boring into stems, roots, fruits, and seeds example. shoot borer, cotton boll weevil, grain weevil, etc.
     Examples of plant pests are the Gundhy bug that affects rice, shoot borer that affects sugar cane, aphid that affects mustard, etc.
3. Microorganisms or pathogens cause diseases in crop plants. Pathogens can be bacteria, fungi, or viruses. These pathogens are generally transmitted through soil, water, and air.

Preventive measures of insect pests and weeds :

1. Using pesticides is the most common method used to eradicate weeds, pests, and infectious diseases. These chemicals are generally sprayed on crops.

1. • Herbicides are used to eradicate weeds.
   • Fungicides are used to destroy the fungus.
   • Insecticides are used against insects.
     Chemicals should be used in limited amounts. Excessive use of chemicals can lead to several environmental problems. Moreover, these chemicals are poisonous to plants and animals.
2. The process of removing weeds from the cultivated field is called weeding. Weeds can be eradicated by the following methods:
   1. Mechanical removal: It involves pulling weeds with a hand. You must have seen farmers sitting in the field and uprooting certain plants with Khurpi. What are they doing? Farmers are actually uprooting the undesirable plants that are grown along with the main crop. Removal of weeds by using a trowel (Khurpi) and harrow is a manual method of removing weeds.
   2. Proper soil and seed preparation
   3. Timely sowing of crops, intercropping, and crop rotation. Weeds are very choosy about the crops with which they grow. Rotating the crop that has different nutrient requirements in the same field, disturbs the weed’s life cycle and reduces their growth in the same field.
   4. Use of a resistant variety of crops, which resist the attack of pathogens
   5. Proper plowing before sowing seeds helps in uprooting weeds.
   6. Spraying special chemicals called weedicides, like 2,4-D, Butachlor, Atrazine etc. on weeds.

Question 1. Why growth of weeds in the fields is harmful?
Answer: Weeds compete with the crops for nutrients, water, space, and light. They grow quickly, pick up more nutrients and water, and deprive the crop plants of essential inputs. As a result, the growth and yield of crop is reduced.

Question 2. A farmer was using excessive amounts of pesticides to safeguard the crop from blight. Will this have any ill effect on mankind? Justify.
Answer: Pesticides are toxic, poisonous, and often nonbiodegradable chemical compounds. They may have long-term damage to mankind. They cause irritation to the skin and the respiratory system.

Storage of Grains

After harvesting, the grains are stored in storehouses. There are certain factors (biotic and abiotic) that affect the produce after harvesting.

Different biotic and abiotic factors that affect the storage of grains are listed below in table

These Factors Result In:

• Weight loss
• Poor seed quality
• Poor germination capacity
• Discoloration of grains
• Poor marketability
• Infestation by insects, pests, etc

These factors bring down the cost and profits. Therefore, proper management of stored grains is important.

Preventive Measures to be Taken Before Storing the Food Grains

1. Maintenance of Hygiene: This includes:
   • Cleaning of floors before storing the grains.
   • The containers used for storing grains should be clean and dry with air-tight lids.
   • Frequent chemical fumigation to kill pests, fungi, etc.
   • Proper aeration and ventilation to control moisture and temperature levels.
2. Drying: The grains can be dried in the sun or by blowing hot air on them. They are dried by spreading them over plastic sheets or on cemented floors. This is because, if the grains are spread directly on the ground, they will absorb more moisture from the ground.
3. Maintaining storage containers: Godowns gunny bags or tanks or earthen pots used for storage should be free of cracks and holes and should be clean.
4. Chemical treatment: Spraying or fumigation (insecticide solution converted into fumes) of godowns and containers with insecticides and fungicides should be done before storage. Care should be taken to ascertain that the grains for consumption by human beings are not treated with chemicals poisonous to human beings. Grains are often treated with neem kernel powder or pepper or mineral oil which prevents the laying of eggs by insect pests.
5. Use of improved storage structures: Structures that are airtight, rat-proof, moisture-proof and can maintain a steady temperature are now used for storage. A few of them are named Pusa bin, Pusa cubicle, and Pusa other.

Animal Husbandry

• Ever since the beginning of civilization, humans have been trying to make use of animals around them for many requirements, such as food (milk, meat, and egg), clothing (wool), labor (carrying the load) security, etc. The development of desirable qualities in all such animal species, through creating better breeds, has been an important human achievement.
• For this, humans have consistently tried to improve the breeds of domesticated animals to make them more useful for them. The branch of science, that deals with the study of various breeds of domesticated animals and their management for obtaining better products and services, is known as animal husbandry.
• The term husbandry is derived from the word “husband”, which means “one who takes care”. Animal husbandry is the science of managing animal livestock. It involves feeding, breeding, and controlling diseases in farm animals. It involves the rearing of animals like cattle, poultry, and fish to obtain desired products from them.
  • Milk-giving (milch) animals: Cows, buffaloes, and goats who give us milk.
  • Meat and egg-giving animals: Pigs, cattle, goats, sheep, fowls, and ducks are the main sources of meat. From hens and ducks, we get eggs.
  • Working (draught) animals: Bullocks, buffaloes, camels, and horses are draught animals used for doing work in the field and for the transportation of goods and human beings. Mules are also used especially by the army to take things from one place to another in the hilly areas.

Need for Animal Husbandry

1. To increase milk production
2. To increase egg production
3. To increase meat production
4. To increase fish production
5. For proper utilization of cattle wastes like urine and feces. Cattle wastes are natural manure that enriches our soil and is used to generate biogas fuel.

Cattle Farming

• Have you ever visited a dairy farm? Many products like curd, cheese, butter, etc. are produced in a dairy. A dairy farm rears cows and buffaloes, which provide milk, the primary material for all these products.
• Milk as drawn from the cattle is known as full cream milk. When the cream is separated, the remaining milk is called toned milk.

This milk contains no fat and is known as skimmed milk.

The various milk products are:

1. Cream: It is prepared by churning milk. The fat comes on the top which is separated by draining out the liquid. It is known as a cream with 10-70% fat content.
2. Curd: Milk is converted to curd due to bacterial activities.
3. Butter Milk: It is the leftover liquid after the removal of butter.
4. Ghee: After heating butter, the water evaporates and the fat contents are almost 100%, forming ghee.

Cattle Breeds

In India, two different species of cattle are widely reared, Bos indicus (cow) and Bos bubalis (buffalo). The purpose of cattle farming is usually for the production of milk and labor in agricultural fields.

1. Milch animals (Milk-giving animals): Female dairy animals used to obtain milk are known as milch animals. The production of milk depends upon the lactation period.

Lactation Period is the period of milk production between the birth of a young one and the next pregnancy and it usually lasts about 300 days.

2. Draught animals (Working animals): Male animals engaged in agricultural fields for labor work like carting, irrigation, tilling, etc. are called draught animals.

Animal Breeding

• Animal breeding is the method of mating closely related individuals. In this process, two individuals of desirable characters are selected as parents. These are then crossed to obtain new breeds of animals. The new breed so obtained possesses the characteristics of both.
• For example, exotic or foreign breeds like Jersey, Brown Swiss, etc. are selected for increased milk production while local breeds like Red Sindhi, Sahiwal, etc. are selected for being highly resistant to diseases.
• These two breeds are crossed to produce a hybrid breed, in which both characteristics are available. Therefore, the offspring not only produces more milk but is also more resistant to diseases.

Objectives of Animal Breeding:

1. To increase the yield of animals.
2. To improve the desirable qualities of the animal produce.
3. To produce disease-resistant varieties of animals.

A breed is a special variety of animals within a species. It is similar in most characteristics such as general appearance, size, configuration, and features to other members of the same species. Jersey and Brown Swiss are examples of foreign breeds of cattle. These two varieties of cattle have the ability to produce abundant quantities of milk. This milk is very nutritious with high protein content.

It is of three types:

1. Local or Desi or Indigenous breed: They are high-yielding varieties of indigenous (Indian) breed examples. Gir, Sahiwal, Thararkar, Kankrej etc.

2. Foreign or exotic breed: They are high-yielding varieties that have been imported from foreign and reared widely in India example. Holstein, Friesian, Jersey, Swiss, etc

3. Improved Breeds: They are hybrids that possess characteristics of both indigenous and exotic. example. Friewal, Karan Swiss.

There are several methods employed in animal breeding, which can be classified into the following categories:

1. Natural methods: of breeding include inbreeding and out-breeding. Breeding between animals of the same breed is known as inbreeding while breeding between animals of different breeds is known as outbreeding. Out-breeding of animals is of three types:
   1. Out-crossing: In this type of out-breeding, the mating of animals occurs within the same breed. Thus, they have no common ancestors up to the last 4-5 generations.
   2. Cross-breeding: In this type of out-breeding, mating occurs between different breeds of the same species, thereby producing a hybrid.
   3. Interspecific hybridization: In this type of out-breeding, mating occurs between different species.
2. Artificial methods of breeding include modern techniques of breeding.

It involves controlled breeding experiments, which are of two types:-

1. Artificial insemination: It is a process of introducing the semen (collected from the male) into the oviduct or the uterus of the female body by the breeder. This method of breeding helps the breeder overcome certain problems faced in abnormal mating.
2. Multiple ovulation embryo technologies (MOET): It is a technique for cattle improvement in which super-ovulation is induced by a hormone injection.
3. Then, fertilization is achieved by artificial insemination and early embryos are collected. Each of these embryos is then transplanted into the surrogate mother for further development of the embryo.

Advantages of artificial method of breeding:

The best method to carry out animal breeding is the artificial method of breeding, which includes artificial insemination and MOET technology.

1. These technologies are scientific in nature. They help overcome problems of normal mating and have a high success rate of crossing between mature males and females.
2. It ensures the production of hybrids with the desired qualities.
3. This method is highly economical as a small amount of semen from the male can be used to inseminate several cattle.
4. This method is more reliable and hygienic than the natural method of breeding animals by mating

Farm Management Practices :

Farm management practices play an important role in improving our livestock. It looks after the health of animals as well as the production of clean milk.

Farm management practices have four components:

1. Feeding
2. Housing
3. Grooming
4.  Health care

Let us discuss each of these one by one.

1. Feeding of Cattle

• All animals must be fed properly. The food should contain essential nutrients required for the growth, development, and general maintenance of the body. The food that contains essential nutrients like carbohydrates, proteins, fats, minerals, vitamins, and water is known as feed.
• The main feed of cows and buffaloes is grass but this does not provide them all the nourishment. They require a balanced diet in the form of roughage which is firous food containing large amounts of fire such as hay fodder, leguminous plants-soybeans, peas, and cereals like maize, jowar, etc.
• The feed requirement of an animal depends upon age, growth, pregnancy, nature of work, and state of health.

For example, the food requirement of milch animals is of two types:

1. The food helps in maintaining normal metabolic activities of the body.
2. The food that is required during milk milk-producing period i.e. lactation period.

The cattle feed consists of two components:

1. Concentrates: Concentrates are rich in nutrients, such as carbohydrates, proteins, fats, minerals, and vitamins, with very little fibrous matter. They are provided in the form of oil cakes, grains and seeds, rice bran, Grain chaff, etc.
2. Roughage: Roughage is a coarse and fibrous substance that has a low nutrient content. It includes feed like straw and stems of cereal crops.

A poor quality of feed directly affects the yield of milk in cows and buffaloes.

2. Housing

Providing proper shelter to cattle is an important part of animal husbandry. It is necessary to protect animals from too much heat, rain, and cold. Cattle shelters have well-demarcated partially or completely covered areas where cattle can live comfortably and are protected from predators as well as natural factors like heat, cold, etc.

Characteristics of a good animal shelter:

1. The shelter should be spacious. Each animal should get enough space to stay comfortably. It should not be overcrowded.
2. The shelter should be clean, dry, airy and well-ventilated.
3. It should have proper arrangements for hygienic disposal of animal wastes like urine and excreta.
4. There should be proper arrangements for clean drinking water. Plenty of water should be available for cleaning the shelter and bathing animals.
5. Prevention and cure of diseases at the right time should be ensured. Shelters should protect the animals from various diseases. The cattle shed to be properly covered with cemented floors having slopes for quick drainages.

3. Grooming

Cattle must be groomed regularly so as to remove dirt and loose hair from their body. Also, grooming removes parasites. Washing of animals should be done at regular times to further clean them so that they provide clean milk.

4. Health Care

Like human beings, castles are also prone to many infectious diseases. These diseases may affect milk production and may even cause death.

Some of the common diseases of cattle are:

1. Viral diseases: These are caused by a virus and include foot and mouth disease, Rinderpest (cattle plague), Cowpox, etc.
2. Bacterial diseases: These are caused by bacteria and example includes Anthrax, Salmonellosis, and Tuberculosis etc.

Prevention of cattle diseases:

1. Cattle should be kept in a spacious, airy shelter with proper light and ventilation.
2. They should be given regular baths and grooming to keep them protected from diseases.
3. They should be given good, nutritive feed which will help them to resist infections.
4. Each and every cattle should be vaccinated at regular intervals to immunize them against common infections and diseases.
5.  The shelter of animals should be cleaned properly and regularly.

Benefits of cattle farming:

1. Good quality and quantity of milk can be produced.
2. Draught labor animals can be produced for agricultural work.
3. New varieties that are resistant to diseases can be produced by crossing two varieties with the desired traits.

2. Poultry Farming

Poultry is the rearing of domesticated birds –chicken, ducks, geese, and turkey, for eggs and meat. It is one of the fastest-growing segments of animal husbandry, as it is comparatively easy to start and maintain. It is the cheapest source of animal proteins for the non-vegetarian population.

There are two kinds of poultry:

1. Broilers: The poultry reared for obtaining meat is called chicken or broiler.
2. Layers: Poultry reared for obtaining eggs is called egger or layers.

How come you will know whether given eggs are of good quality or not? To understand this, let us perform a small activity.

Activity

• Take a few eggs and put them all in a container containing warm water. What did you observe? You will find that some of the eggs may be flat in water, while some of them will settle at the bottom of the containers.
• These settled eggs are of good quality while floating eggs are spoiled ones. This is because the shell is made up of calcium carbonate. Its deficiency results in a soft shell and makes it lighter in weight

Poultry Breeds

Poultry breeds are divided into three categories:

1. Indigenous or desi breeds: These include Aseel, Kadaknath, Chattisgarh, and Bursa. These desi breeds are strong and possess natural immunity against common diseases. However, they have certain disadvantages:

1. They are smaller in size.
2. They are slow-growing.
3. They lay small-sized eggs.
4. They produce less number of eggs i.e. 60 eggs/year.

2. Exotic breeds: These are foreign breeds that have been successfully acclimatized in India. The example includes White Leghorn and Rhode Island Red. They have high egg-laying capacity but carry less flesh as compared to indigenous breeds.

3. Crossbreeds: These are improved breeds of poultry. The majority of present-day chickens are cross-bred blocks. For example, HH260, IBL-80, B-77 etc.

The crossbreeds of chicken have few advantages over the indigenous breed, such as,

1. They lay more eggs i.e. 200 eggs/year.
2. They yield more meat than desi varieties.
3. The eggs produced are quite large as compared to indigenous breeds.
4. Crossbreeds consume less feed as compared to indigenous breeds.
5. They are best suited to the Indian climate.

Variety Improvement

It involves cross-breeding between Indigenous (Indian) and Exotic (foreign) breeds to develop improved varieties.

The improved varieties are developed for the following desirable traits:

1. To produce improved quality and quantity of chicks.
2. To develop dwarf broiler parent for commercial production for tolerance to high temperature.
3. To develop a variety that has low maintenance requirements.
4. To develop varieties, which utilize more cheap fibrous diet.
5. To develop the reduced size of egg-laying birds, without reduction in the size of eggs.

Need for Poultry Farming

1. Egg Production: Hens (Female fowls) raised for egg production are layers. For increasing egg production for the development of new improved variety with respect to quantity and quality of eggs, the following points are considered:
   • Egg number/weight/size/shape
   • Shell color/quality
   • The internal quality of egg
   • Body weight
   • Feed efficiency
   • Sexual maturity etc.
2. Meat Production: Fowls raised to obtain meat are called broilers. They are generally males but can also be female. Broilers are fed with vitamin-rich supplementary feed for a good growth rate and better feed efficiency. Care is taken to maintain feathering and carcass quality.

Management Practices

Good management practices are required to produce good quality birds. Nutritional, environmental, and housing conditions required by broilers are different from those required by egg layers.

The good management practices include

1. Maintenance of temperature and hygienic conditions in housing
2. Poultry feed
3. Prevention and control of diseases and pests.

Housing and Feed: Layers are meant for egg production, whereas broilers are meant for poultry meat. They both require different types of care.

Depending upon the requirement of meat or egg production, poultry feed mainly consists of maize, rice, wheat bran, ground nut cake, fish meal, limestones, bone meal, common salt, vitamins, and minerals.

Care for the layers: Layers have two distinct phases in their life:

1. Growing period, up to sexual maturity: The chickens at this stage are called growers. They require enough space. The feed is given in a restricted and calculated manner.
2. Laying period: The period from sexual maturity till the end of egg laying is called the laying period. The chicks are known as eggers or layers. The layers, like growers, require enough space and adequate lighting. These factors have a favorable effect on the laying output of the hens.

The feed given to layers should be rich in vitamins, minerals, and micronutrients.

Care for broilers: A broiler chicken, for proper growth, requires vitamin-rich supplements, especially vitamins A and K. Also, their diet includes protein-rich food and enough fat. They also require extra care and maintenance to increase their survival rate in comparison to egg layers.

Shelter

Characteristics of a good poultry shelter:

1. The shelter should be clean, dry, ventilated and well-illuminated
2. It should be spacious and airy. Birds of different ages, like growing, egg-laying and brooding should be housed separately.
3. The floor of the house should be covered with a litter of some dry absorptive material; which keeps the floor dry and warm.
4. The poultry shed should be rat-proof and should be well protected from cat and dogs.
5. It should have a proper temperature.

Diseases

Poultry birds are prone to many infectious diseases. These diseases may affect their growth and may even cause death.

Some common poultry diseases are:

• Bacterial diseases, like Cholera, Diarrhoea, Tuberculosis
• Viral diseases, like Ranikhet, Bird fl
• Fungal diseases like Aspergillosis

Prevention of diseases:

1. Poultry farms should be spacious, airy, and well-ventilated.
2. The shelter should be cleaned properly and regularly.
3. Quick and hygienic disposal of excreta should be ensured.
4. Birds should be vaccinated against common diseases and infections.
5. Good nutritive, hygienic feed and clean water should be given to poultry birds.
6. During winters, windows and walls of the shed of the poultry farm are covered to protect the birds from cold

Question 1. Write down three management practices that are common in dairy and poultry farming.
Answer:

1. Spacious shelter: The shelter of both dairy and poultry farm animals should be clean, spacious, airy, well-ventilated, and safe.
2. Proper feed: A regular, proper, and nourishing diet and fresh water should be provided to these animals.
3. Timely vaccination: Animals should be properly vaccinated and checked for sickness.

3. Fish Production

Fish is an aquatic food that is a rich source of proteins. It is highly nutritious and easily digestible. A large section of the Indian population especially those living in the coastal areas uses fish as food.

Fisheries: It is the occupation of catching fish, prawns, lobsters, oysters, etc.

On the basis of the mode of obtaining fish, fisheries are of two types:

1. Capture fishing: It is the process of obtaining fish from natural resources, both marine and inland.
2. Culture fishery: It is the practice of farming fish. It is also known as fish farming or pisciculture.

Aquaculture: The growing of various types of aquatic animals that are of high economic value such as prawns, lobsters, fishes, crabs, etc. is called aquaculture.

Marine Fisheries: They are fish-catching areas found in the sea. It is of three types: coastal, offshore, and deep sea. The edible marine capture fish are tuna, sardines, Bombay duck, pamphlets, etc.

Mariculture: The culture of marine fish for commercial use is called Mariculture. For example, Mullets, Bhetki, Pearl spots, Eel, and Milkfish. Mariculture is growing rapidly as the demand for fish is decreasing while the stock is declining due to excessive exploitation from the sea.

Inland fisheries: The fisheries that deal with fresh and brackish water are known as inland fisheries. Fresh water occurs in rivers, reservoirs, lakes, and ponds while brackish water is found in estuaries and lagoons. Inland fisheries account for about 50% of total fish production in the country.

Inland fisheries are of two types: Culture fishery and Capture fishery.

Cultural fishery is a type of fishery practiced in small water bodies where fish is first reared and then harvested.

The fish culture is of different types:

1. Monoculture, where a single species of fish is grown.
2. Monosex culture, where fish of only one sex is grown.
3. Poly-culture, where a combination of five to six species is grown.

Composite Fish Culture

• Due to over-exploitation and pollution, the availability of fish in natural water has declined considerably, which in turn has forced scientists to adopt various methods to increase its production.
• Farming fish under artificial conditions is the easiest way of increasing fish production and its availability for consumption. Farmers can take up fish culture in village ponds; tanks etc.
• And can improve their financial position, The technology developed for fish culture in which more than one type of fish is cultured simultaneously is known as composite fish culture. The technology enables to get maximum fish production from a pond or tank.
• Fishes with different food habitats are chosen so that they do not compete for food among themselves. For example, in an experiment, a combination of five to six species was used.
• Out of six species, three are of Indian origin (Catla, Rohu, and Mrigal) and three are exotic (Silver carp, Grass carp, and Common carp) from China.
• These six species have complementary feeding habits and do not harm each other. Basically, it constituted a good example of polyculture.

The food habits of six species are :

1. Catla is a surface feeder that feeds on small animals.
2. Silver carp is also a surface feeder but feeds on phytoplankton.
3. Rohu feeds in the middle zone of the pond
4. Grass carp feed on water weeds.
5. Mrigal carp is a bottom feeder, which feeds on decaying plants and detritus.
6. Common carp is an omnivorous bottom feeder. It feeds on all types of living organisms.

Advantages of Composite Fish Culture:

1. Fishes do not compete among themselves for food as they all have different types of food habits.
2. It ensures a complete utilization of food resources in the pond.
3. It increases the yield of fish.

4. Bee Keeping

The practice of beekeeping is called apiculture (Latin. apis-bee, culture-cultivate). Apiculture is the rearing, care, and management of honey bees for obtaining products like honey, propolis, bee venom, etc.

Importance of Bee Keeping:

1. It provides honey, a valuable nutritional food.
2. It provides beeswax. Beeswax is secreted by the wax glands located on the underside of the last four abdominal segments (4th to 7th) of the worker bee. This wax is used in constructing bee combs in which the colony of the bees develops. Bee wax has many uses in the industry. It is used in cosmetics, creams, and ointments.
3. It provides Propolis, which is antiseptic and antibiotic.
4. Bee venom is used in the treatment of rheumatoid arthritis.
5. Honey bees are excellent pollinating agents. Thus, it helps in increasing agricultural yield.

Purity Standards

• The term “adulterated honey” implies that the honey has been mixed with glucose, dextrose, molasses, corn syrup, sugar syrup, inverted sugar, flour, starch, or any other similar product, other than the floral nectar gathered, processed, and stored in the comb by honey bees.
• There is no ready method to test the purity of honey by the customers. Homogenous granulation is a probable sign of its purity.

However, let us perform a small activity to understand the purity of honey.

• Take a cotton wick and dip it in honey. Now burn the wick with a matchstick, if it burns, it is pure and if it is adulterated, the presence of water will not allow the honey to burn, and if still it burns, it produces a cracking sound.
• Generally, honey is adulterated by adding syrup of jaggery. Pure honey does not dissolve in water but impure honey dissolves. So, to test its purity, mix a spoon of honey in a cup of water and find out whether it dissolves or not.

Common Species of Honey bee:

There are two varieties of honey bees that are used for the commercial production of honey in India.

1. Indigenous varieties, which include:
   • Apis cerana indica (Indian bee)
   • Apis dorsate (Rock bee)
   • Apis flare (Little bee)
2. Exotic varieties, which include:
   • Apis mellifera (Italian or European bee)
   • Apis Adamson (South African bee)

The Honey Bee Colony

Honey bees are social insects that live in colonies in nests or hives. There are different groups of bees in the same colony that perform different tasks.

A honey bee colony has three castes:

1. Queen: The honey bee Queen is the supreme bee in a colony. All the activities in the hive revolve around her. Basically, she is the mother of the colony. She is responsible for laying eggs and lays about 2000 eggs in a day. She lays two types of eggs:
   • Fertilized eggs that produce either sterile workers or fertile females, i.e., new queen.
   • Unfertilized eggs that produce drones.
     The queen lives for about 3 to 4 years.
2. Workers: They are the most active members of the colony. They are actually imperfectly developed females, which cannot reproduce. Workers live for 3 to 12 months. The function of workers changes with age.
   • During 1 first half of their life cycle, they do indoor duties. Each worker bee acts as a scavenger, cleaning the hive, like walls and floor of empty cells of the colony for reuse.
   • They also start feeding the entire brood, with a mixture of honey and pollen. By the 7th day, it starts producing royal jelly. Royal jelly is fed to the queen and future queen bees. They also defend the colony from intruders by stinging.
   • During the second half, they become field workers and perform duties outside the colony. They explore new sources of nectar. They collect nectar, pollen, and propolis. The nectar collected changes into honey in their crops.
   • Drones: Drones are male bees produced by unfertilized eggs. They are males of the colony and depend for food on worker bees. rones are stingless and their main role is to mate with the queen.

Formation of different castes in honey bee

Management of High Yield of Honey

Apis mellifera, an Italian variety of honey bee, is commonly used for producing honey at commercial purposes. This variety is preferred and domesticated in our country as:

1. Apis mellifera is gentle in nature.
2. It has a good honey collection capacity
3. It has the ability to protect itself from enemies.
4. It has a prolific queen with less swarming

Let us now discuss the points that need to be considered in order to obtain good quality and high yield of honey.

1. Beehive: It is made of a series of square boxes without tops or bottoms, set one above the other. This hive has a floor at the bottom a crown board at the top, and a roof all over. Inside these boxes, wooden frames are vertically hung parallel to each other. The wooden frames are filled with sheets of wax foundation on which the combs are built by the bees.

The only entrance to the hive is below the large bottom box (brood chamber). The queen is usually confined to the brood chamber. The boxes termed “supers” are used for the storage of honey. The queen is prevented from going to the “supers” by the “queen excluder” who allows only the workers to move.

2. Apiary location: Apiary is a place where bees are raised and bred to get honey. It has a number of bee hives. It is set in a locality rich in vegetation, especially flowering plants. The hive should face the east side as it should receive sunlight during the morning and evening and some shade during mid-day.

3. Honey flow and season: To increase the yield of honey, apiaries should be established, at a location where there is an abundance of flora. The total time period during which honey bees collect nectar and pollens is called the honey flow period. This helps the bees to collect nectar and pollens in larger amounts which is ultimately converted into honey.

4. Swarming: Swarming is a natural phenomenon whereby the mass movement of bees takes place from one place to another. It takes place in the spring season for the purpose of reproduction. It is an old queen accompanied by a huge population of workers flinging to start a new hive. Swarms are collected from where they are settled. Some kind of a container is needed to collect the bees. The container is usually a straw basket with a lid.

5. Selection of variety: For honey production, the bee varieties with the following desirable characteristics are considered.

1. The variety yields a high quantity of honey.
2. Variety that does not sting much.
3. A variety that stays in the beehive for long durations.
4. A variety that breeds very well.

6. Site for beekeeping: A suitable site for apiary should be selected. It should have good pasturage which has a longer honey flow time.

Pasturage:

Pasturage is the availability of flowers from which bees collect nectar and pollen. The fruit trees, ornamental plants, and forest trees comprise important bee pasturage. It is related to the production of honey as it determines the taste and quantity of honey

Diseases of Honey Bees:

Honey bees are prone to many infectious diseases. These diseases may affect their yield. They are commonly infected by viruses, bacteria, fungi, and protozoa.

1. Bacterial diseases: Example. Septicemia is caused by the Bacteria Bacillus apisceptious.
2. Protozoan diseases: Example. Nosema disease, caused by Nosema APIs, and Amoeba disease caused by Vahlkampfi mollified.
3. Fungi: Example. Brood foul disease caused by Schizomycetes.

Enemies of Honey Bees:

Common pests of honey bees are wasps, wax moths, mites, and king crows.

1. Wasps are controlled manually by destroying wasp nests from the locality of the apiary.
2. The wax moth is controlled by exposing bees in the bee hive to the sun, i.e. by increasing temperature.
3. Bees eater birds like crows, sparrows, etc. are scared away by some device.

Why Do We Fall Ill?

• Food is the basic necessity of life. We all know that a regular supply of food is essential for human beings in order to keep fit and carry on all life processes. Thus, proper food is, therefore, a basic necessity for the proper functioning of cells, their tissues, and organs.
• Anything that disturbs the proper functioning of cells, tissues, and organs will result in the lack of proper activity of the body or an unhealthy body. Thus, health is considered to be the state of perfect functioning of body and mind, unhindered by diseases. So what do you understand by a healthy individual? An individual free of disease is termed healthy.
• However, health has a different meaning in different contexts. For example, for a grandfather, the ability to go out for exercise is good health. If he is unable to do so, it is considered his health is not good. Similarly, a youngster is healthy, if he can run, jump, and play. A student who remains active and attentive in class is said to have a healthy attitude.
• Therefore, good health is a healthy body with a healthy mind and a healthy attitude.
• Health does not simply mean “absence of disease” or “physical finess”. It could be defined as a state of complete physical, social, and mental well-being.

Read And Learn More: NEET Class 9 Biology Notes

Importance of Good Heath:

1. It increases our efficiency in doing work. This increases productivity and brings economic prosperity.
2. It makes the man happy and cheerful.
3. A healthy person can give proper attention to others in the family.
4. It gives a condition for our purposeful existence in this world.
5. It also increases the longevity of people and reduces infant and maternal mortality.

Personal And Community Issues In Relation To Health:

Good health, which means a state of physical, social, and mental well-being, implies that:

• Health cannot be achieved by individuals alone.
• Health depends upon the surroundings or one’s environment.

The environment can be:

1. Physical related to heat, storms, cyclones, floods, etc.
2. Social is related to the society in which one lives. The social environment controls not only social health but also the physical health of the individual through public health services.

There are certain factors that have an adverse effect on human health:

Let us discuss some of these factors:

1. Public health services: Public health services ensure a clean environment around our surroundings and protect the public from outbreaks of diseases. It ensures the removal of garbage, drainage and sewage services, proper drinking water, pest control, vaccination, and other health care services. If these services are faulty, the health of individuals is adversely affected despite taking the best-balanced food and keeping the best personal hygiene. For instance, if garbage is not collected and drains are not cleaned, pests and vectors might breed in the area resulting in the spread of disease.
2. Economic status of an individual: Good economic condition and job are essential for maintaining good health of an individual. This enables an individual to consume a wholesome balanced diet, which is very much required for keeping everyone in the family healthy.
3. Social equality and Harmony: Good health is required for participating in one another’s joys and sorrows, helping others, and receiving help at the time of need. This would make everyone in the community happy and healthy.
4. Personal Hygiene: It includes personal cleanliness such as cleaning teeth, taking baths regularly, taking care of eyes, breathing through the nose, wearing cleaned clothes, etc. Besides personal hygiene, timely vaccination and timely protection from vectors of disease are important for keeping an individual and community healthy.

Disease (Dis-Without, Ease-Comfort)

• You all must, at one time or another in your life, have suffered from fever, body aches, cold, cough, or vomiting. You must have felt uncomfortable. Such a condition where you feel uncomfortable or uneasy is known as a disease.
• It is just the opposite of health. It is defined as the malfunctioning of body organs due to one reason or another.
• So, what is a disease? A Disease can be defined as any condition that may lead to discomfort, distress, health problems, or death of the affected person. It may be due to defective heredity, inappropriate diet, disturbed metabolism or pathogenic attack.
• A person is said to be disease-free if there is no discomfort or derangement of the functioning of the body.

Difference between a healthy and a disease-free state of the human body:

• The state of not having any disease is not the same as being healthy. Good health is the ability of an individual to realize his or her full potential. For example, if an athlete is tired after running about 100 m, then he cannot be called a diseased person.
• However, he is not healthy either. Therefore, it can be concluded that one can have poor health without having any identifiable disease.

Diseases and Their Causes:

• Disease means uncomfortable. Disruption in the functioning of any tissue, organ or organ system will cause discomfort or disease.
• The diseases are diagnosed with the help of symptoms or signs.

Symptoms: Symptoms are evidence of the presence of diseases.

• The malfunctioning of organs produces external symptoms of diseases. It indicates that there is something wrong with the body.
• It can be in the form of structural and functional changes in the body or body part. For example, cold, cough, loose motions, pain in the abdomen, headache, fever etc are symptoms of certain diseases.
• However, symptoms do not give any exact cause of the disease. For example, headaches can be due to a number of diseases, like typhoid, jaundice or malaria. Sometimes, it is simply due to the day’s heavy work or exam stress.

Sign: Signs are definite indications of the disease. It is on the basis of the symptoms that the physician searches for definite clues or signs of the disease and sometimes goes for laboratory tests to confirm the disease.

Difference between Symptoms and Signs:

Causes of Diseases:

Causes of diseases are basically agents and factors that produce diseases in the body. Although there can be a number of causes for a disease, they can be broadly divided into immediate causes and contributory causes.

1. Immediate causes: It is the primary cause of the disease. Hence, it is also known as first level of cause. It includes external agents like micro-organisms. Organisms like virus, bacteria, and other micro-organisms can cause diseases in a person. Suppose an individual is suffering from diarrhea. The immediate or the first level of cause is the pathogen, which may be viral or bacterial infection.
2. Contributory causes: Even though a virus can be the immediate cause of a disease, other associated causes might allow the entry of the virus into the body. These causes are known as contributory causes.

These include the following conditions:

1. Unhealthy condition: Infectious agents like virus and bacteria enter the body through contaminated food or water. Thus, the consumption of contaminated food or water can be another cause of disease.
2. Improper public service: The lack of proper public service is the main reason for the lack of clean drinking water and food.
3. Poverty: Lack of nourishment can also lead to the occurrence of diseases in a person. There are a number of children consuming contaminated food or water. Then, why do only some children get diarrhea while others remain disease-free? It is because, a healthy body or a well-nourished body is less likely to catch a disease when exposed to disease-causing agents, whereas a poorly nourished body will easily become diseased.
4. Genetic differences: A child might have a genetic program due to which it can catch diarrhoea on immediate exposure. Do people get diseases only for a short period or do people suffer from a particular disease throughout their lifetime? On the basis of duration, a disease can be classified into two broad categories:
   1. Acute diseases: Diseases that last for only a short period of time are known as acute diseases. However, they spread rapidly in the body showing intense symptoms. They can be mild, severe, or fatal. Examples are cold, cough, inflenza, typhoid etc.
   2. Chronic diseases: Diseases that last for a longer period are called chronic diseases. They can also be mild, severe, or fatal. They do not spread rapidly; instead, they develop slowly over a period of time. Examples are tuberculosis, cancer, diabetes, kidney stones etc.

Difference between acute and chronic disease:

Types of Diseases:

Diseases are broadly classified into two categories:

1. Congenital Diseases: These are diseases that have been present since birth. For instance, a hole in the heart of an infant. They are caused by some genetic abnormalities or metabolic disorders or malfunctioning of an organ.
2. Acquired Diseases: These are diseases that may occur after birth during one’s lifetime. Based on their ability or inability to spread from one individual to another, acquired diseases are of two types:
   1. Infectious or Communicable diseases: The diseases that can be transmitted from a diseased person to a healthy person by means of infectious agents are known as infectious or communicable diseases. For example, tuberculosis, measles, malaria etc.
   2. Noninfectious or Non-communicable diseases: The diseases that cannot be transmitted from an affected individual to a healthy person are known as non-infectious or non-communicable diseases. For example, high blood pressure, Cancer, Allergy, Obesity, etc.

Non-infectious diseases are not caused by any pathogen or living organism. They are mostly due to internal or intrinsic non-infectious causes. For example, High blood pressure is caused due to lack of exercise or excessive weight. Similarly, Cancer is caused due to genetic abnormalities.

Difference between Infectious (Communicable) and Non-infectious (Non-communicable) diseases:

Non-infectious diseases are further classified as:

1. Degenerative diseases: These diseases are caused by the malfunction of some vital organs of the body. E.g. heart failure.
2. Deficiency diseases: These are caused due to nutritional deficiency such as that of minerals or vitamins in the diet. E.g. anemia (due to deficiency of B12), Beri- beri (due to deficiency of vitamin B).
3. Allergies: These are caused due to hypersensitivity of the body to certain foreign substances.
4. Cancer: This is an abnormal, uncontrolled, and unwanted growth of cells. E.g. Breast cancer, leukemia

Agents Causing Diseases:

By now, you have learned that, communicable diseases are those diseases that can be transmitted from one person to another. But have you ever thought how a disease is transmitted from one person to another? Anyways, before answering this question, let us first understand about various agents that cause disease.

Agents that cause diseases are known as infectious agents. The various infectious agents are bacteria, viruses, protozoan, helminths and fungi.

1. Bacteria: Bacteria are unicellular organisms. They are larger than viruses. Only some bacteria cause diseases while others are useful in nature. Whooping cough, typhoid, cholera, anthrax, etc. are some human diseases caused by bacteria.
2. Fungi: Fungi are plant-like organisms, which are
   heterotrophic in nature. They lack chlorophyll. Their cells have cell walls. Athlete’s foot, ringworm, etc. are some human diseases caused by fungi.
3. Protozoa: They are simple, primitive unicellular organisms, which include Amoeba, Trypanosoma, and Leishmania. They are often found in water as they require moisture for survival. Hence, they cause diseases through contaminated water. Amoebiasis, kala-azar, malaria, African sleeping sickness, etc. are some diseases caused by protozoa.
4. Worms: Worms are parasites, which infect the intestines of human beings and animals. Roundworms, pinworms, hookworms, and tapeworms are some examples of disease-causing worms. Diarrhea, anemia, liver rot, etc. are some diseases caused by worms

If there is bacterial infection along with the common cold, the antibiotic will prove to be effective, but only against the bacterial part of an infection.

Question 1. List down at least three points of precautions that need to be taken while using antibiotics.
Answer:

1. Always take antibiotics on the advice of a well-qualified doctor.
2. The course of antibiotics should be completed as per the prescription given by the doctor.
3. Always take antibiotics in the right amount and at the right time. An inappropriate dose of antibiotic makes it ineffective. Also, its excessive consumption may kill the useful bacteria present in our bodies.

Question 2. Why it is advised to take an appropriate dose of antibiotics?
Answer:

It is advised to take the appropriate dose of antibiotics because under dose of antibiotic makes it ineffective, while its excessive consumption may kill the useful bacteria present in our body

Let us now explore the various modes of transmission of diseases:

Modes of Transmission of Diseases:

Diseases can spread through the following means:

1. By air: You must have observed that when you sit near a person infected with a cold, you catch it too? Can you explain why? It happens because the virus that causes cold can reach your body through air. Hence, the common cold is an airborne disease.
2. A number of disease-causing microbes spread through the air. The pathogens may reach the body through little droplets throughout when an infected person sneezes or coughs. A healthy individual standing nearby can inhale these droplets, causing infection in that person.
   Diseases spreading through the air are the common cold, Pneumonia, Tuberculosis, Diphtheria etc. Airborne diseases are more common in crowded areas as well as in poorly ventilated rooms.
3. By water and food: Some diseases are transmitted when excretions from an infected person containing causal microorganisms get mixed with drinking water. Consumption of this contaminated water leads to the spread of diseases.
   In addition, when food is prepared using this contaminated water, it can lead to food-borne diseases. Some water and food-borne diseases are cholera, typhoid, hepatitis A, Jaundice, Diarrhoea etc.
4. Direct physical contact: Sexual act involves close contact between two people, which leads to the transfer of diseases such as syphilis, gonorrhea, AIDS, etc. These diseases are known as sexually transmitted diseases. However, casual physical contact such as handshake, hugging, and kissing do not lead to the transfer of these diseases.
   Diseases that spread through sexual contact are AIDS, Syphilis, and gonorrhea.
5. Blood-to-blood contact: This type of contact is established through blood transfusion or during pregnancy (between mother and baby) and through breastfeeding. A disease that spreads through blood is AIDS.
6. Animals or vector-borne diseases: Organisms that do not cause diseases themselves, but spread infection by transferring disease-causing microorganisms from an infected person to others are known as vectors.

Mosquitoes are vectors of malaria. Malaria is caused by the protozoan Plasmodium. This protozoan is carried from an infected person to a healthy person by Female Anopheles mosquitoes.

• The female Anopheles mosquito requires highly nutritious blood to lay eggs, so they feed on warm-blooded animals.
• The female mosquito that bites an infected person can transfer the disease-causing microorganism from an infected person’s blood to a healthy person.
• Another common vector is useful. Houseflies carry the causative organisms of cholera on their legs and mouth parts from the feces and sputum of infected persons to food and drinks and contaminate them. When this contaminated food is taken by a healthy person, he gets the infection.

Diseases that spread through vectors are: Malaria, Rabies

Organ-Specific And Tissue-Specific Manifestations Of Disease-Causing Microbes

• We know that disease-causing microorganisms can enter our body through various agencies such as air, water, food, or some animals.
• But what happens when a microbe enters our body? Does our body show any reaction to the entry of a foreign microorganism? Let us explore.

Effects of microbes on the body:

It is believed that microbes affect specific organs depending on the site of their entry.

For example:

• If a microbe enters our body through the nose, then it is most likely to reach the lungs. The bacterium that causes tuberculosis enters via the nose and affects the lungs.
• If a microbe enters through the mouth, then they either stay in the gut lining (as in typhoid) or affect the liver (as in jaundice).
• However, this may not always be true.
• The AIDS virus enters the body through sexual contact and then spreads to lymph nodes all over the body.
• Similarly, malaria-causing Plasmodium enters through blood, goes to the liver to multiply, and then passes into the red blood cells of the body.

Thus, signs and symptoms of a disease depend upon the affected tissue or organ.

Tissue or organ-specific effects:

• If the lungs are the target, then the symptoms will be coughing and breathlessness.
• If the liver is the target, then it will result in jaundice.
• If the brain is the target, then it will result in fis, vomiting, headache, etc.

In addition to these tissue-specific effects, there will be some common effects, which can be divided into two types:

1. Local effects: They include swelling, pain, joint stiffness, joint pain, etc. They occur only at the site of infection.
2. General effects: They include fever, chills, headaches, fatigue, loss of appetite, etc. They occur in the body.

Let us now discuss, how these effects arise in the body.

• Most of the mentioned effects depend upon the immune system of the body. An active immune system directs many cells to the site of infection to kill the pathogens or disease-causing microorganisms.
• This response of the immune system is known as an inflmmatory response.
• The general and local effects are caused due to inflmmation.

Inflammation:

Inflammation is the process by which the body’s immune system (white blood cells and some chemicals) show response to protect the body from infection. The immune system fights off these foreign substances by triggering general and local effects.

What happens when the immune system is damaged? If the immune system is damaged, then the body will not be able to fight infections. Then, any minor disease can prove fatal.

There are certain conditions where the immune system is unable to protect the body.

They are as follows:

• Severe diseases: In HIV infection, the virus damages the immune system. Therefore, the body is not able to fight minor infections such as cold and cough. In such cases, a minor cold can become pneumonia. Similarly, a minor gut infection can lead to diarrhea. Thus, these minor infections can kill an HIV-AIDS patient.
• Number of microbes: Severity of a disease also depends upon the number of microbes in the body. If the number of microbes is small, then the disease may be minor. However, if the number of microbes is large, then the disease can be life-threatening.

Principles of Treatment:

There are two ways to treat an infectious disease.

These are:

1. By reducing the effect of disease without killing the infectious agents. This could be done by two methods:
   1. By taking medicines to reduce the fever or pain or to stop loose motion as the case may be.
   2. By taking complete bed rest. Bed rest is advised to conserve energy and to make the same available for healing.
2. By eliminating or killing the cause of the disease. For complete recovery from the disease, it is essential that antibiotics specific to the disease-causing micro-organisms are taken. Antibiotics are drugs which can block the biochemical life processes of bacteria without harming human cells

Antibiotics:

• Antibiotics are chemicals produced by micro-organisms mainly bacteria and viruses, to kill other disease-causing micro-organisms.
• These medicines either kill or stop the growth of disease-causing microorganisms.
• The first antibiotic was penicillin, which was developed in 1940s in response to the need to treat soldiers in the Second World War.
• There are now about 50 to 100 commercially available antibiotics. Tetracycline, Streptomycin and Erythromycin are some other examples of antibiotics.

Antibiotics are characterized by their range of effectiveness and their mode of action against the pathogens.

• Broad-spectrum antibiotics kill a wide range of bacteria.
• Narrow-spectrum antibiotics are effective against only a few types of bacteria. To kill a specific pathogen, you have to use narrow spectrum antibiotics which are specific for the disease.

Antibiotics interfere with the growth or metabolism of the pathogen in a variety of ways. For example,

1. The antibiotic, penicillin inhibits the enzymes that are involved in the formation of bacterial cell wall. As a result of weakened cell wall, the immune cells such as white blood cells enter into bacterial cell and causes cell lysis. Cell lysis is the process of destruction of cells such as blood cell and bacteria.
2. Streptomycin binds to bacterial ribosomes, preventing protein synthesis and enzyme synthesis. The lack of protein affects bacterial function and result in its death. Streptomycin does not interfere with the synthesis of proteins in the cells of the patient taking the drug.

Principles of Preventing Diseases:

As we all know, prevention is always better than cure. Every infection brings about misery not only to the affected person but also to a number of others connected to the same.

Therefore, it is necessary to prevent the infectious diseases. A disease can be prevented by two ways:

1. General Ways of Preventing Infectious Diseases:

These are:

1. Preventing the spread of a disease:
   1. To prevent airborne diseases
      1. Stay away from the diseased person.
      2. Wear a mask when you need to contact a diseased person.
      3. Cover your mouth and nose while coughing or sneezing to prevent the spread of the disease.
   2. To prevent waterborne diseases:
      1. Ensure proper disposal of sewage.
      2. Ensure safe drinking water supply.
   3. To prevent vector-borne diseases:
      1. Provide a clean environment, which helps in preventing vectors like mosquitoes from breeding.
      2. Availability of proper nutrition. If proper and suffiient nutrition is not available, the immune system of the body will not function properly.

Immune System:

• How does immune system help in fighting against diseases? The immune system develops strength in the body to fight off microbes.
• It is made up of special cells, proteins, and organs which protect the body against micro-organisms.
• White blood cells are a part of the immune system. These cells destroy disease-causing micro-organisms.
• They are produced in the thymus, bone marrow, and spleen (lymphoid organs).
• These white blood cells or leukocytes defend the body against antigens.
• Antigens are foreign substances (e.g. bacteria, virus) that invade our body.
• Antigens trigger the production of antibodies by the immune system.
• Antibodies are body’s defensive cells that fight against several infectious foreign substances i.e. antigens.
• Each type of antibodies is specific to a particular antigen and makes it harmless.

Reaction between antibody and antigen:

It involves three main steps:

• The lymphocytes recognize antigens on the surface of bacteria as foreign and produce antibodies against them.
• Antibodies and antigens form immune complexes on surface of bacteria, making the bacteria clump together.
• This stimulates the phagocytosis (engulfment) of bacteria, which are then destroyed inside the vacuole.

Immunity:

Immunity is Defined as protection of the body against an infectious (foreign) agent. The immunity developed by the body against a disease after the vaccination is divided into two types:

• Temporary Immunity: It is the immunity developed for a short period of time.
  Example: Cholera vaccine, where immunity lasts for about 6 months.
• Permanent Immunity: It is immunity that last throughout life.
  Example: Small Pox vaccine where immunity lasts throughout life

2. Specific ways of Preventing Diseases: It refers to the defense provided by the immune system of a person.

You must have observed that if you are suffering from cold and cough, others around you try to keep away? This is because people around may get exposed to infection. But at the same time, sometimes, it is observed that all of them do not catch infection. Have you ever thought why it happens so? This is because our bodies have an immune system that protects us from various microorganisms.

Immunity is the ability of body to protect itself from infection and diseases. The immune response varies from person to person. This is why; some people are more sensitive or prone to infection than other. For example, if a child has suffered from smallpox once, then there is almost no chance of him suffering from it again. This happens because, when the immune system of the body encounters a virus or an antigen for the first time, it reacts against it and remembers it.

Therefore, when the virus enters the body for a second time, the immune system reacts more strongly to prevent the chances of suffering from the disease again. Therefore, it can be concluded that if we infect the body of a person with something that mimics the microbe, then the immune system will remember it and will prevent the actual disease-causing microbe from causing any disease

Vaccination

• You must have seen on television or read in the newspapers about Pulse Polio Day when children between the age group of 0-5 years are given the polio vaccine. So, what is a vaccine? What is meant by the term vaccination? Let us explore.
• Vaccination may be Defined as the protection of the body from communicable diseases by the administration of some agents that mimic the microbe. The agent can be a suspension of killed or attenuated microbes or a substance that mimics the disease-causing microbes. This is known as a vaccine.
• Vaccines protect humans and other animals from several diseases such as Cholera, Typhoid, Tuberculosis, Hepatitis, Chicken pox, Measles, Polio, and Small pox.

In vaccination, a vaccine containing an antigen is injected inside the body of an organism.

• Antigens once inside the body, stimulate the body’s defensive mechanism to produce antibodies.
• Antibodies arse body’s defensive cells that fight against several infectious foreign substances mostly germs. This is the primary immune response and thereby lymphocytes are generated.
• When the vaccinated person is attacked by the same pathogen, the memory cells recognise the antigen quickly and control the invaders by producing a larger number of lymphocytes and antibodies.
• These fight against the antigen, thus protecting the organism against the disease

• Vaccination is based on specific ways of defense provided by the immune system of a person. For example, if a child has suffered from smallpox once, then there is almost no chance of him/her suffering from it again. This happens because when the immune system of the body encounters a virus for the first time, it reacts against it and remembers it.
• Therefore, when smallpox virus attacks the body for a second time, the immune system reacts strongly to prevent the chances of suffering from the disease again.
• Therefore, it can be concluded that if we infect the body of a person with something that mimics the microbe, then the immune system will remember it, and prevent the actual disease-causing microbe from causing any disease. It forms the basis of vaccination.
• Vaccines are available against many diseases like tetanus, polio, measles, hepatitis B, whooping cough, yellow fever etc.

Question 1. What are the vaccinations that you have received?
Answer: Hepatitis B, DTP, polio, chickenpox, and MMR are some of the vaccines that you must have received.

Question 2. While going abroad, Sonia was asked to get vaccinated against certain diseases. Why?
Answer:

• An individual, as Sonia in this case, maybe a carrier of some disease and may take that particular disease to a foreign country.
• Therefore, all visitors to a foreign country are vaccinated against the disease which is not prevalent in that country.
• Diseases are caused by different causative agents. These agents are known as pathogens. Hence, the pathogen is Defined as living organisms that cause disease.
• Let us discuss various types of diseases, their mode of transmission and preventive measures.

Viral Diseases

1. Jaundice/Hepatitis:

Pathogen: Hepatitis virus.

Mode of transmission: Hepatitis A is transmitted mostly by contaminated food and water while hepatitis B is transmitted by contact with infected body secretions.

Symptoms:

1. Fever and loss of appetite
2. Nausea and vomiting
3. Yellowness of skin
4. Itching of skin due to bile pigments
5. Urine deep yellow in colour
6. Enlarged liver
7. Headache and joint pains

Prevention and Cure:

1. Adequate bed rest.
2. Carbohydrate-rich diet should be given to the patients. Consumption of protein and fat should be limited.
3. Eating hygienic food and drinking disinfected water.

2. Rabies (Also known as hydrophobia):

Pathogen: Rabies virus

Mode of transmission: Biting of rabid dog or cat.

Symptoms:

1. Severe headache and high fever.
2. Painful contraction of muscles of throat and chest.
3. Choking feelings and fear of death.

Prevention and cure:

1. Compulsory immunization of pet dogs and cats with anti-rabies vaccine.
2. Killing of rabid animals if it shows excessive salivation and tries to seek isolation.
3. It can be treated by Pasteur treatment in which 14 injections are given one by one on each day. However, these days, fie dose of anti-rabies vaccine are given at an interval of 0. 3, 7, 14 and 30th day of a dog bite.

3. Polio:

Pathogen: Poliovirus

Mode of transmission: Through food or water contaminated with stool and urine of patients.

• The polio virus enters the body through food and water and reaches the intestine and from there, it enters the central nervous system (brain and spinal cord) via bloodstream and lymphatic systems.
• In central nervous system, the virus destroys the motor nerve cells of spinal cord that is responsible for the muscular control. Therefore, the muscles of a polio-infected person become unable to carry out the normal functions.

Symptoms:

• Headache and fever followed by loss of head support.
• As the virus damages the brain and nerves of the spinal cord, the legs become paralyzed.
• Stiffness of neck and convulsions.

Prevention and Cure:

• Polio vaccine drops are given to children at certain intervals.
• The Pulse Polio program is a program organized in our country to give polio vaccines to children. It was launched in 1995-1996 to cover all children below the age of 3 years.

4. Influenza (commonly known as flu): Compared to the common cold, influenza is a more severe illness.

Pathogen: Myxivirus influenza (influenza virus), which attacks our body’s cells.

Mode of transmission: Through air.

Symptoms:

1. Fever
2. Respiratory tract infection symptoms such as cough, sore throat, running nose, headache, pain in muscles, and fatigue.

Prevention and Cure:

1. By annual influenza vaccination.
2. Person suffering from inflenza should drink plenty of water.
3. Consult a doctor immediately for treatment.

Influenza Virus:

There are many strains of influenza virus. The virus mutates all the time and new variations (strains) arise. This constant change enables the virus to evade the immune system of its host.

Unfortunately, immunity against one strain (which is conferred by exposure or immunization) does not protect against other strains. A person infected with influenza virus develops antibodies against that virus; as the virus changes, the antibodies against the virus do not recognize the changed virus, and influenza can recur, caused by the changed or mutated virus.

5. Dengue:

Pathogen: Virus

Symptoms:

1. Sudden onset of high fever, which may last for 4-5 days.
2. Severe headache mostly in the forehead.
3. Pain in muscles, and joints. Body aches.
4. Pain behind the eyes which worsens with eye movement.
5. Vomiting or nausea.

Prevention and Cure:

1. Avoid water stagnation for more than 72 hours so that the mosquitoes do not breed there.
2. Prevent mosquito breeding in stored water bodies, like ponds, wells etc,
3. Destroy discarded objects like old tires, bottles, etc. as they collect and store rainwater.
4. Use mosquito repellents and wear long-sleeved clothes to curtail exposure.
5. Use mosquito nets, also during the daytime.
6. Avoid outdoor activities during dawn or dusk when these mosquitoes are most active.

Dengue:

Dengue is of two types:

1. Dengue fever: It is characterized by an onset of sudden high fever, severe headache, and pain behind the eyes and in the muscles and joints.
2. Dengue hemorrhagic fever: It is an acute infectious viral disease. It is an advanced stage of dengue fever. It is characterized by fever during the initial phase and other symptoms like headache, pain in the eye, joint pain, and muscle pain, followed by signs of bleeding, red tiny spots on the skin, and bleeding from the nose and gums.

How does Dengue spread?

Dengue spreads through the bite of an infected Aedes aegypti mosquito. The transmission of the disease occurs when a mosquito bites an infected person and subsequently bites a healthy person. In doing so, it transmits blood containing the virus to the healthy person and the person becomes infected with dengue. The first symptoms of the disease occur about 5 to 7 days after the infected bite.

Aedes mosquito rests indoors, in closets and other dark places, and is active during the daytime. Outside, it rests where it is cool and shaded. The female mosquito lays her eggs in stagnant water containers such as coolers, tires, empty buckets etc., in and around homes, and other areas in towns or villages. These eggs become adults in about 10 days.

Question 1. Wearing socks and full sleeves at night will prevent the attack from dengue. Do you agree with this statement?
Answer:

No, Dengue is caused by the biting of an Aedes mosquito which is active during the time only.

6. Chickenpox:

Pathogen: Varicella virus

Modes of transmission: By contact

Symptoms:

1. Fever, headache, and loss of appetite.
2. Dark red-coloured rash on the back and chest which spreads on the whole body. Later, rashes change into vesicles. After few days these vesicles start drying up and scabs (crusts) are formed. These scabs start falling.

Prevention and Cure:

There is no vaccine against chicken pox as yet.

But precautions must be taken as follows:

1. The patient should be kept in isolation.
2. Clothing, utensils, etc. used by the patient should be sterilized.
3. Fallen scabs should be collected and burnt.

7. AIDS (Acquired Immuno Deficiency Syndrome): The word “immune deficiency” signifies that the immune system becomes very weak. It is a disorder of the cell-mediated immune system of the body.

Lymphocytes are the main cells of the immune system i.e. T-lymphocytes and B-lymphocytes. ‘Helper T’ lymphocytes play a great role in regulating the immune system. Damages or destruction of ‘Helper’ lymphocytes lead to the development of a cellular immune deficiency which makes the patient susceptible to a wide variety of infections.

Pathogen: HIV (Human Immunodeficiency Virus)

Mode of transmission:

1. Sexual contact with the affected person. In India, the most common route of HIV transmission is through unprotected sex.
2. Using the same syringe as that of the affected person.
3. Transfusion of blood contaminated with human immune deficiency virus.
4. From mother to newborn baby during pregnancy or during birth.

Symptoms:

1. A type of lung disease develops (tuberculosis).
2. Skin cancer may be observed.
3. Nerves are affected.
4. The brain gets badly damaged with the loss of memory, loss of ability to speak and to think.
5. The number of platelets (thrombocytes) becomes less which may cause hemorrhage.
6. In severe cases, the patient shows swollen lymph nodes, fever and loss of weight.

A full-blown (disease at its peak) AIDS patient, may die within three years.

Prevention and Cure:

No medicine or vaccine is known to be available against HIV infection. Therefore, care has to be taken through the following measures:

1. There should not be any sexual contact with the person who has HIV infection
2. Use a disposable syringe and needle.
3. Before receiving blood for transfusion, one should ensure that it has been screened for HIV.
4. Condom should always be used during intercourse.
5. People should be educated about AIDS transmission.

Facts About Hiv Transmission:

• HIV is a weak virus and hard to get infected with. It cannot be transmitted through air or water outside the human body.
• A person cannot get AIDS by hugging or sneezing of an infected person, insect bites (including mosquitoes), or sharing the same comb, plates, glass, handkerchiefs, knives or cutlery.
• A person cannot get AIDS by using public toilets, swimming pools, showers, and telephones.
• HIV is not transmitted by being near to someone, touching someone or working with someone who is suffering from AIDS.

Question 1. Why AIDS is considered a “syndrome” and not a ‘disease’?
Answer:

A syndrome is a group of symptoms, signs, or physical or physiological disturbances that are due to a common cause. AIDS is considered as a syndrome because it is a complex of disease and symptoms that develop due to the failure of the immune system of the body. HIV that causes AIDS damages the immune system of the patient. As a result, even a small cold leads to pneumonia; a minor infection leads to severe diarrhea and blood loss and simple skin rashes develop into ulcers.

Bacterial Diseases

1. Tuberculosis:

Pathogen: Mycobacterium tuberculosis. The bacterium releases a toxin called tuberculin.

Mode of transmission: Directly by sneezing, coughing or spitting or indirectly by air-borne pathogen discharged through sputum, cough, and sneeze of an infected person.

Symptoms:

1. Persistent fever and cough
2. Chest pain and breathlessness
3. Sputum containing blood
4. Loss of weight and weakness.

Prevention and Cure:

1. Isolation of TB patients to avoid the spread of disease.
2. Use of handkerchief while coughing and sneezing
3. BCG (Bacillus Calmette Guerin) vaccine provides immunity.
4. Living rooms should be clean, neat, and airy.

2. Typhoid:

Pathogen: Salmonella typhi bacteria.

Mode of transmission: Through contaminated food and water and house flies.

Symptoms:

1. Continuous fever, headache, and slow pulse rate.
2. Reddish rashes appear on the upper abdomen.
3. Diarrhea which becomes hemorrhagic (loss of blood)

Prevention and Cure:

1. Proper sanitation and cleanliness should be maintained.
2. Proper disposal of excreta of the patient.
3. Antibiotics should be administered.
4. Disinfection of water and proper cooking of food should be done.
5. TAB-vaccine provides immunity for 3 years.

3. Cholera:

Pathogen: Vibrio cholerae (Comma shaped bacterium)

Mode of transmission: Through contaminated food and water. House fl is the carrier.

Symptoms:

1. Acute diarrhoea
2. Muscular cramps
3. Loss of minerals through urine
4. Dehydration, which can lead to the death of an individual

Prevention and Cure:

1. Cholera vaccination should be given.
2. Proper washing and cooking of food should be done.
3. Electrolytes (Na, K, sugar, etc.) dissolved in water should be given to the patient to check dehydration. In market it is available as ORS (Oral Rehydration solution).
4. Underground disposal of excreta.
5. Proper covering of eatables to prevent contamination.

Oral Rehydration Solution (ORS):

It is an ideal solution to prevent dehydration in child. It can be prepared as follows:

1. Take a glass of water and add
   1. Three teaspoonfuls of sugar
   2. A quarter teaspoonful of common salt.
   3. A pinch of sodium bicarbonate
   4. A few drops of lemon juice
2. Mix the entire content well and give this solution to the patient having cholera or diarrhoea at least fie to six times a day to prevent dehydration.

Protozoan Diseases

1. Malaria:

Pathogen: Malarial parasite, Plasmodium

Mode of transmission: By bite of female Anopheles mosquito. Male Anopheles mosquito feed upon plant juices.

Symptoms:

1. Headache, nausea and muscular pain
2. Feeling of chill and shivering followed by fever which becomes normal along with sweating after some time.
3. Patient becomes weak, exhausted and anaemic.
4. The malaria may secondarily cause enlargement of liver and spleen.

Prevention and Cure:

1. Wire-gauzing of doors, windows etc to check the entry of mosquitoes.
2. Use of mosquito net and mosquito repellents.
3. Taking care of coolers, flwer pots and uncovered water containers to prevent breeding of mosquitoes.
4. Sprinkling of kerosene oil in ditches or other open spaces where water gets collected.
5. All the mosquito breeding places like ponds and ditches should be destroyed or covered.
6. Use of insect repellants to prevent mosquito bite.

2. Amoebiasis (Amoebic dysentery):

Pathogen: Entamoeba histolytica

Mode of transmission: Through contaminated food and water.

Symptoms:

1. Formation of ulcers in intestine.
2. Feeling of abdominal pain and nausea.
3. Acute diarrhoea and mucus in stool.

Prevention and Cure:

1. Proper sanitation should be maintained.
2. Vegetables and fruits should be properly washed before eating.
3. Antibiotics may be given to the patients.

Helminthal Diseases (Worms)

1. Filariasis:

Pathogen: Wuchereria bancrofti, fiarial worm

Mode of transmission: Biting of mosquitoes- Aedes and Culex

Symptoms:

1. Fever
2. Collection of endothelial cells and metabolites in the wall of lymph vessels.
3. Swelling of legs which appear as the legs of an elephant, so this disease is also called elephantiasis

Prevention and Cure:

1. Wire gauzing of doors, windows etc to check the entry of mosquitoes.
2. The water collected in tanks or other articles should be properly covered to prevent the breeding of mosquitoes.
3. A sprinkling of kerosene oil on ponds and ditches to kill the larva.

Question 1. “Precaution is always better than cure.” What precautions would you take to prove this statement?
Answer:

Precaution is always better than cure as diseases always cause some damage to the body.

Important precautions for preventing diseases are:

1. Hygienic environment
2. Personal hygiene
3. Intake of proper nutrition
4. Intake of clean food and clean water
5. Regular exercise
6. Sound sleep

Diversity in Living Organism Introduction

• Just look around, you see a large variety of living organisms, be it a plant, tree, bird, dog, spider, lizard and so on. Besides these, there are different kinds of crop plants like rice, wheat, and sugarcane.
• Then, there are wild plants like keekar. In a forest, you would find strange wild animals and plants. In a sea, you would find aquatic animals like whale, corals, sea anemones, etc.
• In a pond, you would find fish, earthworms, frog, and some water birds. Then, there are a number of parasites like ticks and mites.
• Besides these, there are several organisms that we cannot see by our naked eyes but they are all around us.
• All these organisms show similarities indicating mutual relationships. At the same time, these organisms are very different from all others to a lesser or greater extent.
• The diversity is not only present amongst different organisms but also among individuals of same organism.

Read And Learn More: NEET Class 9 Biology Notes

Diversity in Living Organism Activity:

Let us perform an activity to understand how diversity is found among individuals of same organism?

Consider yourself and your friend.

• Are you both of same height?
• Does your eye, nose or any other part look exactly like your friend’s?
• Is your hand span the same as your friend’s hand-span?

You would find that you both are roughly of same age but no external feature is similar in two of you- be it eyes, height, shape of mouth, nose, body shape etc.

• But if you compare a monkey with yourself and your friend, what would you see?
• Obviously, you would find that you and your friend have a lot of similarities and you both are quite different from Monkey.
• But, suppose you add a dog to your comparison? Then you would find that the monkey had more similarities with us than a dog.
• Now think of all the different forms of organisms that occur on earth.
• There are more than a million kinds of living things that exhibit an infinite variety in form, structure and living places.
• The range of variation found among microorganisms, plants, fungi, and animals is known as biodiversity.

Biodiversity is the richness of species of living organisms. Currently there are 1.7-1.8 million organisms, all of which are unique in themselves. With such a vast number of organisms, it becomes almost impossible for us to study each and every one of them at the individual level. Thus this task of studying the diversity of living organisms can be made easier and effective if these organisms are arranged in an orderly manner.

Before this, let us recognize the vast diversity in the living world both in size and complexity.

Variety in Size:

Think of the following varieties of plants:

• Huge trees like banyan, peepal, pine and so on. They have profuse branches and lots of leaves.
• Trees like palms and coconuts, with almost no branches.
• Medium-sized plants like banyan, rose, sugarcane, wheat etc.
• There are almost shortest lawn grass.

Similarly, there are huge varieties of animals on the earth Think of the following:

• Animals ranging from huge elephants or whales in the sea through the medium-sized dog to the small insects like butterflies or ants.
• Tiny animals like bacteria and Amoeba, which cannot be seen through naked eyes.

Variety in Complexity:

Examples:

In animals:

• Human body: Human body is extremely complex with so many different organs. Each organ in turn is composed of a variety of cells, each performing different tasks.
• Bird’s body: The body of bird is complex in some other ways. They have wings supported by bones and covered by feathers.
• Frog body: The body of frog is less complex than ours. They have three-chambered heart whereas we (human body) have four chambered heart.

In plants:

• Trees with tough wood produce flowers, fruits and seeds. On the contrary, trees like Pine produce seeds but no fruits.
• Plants like ferns produce neither seeds nor fruits but they do have leaves and roots.
• Organisms, like fungi have neither leaves, nor stem nor roots. Fungi have a network of fiaments.
• Green plants have green colour pigment called chlorophyll and thus can synthesise their own food while there are non green plants like fungi which can decompose food and absorb nutrition directly

Classification

There are enormous varieties of living organisms on earth. This enormous variety of life around us has evolved on the earth over millions of years. Some are closely related to each other, some are distantly similar and some are very different.It is practically impossible to study each and every individual. Also it is very difficult to remember their names, characters and uses.

Grouping and classifying organisms on the basis of similarities and differences helps us to know about them even if we have not seen them directly. Thus, classification is the arrangement of organisms into groups and subgroups on the basis of their similarities and dissimilarities.

Importance of Classification:

• Classification makes the study of large number of living organisms easy.
• It gives an idea of whole range of diversity found in organisms.
• It provides information about inter-relationships among organisms.
• It gives an idea of the evolution of various groups of organisms. Evolution is the complex process by which the characteristics of living organisms change over many generations.
• It gives a system for the identification of known and unknown organisms.

Classification and Evolution:

• All living organisms are identified and categorized on the basis of their body design in form and function. Some characteristics are likely to make more wide-ranging changes in body design than others. There is a role of time in this as well. So, once a certain body design comes into existence, it will shape the effects of all other subsequent design changes, simply because it already exists.
• In other words, characteristics that came into existence earlier are likely to be more basic than characteristics that have come into existence later.
• This means that the classification of life forms is closely related to their evolution. So, what an evolution is? Evolution is the accumulation of inherited changes within populations over time. A population is a group of individuals of one species that live in the same geographic area at the same time. The term evolution does not refer to changes that occur in an individual within its lifetime.
• Instead, it refers to changes in the characteristics of populations over the course of generations. These changes may be so small that they are difficult to detect or so great that the population differs markedly from its ancestral population. Eventually, two populations may diverge to such a degree that we refer to them as different species.

Evolution has two main perspectives:

Microevolution: The minor evolutionary changes of populations usually viewed over a few generations, is known as microevolution.

1. Macroevolution: The major evolutionary events usually viewed over a long period, such as formation of different species from common ancestors, is known as macroevolution.
2. Based on evolution, organisms can be divided into two types:
3. Primitive organism or lower organism: It is an organism which has a simple body structure and ancient body design that have not changed much over a period of time.
4. Advanced organism or higher organism: Organisms that have complex body structure and evolution, are known as advanced organisms.

For example, An Amoeba is more primitive than starfish. Amoeba has a simple body structure and primitive features as compared to starfish.

Basis of Classification:

• Organisms are classified on the basis of characteristics. It could be in terms of appearance or behavior. These characteristics give clues about how species evolved.
• The most important thing is to decide which characteristic is to be used as the basis for the broadest divisions. Then we will have to pick the next set of characteristics for making sub-groups within these divisions. This process of classification within each group can then continue using new characteristics each time.
• But before this, let us understand what a characteristic is? A characteristic is a particular form or a particular function found in large number of organisms.
• For example Most ofus have five figers on each hand. This is a human characteristic. Humans can run but banyan tree cannot, is also a characteristic, which can be used to classify humans and trees.
• Characteristics that create fundamental differences among life forms are used for raising kingdoms, divisions and other larger groups. New traits of lesser fundamental nature in turn are used to produce small groups and their sub-groups.
• It is just like building a wall of stone. The stones used will have different shapes and sizes. The stones at the top of the wall would not inflence the choice of stones that come below them.
• On the other hand, the shapes and sizes of stones in the lowermost layer will decide the shape and size of the next layer and so on. The stones in the lowermost layer are like the characteristics that decide the broadest divisions among living organisms.

They are independent of any other characteristics in their effects on the form and function of the organism. The characteristics in the next level would be dependent on the previous one and would decide the variety in the next level.

In this way, we can build up a whole hierarchy of mutually related characteristics to be used for classification

Hierarchy of Classification:

• Classification is not a single-step process but involves a hierarchy of steps. Each step in the hierarchy represents a rank or category. Since the category is a part of overall taxonomic arrangement, it is called the taxonomic category. All categories together constitute the taxonomic hierarchy.
• Each category, referred to as a unit of classification, in fact, represents a rank and is commonly termed as a taxon (plural. taxa). The taxa ranges from having very broad characteristics to much more specific characteristics.

• Species: The smallest taxon is species. At the species level, organisms look alike and are able to breed with one another.
• Genus: The next largest taxon is genus. At the genus level, there is a group ofsimilar species that are closely related.
• Family: Agroup oftwo more genera (plural ofgenus) with common characteristics make a family. For example, lion (Panthera leo), tiger (Panthera tigris) and the domestic cat (Felis domesticus) make the family Felidae.
• Order: A group ofrelated families make an order. For example, the family ofcats (Felidae) and the family ofdogs, foxes, etc. (Canidae) is grouped under the order Carnivora.
• Class: Related orders make a class. For example, several orders like those of the tigers, cats, dogs, monkeys, bats and humans belong to the class Mammalia.
• Phylum: A phylum is the largest category with related classes grouped together. For example, the classes ofmammals, birds, reptiles, amphibians and fishes together constitute the phylum Chordata. In plants, the corresponding category is named division.
• Kingdom: Kingdom is the largest group of organisms differentiated on very general similarities. For example, plant and animal kingdoms. The plant kingdom comprises all kinds of plants while animal kingdom comprises all kinds ofanimals.

The hierarchical classification of human is:

• Kingdom- Animalia
• Phylum- Chordata
• Class- Mammalia
• Order- Primata
• Family- Hominidae
• Genus- Homo
• Species- sapiens

Now you must be wondering how organisms are placed in various categories?

• The basic requirement to categorize organism is to have knowledge of characters of an individual or group of organisms.
• So, we choose the fundamental characteristics among several other characteristics. For example, plants differ from animals in the absence of locomotion, chloroplasts, cell wall etc.
• But only locomotion is considered as the basic fundamental feature and is used to distinguish between plants and animals.
• This is because the absence of locomotion in plants gave rise to many structural changes such as the presence of cell wall for protection and the presence of chloroplast for photosynthesis, as they cannot move around in search of food like animals.
• Thus, all these features are a result of locomotion and therefore, locomotion is considered to be a fundamental characteristic. By choosing the fundamental characteristic, we can make broad division in living organisms as the next level of characteristic is dependent on these. This goes on to form a hierarchy of characteristics.
• Let us know and discuss how an organism is named.

Naming An Organism- Binomial Nomenclature:

Biologists have devised techniques for identification, naming and grouping of various organisms. There is a need to standardize the naming of living organisms such that a particular organism is known by the same name all over the world. This process is called nomenclature. Nomenclature is the process of giving scientific names to plants and animals.

Thus, in order to facilitate the study, numbers of scientists have established procedures to assign a scientific name to each known organism. This is acceptable to biologists all over the world.

Scientific names are based on agreed principles and criteria, which are provided in International Code for Botanical Nomenclature (ICBN) and the International Code of Zoological Nomenclature (ICZN) for plants and animals respectively. The scientific names ensure that each organism has only one name. Biologists follow universally accepted principles to provide scientific names to known organisms.

Carl Linnaeus devised a binomial system of nomenclature in which an organism is given two names.

• A generic name that it shares with other closely related organisms which has features similar enough to place them in the same group.
• A specific name that distinguishes the organism from all other species. No other organism can have the same combination of genus and species.

Certain conventions are followed while writing the scientifi names:

1. The name of the genus begins with a capital letter.
2. The name of the species begins with a small letter.
3. When printed, the scientific name is given in italics.
4. When written by hand, the genus name and the species name have to be underlined separately

Let us understand the way of providing scientific names by taking an example of mango.  The scientific name of mango is written as Mangifera indica. In this, Mangifera represents the genus while indica, is a particular species, or a specific epithet. Similarly, the scientific name of human is written as Homo sapiens.

Other universal rules of nomenclature are as follows:

1. Biological names are generally in Latin and written in italics. They are Latinised or derived from Latin irrespective of their origin.
2. The first word in a biological name represents the genus while the second component denotes the specific epithet.

Question 1. Rewrite the scientific names of the following organisms in their correct form.
Answer:

Question 2. Rearrange the following in the correct sequence starting from smallest to highest category. Genus, Species, Order, Class, Family, Kingdom, Phylum
Answer: Species, Genus, Family, Order, Class, Phylum, Kingdom

The Two Kingdom Classification

Linnaeus classified the living world into two kingdoms- Plantae and Animalia in 1758.

1. Kingdom Plantae: The plant kingdom comprises all kinds of plants. It includes Bacteria, Fungi, Algae, Bryophytes, Ferns, Gymnosperms and Angiosperms.
2. Kingdom Animalia: The animal kingdom comprises all kinds of animals. It includes protozoans, Hydra, worms, insects, spiders, fishes, frogs, snakes, birds and mammals including humans. Classification of organisms into plants and animals were easily done and was easy to understand, inspite, a large number of organisms did not fall into either category.

For example:

• Euglena cannot be assigned with certainty to a specific kingdom because it shares characteristics of both plants and animals. It possesses chlorophyll like plants but lacks cell wall. It has autotrophic mode of nutrition but in dark it has heterotrophic mode of nutrition like animals.

• Similarly, Virus belongs to neither plant kingdom nor the animal kingdom, as they share characteristics of both living and non-living organisms.

Hence the two kingdom classification used for a long time was found inadequate. To overcome such problems a new scheme of classification was recommended by R.H. Whittaker in 1969.

The Five Kingdom Classification

R.H. Whittaker proposed a five-kingdom classification of living organisms on the basis of Linnaeus’ two kingdoms classification. The five kingdoms proposed by Whittaker are Monera, Protista, Fungi, Plantae, Animalia.

The main criteria in this classification are as follows:

1. On the basis of absence or presence of membrane-bound organelles: All living organisms are divided into two broad categories of prokaryotes and eukaryotes. This division led to the formation of kingdom MONERA, which includes all prokaryotes.
2. On the basis of cellularity (whether organisms are unicellular or multicellular): Unicellular eukaryotes form kingdom PROTISTA, and multicellular eukaryotes form kingdom FUNGI, PLANTAE, and ANIMALIA.
3. Cell wall: The kingdom ANIMALIA are then separated from kingdom PLANTAE on the basis of cell wall. Kingdom animalia lack cell wall.
4. Mode of nutrition: Since, fungi and plants both contain a cell wall; they are separated into different kingdoms on the basis of their modes of nutrition. FUNGI have saprophytic mode of nutrition while PLANTS have autotrophic mode of nutrition.

Let us now study each of these five kingdoms one by one.

1. Kingdom Monera (Unicellular prokaryotes): It is a kingdom of prokaryotes and includes bacteria and blue-green algae.

Characteristics:

1. Monera includes unicellular (single-celled) organisms.
2. They are prokaryotes. Their chromosome material is not enclosed within a nuclear membrane. It means, their genetic material is not organized into a nucleus. It lies directly inside the cytoplasm and is called nucleoid.
3. Membrane-bound cell organelles like mitochondria; golgi apparatus, lysosomes, etc are absent.
4. Cell wall may or may not be present.
5. The mode of nutrition may be autotrophic or heterotrophic.

Examples: Bacteria (Vibrio cholerae, Salmonella typhi) and blue-green algae (e.g. Anabaena, Nostoc)

2. Kingdom Protista (Greek protistos- First of all)- Unicellular eukaryotes:

Characteristics:

• Protista includes unicellular (single-celled) organisms.
• They are eukaryotes. They have well-defined membrane-bound nucleus.
• Membrane bound organelles like nucleus, mitochondria, endoplasmic reticulum, golgi bodies are present.
• Cell walls like Monerans, may or may not be present.
• The mode of nutrition is diverse.
  • Some protists like Amoeba and Paramecium can ingest food like animals.
  • Some protists like Euglena have chlorophyll and manufacture their own food like the plants. In the absence of light they become heterotrophic and ingest other protists like protozoa. This dual mode of feeding resulted in their placement both in plant and animal kingdom.

Examples: Diatoms, Euglena, Amoeba, Paramecium

3. Kingdom Fungi (Latin fungus- Mushroom)- Common bread molds (Rhizopus and Mucor), Mushrooms are some common types of fungi.

Characteristics:

1. Fungi are basically multi-cellular. Yeast is an exception in being unicellular.
2. The body of fungi is made of thread-like structures called hyphae. The hyphae grow in the form of a mat like structure called mycelium.
3. The cell wall is generally composed of chitin (a nitrogen containing carbohydrate).
4. They do not contain chlorophyll and hence are heterotrophic. Most of them are decomposers, hence fungi are also known as kingdom of multi-cellular decomposers. They may be saprophytic (depend on dead or decaying organic matter for their food) or may be parasitic (depend on living organisms for their food).

For example: Yeast, Mushroom (Agaricus), Rhizopus (Bread Mould), Penicillium.

Lichen:

Lichens are dual organisms that are formed by permanent symbiotic association between an algae and a fungus. They co-exist for mutual benefic. This type of relationship is known as symbiosis. The alga manufactures food for itself and for the fungus.

Fungus provides protection to alga and helps in fiation and absorption of water and minerals. Lichens can tolerate prolonged drought and drastic variations in temperature. Also, they are very sensitive to air pollution.

4. Kingdom Plantae (Multicellular Eukaryotes):

Characteristics:

1. They are multicellular eukaryotes.
2. All plants contain plastids. Plastids are double membrane organelle that possesses photosynthetic pigments. They are called chloroplast.
3. They are usually autotrophic. Chloroplast contains a green colour pigment called chlorophyll and prepares own food by the process ofphotosynthesis.
4. Cells have cell wall made ofcellulose.

Kingdom plantae shows a lot of diversity, because of which, it has been divided into four divisions: Algae, Bryophyta, Pteridophyta, and Spermatophyta (Gymnosperms and Angiosperms)

1. Division thallophytic (Greek: thallus-undifferentiated, phyton-plant):

Characteristics:

1. Plants of this division do not have well-differentiated body designs.
2. The body design is simple (i.e. not differentiated into stem, root, and leaves). It is often called thallus.
3. They are unicellular.

Thallophyta includes a single sub-division of algae.

Algae:

1. Algae are thallophytes that are capable of manufacturing their own food through photosynthesis.
2. The body of algae is simple with little differentiation of body design.
3. The form and size of algae is highly variable. The size ranges from unicellular microscopic forms like Chlamydomonas to colonial forms like Volvox and to the filamentous forms like Ulothrix and Spirogyra.
4. They are of three main groups: Green algae, Red algae and Brown algae.

Algae are responsible for almost 50% of fiation (Photosynthesis). Algae are also used as food; some important algae which are used as food are Porphyra, Laminaria and Sargassum.

Examples: Spirogyra, Ulothrix, Chara, Volvox, etc.

2. Division bryophyta (Greek: bryon-moss, phyton-plant):

You must have seen green velvety layer growing on damp soil or on the walls of flower-pots. What are these? Actually these are
Bryophytes i.e. mosses or liverworts.

Characteristics:

1. It is a division of non-vascular plants having an embryo stage in their developmental process.
2. They are the simplest land plants and are known as amphibians
   of plant kingdom as they live in moist areas.
3. The plant body is commonly differentiated to form stem and
   leaf-like structure.
4. It is thallus like and prostrate or erect and attached to
   the substratum by unicellular or multi-cellular rhizoids.
5. They have no specialized tissue for the conduction of water and other substances from one part of the body to another.
6. Plant body ofbryophytes is gametophyte. Sporophyte lives as a parasite over it.
7. The sex organs are multicellular, male sex organ is called antheridium and produces antherozoids whereas female sex organ is archegonium and produces a single egg.

Examples: It includes various mosses and liverworts.

3. Division pteridophyta (Greek. pteris-fern, phyton-plant):

Characteristics:

1. It is a division of seedless vascular plants. Hence commonly known as vascular cryptogams.
2. Pteridophytes represent the highest group of cryptogamae.
3. Unlike bryophytes, the main dominant plant body is sporophyte which is differentiated into true root, stem and leaves.
4. They have well developed vascular system (Xylem and Phloem).
5. Sporophytes bear sporangia which produces spore, on germination these spores give rise to gametophyte called prothallus. Prothallus bears the male and female sex organs antheridia and archegonia respectively.
6. Seeds are absent. They produce naked embryos called spores.

Examples: Selaginella, Equisetum, Marsilea, etc

4. Spermatophyta (Greek. sperma: seed, phyton: plant):

Characteristics:

1. It is a division of seed-producing plants. A seed has an embryo that contains reserve food for its future growth.
2. The main plant body is sporophyte which is differentiated into stem, leaves and roots.
3. Male and female gametophytes are distinct. They are small and dependent on sporophyte for their nutrition.
4. They have well-developed vascular tissues throughout the plant body. ‘
5. The reproductive process produces seeds which on germination forms a new plant.

Spermatophyta has two sub-divisions- Gymnospermae and Angiospermae.

Sub-division Gymnospermae (Greek. Gymnos-naked, sperma-seed):

Characteristics:

1. Gymnosperms include plants that bear naked seeds.
2. Plants are evergreen, woody and perennial. It includes medium sized trees, and shrubs
3. Sporangia are formed over modified leaflike structure called sporophylls.
4. Sporophylls are of two types: Megasporophyll bears megasporangium (ovule) whereas microsporophyll bears microsporangium (pollen sac).
5. The microsporophyll and megasporophyll form the male and female cones which produced male and female gametes respectively.

Examples: Cycas, Pinus (Pine), Cedrus (Deodar) Cycas Pinus

Sub-division Angiospermae (Greek. Angios-cover, spermae-seed)

Characteristics:

1. These are flowering plants, in which seeds are enclosed by a protective structure called fruits.
2. These are highly evolved group of plants.
3. Sporophylls are aggregated to form flowers.
4. The reproductive organs are aggregated into flowers. The male sex organs are called stamen and female sex organs are called pistil.
5. The seed contains an embryo together with the nourishment-containing cotyledons (one in some and two in others).

On the basis of number of cotyledons (fleshy embryonic leaves), the angiosperms are divided into two groups:

1. Dicotyledonae (Dicots):

1. The angiosperms with two cotyledons are called dicots.
2. Their leaves have reticualte venation with a network of veins.
3. The root system has prominent tap root.
4. The flowers have five or multiple office petals.

Examples: Pea, potato, Rose, Banyan, Apple, etc.

2. Monocotyledonae (Moncots):

1. The angiosperms with only one cotyledon are called monocots.
2. Their leaves have parallel venation.
3. The root system consists of firous roots.
4. The flowers have three or multiple of three petals.

Examples: Maize, wheat, rice, sugarcane, Banyan, Coconut etc.

Activity:

Let us perform a small activity to understand the difference between monocot and dicot plant:

1. Take some seeds of green gram, wheat, maize, and peas.
2. Soak them in water.
3. Once they become tender, try to split the seed.

What did you observe? Do all the seeds break into two nearly equal halves?

The seeds that split open into two equal halves are dicot seeds and the seeds that do not split in equal halves are the monocot seeds.

Question 1. Name the kingdom to which the following organisms belong.

1. Algae
Asnwer: Plantae: Thallophyta

2. Blue-green algae
Answer: Monera

3. Ferns
Answer: Plantae: Pteridophyta

4. Mushroom
Answer: Fungi

5. Flowering plant
Answer: Plantae: Angiospermae

Question 2. What are the three basic criteria that have been taken into consideration for the five kingdom classification of living organism?

Three criteria are:

1. Unicellular or multi-cellular
2. Eukaryotes or prokaryotes
3. Autotrophs or heterotrophes

5. Kingdom Animalia (Multi-cellular Eukaryotes):

Characteristics:

1. Members of kingdom animalia are multi-cellular eukaryotes.
2. They have heterotrophic mode of nutrition.
3. Almost all the animals are mobile. They move about in search of food or for other needs. Sponges and corals are however sedentary.
4. Cell wall is absent.

The kingdom Animalia is very vast and highly varied. It is subdivided into following nine phyla:

1. Porifera (Sponges)
2. Cnidaria or coelenterate (Jelly fishes and corals)
3. Platyhelminthes (Flatworms)
4. Aschelminthes (Roundworms)
5. Annelida (Earthworms)
6. Arthropoda (Insects, crabs, Spider)
7. Mollusca (Snails)
8. Echinodermata (Starfish, Sea urchins)
9. Chordata (Animals with backbone)

Basis of Classification of Animals:

1. Organization: Organisation is the structural differentiation of animal body. It can be divided into three levels:

1. Cellular level: In cellular level of organization, tissues do not differentiate. However, different types of cells may occur. e.g. Porifera (sponges).
2. Tissue level: In tissue level of organization, cells are organized into tissues but organs are absent. e.g. Coelenterata.
3. Organ level: In organ level of organization, cells are organized into tissues, tissues into organs and organs into organ system. e.g. Nemathelminthes and higher animals.

2. Body Symmetry:

Body symmetry is defined as similarity in arrangement of parts. It is of two types:

1. Radial symmetry: In radial symmetry, the body can be divided into two equal halves by any vertical plane passing through the central axis. It is found in Sponges, Coelenterates and Echinoderms.
2. Bilateral symmetry: In bilateral symmetry, body is divisible into two equal halves by only one plane. It is found in platyhelminthes, nematode, annelida, mollusca, arthropoda and chordate.

3. Germinal Layers: Germinal layers are primary layers that differentiate in embryo to form tissues and organs. It includes outer ectoderm, middle mesoderm and inner endoderm.

On the basis of germinal layers, animals are of two types:

1. Diploblastic animals: Animals that have two germinal layers- outer ectoderm and inner endoderm are called diploblastic. Mesoderm is absent in these animals. It includes Porifera and Coelenterate.
2. Triploblastic animals: Animals that bear three germinal layers- ectoderm, mesoderm and endoderm is known as triploblastic. It includes Plateyhelminthes to Chordate.

4. Coelom (Body Cavity): Coelom is a mesoderm-lined flid filed cavity that occurs between the alimentary canal and body wall. It provides shock proofenvironment to various body organs.

On the basis of the presence or absence of coelom, animals are divided into three types:

1. Acoelomate: Animals that lack coelom are acoelomate.
   Examples: Porifera, Coelenterata, Platyhelminthes.
2. Pseudocoelomate: Pseudocoelomate lacks true coelom. A cavity called pseudocoelom is present, which is not lined by mesoderm.
   Example: Nemathelminthes.
3. Coelomate: A true coelom lined by mesoderm is present.
   Example: Annelida, Mollusca, Arthropoda, Echinodermata and chordata

1. Phylum Porifera (Animals bearing pores):

1. These are the simplest multicellular, diploblastic, acoelomate animals.
2. They are mostly marine but few are found in freshwater.
3. Body consists ofa hollow tube, and found attached to the rocks.
4. The cells are loosely held together and do not form tissues.
5. They have porous body with numerous pores for entry of water carrying food and oxygen and a single opening for the exit of water.

Examples: Spongilla, Sycon, Euplectella.

2. Phylum Colenterata (Cnidaria):

1. They are exclusively marine animals except for few like Hydra that are found in fresh water.
2. They are multicellular, diploblastic animals with tissue grade of organization.
3. Body shows radial symmetry with a central gastrovascular cavity with a single opening, called hypostome.
4. Tentacles that surround the mouth capture the prey paralyzed by their stinging cells and push it into the mouth. The same mouth throws the undigested left out food out of the body again.

Examples: Hydra, Aurelia (Jelly fish), Physalia (Portugese man of war).

3. Phylum Platyhelminthes (platy: flt, helminthes-worms): Flat worms

1. The body is soft, elongated, dorso-ventrally flattened and leaflike with bilateral symmetry. Hence, known as flatworms.
2. The animals are triploblastic, acoelomate with tissue grade of organization.
3. They are generally endoparasites found in animals including human beings.
4. Digestive cavity (when present) with a single opening, the mouth. Anus is absent.
5. A specialized cell called flme cell helps in osmoregulation and excretion.

Examples: Planaria, Taenia (Tape worm), Fasciola (Liver flke).

4. Phylum Nemathelminthes (nema-thread, helminth-worm)- Roundworms:

1. The body of organisms belonging to this phylum are cylindrical and elongated.
2. They are bilaterally symmetrical, triploblastic and pseudocoelomate animals with organ level of organization.
3. Alimentary canal is complete with well developed muscular pharynx and anus.
4. Sexes are separate (dioecious) i.e. male and females are distinct.

Examples: Ascaris (Round worm), Wuchereia (Filaria worm), etc.

5. Phylum Annelida (annulus-ring, lidos-form): The segmented animals

1. Annelids are bilaterally symmetrical, triploblastic and coelomate animals.
2. They are soft, elongated, vermiform, cylindrical or dorsoventrally flattened.
3. They exhibit organ-system level ofbody organization.
4. Body is metamerically segmented externally by transverse grooves and internally by septa.
5. Digestive system is well developed. Alimentary canal is tube like and extends straight from mouth to anus.

Examples: Nereis, Pheretima (Earthworm), Leech, etc

6. Phylum Arthropoda (arthro-jointed, poda-legs): Animals with jointed legs

1. This is the largest phylum of Animalia which includes insects.
2. The body is triploblastic, bilaterally symmetrical and metamerically segmented with organ level of organization.
3. Body is also covered by a hard chitinous exoskeleton.
4. The body consists of head, thorax and abdomen with jointed legs.
5. Alimentary canal is complete. Mouth and anus lies at the opposite ends of the body.
6. Excretion takes place by Malpighian tubules (insects) and green glands (crab and prawn).

Examples: This is the biggest phylum with four major kinds of organisms.

1. Insects, such as cockroaches and butterflies, have three pairs of legs and usually two pairs of wings.
2. Spiders and scorpions have four pairs of legs.
3. Prawns and crabs have many pairs of legs.
4. Centipedes (hundred legs) and millipedes (thousand legs) have paired legs on each body segment.

7. Phylum Mollusca (Soft-bodied animals):

1. It is the second-largest phylum of the animal kingdom and an ancient group that lived on this planet from over 500 million years.
2. They are triploblastic coelomates and usually with bilateral symmetry.
3. They are terrestrial, marine, and freshwater inhabitants.
4. The body is soft and divided into three regions- head, dorsal visceral mass, and ventral foot. Foot is meant for creeping and for other kinds of locomotion.
5. The body is protected by a hard calcareous shell.

Examples: Snails, Slugs, Octopus, Cuttlefish, etc.

8. Phylum Echinodedrmata (echinos: spiny, derma: skin): The spiny-skinned animals

1. All are marine, triploblastic and coelomate.
2. Adults are radially symmetrical and larvae are bilaterally symmetrical.
3. The most distinctive feature is the presence of water vascular system with an array of radiating canals and tube-like appendages called tube feet. Tube feet are used for locomotion, capturing of food and respiration.
4. Exoskeleton is spiny.
5. Head is absent and five radially arranged arms are present.

Examples: Starfish, Sea urchin, Sea cucumber etc.

9. Phylum Chordata (Greek. Chorde-string):

1. It is a phylum of triploblastic bilaterally symmetrical animals.
2. All members of this phylum possess:
   1. Flexible rod-like notochord along the mid-dorsal axis of the body. The notochord is later replaced by a backbone (vertebral column).
   2. A hollow dorsal nerve cord.
   3. Paired gill slits
   4. A tail extending behind the anal opening.

Phylum Chordata is divided into three sub-phyla:

1. Subphylum Urochordata (uro:tail): In urochordata, the notochord is present in the tail of the larva and disappears in the adult.

Example: Herdmania.

2. Subphylum Cephalochordata (cephalo: head): In cephalochordata, notochord extends upto the anterior end of the body and persists throughout the life.

Example: Amphioxus

Subphylum Vertebrata: In organisms belonging to sub phylum Vertebrata, notochord is replaced by vertebral column in adults. It is the largest group in Chordata

Vertebrata is divided into two subphyla, i.e. Agnatha and Gnathostomata:

1. Agnatha includes a single class Cyclostomata, while
2. Gnathostomota is divided into six classes: Chondrichthyes (fiSh), Osteichthyes (fish), Amphibia (frog), Reptilia (lizard), Aves (birds) and Mammalia (Animals with milk gland).

1. Class: Cyclostomata:

1. All members of cyclostomata are ectoparasites on some fishes.
2. Body is long, elongated with 6-15 pairs of gill slits for respiration.
3. Skin is smooth, soft, slimy and scaleless.
4. Cyclostomata includes vertebrates which have suctoral mouth. Mouth does not possess jaws. The group is therefore, called agnatha.
5. Endoskeleton is cartilaginous, notochord persist throughout life.
6. Heart is two chambered and circulation is closed type.

Example: Lamprey

1. Superclass: Pisces:

1. They are exclusively aquatic animals with streamlined body covered with scales.
2. Pisces are cold-blooded animals.
3. Notochord is persistent.
4. Heart is two chambered and respiration occurs by gills. Gills are able to withdraw oxygen dissolved in water.
5. They have fis for locomotion and balancing.

Pisces is divided into two classes:

I. Class: Chondrichthyes (Cartilaginous fishes):

1. Cartilaginous fishes have their skeleton made of cartilage.
2. Gills are exposed (not covered by any gill cover). Operculum is absent.
3. The swim bladder is absent.
4. The mouth is ventral in position.

Example: Shark

2. Class: Osteichthyes (Bony Fishes):

1. Bony fishes have skeletons made of bones.
2. Gills are covered by an operculum.
3. The swim bladder is present.
4. The mouth is terminal in position.

Example: Rohu, Catla etc.

2. Superclass: Tetra Poda: [Greek tetra = four, podas = foot]]

1. Class: Amphibia (amphi: dual, bios-life):

1. The animlas are amphibious in nature that means they can live on land as well as in water.
2. Like pisces, they are cold blooded animals. Body temperature changes with that of external environment.
3. Skin is smooth and without scales. It has large number of mucus glands that keep the skin moist.
4. Alimentary canal, urinary and reproductive tracts open into a common chamber called cloaca which opens to the exterior.
5. Respiration is by gills, lungs and through skin.
6. The heart is three chambered (two auricles and one ventricle).
7. They lay eggs in water.

Examples: Toad, Frog, Salamanders, Newt, etc.

2. Class Reptilia (Latin. Repre: to crawl): Creeping vertebrates:

1. They are mostly terrestrial animals and their body is covered by dry and cornifind skin, epidermal scales.
2. Body varies in form and is usually divided into head, neck, trunk and tail.
3. Reptiles are poikilotherms (cold blooded animals).
4. Respiration takes place through lungs.
5. Heart is three chambered except for crocodiles which have four chambered heart.
6. They lay eggs on land. They are oviparous.

Examples: Lizards, Snakes, Turtles etc.

3. Class Aves (Latin. Avis: bird):

1. The body is streamlined to reduce air resistance during flight.
2. They are warm-blooded, tetrapodous vertebrates.
3. They are the fling animals, having exoskeleton of feathers.
4. Forelimbs are modified into wings while hind limbs have four clawed digits meant for walking, running or perching.
5. Jaws are prolonged to form horny beak. Teeth are absent.
6. Bones are very light because of air spaces. This helps the bird to lighten the body weight for flight.
7. They lay eggs with calcareous shell. They are oviparous.
8. Heart is four-chambered.
9. Respiratory system possesses well-developed lungs with air sacs attached to them.
10. Birds have keen sense of sight.

Examples: Ostrich, Crow, Parrot, Eagle, Pigeon etc.

4. Class Mammalia (latin. Mamma: breast):

1. They are the most evolved animals of animal kingdom. They have well developed brain.
2. They are endothermous (warm-blooded) animals. They maintain a fied body temperature.
3. The body is covered by hair. Skin has sweat glands to regulate their body temperature.
4. The females have milk producing glands called mammary glands.
5. They are the only animals which-nourish their young ones with milk.
6. Two pairs of pentadactayl limbs are present. Digits in the fore limbs and hind limbs are generally five and ending as claws, nail and hoof.
7. Limbs are variously adapted for walking, running, climbing, burrowing, swimming or fling.
8. Respiration occurs by lungs, heart is four-chambered.
9. They generally give birth to young ones except Platypus and Echidna that lays eggs. Kangaroos give birth to very poorly developed young ones.

Examples: Kangaroo, Dog, Man, Chimpanzee, Elephant, etc.

Question 1. Name the phylum showing the following characteristics:

1. Soft body enclosed in a hard calcareous shell.
Answer: Mollusca

2. Body supported by flxible rod like notochord.
Answer: Chordata

3. Animals with jointed legs.
Answer: Arthropoda

Question 2. Identify the correct matching pairs of phylum/class and its examples.

1. Chordata: Sparrow
2. Pisces: Whale
3. Amphibia: Crocodile
4. Mammalia: Kangaroo
5. Reptilia: Toad

Answer:

(1) and (2) are correctly matched pairs of phylum/class and its examples.

Question 3. Name the phylum to which following organisms belong.

1. Butterfly
Answer: Arthropoda

2. Starfish
Answer: Echinodermata

3. Jellyfish
Answer: Coelenterata

4. Tapeworm
Answer: Platyhelminthes

5. Sponge
Answer: Porifera

Choose the correct answer for the following questions:

Question 1. Which of the following birds is not capable of offling?

1. Peacock
2. Sparrow
3. Owl
4. Kiwi

Answer: 4. Kiwi

Question 2. Which of the following animal is capable of changing its body color?

1. King cobra
2. Chameleon
3. House lizard
4. Flying lizard

Answer: 2. Chameleon

Question 3. Which of the following is not a bird?

1. Owl
2. Bat
3. Kite
4. Ostrich

Answer: 2. Bat

Question 4. Which of the following is a mammal?

1. Crocodile
2. Whale
3. Shark
4. Turtle

Answer: 2. Whale

Question 5. Which of the following is not a fish?

1. Flyingfish
2. Catfish
3. Dogfish
4. Silverfish

Answer: 4. Silverfish

Chapter 2 Tissues Introduction

• All living organisms are made up of cells. As you have learned, the cell is the fundamental and structural unit of organisms.
• Unicellular organisms like Amoeba and Paramecium have a single cell in their body.
• The single cell performs all basic life activities like movement, intake of food, digestion, respiration, excretion, reproduction, etc.
• However, in multi-cellular organisms, there are millions of cells. Each cell is specialized to perform different functions.
• They show the division of labor. Division of labor has been made possible by the specialization of cells and their grouping with each specialized cluster of cells in a definite place in the body.
• For example, in the animal body, muscle cells help in the movement of body, nerve cells help in the conduction of message and blood cells helps in the transport of materials.
• Likewise, in plants, cells of phloem conduct food from leaves to another part of the plant.
• The specialization is achieved due to differentiation whereby cells occupy a definite shape, size, structure and functions.
• Hence, in multi-cellular organisms with a higher degree of differentiation and specialization, the group of cells aggregates collectively to perform a particular function.
• Such a group of cells are called tissues.

Read And Learn More: NEET Class 9 Biology Notes

What is tissue? Tissue is a group of cells with a common origin, structure and function that work together to perform a particular function.

For example, Blood, bone, and cartilage are some examples of animal tissues while xylem, phloem, parenchyma etc are different types of tissues found in plants.

Let us discuss the importance of tissues in living organism:

• It brings about division of labour in multi cellular organisms. The division of labour increases the survival rate of multi cellular organism.
• Tissues become organized to form organs, which in turn forms organ systems. This increases the effiiency of multi-cellular organisms.
• Tissue decreases the workload of individual cells.

Now, Do plants and animals have same types of tissues.? No! Though plants and animals have similar types of life processes but due to difference in their organization, life style and mode of living, they do not have similar types of tissues.

Let us have a look at how plant and animal tissues are different from each other.

Difference table between plant and animal tissues:

Structural Organization Of Tissues

• As we have learnt, the smallest unit of life in any living organism is cells. The cell has a very complex system of organelles and each organelle is concerned with a particular task.
• Thus, there is a division of labour at the cellular level. As evolution progressed and larger and larger organism appeared with enormous number of cells in the body, it became necessary that the bodies’ function are distributed among group of cells called tissues and even among group of tissues.
• Such higher and higher grouping of cells or tissue is known as levels of organization.

These levels are Cellular level, Tissue level, Organ level, Organ system and Organism.

1. Cells group together to form tissue, which in turn are grouped together into larger functional units called organs.
2. Tissues are aggregate of cells of same origin and having same function. For example, the surface epithelium of our skin or dividing cells of the root cap of a plant.
3. Organ is a group of various tissues that performs a specifi function. For example, stomach and intestine are organs to digest food.
4. Similarly, lungs and trachea are organs meant for respiration. All these organs are collections of various tissues like connective, epithelial, muscular and nervous tissue.
5. Like wise in plants, stem, root, leaves and flwers are different organs that perform different functions. They are made of different tissues like parenchyma, collenchyma, sclerenchyma, xylem and phloem.
6. Various organs group together to form even larger functional units called organ systems.
7. Organ system is a combination of a set of organs all of which are usually devoted to one general function.
8. For example, Respiratory system (consisting of lungs, trachea, bronchi, diaphragm etc) in man, or the shoot system (consisting of leaves, stem, and branches, etc) in a plant are example of organ system that works in a coordinated way.
9. The complete individual comprised of different organ system is known as organism. For example, Man, Dog, Cat or a Mustard plant.

Thus, the different level of organization of the living body is:

Cells → Tissues → Organs → Organ Systems → Organism

Question 1. The main organs of various system has been given. Find out their respective organ system
Answer:

In this chapter, we will be discussing various kinds of plant and animal tissues, in detail.

Plant Tissues

On the basis of their ability to divide, plant tissues are divided into two types:

1. Meristematic tissues (Dividing tissues): It consists of undifferentiated actively dividing cells.
2. Permanent tissues (Non-dividing tissues): It consists of differentiated cells that have lost the ability to divide.

Let us discuss each of these tissues one by one.

1. Meristematic Tissues:

1. Meristematic tissues are thin-walled compactly arranged, immature cells that keep on dividing continuously.
2. The new cells produced are initially Meristematic. Slowly, they grow, differentiate and mature into permanent tissues.
3. Characteristic features of Meristematic tissues:
4. The meristematic cells are spherical, or polygonal in shape.
5. The cells are compactly arranged without inter-cellular spaces.
6. The cell wall is thin, elastic and is made of cellulose.
7. Each cell has abundant cytoplasm and prominent nuclei. Vacuoles may or may not be present.

Functions: Meristematic tissue divides continuously to form a number of new cells and help in growth of tissue.

Location: On the basis of position in the plant body, meristematic tissues are divided into three types:

1. Apical Meristems: They are found at the growing tips of roots and stems.
   Function: It brings about growth in length of root and stem.
2. Lateral Meristem: It occurs on the sides almost parallel to the long axis of the root and stem.
   Function: It increases the width or girth of the stem and root.
3. Intercalary Meristem: It occurs at the base of the leaves or at the base of internodes.
   Function: It increases the length of the internode

2. Permanent Tissue:

• Permanent tissues are tissues that have lost the ability to divide, and have attained a defiite form and size.
• They are actually derived from Meristematic cells. Different type of permanent tissues is formed due to differences in their specialization.

Characteristic features of Permanent tissue:

1. The cells of permanent tissues normally do not divide.
2. The cells may be thin walled (living) or thick walled (dead).
3. Permanent cells are specialized to perform a particular function.
4. The cells have attained defiite shape and size.

Difference between Meristematic tissue and Permanent tissue:

Depending on the type of cells, permanent tissues are divided into two types:

1. Simple Tissue:

Simple tissue is made up of only one kind of cells forming a uniform mass. The cells are similar in structure, origin and function.

Simple permanent tissues are of three types: Parenchyma, Collenchyma and Sclerenchyma

Parenchyma: Parenchyma is widely distributed in plant body such as stems, roots, leaves and flower.

They are found in the cortex of root, ground tissue in stems and mesophyll of leaves.

1. Characteristic features:Cells are isodiametric i.e. equally expanded on all sides.
2. Cells may be oval, round or polygonal in outline.
3. Nucleus is present and hence, living.
4. The cell walls are thin and made of cellulose.
5. Cytoplasm is dense with a central vacuole.
6. Cells are loosely packed with large intercellular spaces between the cells.
7. It may contain chlorophyll. Parenchyma containing chlorophyll is called chlorenchyma.
8. It is the seat of photosynthesis.
9. The parenchyma that encloses large air cavities is known as aerenchyma. Aerenchyma provides buoyancy to aquatic plants.

Functions:

1. Parenchyma stores and assimilates food.
2. They give mechanical support to the plant body by maintaining turgidity.
3. The presence of intercellular spaces in between parenchyma cells helps in the exchange of gases.
4. It prepares food if chlorophyll is present.
5. It stores waste products like gum, crystal, tannin and resins

2. Collenchyma: Collenchyma is a strong and flexible tissue that provides flexibility to soft aerial parts.

They are found below the epidermis in leaf stalks, leaf mid-ribs, and herbaceous dicot stems.

Characteristics features:

1. Collenchyma cells are elongated cells with thick primary walls.
2. Cell wall is unevenly thickened with cellulose at the corners.
3. Intercellular spaces are absent.
4. Nucleus is present and hence the tissue is living.
5. Few chloroplasts may be present in the cells.

Functions:

1. Collenchyma provides mechanical support to the stem.
2. It provides flexibility to soft aerial parts so that they can bend without breaking.
3. Collenchyma cells may contain chloroplasts and thus take part in photosynthesis.

3. Sclerenchyma: Like collenchyma, sclerenchyma is also a strengthening tissue.

It is found in and around the vascular tissue, under the skin i.e. the epidermis in dicot stems.

Characteristic feature:

1. Cells are long, narrow, thick and lignified usually pointed at both ends.
2. The cell wall is evenly thickened with lignin. Lignin is a waterproof material.
3. Intercellular spaces are absent.
4. Nucleus is absent and hence the tissue is made up of dead cells.
5. Middle lamella i.e. the wall between adjacent cells is conspicuous.

Sclerenchyma cells are of two types:

• Fibres: They are long, narrow and pointed cells.
  Location: Fibres are found in and around the vascular tissue. It may also occur below the epidermis. Fibres help in the transportation of water in plants.
• Sclereids: The cells are thick-walled, hard and strongly lignified. They are shorter, iso-diametric or irregular cells.
  Location: Sclereids are found in the cortex, pith, phloem, hard seeds, nuts and stony fruits.

The flesh of pear and guava are sometimes gritty. Have you ever thought why it is so? It is due to the presence of sclereids. Sclereids give firmness and hardness to the part concerned.

Functions:

1. Sclerenchyma gives mechanical support to the plant by giving rigidity, flexibility and elasticity to the plant body.
2. It forms a protective covering around seeds and nuts.

2. Complex Tissue:

• Complex tissue is made up of more than one type of cells that work together to perform a particular function.
• Complex tissues are of two types: Xylem and Phloem.

1. Xylem (Greek xylo= wood): The Xylem is a complex permanent tissue that conducts water and minerals upward from root to the plant. It is also known as wood.

Xylem consists of four types of elements:

1. Tracheids: Tracheids are long, tubular dead cells with wide lumen and tapering ends. The cell wall is thick with lignin. They have pores in their walls.
2. Vessels: A vessel is a cylindrical tube like structure that are placed one above the other end to end. It is a non-living cell with lignified walls. They generally possess pits.
   Function: Tracheids and vessels both are main conducting elements in the xylem. Vessels are more effiient than tracheids.
3. Xylem fires: They are long, non-living cells with very thick lignin deposition on the walls. They have a narrow lumen and tapering ends.
   Function: Xylem fires provide mechanical support to the plant.
4. Xylem parenchyma: They are living cells with cellulosic cell wall.
   Function: They help in storage of starch and other materials. They also help in lateral conduction of water

2. Phloem (Greek= Phloeis= inner bark): Phloem is a complex permanent tissue that conducts food synthesized in the leaves to different parts of the plant body.

Unlike, xylem, conduction of food occur both in upward and downward directions (From leaves to storage organs and from storage organs to growing organs).

Phloem consists of four types of elements:

1. Sieve tubes: Sieve tubes are elongated, cylindrical tubes with perforated end walls between adjacent sieve tube cells. Sieve tube cells are placed end to end in a linear row. The perforated end walls are called sieve plates. Sieve tube cells have vacuolated cytoplasm and lack a nucleus.
2. Companion cells: Companion cells are associated with sieve tubes. They are thin-walled cells that lie on the sides of sieve tube cells. Companion cells have dense cytoplasm and prominent nuclei.
   Functions: They help sieve tubes in the conduction of food material by maintaining a proper pressure gradient in the sieve tube cells.
3. Phloem Parenchyma: The phloem parenchyma cells are thin-walled and living.
   Functions: They help in storage and slow lateral conduction of food.
4. Phloem fires: They are the only non-living (dead) component of phloem. They are thick-walled elongated and spindle shaped cells with narrow lumen.
   Functions: Phloem fires provide mechanical support to the tissue. Phloem fires are source of commercial fires. E.g. Jute, Hemp, Flax etc

Protective Tissue:

Protective tissues are the outer layer of cells that protect the plant parts like stem, roots, leaves, flowers and fruits.

They are of two types:

1. Epidermis:

• The epidermis is the outermost protective layer of the plant body. It is usually a single layer.
• The cells are elongated and closely packed without any intercellular spaces between them.
• The outermost layer of cell is covered with a waterproof coating or layer called cuticle. Cuticle is made up of a waxy substance called cutin.

At places, the epidermis is not continuous and bears minute pores called stomata. Stomata consist of an opening called the stomatal opening which is surrounded by two specialized kidney-shaped cells called guard cells. Guard cells are specialized epidermal cells. As guard cells become turgid, they create a pore in between their thick inner walls. Pores help in the exchange of gases. It is also the seat of transpiration.

Tissues In The Lab

• How do epidermal cells help in gaseous exchange? Let us perform an activity.
• Take a freshly plucked leaf of a Rhoeo plant. Stretch it from the upper side and break it by applying pressure. While breaking it, stretch gently so that peel projects out.
• Place this peel in a petri dish filled with water. Add a few drops of safranine stain to it. Observe it under a microscope.
• What did you observe? You will find tiny pores of stomata along with the epidermal cells.
• The stomata are bound by a pair of guard cells. Guard cells are the two curved cells on either side of the pore.
• By changing their shape they can open or close the pore. When guard cells absorb water, they bend outwards, so that the pore between them opens up. When they lose water they go back to a less curved shape, closing the pore between them.

Functions of stomata:

1. Stomata help in the exchange of gases, like oxygen and carbon dioxide.
2. It also helps in transpiration. Transpiration is the loss of water form the plant into the outside atmosphere.

Activity:

• To show that leaves give out water vapour through transpiration.
• Take a flower pot. Enclose a branch or the whole plant in a transparent plastic bag. Tie the plastic bag tightly around the stem to make sure that air does not enter or leave it. Leave the plant as such for 1-2 hours. What did you observe?

Observation: You will find a few drops of water inside the bag.

Conclusion: Water escapes into the air in the form of water vapor through the breathing pores (called stomata), which are found on the upper or lower surfaces of the leaves.

Functions of epidermis:

1. The main function of the epidermis is to protect the plant body from entry of pathogens and pest.
2. The presence of cuticle in the epidermis reduces the evaporation of water. It checks the rate of water loss from aerial parts.
3. The epidermis of root along with root hairs helps in the absorption of water and minerals from the soil.
4. The stomata regulate the exchange of gases and also help in transpiration.

2. Cork:

• Cork is the outer protective tissue of older stems and roots. Cork cells are rectangular in shape and are arranged compactly in several layers.
• They are dead cells and lack intercellular spaces. The walls of cork cells are heavily thickened by the deposition of suberin.
• Suberin makes the cork cells impermeable to water and gases. At places, cork possesses small aerating pores called lenticels.

Functions of cork:

1. Cork prevents the entry of harmful micro-organisms into the plant body.
2. It prevents desiccation, by preventing loss of water by evaporation.
3. It protects plant body against mechanical injury, extreme temperature and infections.
4. Cork possesses lenticels which help in exchange of gases between tissue and the atmosphere.
5. Though cork is light, impervious, non-reacting and insulating, it is commercially used in the manufacture of stoppers for bottles, shock absorbers, sports good, insulation board etc.

Question 1. How epidermis protects the plant body against the invasion of parasites?
Answer:

The epidermis does not allow the parasites to gain entry into the internal tissues due to

1. Absence of intercellular spaces
2. Thick outer walls
3. Deposition of cutin wax in the cuticle covering the epidermis
4. Deposition of silica

Animal Tissues

• Do you know, the working of animal body is coordinated by tissues and organs present in their body.
• For example, breathing occurs due to contraction and relaxation of certain muscles.
• During the process, the intake of air (inhalation) provides oxygen to blood inside lungs while carbon dioxide present in blood passes into the air via exhalation.
• Thus, the blood carries oxygen and food to all cells. What are these blood and muscles? These are actually types of tissues.
• Blood is a type of connective tissue while muscle is a example of muscular tissue.

On the basis of structure and function, animal tissues are divided into four types:

Let us now discuss each of these tissues one by one in detail.

1. Epithelial Tissue:

• Epithelial Tissue is the simplest animal tissue that forms the continuous sheet of closely packed cells that covers all external and internal surface of the animal body.
• Thus, it is also known as covering tissue. The epithelial cells lie close together with little or no intercellular substance.
• The cells are held together by various types of junctions and small amount of cementing materials.
• The epithelial membrane rests over an extra-cellular layer of white, non-elastic collagen fires called basement membrane. This membrane connects the epithelial tissue to the underlying connective tissue.

Location: It occurs over the skin, lining of mouth and other parts of alimentary canal, lung alveoli, lining of respiratory tract, kidney tubules, urinary tract, reproductive tract, blood vessels, etc.

Functions:

1. It protects the underlying tissues against mechanical injury, dehydration and infection by micro-organisms.
2. Epithelium lining the lung alveoli allows exchange of gases between blood and alveolar air.
3. Epithelium lining the uriniferous tubules helps in ultrafiltration, secretion and reabsorption to produce urine.
4. Glandular epithelium produces secretions. For example, tears, mucus, intestinal juice etc.
5. Ciliated epithelium helps in movement of various types of materials. For example, dust particles in respiratory tract, ovum in the oviduct etc.
6. Some epithelial cells like that of intestinal mucosa become specialized for absorption.

Types of Epithelial Tissue:

On the basis of arrangement of layers, epithelial tissues are classified into two types:

1. Simple epithelium: The epithelial cells arranged in a single layer are known as simple epithelium.
2. Stratified epithelium: The epithelial cells arranged in many layers are known as stratified epithelium. It is found in the body, where there is lot of wear and tear. For example, skin, inner lining of cheeks, etc.

On the basis of cell shapes, the epithelial tissues are classified as:

1. Squamous epithelium: It is made of thin, flat, irregular-shaped cells that fit together to form a compact tissue.

The margins may be smooth or wavy. Squamous epithelium can be single-layered (simple) or multilayered (stratified).

Stratified Squamous epithelium: Unlike Squamous epithelium, cells of this tissue are arranged in many layers.

The basal layer lies in contact with basement membrane, so that new cells can be added on older surface cells as they are torn away.

They are found in skin and cover the external dry surface of the skin. The epithelium is water-proof and highly resistant to mechanical injury.

Location:

1. Simple Squamous epithelium is found in lung alveoli, Bowman’s capsule, blood capillaries etc.
2. Stratified Squamous epithelium lines the cavities and ducts.

Function:

• It protects the underlying structures from mechanical injury and germs.
• As squamous epithelium lines the Bowman’s capsule, it helps in ultrafiltration.
• In blood capillaries, the epithelium helps in exchange of materials between blood and tissue.
• In the alveoli of lungs, epithelium helps in exchange of gases between blood and atmosphere.
• Stratified Squamous epithelium provides protection against abrasion by sloughing off the outermost layer.

2. Cuboidal epithelium: The Cuboidal epithelium is made up of cube like cells, which are square in section but they are polygonal in surface view. The nucleus is centrally placed and round in structure.

Microvilli may be present on the free surface which increases the surface area of absorption.

Location: They are found in the uriniferous tubules, thyroid vesicles, salivary and pancreatic ducts.

Functions:

• The cuboidal epithelium helps in secretion, excretion and absorption.
• It also provides mechanical support to the part where they are found

3. Columnar Epithelium: Columnar epithelium is tall and pillar-like. The nucleus is oval and lies at the base. The free surface bears a number of tiny figer-like projections called microvilli. Microvilli increase the surface area for absorption.

Location: They are found in the lining layer of stomach, intestine and their glands. They are also present in the salivary glands, sweat glands, tear glands, and covering of epiglottis.

Functions:

1. Columnar epithelium lines the intestine and is specialized to absorb nutrients.
2. Goblet cell is a modified columnar cell, which produces mucus.
3. It also provides protection to the underlying tissues.

On the basis of specific functions, the epithelial tissue is classified into ciliated and glandular epithelium:

4. Ciliated epithelium: Ciliated epithelium is Cuboidal or columnar cells that bear cilia at their free surface.

Location:

Ciliated Cuboidal epithelium is found in sperm ducts and uriniferous tubules.

The ciliated columnar epithelium is found in the inner lining of the respiratory tract (trachea or windpipe) and oviducts.

Functions:

The beating of cilia helps to keep the unwanted particles from entering into the lungs. Cilia also help in pushing the ovum in oviduct.

5. Glandular epithelium: Glandular epithelium is actually a modification of columnar epithelium. The epithelium is infolded to form multicellular glands.

Location: The glandular epithelium is found lining the intestine and glands.

Function: The glands are specialized for the secretion of specific chemicals.

For example sweat glands secrete sweat, similarly oil is secreted from oil glands, enzymes from digestive glands, hormones from endocrine glands, mucus from mucus glands, etc.

2. Connective Tissue:

Connective tissue is a fundamental animal tissue that has scattered living cells embedded in matrix.

The matrix and cells are different in different connective tissues. Matrix is the ground substance and is secreted by the living cells of the connective
tissue. It may be jelly-like, flied or solid.

It is the most abundant tissue of the animal body. It helps in connecting, binding, packing and supporting different structures of the animal body. Thus, it helps the body to function as an integrated whole.

Functions of connective tissue:

1. It helps in binding the different structures of the body. For example, muscle with bone, bone with bone, and muscle with skin.
2. It forms the packing material in different organs.
3. Skeletal connective tissue like bones and cartilage forms supportive framework of the body.
4. Fluid connective tissue like blood forms an internal transport system of the body.
5. The cells present inside connective tissue protect the body against microbes and toxins.
6. It also forms shock-absorbing cushions around organs like the eye, heart and kidneys.

Based on the nature of the matrix, connective tissue is divided into three types:

1. Connective Tissue proper (the matrix is Jelly-like, i.e. less rigid)
2. Skeletal Tissue (matrix is solid i.e. rigid)
3. Vascular Tissue (matrix is a flied called plasma)

Types of Connective Tissues:

1. Connective Tissue Proper: It is type of connective tissue that has a jelly-like matrix and three types of fibers- white collagen, yellow elastin and reticular fires. The living cells present may include fibroblasts, mast cells, plasma cells, Macrophages and lymphocytes.

It is of two types:

1. Loose connective tissue proper- It has fewer fires and more of matrix. Examples: Areolar tissue and Adipose tissue.
2. Dense connective tissue proper- It has more of fires and less amount of matrix.

Examples: Tendon, Ligament

Areolar Tissue: It is the most widely spread connective tissue in the body. The non-living intercellular matrix contains irregular shaped cells and two kinds of fires.

The cells forming the tissue are:

1. Fibroblasts: form the yellow fires, made of elastin and white fires, made of collagen in the matrix.
2. Macrophages: help in engulfing the bacteria and micro-organisms.
3. Mast cells: secrete heparin. Heparin helps in clotting of blood.

Location: Areolar tissues are found inside organs, around blood vessels, muscles and nerve. It also occurs below sub-cutaneous tissue and structures like muscles and skin.

Functions:

1. It helps in binding skin with underlying parts.
2. It provides packing material in various organs.
3. It provides material for repair of injury.
4. Macrophages present in tissue feed on microbes, produce antibodies to fiht against infection.
5. Mast cells in tissue are involved in allergic reactions

2. Adipose Tissue: It is a type of connective tissue that is specialized to store fat called adipose cells.

The fats are stored inside cells called adipocytes. Adipocytes are large cells with one or more globules of fat and peripheral cytoplasm with nucleus at one end.

Like areolar tissue, the adipose tissue also has soft jelly like matrix, living cells like fibroblasts, macrophages, mast cells etc and two types of fibers called collagen and elastin.

Location: The tissue is found below the skin, around internal organs and inside yellow bone marrow.

Functions:

1. Adipose tissue acts as storage tissue that stores fat in reserve for use when required.
2. It acts as shock absorbing cushion around certain organs.
3. It forms an insulating layer below the skin. It keeps the body warm.

3. Fibrous Tissue: Fibrous tissue is mainly made of firoblasts. Fibroblasts form tendons and ligaments.

1. Tendon: Tendon is a tough, non- fibrous, dense, white fibrous connective tissue. It has great strength but limited flexibility.
   Function: It joins a skeletal muscle to a bone, thereby helping the bone to move on contraction and relaxation of the muscle.
2. Ligament: Ligament is a dense yellow fibrous connective tissue. It has considerable strength and high elasticity.
   Function: The ligament binds a bone with another bone, thereby allowing bending and rotation movements over a joint.

Difference between tendon and ligament:

2. Supportive Connective Tissue: It is a connective tissue in which the matrix is rigid and the living cells occur in fluid-filed spaces called lacunae.

It is also known as skeletal tissue and is of two types.

1. Cartilage: Cartilage is a non-porous, firm but flexible supportive tissue. It has a solid matrix which is composed of chondrin.

Chondrin is secreted by the chondrocytes. Chondrocytes lie in the matrix singly or in groups of two or four surrounded by fluid-filed space called lacunae.

Cartilage is usually covered by a tough fibrous membrane called perichondrium.

Location: Cartilage is found in the nose tip, ear pinna, epiglottis, larynx, rings of trachea and bronchi, sternal ends of ribs, and tips of several bones.

Function: It provides support and flexibility to various parts of the body

2. Bone: Bone is a strong, rigid, and non-flexible tissue. Bone is the hardest tissue of the body.

• It consists of a solid matrix with flied-filed lacunae having osteocytes or bone cells.
• Matrix is composed of a collagenous protein complex called ossein and mineral matter like salts of calcium, phosphorus, and magnesium. The hardness of bone is due to the deposition of mineral matter.
• The matrix in mammalian bone like in thigh bone, is arranged in concentric rings or lamellae around nutrient-filed haversian canals.
• The osteocytes lie on the lamellae and give out branched processes that join with those of the adjoining cells.
• Some bones have a central cavity that contains a tissue that produces blood cells.
• The soft connective tissue present in the bone cavity is known as bone marrow.
• The sheath of bone is called the periosteum. A layer of osteoblasts or bone-forming cells lie below it.

Bones are of two types:

• Spongy bone, in which bone cells are irregularly arranged. Such bones are found at the ends of the long bones.
• Compact bone, in which cells are arranged in circles or lamellae around a central canal, haversian canal

Location: Bones are found all around the body. It forms the supportive framework of the body.

Function:

1. It forms the supportive framework of the body.
2. It provides a surface for attachment to many muscles.
3. It forms joints that take part in body movement and locomotion.
4. The red bone marrow of bones forms blood cells.
5. Bone is a reservoir of calcium, phosphorus, and other minerals.

Question 1. Which tissue smoothens bone surfaces at the joint?
Answer: Cartilage

Fluid Connective Tissue: It consists of cells and matrix without fibers. Plasma is the extra cellular flied of matrix, the ground substance. Blood and Lymph are two types of flied connective tissue.

Blood:

Blood is a bright red coloured flied connective tissue. It is a complex of straw-coloured flied plasma in which various kinds of cells are embedded. Plasma contains large number of proteins like Fibroblast, Albumin and Globulin.

The blood cells embedded inside plasma are:

1. Erythrocytes (Red Blood cells): Red blood cells are coloured enucleated living cells. It contains a red colour pigment called haemoglobin that takes part in transport of oxygen. It also carry small amount of carbon dioxide.
2. Leucocytes (White blood cells): They are colourless nucleated cells that have the ability to change their shape like Amoeba. White blood cells protect the body from diseases and help in healing of wound.
3. Thrombocytes (Blood Platelets): Blood platelets are non-nucleated, oval to rounded colourless cells. It helps in clotting of blood

Tissues In The Lab

Take a drop of blood in a clean slide and observe the slide under a microscope. What did you observe? You will fid different types of blood cells in it. Try to identify them and write their functions.

White Blood Cells/Leucocytes:

White blood cells are colorless, nucleated cells. Their amoeboid nature helps them to squeeze through the walls of the blood vessels in order to capture and engulf bacteria. They lack hemoglobin and hence are colorless. They are actually larger than red blood cells.

Based on the shape of nucleus and structure of the cytoplasm, leucocytes are broadly classified into two types.

1. Granulocytes: They are irregular shaped cells, with distinct and lobed nucleus. Their cytoplasm is granular.

It is further classified into three types:

1. Basophils: Their cytoplasm is large but with less number of granules. The nucleus is two or three-lobed. They develop into mast cells of connective tissue.
2. Eosinophils: They are more numerous in blood than basophils. Nucleus is bilobed. They are generally found in the wall of alimentary canal and blood capillaries. Eosinophils are thought to protect the body against allergies.
3. Neutrophils: The nucleus is formed of two or more lobes that are attached with each other.
4. They are about 67% of the total leucocytes in blood. Their function is phagocytosis of bacteria.

2. Agranuloctyes: Their cytoplasm is devoid of granules. Nucleus is large.
Based on their size, agranulocytes are of two types:

1. Lymphocytes: They are small in size but with large nucleus. It comprises about 28% of the total leucocytes in the blood. Their functions are phagocytosis and antibody- production. Phagocytosis is the process of engulfig solid particles.
2. Monocytes: Monocytes have kidney shaped nucleus. They function as tissue macrophages feeding on dead tissues.

Location: Blood flows continuously all over the body inside the blood vessels- Arteries, Veins and Capillaries.

Functions:

1. Blood transports gases like oxygen and carbon dioxide.
2. It also transports food materials like glucose, amino acids and fatty acids.
3. Blood regulates body temperature by conducting heat within the body.
4. Blood transports excretory products like urea and uric acid to the kidneys.
5. White blood cells fiht against infection and protect the body from foreign agents. They are basically soldiers of the body.
6. Blood platelets help in clotting of blood.

2. Lymph:

Lymph is a light, yellow coloured flied connective tissue, consisting of plasma and white blood cells. It is devoid of red blood cells and blood platelets.

Location: Lymph flows through lymph vessels and lymph capillaries. Most of the tissues and organs pour their secretions and excretions into lymph instead of blood. However, lymph is ultimately passed into blood.

Functions:

1. It helps in the exchange of materials between blood and tissue flied. Actually, it acts as a middleman between tissues and blood.
2. It brings carbon dioxide and wastes from tissues to blood and nutrients, oxygen etc from blood to tissues.
3. The lymph nodes and lymphoid organs (like the spleen) function as traps for microbes.
4. Lacteal, a special type of lymph vessel present in intestinal villi helps in the absorption of fat from the intestine.
5. The lymph also maintains the blood volume by removing or adding excess plasma.

Difference between Blood and Lymph:

Question 1. Why blood is considered to be connective tissue?
Answer:

Blood is considered fluid connective tissue because:

1. Blood consists of living cells scattered in an abundant matrix. The matrix is liquid or plasma in blood.
2. Blood connects all parts of the body. It circulates throughout the body, receiving, and providing materials to all tissues and organs.

Question 2. What will happen if lymph is not returned to blood?
Answer:

The blood volume will decrease and passage of substances from tissues to blood and blood to tissue would be disturbed.

3. Muscular Tissue:

• Muscular tissue is a contractile tissue that occupies more than 40% of total weight of the body.
• Each and every movement, every breath, every mouthful you chew-all these actions are carried out by the body’s muscle cells.

Structure of Muscular tissue: Muscular tissue is composed of contractile proteins inside cells.

• Cells of muscular tissue are elongated and are known as muscle fires. Because of their elongated shape, muscle cells are known as muscle fires.
• The group of muscle fires is known as muscles. The muscle fire is covered by a sheath of membrane called Sarcolemma.
• The cytoplasm of muscle fire contains a large number of fie longitudinally running firils called myofirils.
• Myofirils are actually the contractile elements of muscle fires. Each myofiril has two types of protein fiaments called thicker myosin and thinner actin.
• The actin and myosin fiaments slide past each other to shorten the firils causing the whole muscle to contract.
• The cytoplasm is called the sarcoplasm.

Working of Muscles: Muscles are attached to the bones of the skeleton by a cord called a tendon. If you want to lift your forearms, the brain sends a signal to your arms muscles through nerves. As a result, the muscle contracts (becomes smaller) and pulls the bones of forearm up.

Voluntary And Involuntary Muscles:

There are two kinds of muscles:

1. Voluntary Muscles are those muscles, that function as per the direction of conscious will. The brain can stop or start then. For example, skeletal muscles come into use when we walk.
2. Involuntary muscles are those muscles, that function on their own, independent of conscious will. Brain cannot stop or start them. For example, breathing in and out of air.

1. Differentiate the following activities on the basis of voluntary and involuntary muscles.

Question 1. Jumping of frog

Answer: Voluntary muscle

Question 2.  Movement of food in your intestine

Answer: Involuntary muscle

Question 3. Writing with hand

Answer: Voluntary muscle

Question 4. Pumping of heart

Answer: Involuntary muscle

Types of Muscle Fibres:

On the basis of their location, structure and function, there are three types of muscle fires.

1. Striated muscle fire
2. Unstriated muscle fire
3. Cardiac muscle fire

1. Striated Muscle Fibres: (Also known as striped, skeletal or voluntary muscle fires):

• Each striated muscle fire is long, cylindrical, unbranched with multinucleated condition.
• It bears striations in the form of alternate light and dark bands.
• The fires have blunt ends.
• A number of oval nuclei occur peripherally in each fire below the sarcolemma.
• The muscle has the ability to contract rapidly and thus is responsible for quick movements.
• The muscles are also known as voluntary because their contraction is under the control of will.
• They get fatigued soon

Location: They are found in the limbs, face, neck and body wall.

Function:

1. Striated muscle attached to bones helps in body movement.
2. It controls the breaking, chewing and swallowing of food.
3. It helps in breathing activity.
4. The muscles also control the blinking of eyes.

2. Unstriated Muscle Fibres: (Also known as Non-striated, Smooth or involuntary muscle fires)

• Each smooth muscle fire is spindle-shaped, unbranched and uni-nucleated cell.
• The muscle fires do not show striations.
• The fires have pointed ends.
• The muscles contract and relax very slowly.
• They are known as involuntary muscles as their movement is not controlled by the mind.
• Fatigue is rare in smooth muscle fires.

Location: They are found in the walls of organs like stomach, intestines, blood vessels, ureters, bronchi, lungs, urinary bladder, iris etc.

Functions:

1. In intestine, smooth muscle fire helps to push the food down along the alimentary canal by peristalsis.
2. Emptying of urinary bladder occurs due to contraction of smooth muscles.
3. Involuntary movement of iris and ciliary body of eye helps in automatic adjustment of amount of light and focusing of object based on distance.

3. Cardiac Muscle Fibres: (Also known as involuntary muscles)

• They are small, cylindrical, branched, and involuntary muscle fire.
• The fires have broad ends.
• They have transverse striations with light and dark bands. However striations are fainter than those of striated muscle fires.
• Special electrical junctions called intercalated discs are present at intervals in the fires.
• Cells are uninucleated. Nucleus is centrally placed.
• The muscles show rhythmic contractions.
• They are involuntary muscle fires. They are not under the control of one’s will.
• They seldom get fatigued. They keep on performing their function throughout life.

Location: Cardiac muscle fires are found in the walls of the heart.

Function: The rapid contraction and relaxation of cardiac muscle fires helps in pumping of blood through heart.

Difference between Striated, Smooth and Cardiac muscle fires:

Functions of Muscle fires:

1. Excitability: They can respond to stimuli.
2. Extensibility: They have the ability to get stretched.
3. Contractibility: They can contract.
4. Elasticity: They can move back to the original position

4. Nervous Tissue:

• Nervous tissue is specialized to transmit messages in our body. They can receive, integrate and transmit stimuli to various parts of the body.
• It is devoid of matrix. Its cell is surrounded by a special connective tissue cell.
• Nervous tissue contains two types of cells: Neuron and neuroglial cells.

Neuron: It is the functional unit of nervous tissue. It is also known as nerve cells. They are the longest cells of the body reaching upto a metre in length.

Each neuron is made of three parts:

1. Cell body (Cyton): It is a broader nucleated part of a neuron. Its cytoplasm is called Neuroplasm. Neuroplasm contains two special structure called neurofirils and Nissl granules.
   • Neurofibrils are fie fibrils involved in the transmission of impulses.
   • Nissl granules are ribosome containing structures. They are made of RNA and protein.
2. Dendrons: Dendrons are small, branched protoplasmic outgrowths of cell body. Like cyton, dendrites also possess neurofirils and Nissl granules. Dendrons further branch into many thin dendrites.
   Function: Dendrites receive impulses and transmit the same towards cyton.
3. Axon: Axon is a single, long, fire like process generally arising singly from the cell body of a neuron. It is devoid of Nissl granules. However, it contains neurofirils. Axon is surrounded by a sheath called neurolemma of a special connective tissue called Schwann cells.

The axon forms five branches at its terminal end called nerve endings. The nerve ending has knobbed ends in contact with muscles, glands, skin etc for providing an impulse for activity.  Each such junction is called synapse. Synapse is meant for the transmission of impulses from one neuron to another.

Function: Axon carries impulses towards the cell body.

The transmission of impulses is usually carried out with the help of a neurotransmitter like acetylcholine.

Difference between Axon and Dendrite:

Synapse:

• Synapse is a junction between two neurons. The terminal knobbed branch end of an axon are connected with dendrite branches of an adjacent neuron.
• This gap junction helps in transmission of impulse from one neuron to the next.
• The transmission of impulse is generally carried out with the help of a neurotransmitter chemical like acetylcholine.

Transmission of Nerve Impulse:

• As stimulus is passed on, the branching dendrites receive the stimulus and transmit through the cyton to the axon.
• From axon, the impulse is transmitted through its variously branched end into either a muscle (in order to contract) or to a gland (in order to secrete).

Question 1. What is the direction of the “flw of impulse” within a nerve cell?

1. Dendrite to axon
2. Axon to dendrites

Answer:

The branching dendrites receive the stimulus and transmit through the cyton (cell body) to axon, which fially transmits it through its branched end, either to muscle or gland.

Location of nervous tissue: They are present in brain, spinal cord and nerves.

Functions:

• It picks and conducts messages from one part of body to another.
• They also receive all types of sensations like sight, sound, smell, pain, touch etc. from the outside environment and send the message to the brain and the spinal cord.
• In turn, impulses from the brain and spinal cord are carried to the various organs.
• Nervous tissue provides responses to all types of stimuli.
• It exerts control over entire body activities by coordinating the functioning of different body parts.

Chapter 1 Biology The Fundamental Unit of Life Introduction:

• Our Earth is inhabited by millions of different kinds of living organisms. These living organisms are bacteria, fungi, plants, and animals. Although the great diversity of organisms look very different from each other but all these organisms exhibit a unique similarity in their organization.
• Can you guess the structure, which is common to all these organisms? Yes, it is the cell. The bodies of all living organisms are made up of microscopic units called cells. Each of us has about 50 million cells-an enormous number which is diffiult to imagine.
• Thus, the cell is the basic structural and functional unit of living organisms. Cell Biology is the study of cells in all aspects of structure and function.

Read And Learn More: NEET Class 9 Biology Notes

Discovery Of The Cell

• In 1665, Robert Hooke, an English scientist, saw cells for the fist time in a thin slice of cork with its microscope. He observed and described the cells as “Honeycomb” like structures. He named the box-like compartments as cellular or cells. The term “cell” is derived from the Latin word cella which means little room or hollow space.
• In 1674, Van Leeuwenhoek, a Dutch Scientist, studied living cells for the fist time with the help of an improved microscope, which he himself had made. Though he was the fist one to observe “cells”, but he did not use the term “cell”.
• In 1838, two biologists, J.M Schleiden and T.Schwann proposed the “Cell Theory”. According to them, the cell is the structural and functional unit of all living beings.
• In 1855, Rudolf Virchow, a German pathologist proposed that all cells arise from pre-existing cells. He stated this in Latin as “Omnis cellula-e- cellula”.

Cells theory, therefore, states that

1. All living organisms are composed of one or more cells
2. The cell is the basic unit of life.
3. Cells develop from pre-existing cells.

Cell Shape Size And Number

Look at the structure of onion peel cells. Do all cells look alike in shape and size? Yes, all cells are of the same shape and almost of same size.

Let’s have a look at cells from the different parts of plant body. Now Are all cells the same? No, they are not.

Now if we look at the cells from different parts of the human body. They too don’t look alike in shape and size. As you can see, the cells are different in shapes and size.

Plant cells are different from animal cells. Plant cells in a root are different to those in the stem or in the leaf. Animal cells, including cells in our bodies are all sorts of different shapes and sizes. It means cells vary in number, shape and size in different organisms and also in different parts of the same organism. Infact, the shape and size of cells are related to the function they perform. For example, in plants, xylem and phloem are elongated in shape and help in conduction of water and food. Similarly, in animals, nerve cells are long and branched that help in conduction of information from one part of body to another.

Cell Size

The size of the cell ranges between broad limits. Some cells are extremely small and can be seen only when magnifid and is visible only with a microscope since, they are only a few micrometres in diameter. Cells are limited in size by the ratio between their outer surface area and their volume. Small cells have more surface area for their volume of cytoplasm than large cells. As cell grows, the amount of surface area becomes too small to allow materials to enter and leave the cell quickly enough.

Cell size is also limited by the amount of cytoplasmic activity that the cell’s nucleus can control.

Actually the size of the animal is dependent on the number of cells and not the size of the cells. The cell size remains constant for a particular cell and is independent of the size of the organism. The large size of the elephant is due to the larger number of cells present in its body.

Cells are measured in micrometres. A micrometer is one thousandth of a millimetre.

Question1.  Why cells are small in size?
Answer:

Cells are small in size because :

1. The cells nucleus can only control a certain amount of active cytoplasm.
2. Also, the cells are limited in size because of their surface area to volume ratio.

A group of small cells has a relatively larger surface area than a single large cell of same volume. A cell requires nutrients, oxygen and other materials for its survival. So, as cells grow larger at some point, its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cell’s need. Thus, as cell increases in size, its surface to volume ratio decreases that causes the cell to function less effiiently.

Cell Shape

The shape of the cells is more variable than their size. The shape of the cell may be spherical, oval, elliptical, spindle shaped, polygonal or flt-plate like. The shape of the cell is determined by the specifi function of the cell. Some of the cells like Amoeba and white blood cells can change their shape while most of the plant cells and animal cells have almost fied shapes.

Among unicellular organisms, for example, in Amoeba, the shape of the cell (body) is irregular, while among multi-cellular organisms like in plants, the xylem and phloem elements are elongated tubular structures so as to help in conduction of water and minerals; the dividing Meristematic cells are isodiametric in shape.

Similarly in animal cells, the nerve cells are elongated thread like which enables an effiient communication system, the muscle cells are elongated and contractile that helps in the movement of bones, while the red blood cells are biconcave shaped. This kind of shape of RBCs helps the RBCs to easily move through capillaries and thus permit gaseous exchange.

Cell Volume

The volume of a cell is constant for a particular cell type. It is independent of the size of the organism. For example, the kidney or pancreatic cells are about of same size as in dog or cat. The difference in total mass of the organism or organ depends on the number, not on the volume of the cells.

Cell Number

The number of cells varies in all living organisms. Based on the number of cells, the organisms are divided into two types.

1. Unicellular organisms (Single-celled organisms): The organisms made up of single cells are called unicellular organisms. Amoeba, Paramecium, bacteria etc are examples of unicellular organisms. The single cells have the ability to perform all the life processes like digestion, respiration, excretion, growth and reproduction. In these cells, there is no division of labour as the single cells have to perform all the activities.

2. Multi-cellular organisms (Multi-celled organisms): The organisms made up of a number of cells are called multi-cellular organisms. Fungi, plants and animals are example of multi-cellular organisms. All the cells of multi-cellular organisms have a similar basic structure and similar basic life activities. These cells group together to produce different tissues. Tissue forms organs and organs give rise to organ system that performs specialized functions.

The increasing order of complexity in multicellular organisms is: Cell → Tissue → Organ→ Organ System → organism

Let us summarize difference between unicellular and multi-cellular organisms

Each cell is an amazing world into itself. It can take in nutrients, convert them into energy, carry out specialized function and reproduce as necessary. Even more amazing is that each cell stores its own set of instructions for carrying out each of its activities.

Cells are of two types :

1. Plant Cell
2. Animal Cell

Though many things are common between animal and plants cell but they differ in some way.

Animal cell differ from plant cells in terms of structure and types of organelles

The Fundamental Unit of Life In the lab

Let us perform an experiment to study plant and animal cells with a microscope.

Part A: Plant cells (Onion skin mount):

Procedure:

1. Take an onion piece and peel the delicate transparent tissue from its inner surface using forceps.
2. Place this tissue, unwrinkled in a small drop of water on a glass slide.
3. Then add a small drop of Safranine stain to the tissue and cover it with a cover slip. While placing the coverslip ensure that there is no air bubbles under the coverslip.
4. Now observe the slide under a microscope.

Observation: You will see several small rectangular shaped cells. The boundary of each cell is covered by a cell nembrane which in turn is covered by another thick covering called the cell wall. In the center of cell, there is a dense round body called the nucleus. In between the nucleus and the cell membrane, there is a jelly like substance called cytoplasm.

Part B: Animal cells (Cheek cells):

Procedure:

1. Take a clean glass slide and place a drop of water on it.
2. Gently scrap the inside of your cheek with the blunt end of a clean toothpick.
3. Then stir the material on the toothpick in the drop of water on the slide.
4. Add a small drop of methylene blue stain on the slide.
5. Now carefully place a coverslip over the slide and observe the slide under microscope.

Observation: You can see large number of irregular shaped cells with a thin cell membrane. Cell wall is absent in animal cells. In the center of cell, nucleus is present. It is stained dark blue.

Structural Organisation Of A Cell

A cell is the basic unit of life. It performs all basic life functions like intake of food, excretion, metabolism, respiration, growth and reproduction. However, there is no mixing up of different functions. Infact, there is a division of labour. For this, a cell usually possesses a number of components called cell organelles. Each cell organelle performs specifi functions. Hence, a cell may be defied as a unit of protoplasm, bounded by a cell membrane or plasma membrane.

Plant cells are different from animal cells. Plant cells in a root are different to those in the stem or in the leaf. Animal cells, including cells in our bodies are all sorts of different shapes and sizes. It means cells vary in number, shape and size in different organisms and also in different parts of same organism. Infact, the shape and size of cells are related to the function they perform. For example, in plants, xylem and phloem are elongated in shape and help in conduction of water and food. Similarly, in animals, nerve cells are long and branched that help in conduction of information from one part of body to another.

Cell Size:

The size of the cell ranges between broad limits. Some cells are extremely small and can be seen only when magnifid and is visible only with a microscope since, they are only a few micrometres in diameter. Cells are limited in size by the ratio between their outer surface area and their volume. Small cells have more surface area for their volume of cytoplasm than large cells. As cell grows, the amount of surface area becomes too small to allow materials to enter and leave the cell quickly enough.

• Cell size is also limited by the amount of cytoplasmic activity that the cell’s nucleus can control.
• The smallest cell found is a mycoplasma cell, which is about 0.1 micron in diameter.
• The longest cells are the nerve cells, measuring about a metre in length.
• The largest cells are represented by eggs of Ostrich, which is about 170-135 mm.

Actually the size of the animal is dependent on the number of cells and not the size of the cells. The cell size remains constant for a particular cell and is independent of the size of the organism. The large size of the elephant is due to the larger number of cells present in its body.

Cells are measured in micrometres. A micrometer is one thousandth of a millimetre.

Question 1. Why cells are small in size?
Answer:

Cells are small in size because:

1. The cells nucleus can only control a certain amount of active cytoplasm.
2. Also, the cells are limited in size because of their surface area to volume ratio.

A group of small cells has a relatively larger surface area than a single large cell of same volume. A cell requires nutrients, oxygen and other materials for its survival. So, as cells grow larger at some point, its surface area becomes too small to allow these materials to enter the cell quickly enough to meet the cell’s need. Thus, as cell increases in size, its surface to volume ratio decreases that causes the cell to function less effiiently

Discovery Of The Cell

In 1665, Robert Hooke, an English scientist, saw cells for the fist time in a thin slice of cork with its microscope. He observed and described the cells as “Honey comb” like structures. He named the box-like compartments as cellulae or cells. The term “cell” is derived from a Latin word cella which means little room or hollow space.

In 1674, Van Leeuwenhoek, a Dutch Scientist, studied living cells for the fist time with the help of an improved microscope, which he himself had made. Though he was the fist one to observe “cells”, but he did not use the term “cell”.

In 1838, two biologists, J.M Schleiden and T.Schwann proposed the “Cell Theory”. According to them, the cell is the structural and functional unit of all living beings.

In 1855, Rudolf Virchow, a German pathologist proposed that all cells arise from pre-existing cells. He stated this in Latin as “Omnis cellula-e- cellula”.

Cells theory, therefore, states that

1. All living organisms are composed of one or more cells
2. The cell is the basic unit of life.
3. Cells develop from pre-existing cells.

Cell Shape Size And Number

Look at the structure of onion peel cells. Do all cells look alike in shape and size? Yes, all cells are of the same shape and almost of same size.

Let’s have a look at cells from the different parts of plant body. Now Are all cells the same? No, they are not.

Now if we look at the cells from different parts of human body. They too don’t look alike in shape and size. As you can see, the cells are different in shapes and size.

1. Diffusion: The process of movement of substance from the region of higher water concentration to the region of lower concentration, so as to spread the substance uniformly in the given space is known as diffusion. The process does not require energy.

For example: Transport of CO₂ and O₂ across the membrane. The gases like CO₂ and O₂ move across the membrane through diffusion. The process of respiration produces carbon dioxide inside the cell. As the concentrate of CO₂ increases inside the cell as compared to the outside, CO₂ diffuses out of the cell into external medium.

Similarly, the concentration of oxygen is always higher in the external medium (atmosphere) as compared to the cell. Therefore, oxygen diffuses from outside to the inside of cell

Activity:

Let us perform an activity to understand the process of diffusion.

Take a glass beaker half filed with clean water. Put a few drops of coloured ink, say blue colour, into the beaker. What did you
observe?

You would fid that blue coloured ink slowly diffuses into the water until the ink molecules get uniformly distributed. This spontaneous movement of a substance from a region of higher concentration to the region of lower concentration is known as diffusion.

Osmosis: It is defied as the diffusion of water from region of higher concentration to region of lower concentration across the semi-permeable membrane. This kind of movement is along concentration gradient. There is no expenditure of energy.

For example: Movement of water across selectively permeable membrane.

Difference between Diffusion and Osmosis:

Types of Osmosis:

Endosmosis: Endosmosis is the osmotic entry of water into the cell.

Exosmosis: Exosmosis is the osmotic withdrawal of water from the cell.

There are three types of osmotic Solution, which can cause osmosis across semi-permeable membrane.

Hypotonic Solution: (Hypo=less than or lower) : Hypotonic is the Answer: which has lower osmotic concentration than the cell.

Hypertonic Solution: (Hyper=more or higher) : Hypertonic is the Answer: that has higher water concentration than the cell.

Isotonic Solution: (Iso=same) : It is the Answer: that has same osmotic concentration as inside the cell.

The Fundamental Unit of Life In the Lab

Let us perform an activity to understand the three types of Answer: and the process of osmosis.

Take an animal or a plant cell. Place it in a medium that has higher water concentration than the cell. What will happen? The cell will gain water by endosmosis. Such type of Solution is known as hypotonic Solution. Since, water molecules are free to pass across the cell membrane in both directions, so when cell is placed in a hypotonic Solution more water will come into the cell than it leaves. As a result, the cell is likely to swell up. As water keeps on moving inside cell, the animal cells burst while the plant cells become turgid but do not burst due to the presence of cell wall.

Now place the plant and animal cell in a medium that has lower water concentration. What will happen? The cell will lose water by exosmosis. Such a Solution is known as a hypertonic Solution. Since, water molecules are free to pass across the membrane, so when cell is placed in hypertonic Solution, the cell will lose water. As a result the cell will shrink. In plant cell, the shrinking protoplasm will contract from cell wall and the process is known as plasmolysis while in animal cell; the whole cell shrinks on all sides to give a wrinkled appearance. This process is known as crenation.

What will happen, if the cell is placed in a medium that has same water concentration as that of cell? There will be no net movement of water across the membrane. Such a Solution is known as isotonic Solution. In isotonic Solution , the amount of water going into and out of cell is same. Hence, there is no movement of water and the size of cell remains the same.

2. Active transport: Active transport is the process of transport of molecules across the plasma membrane against the concentration gradient. The process requires the use of energy. For active transport, the cell membrane possesses ATP mediated carrier protein. Glucose, amino acids and ions pass through plasma membrane by active transport.

Question 1. Why does the skin of your figers shrink when you wash clothes for a long time?
Answer:

Clothes are washed with soap or detergent Solution. The Solutiion is hypertonic as compared to osmotic concentration of our skin cells.

The detergent Solution , therefore, causes exosmosis in the skin cells. Hence, the skin over the figer shrinks while washing clothes for a long time.

Question 2. Classify the following as osmosis or diffusion.

1. Swelling up of raisins on keeping in water.
2. Spreading of virus on sneezing.
3. Fish using oxygen dissolved in water during respiration.
4. Absorption of water by the roots from the soil

Answer:

1. Osmosis
2. Diffusion
3. Diffusion
4. Osmosis

Cell Wall:

Cell wall is a rigid, non-living covering present outside the plasma membrane in plant cells. Animal cells lack a cell wall. Plant cell is made up of cellulose, which is permeable to water, solutes and gases. In fungi, the cell wall is made up of chitin. A cementing layer called middle lamella is present between the walls of two adjacent cells. Middle lamella is formed of pectin, calcium and magnesium pectate.

Difference between Cell wall and Cell membrane:

Functions of Cell Wall:

1. It gives defiite shape to the cells.
2. It provides mechanical strength to plants.
3. It protects the cell against mechanical injury and pathogens.
4. It helps in transport of various substances across it.
5. Cell wall helps the plant cells to withstand a lot of variations in the surrounding environment.
6. Cell wall prevents the bursting of cell on endosmosis as it is quite thick and rigid.

Question 1. Why cell wall is present only in plant cell?
Answer:

Plants grow tall, towards the sun’s light. So, in order to provide strength and necessary support, the plants have cell wall and is present only in plant cell.

Nucleus:

Nucleus is the prominent, spherical structure found at the center of the cell. It is the largest organelle present in cell. Basically, nucleus is the controlling centre of all cell activities and hence, it has been described as the brain of the cell. In plant cell, nucleus lies towards the periphery due to the presence of large central vacuole while in animal cell, nucleus lies in the central position.

Structure of Nucleus It is made up of following parts:

1. Nuclear envelope: It is the double membranous structure that separates the nucleus from the cytoplasm. It is mainly made up of proteins and lipids. The membrane is perforated by several nuclear pores, which allows exchange of materials between the nucleus and cytoplasm.

On the basis of presence or absence of nuclear membrane, organisms are divided into two types:

1. Prokaryotes (Pro = Primitive, karyotes = nucleus):  Organism whose cells do not possess a well formed nucleus are known as prokaryotes. Examples, Bacteria, Cyanobacteria, etc. Prokaryotes also lack membrane bound cell organelles. Thus, cell organelles like mitochondria, golgi bodies, ER are absent in prokaryotes.
2. Eukaryotes (Eu= True, karyotes = nucleus): Organisms whose cells possess a nuclear membrane are known as eukaryotes. Cell organelles like mitochondria, golgi bodies, ER are present in eukaryotes.

Examples are plants and animals.

 Difference between Prokaryotes and Eukaryotes:

Nucleoplasm (Nuclear sap): It is colourless cytoplasm within nuclear membrane in which chromatin and nucleoli are suspended.

Nucleolus: It is dense, spherical granular structure found inside the nucleus. Nucleolus is not bounded by a membrane. It is membraneless. It is rich in proteins and RNA. Basically, Nucleolus is the site of ribosome formation. Ribosome, in turn helps in protein synthesis in the cytoplasm.

Chromatin Network: Chromatin is a network of fie thread like coiled fiaments uniformly distributed in the nucleoplasm. It is usually made of DNA and protein. During cell division, chromatin become highly condensed, thick and rod like structures known as chromosomes.

The chromosome contains genes, which are composed of DNA. A gene is the functional unit of a chromosome. These are arranged in a single linear order along the chromosome. One gene is responsible for single characteristic or a single characteristic may be transmitted by a set of genes. Genes are responsible for storing and transmitting hereditary characteristics from one generation to another.

Functions of Nucleus:

1. Nucleus is the chiefcontrolling center of cell. It contains chromosomes which carry genes. Genes are responsible for transmission of hereditary characters from parents to offspring.
2. Nucleus controls all metabolic activities taking place in the cell.
3. It participates directly in cell division to produce genetically identical daughter cell by a process known as mitosis.

Question 1. Do all cells contain a well defied nucleus structure?
Answer:

No. Not all cells contain a well-defied nucleus. The nucleus of bacterial cell is not well organised like the cells of multi-cellular organisms. They do not have nuclear membrane. Such type of cells are known as prokaryotic cells. On the other hand, the cells that have a well-organised nucleus with a nuclear membrane are called eukaryotic cell.

Question 2. Give an example of a human cell which lack a nucleus?
Answer:

Red blood cells. The red blood cells of humans lose their nuclei, which enables them to carry more hemoglobin and thereby more oxygen.

Question 3. How are chromatin, chromatid and chromosomes related to each other?
Answer:

Chromatin is interwined mass of fie thread like structure made of DNA and protein. During the division of a cell, chromatin condenses to form thicker rod like structures called chromosomes. Each chromosome consists of two similar halves called chromatids. The formation of chromosomes having two chromatids is meant for equal distribution of chromatin, which is a hereditary material.

Question 4. Why DNA is called “the blueprint of life”?
Answer:

In the center of all plant and animal cell, there is a copy of organism’s genetic material, called DNA or deoxyribonucleic acid. This DNA carries a complete blue print of the organism that transfers characteristics from one generation to the next. Our DNA comes from our parents and their DNA comes from their parents too. That is why relatives have similar DNA to each other.

4. Cytoplasm:

Cytoplasm occupies the major part of the cell. It is a living component of cell, consisting of transparent, semi-flid granular substance. It is limited on the outside by the cell membrane. Water is the main component of the cytoplasm.

Cytoplasm has two major parts:

1. Cytosol: Cytosol is the flid part of cytoplasm. It is viscous, and contains a number of substances like water, ions, enzymes, vitamins, carbohydrates, lipids and proteins. All major biochemical reactions take place in the cytoplasm.
2. Cell organelles: Cell organelles are tiny, sub-microscopic structures that are specialized to perform specifi functions. These organelles are bounded by a membrane to keep their contents separate from the external environment. These organelles include Mitochondria, Endoplasmic reticulum, Golgi bodies, Plastids, Lysosomes, Peroxisomes, Ribosomes and Centrosomes.

Let’s discuss each of these organelles one by one in detail.

1. Mitochondria (Singular-Mitochondrion):

Mitochondria are rod shaped cell organelles surrounded by a double membrane. The outer membrane is smooth and porous while the inner membrane is folded into large number of figer like structures called cristae. Cristae increase the surface area of the inner membrane, which provides more surface area for the metabolic reactions to take place. The flid inside the mitochondria is called the matrix.

Mitochondria are commonly known as “Powerhouse of the cell”. They contain enzymes necessary for the total oxidation of food and for the release of large amount of energy in the form of ATP molecules. The energy stored in this ATP is used for synthesis of new products and other metabolic process.

Flow chart that describes the fate of glucose in the release of energy:

Mitochondria have the ability to make their own protein, as they contain their own DNA and ribosome. That is why; mitochondrion is also known as semi-autonomous organelle

Functions of Mitochondria:

1. Mitochondria are the site of cellular respiration. They use molecular oxygen from air to oxidize the carbohydrates and fats present in the cell to carbon dioxide and water vapour.
   Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)
2. Mitochondria provide energy in the form of ATP for various metabolic activities of living cells. Since, the mitochondria synthesize ATP, it is also known as power house of cell.

2. Plastids :

Plastids are found only in plant cells. They are absent in animal cells.

On the basis of pigments present in them, plastids are of the following three types:

1. Leucoplasts: Leucoplasts are colourless plastids. They are found in storage cells of roots, seeds and underground stems. They take part in storage of food.
2. Leucoplasts are of three types depending on the storage products : Amyloplasts stores starch, Aleuroplasts stores protein while elaioplasts store oil and fat.
3. Chromoplasts: They are coloured plastids. The colour varies from red, orange, yellow etc due to the presence of carotenoids. They are mostly found in flwers and fruits. They provide colouration to organs for attracting pollinators.
4. Chloroplasts: Chloroplasts are green colour plastids, found in leaves. The green colour is due to the presence of chlorophyll. Chlorophyll traps the solar energy which is used for manufacturing food. They are the sites of photosynthesis.
   So, chloroplasts are the “Kitchen of the cells”.

Structure of chloroplasts: A chloroplast is bounded by two membranes i.e. outer membrane and inner membrane. The inside of chloroplast is clearly marked into a colorless ground matrix called stroma.

1. Stroma is homogenous matrix in which grana is embedded. Stroma contains a variety of photosynthetic enzymes, DNA and ribosomes. It is the site where all chemical reactions occur and starch (sugar) is synthesized.
2. Grana are stacks of membrane bound, flttened sacs containing the molecules of chlorophyll. One thylakoid stack is known as granum. Each thylakoid have chlorophyll molecules on their surface that trap sunlight and take part in process of photosynthesis.
   The stacks of grana are connected by stromal lamellae. The lamellae act like the skeleton of chloroplast, keeping all sacs in safe distance from the other sac. Grana are main functional units of chloroplasts.

Functions of Chloroplast:

Chloroplasts trap solar energy, which is used to manufacture food through photosynthesis. Photosynthesis is the process of synthesizing food (sugar) from carbon dioxide and water in the presence of sunlight.

1. Chromoplasts provide colour to fruits and flwers to attract insects for pollination.
2. Leucoplasts take part in storage of protein, starch and oil.

Question What will happen if chloroplast is taken out of the cell and is illuminated?
Answer:

Chloroplast is a semi-autonomous cell organelle. They have their own DNA and protein. So, if chloroplast is taken out of the cell and illuminated, it can still perform its function of photosynthesis and release oxygen, provided it is kept in isotonic medium and receives raw material of carbon dioxide.

3. Endoplasmic reticulum:

Endoplasmic reticulum is a complex network of membrane bound structure which runs through the cytoplasm. Cisternae are spaces within the folds of the ER membranes. It is connected to both the outer nuclear membrane as well as cell membrane. The membrane has the same structure as the plasma membrane but ribosomes do not have membranes.

Depending on presence or absence of ribosome on the surface of ER, it is divided into two types:

1. Rough Endoplasmic reticulum (RER): It is lined with ribosomes and is rough in appearance, hence, named as rough endoplasmic reticulum. It is the site of protein synthesis.
2. Smooth Endoplasmic reticulum (SER): It contains no ribosomes and hence is smooth in appearance. It helps in lipid and steroid synthesis.

Functions of endoplasmic reticulum:

1. The endoplasmic reticulum helps in the intracellular and intercellular transport of materials. It is the “transport system” of the cell.
2. It transports chemicals between cells and within cells.
3. It provides large surface area for various metabolic reactions.
4. RER is the site of protein synthesis.
5. SER helps in lipid synthesis.
6. SER in liver cells helps in detoxifying many drugs and poisons.
7. Proteins and lipids synthesized on ER are used for making cell membranes. The process is known as membrane biogenesis.

4. Golgi Bodies:

The Golgi body consists of smooth, flattened, membrane-bound, sac-like structures called cisternae. The cisternae are stacked together; placed one above another in parallel rows. It is frequently surrounded by vesicles, which are discharged from the cisternae.

Membranes of the Golgi body may develop connections with membranes of ER to form a complex called an extramembrane system. incoming transport vesicle

The Golgi apparatus receives vesicles from ER on its convex or cis face for elaboration of their contents. They are then dispatched to intracellular and extra cellular targets through vesicles that develop on the sides as well as maturing convex or trans face of apparatus

Functions of Golgi bodies:

1. It is involved in the synthesis and repair of cell membrane.
2. It is also involved in formation of lysosomes and peroxisomes.
3. Secretion is the major function of Golgi apparatus. All types of substances that are secreted and excreted are packed in vesicles
4. by Golgi bodies for passage to the outside. It is the secretory organelle of the cell.
5. Golgi apparatus also takes part in storage, modifiation and packaging of various biochemical products produced by different components of the cell.

5. Lysosomes (Lysis = Breaking down; Soma = Body): Lysosomes are small, spherical vesicle covered by a single membrane. It is scattered all over the cytoplasm.

It contains powerful digestive enzymes (about 40 in number) that are capable of breaking down the organic material. Thus, lysosome serves as an intracellular digestive system, and is called digestive bags.

The digestive enzymes contained in lysosomes are synthesized by RER, and are packed into lysosomes by Golgi bodies. Lysosomes are also called suicidal bags as enzymes contained in them can digest the cell’s own material when damaged or dead.

Functions of Lysosomes:

1. Lysosome helps in intracellular digestion of food particles as they are rich in various digestive enzymes.
2. They help in destruction of foreign particles, as in white blood cells.
3. They help in cleaning up the cell by digesting damaged materials of the cell. Lysosomes are therefore called cellular scavengers.
4. Lysosomes digest the cell’s own material when damaged or dead. Hence, they provide energy during cell starvation by digesting cell’s own parts.

6. Vacuoles:

Vacuoles are membrane bound flid-filed cavities or sacs present in the cytoplasm. They are surrounded by a membrane called tonoplast. The vacuole is filed with a liquid called “cell sap” that contains dissolved salts and sugars.

A single, large vacuole is present in a plant cell. In animal cells, vacuole may or may not be present. If present, they are numerous and smaller in size.

Vacuoles are of three types:

• Sap vacuole: Sap vacuole stores salts, sugar, amino acids, salts and some proteins. Sap vacuole helps in maintaining turgidity and rigidity of the cell. It also maintains the osmotic pressure of water.

• Food vacuole: In single-celled organisms, like Amoeba, the sacs containing ingested food fuse with lysosomes to form food vacuole. The process of digestion takes place inside the food vacuole.
• Contractile vacuole: Contractile vacuole collects liquid from the cell, swells up and rises to the surface and burst to release their contents. They take part in osmoregulation and excretion.

Functions of Vacuole:

In plant cells:

1. Vacuoles help to provide turgidity and rigidity to the cell.
2. Vacuole acts as a store house of pigments and waste products. It also stores useful minerals and salts.
3. Sap vacuole maintains an osmotic concentration which is required for absorption of water.

In animal cells:

1. In single celled organisms, like Amoeba, food vacuole helps in digestion of food particles.
2. Contractile vacuole takes part in osmoregulation and excretion.
3. They store materials such as food, water, sugar and waste products.

7. Centrosome:

Centrosome is a small naked organelle found in the cytoplasm near the outer surface of the nucleus. It encloses two microcylinders called centrioles. The two centrioles lie at right angles to each other.

In plant cells, centrosome is absent and polar caps perform the function of the centrosome.

Functions of centrosome:

1. Centrosome and Centriole help in formation of spindle fires during cell division.
2. Centriole also produces basal bodies that form cilia and flgella.

8. Ribosomes:

Ribosomes are tiny, membrane-less organelle present in the cytoplasm. They are found either in Free State in the cytoplasm or attached to the surface of ER. They are rich in RNA and proteins.

Functions of Ribosome: Ribosomes are sites of protein synthesis. Hence, they are known as protein factories of cell.

Name the organelle which shows analogy written as below:

Difference between Plant and Animal Cell:

Let us summarise the functions of various parts of a cell:

• Chapter 1 The Fundamental Unit of Life Notes
• Chapter 2 Tissues Notes
• Chapter 3 Diversity in Living Organisms Notes
• Chapter 4 Why Do We Fall ill Notes
• Chapter 5 Improvement In Food Resources Notes
• Chapter 6 Natural Resources Notes
• Chapter 7 Origin Of Life Notes