WBBSE Solutions For Class 10 Life Science Chapter 5 Environment And Its Resources Short Answer Questions

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Chapter 5 Environment And Its Resources Short Answer Questions

Question 1. Mention the percentage of nitrogen, oxygen, and carbon dioxide in the air.
Answer:
(1)’Nitrogen’ – 77.17%
(2)Oxygen – 20.60%
(3) Carbon di-oxide – 0.03%

Question 2. What is the Nitrogen Cycle?
Answer: The cyclic rotation of atmospheric nitrogen gas from the atmosphere to soil from soil to the living body and again from the living body to its source is called the nitrogen cycle.

Question 3. What is meant by nitrification?
Answer: The process of conversion of ammonia to nitrite (NO₂) and nitrite to nitrate (NO3) with the help of nitrifying bacteria (such as Nitrosomonas and Nitrobacter) is called nitrification.

Question 4. Mention the different components of an ecosystem.
Answer: There are two components of an ecosystem
(1)Abiotic Soil, water, minerals, air, temperature, light, humidity, etc.
(2)Biotic Producers, consumers, and demmposers.

Question 5. Name two abiotic and three biotic components of the ecosystem.
Answer:
(1) Abiotic:-
(1) soil and
(2) water.

(2) Biotic:-
(1) producers,
(2) consumers,
(3) decomposers.

Wbbse 10th Class Life Science Question Answer

Question 6. What do you understand by the term producer in the ecosystem?
Answer: The autotrophs (green plants) that can convert solar energy into potential chemical energy by the process of photosynthesis are called producers. ExampleMango trees.

Question 7. What is meant by Consumer?
Answer: The organisms that are unable to prepare their food by the process of photosynthesis and directly or indirectly depend on autotrophs for their food, are called consumers. Example Grasshopper, butterflies, toad, snake.

Question 8. Give the name of the denitrifying bacterium and mention its functions.
Answer:
(i) Bacillus denitrificance.
(ii) Function It converts nitrate and nitrite into free form of nitrogen. This also helps to return nitrogen to its source.

Question 9. What is Biomass?
Answer: The weight of all the organisms forming a given population in a given area is called biomass.

Question 10. What do you mean by plankton and nekton?
Answer: PlanktonThe free-floating microorganisms are called plankton.

For example algae and protozoa.
Nekton Swimming animals in the pelagic zone of the sea or lake are called nekton.

Example Fishes and whales.

Question 11. Arrange the following organisms in the correct sequence (from producer to secondary consumer): Kingfisher – Algae – Fish.
Answer: Algae – fish – kingfisher.

Question 12. Explain the food chain in the ecosystem.
Answer: The linear arrangement of living organisms in which one is the food of the other organism and the transfer of food energy occurs systematically is called a food chain. Example:- Grass – Grasshopper – Toad – Snake – peacock.

Question 13. What is meant by decomposer in an ecosystem?
Answer: The saprophytic organisms like bacteria and fungi which decompose the dead body of plants and animals, are called decomposers.

Question 14. Write the names of three organic and three inorganic components of an ecosystem.
Answer:
(1) Organic components –
(1)Carbohydrates,
(2) Proteins,
(3) Fats.

(2) Inorganic components –
(1) Water,
(2) Air,
(3) Minerals (Ca, Mg, Fe, etc.)

Question 15. Indicate with arrows the path of the flow of energy among toads, vultures, grass, snakes, and grasshoppers in a grassland ecosystem.
Answer: Grass > Grasshopper> Toad > Snake > Vulture.

Question 16. Write the difference between the Food chain and the Food web.
Answer:

Question 17. What is a food pyramid?
Answer: Food pyramid The gradual reduction of the trophic level of the food chain of an ecosystem producing a conical pyramid-like structure is called an ecological pyramid. Ex. pyramid of number, pyramid of mass, and pyramid of energy.

Question 18. What disaster would occur in a grassland ecosystem if the application of pesticides kills the decomposer bacteria and fungi The ecosystem will be unbalanced in the absence of decomposers. The dead bodies of plants and animals will be accumulated on the earth.

Question 19. Explain how biotic factors of an ecosystem are dependent on abiotic factors.
Answer: Producers, consumers, and decomposers are biotic factors. Consumers and decomposers obtain their food from producers directly or indirectly. Producers obtain water from the soil and air. These two are raw materials. Sunlight is obtained from the sun. They prepare their food by the process of photosynthesis. Thus biotic factors are dependent on abiotic.

Question 20. Mention the role of producers in an ecosystem.
Answer: Producers use solar energy to prepare their food. This food is the source of food for other living. They also produce oxygen gas. This gas is used by living for respiration.

Question 21. What is meant by conservation?
Answer: The process of proper utilization and management of natural resources (like air, water, soil, etc.) to keep their composition normal for the welfare of human beings is called conservation.

Question 22. Mention two main purposes of conservation.
Answer:
(1) To maintain the balance of ecosystem and
(2) to ensure a continuous yield of useful plants, animals, and materials by establishing a balanced cycle of harvest and renewal.

Wbbse 10th Class Life Science Question Answer

Question 23. What is meant by the conservation of soil?
Answer: To keep the normal balance of the components of soil which are essential for plant growth is called soil conservation.

Question 24. What is a National Park?
Answer: A national park is an area that is strictly reserved for the betterment of wildlife and where activities like forestry, grazing, and cultivation are not allowed. Ex – Kaziranga, Corbett, Gir, Kanha, etc.

Question 25. What do you mean by sanctuary?
Answer: A sanctuary is a protected area that is reserved for the conservation of only animals and human activities like harvesting of timber, and collection of minor forest products, and private ownership rights are allowed so long as they do not interfere with the wellbeing of animals. Ex-Jaldapara, Nagarjun sagar, Dachigam.

Question 26. What is a reserve forest or protected forest?
Answer: It is a forest area that is protected with all its components by the India Forest Act. Entrance without permission is prohibited. Ex-Gorumara, periyar.

Question 27. Mention any two causes of soil erosion.
Answer:
(1) Exposed dry soil without any vegetation.
(2)Overgrazing by cattle.

Question 28. Write two aims and objectives of conservation.
Answer:
(1) To maintain the ecological balance.
(2) To protect the endangered species.

Question 29. The population of deer in a particular forest land has suddenly and rapidly increased. What steps (any two) will you take to bring back a balance in the ecosystem after analyzing the possible causes of the increase in the population of deer?
Answer:
(1) Provide food and water as early as possible.
(2) The tree plantation scheme should be sped up.

Question 30. The biosphere is considered the largest biological system. Give reasons.
Answer: Because the biosphere has a structure made up of all the living and nonliving components of Earth where each component performs a certain function. Their functions make the biosphere dynamic and stable.

Question 31. A plant cannot absorb Nitrogen directly from the air.
Answer: Reasons
(1)Direct nitrogen-absorbing biological processes are absent in plants.
(2)Nitrogen gas is insoluble in water.
(3)Nitrogen is a comparatively less reactive gas.

Question 32. Why is the pyramid of energy always upright?
Answer: The pyramid of energy is always upright because the flow of energy always takes place from producer to consumer, which means in one direction only.

Wbbse 10th Class Life Science Question Answer

Question 33. Name two case studies in India for the food crisis.
Answer:
(1) Irish Famine (1851) induced by fungus Phytophthora – infestans causing late blight of potato.
(2) Great Bengal Famine (1942) induces by the fungus Dreschlera-oryzae causing the Brown spot disease of Rice.

Question 34. Why are windmills located in coastal areas?
Answer: Because the minimum wind velocity required to run a windmill is 20 km/hour, which is possible only in coastal areas.

Question 35. What is geothermal energy?
Answer: The energy obtained from the interior of the earth is called geothermal energy.

Question 36. What is biomass?
Answer: The matter contained in the body of plants and animals is called biomass. It is used to produce energy. It contributes 15% of total energy.

Question 37. What is Eutrophication?
Answer: Excess amounts of untreated sewage and pollutants are dumped into water bodies, accelerating the growth of algae and depleting O₂ content, result in damage to aquatic life and the water smells pungent.

Question 38. Define biomagnification.
Answer: The gradual increase of harmful chemicals like pesticides from one trophic level to another through a food chain is called biomagnification.

Question 39. What is global warming?
Answer: Due to the increase in CO₂ concentration in the atmosphere, the temperature of the earth increases causing the melting of glaciers and polar caps cap is called global warming.

Question 40. What are greenhouse gases?
Answer: The gases which cause the greenhouse effect are called greenhouse gases, eg. Methane, CO₂ water vapor, etc.

Question 41. Define ecology and environment.
Answer:
Ecology :
The natural surrounding of an organism, which affects its life, by directly influencing its activities, is called an environment. It includes both physical and living environments.

Environment:
The branch of science which deals with the interrelationship between the living organism and the environment is called ecology.

E. Flaeckel (1869) first proposed the term ecology.

Question 42. Mention the relationship between the food chain and the food web in the ecosystem.
Answer:
Food Chain :
The sequential process in which one organism consumes another to transfer food energy is called a food chain.

Food web:
The network of various food chains that are interconnected at various trophic levels is called the food web.
Relation: Many food chains of the same habitat form a food web. So, the food chain is a structural and functional unit of the food web. In a food web food chains are interconnected and interdependent.

Question 43. Define two types of ecology.
Answer:
Autecology:
The study of an individual organism or individual species and its interaction with the environment.

Synecology :
The study of a group of organisms or living communities and their interrelationship with the environment.

Question 44. What is meant by nitrogen fixation? Mention the role of symbiotic bacteria in that process.
Answer:
(1) Nitrogen fixation The conversion of atmospheric free nitrogen gas into the form of nitrite (NO₂) and nitrate (NO₃) is called nitrogen fixation.
It takes place in three ways –
(1) Natural fixation,
(2) Biological fixation,
(3) Chemical fixation.

Wbbse 10th Class Life Science Question Answer

(2) Role of symbiotic bacteria in nitrogen fixation Rhizobium bacteria lives in the root nodules of leguminous plants like peas and grams. It converts nitrogen into ammonia in the presence of the enzyme ‘ nitrogenase’. Further, this ammonia is utilized by plants to produce their nitrogenous substances.

N₂ + 3H2 = 2NH₃

Question 45. Discuss in brief the role of free-living and symbiotic bacteria in the fixation of free nitrogen in the soil.
Answer:
(1) Role of free-living bacteria Some saprophytic bacteria live freely in soil and convert free nitrogen into nitrite and nitrate, for example – Azotobacter and Clostridium.
(2) Role of symbiotic bacteria They live in the root nodules of leguminous plants i.e., peas and grams. They convert nitrogen into ammonia in the presence of the enzyme nitrogenase. This ammonia is used to form nitrogenous compounds by the plant.

Question 46. Discuss two important roles of organisms in supplying carbon dioxide to the environment.
Answer: Role of organisms in supplying carbon-di-oxide to the environment –
(1)Respiration Every living organism releases carbon dioxide into the environment during respiration.
(2)DecompositionThe dead bodies of organisms are decomposed by saprophytic bacteria and fungi. The carbon dioxide gas produced during decomposition is returned to the environment.
(3)Burning Carbon dioxide gas returns to the environment due to the burning of different types of fuels, such as coal, petrol, diesel, etc.

Question 47. Explain in brief how energy flows through the living components of the ecosystem.
Answer: The way energy flows in the living components of the ecosystem
(1)Solar energy is the only source of energy flow.
(2)Only producers can transform the solar energy into chemical energy. This chemical energy is stored within food. Solar energy never goes back to the sun from the producer. Primary consumers get their energy from producers and this energy also never goes back to the producers.

In the same way, secondary consumers obtain energy from primary consumers and tertiary consumers get energy from secondary consumers. After the death of producers and consumers, decomposers decompose the dead bodies and obtain energy.
(3) There is a gradual decrease in the energy flow from the beginning to the end of a food chain.

Question 48. What do you mean by reserve forest? Name a reserve forest in West Bengal.
Answer: It is a forest area that is protected with all its components by the India Forest Act. Entrance without permission is prohibited. Ex – Gorumara, periyar.

Question 49. Mention any three ways of water conservation.
Answer: Methods of water conservation
(1)By preventing excess cutting of trees and promoting the practice of excess tree plantation.
(2)By treating sewage and industrial wastes in water treatment plants before releasing them into rivers.
(3)By constructing dams and bunds.

Question 50. Mention in brief the importance of wildlife conservation.
Answer: The importance of wildlife conservation.
(1) Wildlife (plants and animals) maintains the continuity of the ecosystem of nature through the balance of population and food chains.
(2)They keep our environment clean, for example, green plants and scavenger birds.
(3)They are a source of various medicines.
(4)They help to understand the mechanism of evolution.
(5)They are a source of foreign currency, for example, visiting national parks by foreigners.

Question 51. What are decomposers? What role is played by it in an ecosystem?
Answer: Decomposes are also called reducers. The organism gets its nutrients from dead organisms and decaying organic matter, eg. Bacteria, and fungi.

Decomposers and transformers return the chemical nutrients to nature by decomposing and reducing the dead bodies, then these nutrients can be reused by the producers. It takes an important role in recycling the chemical nutrients, which also maintain the balance of the ecosystem.

Question 52. What is the nutrient cycle?
Answer: The cyclic movement of the chemical elements, i.e. nutrient cycling of the biosphere between the living organism to the environment is called the Bio-geo-chemical cycle.

These are the gaseous cycles (Carbon and Oxygen cycle)
Sedimentary cycle (Sulphur & Phosphorus)
Hydrological cycle (Water cycle)

Substances such as oxygen, carbon dioxide, water, and minerals are constantly absorbed by organisms, but as soon as these substances are lost from the physical world, they are replaced by natural processes and balance the ecosystem.

Chapter 5 Environment And Its Resources Descriptive Type Questions And Answers

Question 1. What are the impacts of environmental factors on an organism at the individual level?
Answer:
(1) Light:
The productivity of food in green plants depends on light. Trees are more productive than submerged plants.

Photoperiodism is the phenomenon in which flowering and seed germination depend on the duration of light. Plants are long-day plants (pea, radish), short-day plants(dahlia, Sugarcane), and day-neutral plants (cotton, tomato).

The intensity and color of light also control the process of photosynthesis. Light enhances the pigmentation of skin for many animals too, light is important in what they use.

(2)Temperature:
The plants of tropical regions have a greater number of stomata to regulate temperature. The plants in temperate regions have spiny leaves to reduce the damage caused by frost. Temperature affects the genetics of enzymes and through it the basal metabolism, activity, and other physiological functions of the organism.

A few organisms can tolerate and thrive in a wide range of temperatures. (Eurythermal), but a vast majority of them are restricted to a narrow range of temperatures (Stenothermal).

In some animals body temperature varies with environmental temp, Called poikilo thermic animals (cold-blooded).
Eg fishes, amphibians, and reptiles.

Some animals maintain constant body temperature in any environment, called warm-blooded animals (Homeothermic animals).
Eg birds and mammals.

(3)Humidity:
Animals living in desert regions have few sweat glands and excrete urine very less. Plants growing in arid climates develop features that resist atmospheric dryness. They have less and sunken stomata, waxy leaves, developed tap roof system.

Question 2. What is the impact of environmental factors on an organism at the population level?
Answer:

A group of individuals of the same species inhabiting a particular geographic area at a given period is called a population.

The total number of species in a specific natural habitat is called population density.
The population density changes by change in four basic processes, two of which contribute to an increase and two to a decrease in population –

(1)Natality:
Refers to several births during a given period in the population that are added to initial density.

(2)Mortality :
Mortality is the number of deaths in the population during a given period.

(3)Immigration :
Immigration is the number of individuals of the same species that have come into the habitat from elsewhere during the period under consideration.

(4)Emigration:
Emigration is the number of individuals in the population who left the habitat and lived elsewhere during the period under consideration.

If N is the population density at time (t) then its density at time (t + l)is –
Nt+1 = Nt+ [(B + I)-(D + E)]

Question 3. Explain the interaction among the population at the community level.
Answer:

There is no such habitat and such a situation is even inconceivable. For any species, the minimal requirement is one more species on which it can feed.

Even a plant species, which makes it our food, can not survive alone. It needs soil microbes to break down the organic matter in the soil and return the inorganic nutrients for absorption. This is called interaction in population.
Population interaction

1. Symbiosis or Mutualism:
It is an interspecific co-operation in which two species live in a physically close association and both are benefited by each other.
Eg. Lichen is the association of algae and fungi. Nitrogen-fixing bacteria in nodules of Leguminous plants.

Competition :
Interaction is where members of the same or other species compete with each other to acquire, food, shelter, and water. It may be inter-specific or intra-specific. In the competition process, the fitness of one species is significantly lower in the presence of another species.
Eg. weeds in crop fields compete for food and shelter with crops and finally reduce the productivity of crops.

Predation:
In this type of interaction one species attacks (Predator) another species (Prey) to kill and consume it. The predator obtains nutrients and energy from the prey. The predator keeps the prey population under control.

Biological control methods adopted in agricultural pest control are based on the ability of the predator to regulate the prey population. But if a predator is too efficient and over-exploits its prey, then the prey might become extinct, and following it, the predator will also become extinct for lack of food.

Parasitism:
The interaction in which the parasite gets the benefit and the host gets the loss. Parasite may be –

Ectoparasites – draw nutrients from the outside body of the host.
eg. Female anopheles mosquito, Leech, bedbugs.

Endoparasites – live inside the body of the host and collect nutrients from them.
Eg. – Tapeworm, Ascaris.

Obligatory parasites – the organism leading parasitic life throughout its life cycle.
Eg. Tapeworm, Ascaris.

Facultative parasites – organisms show parasitic behavior in certain periods of their life cycle.
eg. Female anopheles mosquito.

Commensalism :
This is the interaction in which one species benefits and the other is neither harmed nor benefited.
Eg. (1) an orchid growing as an epiphyte on a mango branch and
(2) barnacles growing on the back of the whale benefited while neither the mango tree nor the whale derived any apparent benefit.

Question 4. Explain the interaction between organism and their organizations at the ecosystem level.
Answer:

Functional interrelation between biotic communities and their habitat constitutes an ecosystem.

There are two aspects of the ecosystem.

(1)Structural aspects-

Light – Source of energy of the living world.

Temperature – In the optimum temperature life process functions smoothly. Water – It influences the life of organisms. Aquatic organisms depend on water for their survival.

Atmosphere – The atmospheric pressure varies inversely with the altitude. Lower atmospheric pressure of oxygen and this condition is harmful.

Topography – The altitude, landscape, the amount of light falling on a place or wind blowing add to form the topographic factors of an ecosystem.

Question 5. Difference between food chain and food web.
Answer:

Question 6. What is an ecosystem? Mention the different components of an ecosystem. Briefly describe the role of abiotic and biotic factors which control an ecosystem.
Answer:

Ecosystem :

The basic structural and functional unit of ecology is called an ecosystem.

Components of Ecosystem :
There are two components of the ecosystem –
1. Abiotic,
2. Biotic

1. Abiotic – The non-living constituents of the environment are called abiotic.

Abiotic constituents are divided into three groups :
(1)Inorganic material –
This consists of water, soil, minerals (Ca, K, Mg, Fe, etc.), and gases like oxygen, Carbon dioxide, and nitrogen.

(2)Organic material –
Carbohydrates, proteins, and Fats of dead. organisms constitute the organic material.

(3)Climatic factors –
Rainfall, temperature, light, and humidity are climatic factors.

The principal climatic factor is light (solar energy). This energy is trapped by green plants during photosynthesis and stored as chemical energy in Carbohydrates.

2. Biotic – All the living organisms (plants and animals) of the environment are called biotic.

Biotics are classified into three groups –
(1)Producers,
(2) Consumers,
(3) Decomposers.

(1)Producers:- Green plants and photosynthetic bacteria that can prepare their food by the process of photosynthesis in the presence of sunlight are called producers.
(2)Consumers:- The heterotrophic organisms mostly animals which can not prepare their food by the process of photosynthesis and get it from other organisms, are called consumers.

There are three types of consumers –
(1) Primary consumers – The herbivores that directly eat the plant are called primary consumers.
Ex – goat, rabbit, deer, etc.

(2)Secondary consumers – The animals that eat herbivorous animals are called secondary consumers.
Ex-Fox, fish crow, snake, etc.
(3)Tertiary consumers – The animals that are not eaten by other animals are called tertiary consumers.
Ex – Hawk, owl, vulture, shark, tiger, lion, etc.

(3)Decomposers:- The saprophytic organisms that can decompose the organic materials of dead bodies of living organisms into simple inorganic materials are called decomposers.
Ex – Saprophytic bacteria and fungi.

Question 7. What is a food chain? Name the different types of food chains. Define them.
Answer:

Food chain

(1) The arrangement of living organisms in which food energy passes from producer to consumer in a linear sequence of eat and be eaten is called a food chain.

(2) Types of food chain :
There are three types of food chains –
(1)Grazing food chain,
(2) Detritus food chain,
(3) Parasitic food chain.

(1)Grazing food chain :
The food chain that starts from producers and passes through consumers like primary, and secondary, and terminates with top consumers is called a grazing food chain.
Grasses -> insects -> Amphibians snakes -» peacock.

(2)Detritus food chain –
The food chain starts from dead organic matter, goes into microorganisms, and then to detritus-feeding organisms (detrivores) and their predators is called detritus food chain.
Dead organic matter -» microorganism -» small fish -> large fish.

(3)Parasitic food chain –
This chain passes from larger animals to smaller animals.
Plant -> Man -» Eschertia coli.

Question 8. What is an ecosystem? Explain what is meant by energy flow in an ecosystem.
Answer:

(1) The basic structural and functional unit of ecology is called an ecosystem.

(2) Energy flow in an ecosystem:-
In an ecosystem sun is the main source of energy. In the sun hydrogen is constantly transformed to helium with the release of an enormous amount of energy. This energy leaves the sun and passes into outer space in the form of light and other radiations.

Only a very small amount (0.1% of the total energy falling on earth) of light energy is absorbed by green plants and utilized in the formation of food. The radiant energy of the sun is transformed into chemical energy during photosynthesis. This chemical energy is stored within food (glucose).

Primary consumers feed on producers and thereby get the potential energy of producers. The secondary consumers feed on primary consumers, from where they get their potential energy. Similarly, tertiary consumers get their potential energy from secondary consumers.

The transfer of food energy from producers to various types of consumers is called a food chain.
A large part of energy is lost as heat at each transfer of energy; only a small amount of energy is converted into biomass.

Nature of energy flow in an ecosystem
(1)Solar energy is the only source of energy flow.
(2)Energy flow is unidirectional –
The green plants utilize light energy to prepare their food. This light energy never goes back to the sun. Primary consumers get their energy from the green plants and this energy never goes back to the green plants. The same thing happens with secondary consumers and tertiary consumers.

After the death of plants and animals, decomposers decompose the dead bodies. Heat energy is liberated during decomposition. This heat energy can not be utilized by green plants and animals.

(3) Gradual decrease in the energy flow – There is a gradual decrease in the energy flow from the beginning to the end of a food chain. The primary consumers do not get all the energy obtained by the producers. A part of energy is used by the producers, another part of the energy is lost and the remaining part of the energy is stored.

Question 9. (1) Discuss the role of organisms in the removal of free carbon dioxide from the environment, (2) What is meant by nitrification? Discuss the role of bacteria in this process.
Answer:

(1) Role of organism:-
Terrestrial green plants use free carbon di-oxide of air and aquatic submerged green plants use carbon di-oxide gas which is dissolved in the water for the process of photosynthesis. Some chemosynthetic bacteria, i.e., nitrosomonas also remove free carbon dioxide from the atmosphere for the preparation of their food.
(2)Nitrification:-
The process of conversion of ammonia into nitrite and nitrite into nitrate with the help of bacteria like Nitrosomonas and Nitrobacter respectively is called nitrification.

Question 10. Discuss the significance of cyclic rotation of elements like carbon, oxygen, and nitrogen in the environment.
Answer: Significance of cyclic rotation of carbon, oxygen, and nitrogen in the environment

Importance of carbon cycle:-
(1)Carbon is an important element of organic compounds.
(2)Its simple form C02gas is a raw material for photosynthesis by which green plants prepare their foods in the form of glucose.
(3)It helps in the formation of protoplasm which is a living material,
(4)It maintains the balance of carbon in its source.

Importance of Oxygen cycle:-
(1)It is necessary for respiration.
(2)It helps living to continue their life in this universe, otherwise, in the absence of this process, the universe will become lifeless.
(3)It takes part in the formation of living material, protoplasm.
(4)We cannot imagine a living world in the absence of oxygen.
(5)It helps in combustion.
(6)The cycle of oxygen is essential for different types of organic and inorganic chemical reactions.
(7)This cycle keeps the composition of air fixed/constant.

Importance of nitrogen cycle:-
(1)Nitrogen is an essential element of some important substances like protoplasm, protein, enzymes hormones, etc.
(2)It takes part in the formation of cells, tissue, and organs.
(3)This cycle maintains the balance of nitrogen between living and non-living worlds.

Question 11. What is the main source of nitrogen in higher plants ordinarily? Where do the animals obtain this element? Mention the role of bacteria in the nitrogen cycle.
Answer:

(1) Main source of nitrogen:-
The water soluble nitrogenous compounds present within soil which are formed by the process of fixation are the source of nitrogen in higher plants.
(2)Animals obtain nitrogen from their food (ex. protein)
(3)Role of bacteria in the nitrogen cycle:-
Bacteria take an active part in the completion of the nitrogen cycle.

Different types of bacteria are involved in different stages.
(1)Fixation of atmospheric nitrogen:-
Nitrogen-fixing bacteria convert atmospheric nitrogen gas into nitrite and nitrate such as
Symbiotic bacteria — Rhizobium leguminosorium.
Free-living bacteria – Azotobacter, Clostridium.
(2)Ammonification:-
The ammonifying bacteria convert amino acids into ammonia.
Example – Bacillus-ramosus, Bacillus vulgaris.
(3)Nitrification:-
Nitrosofying bacteria convert ammonia to nitrite and nitrifying bacteria convert nitrite to nitrate.
Example – Nitrosomonas, Nitrobacter.
(4)Denitrification :-
Denitrifying bacteria convert nitrite and nitrate into free atmospheric nitrogen gas. Example – Bacillus suletilis, Bacillus denitrificans.

Question 12. Name the gas which is essential for plants but cannot be absorbed directly from the air. What is the normal percentage of that gas in the air? With the help of a diagram, briefly describe the cycle of the said gas.
Answer:

(1) Name of the gas:- Nitrogen.
(2) The normal percentage of nitrogen gas in atmospheric air is 77.17%.
(3)Process of nitrogen cycle:- The cycle of nitrogen gas is completed in the following stages

(1) Fixation of atmospheric nitrogen:-
The process of conversion of free nitrogen into nitrite and nitrate is called fixation.
This process occurs by three methods –
(1) Natural method,
(2) Chemical method,
(3) Biological method.

(1)Natural Method:-
Nitrogen gas reacts with oxygen gas to produce nitric oxide during electric discharge in the atmosphere. The electric discharge provides energy which is necessary for the reaction. Nitric oxide reacts with oxygen gas to produce nitrogen dioxide. This oxide reacts with rainwater and forms nitrous and nitric acid. These acids react with oxides of metals present in the soil to form their nitrite and nitrate respectively.
N₂ + O₂ = 2NO
2NO + O₂ = 2NO₂
2NO₂ + H₂O = HNO₂ + HNO3
CaO + 2HNO₂ = Ca(NO₂)₂ + H₂O
CaO + 2HNO₃ = Ca(NO₃)₂ + H₂O

(2)Chemical Method:-
In the laboratory nitrogen gas is allowed to react with hydrogen gas to produce ammonia in the presence of iron powder which acts as a catalyst. Now ammonia reacts with carbon dioxide gas to produce urea.
N₂ + 3H₂ = 2NH₃
2NH₃ + CO₂ = (NH2)2CO + H₂O

(3)Biological Method:-
Some bacteria and algae are capable of fixing atmospheric nitrogen.

Nitrogen fixation by bacteria:-
By symbiotic bacteria:-
Rhizobium lives in the root nodules of leguminous plants like peas and gram and converts nitrogen into nitrite and nitrate. Plants use this nitrite and nitrate. Rhizobium takes glucose from the host.

By saprophytic bacteria:-
Azotobacter and Clostridium are present in soil. They convert nitrogen into nitrite and nitrate within their body. Nitrite and nitrate present in their body mix in soil after their death.

By autophytic bacteria:-
Rhodomicrobium (colored) and desulphuricans (colorless) are anaerobic and autophytic. They convert nitrogen into nitrite and nitrate.

Nitrogen fixation by algae:-
Some algae (Nostoc, Anabaena, and Calothrix) convert atmospheric free nitrogen into nitrite and nitrate.

(2)Absorption of fixed nitrogen:-
The nitrite and nitrate forms of compounds produced by the process of fixation are soluble in water. They enter into the cavity of root hairs and finally into the plant cells through absorption.

(3)Assimilation of absorbed nitrogen:-
The nitrogenous compounds are now assimilated by metabolic reactions. Various complex nitrogenous organic compounds like proteins, hormones, enzymes, etc. are formed within the plant body. Animals get nitrogen from the plant. The process of assimilation of plant nitrogenous compounds takes place in the animal body, due to which animal complex nitrogenous organic compounds are formed.

(5)Ammonification:-
Production of ammonia due to the decomposition of complex organic nitrogenous compounds present within the dead bodies of plants and animals with the help of ammonifying bacteria like Bacillus vulgaris and Bacillus ramosus is called ammonification.
Protein – Amino acid, Amino Acid – Ammonia (NH3).

(6)Nitrification:-
The conversion of ammonia into nitrite and nitrate with the help of nitrifying bacteria is called nitrification.
2NH₃ + 3O₂ = 2HNO₂ + 2H₂O + 1,30,000 K. cal. (Nitrosomanas)
2HNO₂ + 02 = 2HNO3 + 35,000 K. cal. (Nitrobacter)

(7)Denitrification :-
The conversion of nitrite and nitrate present within the soil to free nitrogen gas with the help of denitrifying bacteria like Bacillus denitrificans is called denitrification.
5S + 6KNO₃ + 2CaCO₃ = 2K₂SO₄ + 2CaSO₄ + 2CO₂ + 2N₂ + 6,60,000 cal.

Question 13. Discuss the interrelationship among the different components of the system.
Answer:

There are two main components of an ecosystem in

(1) abiotic and
(2) biotic.
Soil, minerals, water, gases, temperature, light, etc. collectively constitute the abiotic part of the ecosystem. Livings like producers, consumers, and decomposers form the biotic part of the ecosystem. Green plants convert solar energy into chemical energy during photosynthesis.

Plants take carbon dioxide and water from their outer sources for photosynthesis and form glucose as food. Oxygen gas is also liberated during this process. Heterophytic plants and all animals obtain their food from the plants. Here animals are called consumers.

Decomposers decompose the dead bodies of producers and consumers by secreting enzymes. Thus they help to return the materials to their respective sources.

There is a cyclic rotation of materials occurring in an active ecosystem and the flow of energy is unidirectional. The energy flows from producer to consumer.

Question 14. Discuss the importance of the carbon cycle, nitrogen cycle, and nitrogen cycle.
Answer:

Importance of carbon cycle:-
(1)Carbon is an important element of organic compounds.
(2)Its simple form CO₂ gas is a raw material for photosynthesis by which green plants prepare their foods in the form of glucose.
(3)It helps, in the formation of protoplasm which is a living material.
(4)It maintains the balance of carbon in its source.

Importance of nitrogen cycle:-
(1)Nitrogen is an essential element of some important substances like protoplasm, protein, enzymes hormones, etc.
(2)It takes part in the formation of cells, tissues, and organs.
(3)This cycle maintains the balance of nitrogen between living and non-living worlds.

Importance of bacteria in the nitrogen cycle:-
(1)They convert atmospheric nitrogen in the form of NO₂ and NO3 so that they can be absorbed by plants,
for example:- Rhizobium.
(2)They decompose the dead bodies of living organisms and change protein into ammonia, for example:- Bacillus vulgaris.
(3)They convert ammonia into nitrite, for example Nitrosomonas.
(4)They convert nitrite into nitrate, for example:- Nitrobacter.
(5)They convert nitrite and nitrate into free nitrogen, for example:- Bacillus denitrificans.

Question 15. Discuss the importance of Tiger conservation, purpose of conservation, soil conservation, water conservation
Answer:

Importance of Tiger conservation:-
(1) The tiger helps in balancing the forest ecosystem.
(2)They are conserved in national parks and zoos for the collection of foreign money.
(3)They are also conserved for recreation, for example:- circus.

Importance of purpose of conservation:-
(1)To keep the environment clean and balanced.
(2)To balance and maintain the continuity of the ecosystem.
(3)To store the nutrients and other necessities in proper quantity.
(4)To protect the living organisms from diseases.
(5)To save the living organisms from disappearance from this universe

Importance of soil conservation:-
(1)To keep the macro and micro essential elements in proper quantity.
(2)To increase the fertility of the soil.
(3)To supply nutrients to the plants for their proper growth.
(4)For the survival of the living organism, i.e., plants depend directly and animals depend indirectly on soil.

Question 16. Discuss the importance of water conservation & forest conservation.
Answer:

Importance of water conservation:-
(1)To protect living organisms from various diseases.
(2)To maintain the balance of the aquatic ecosystem.
(3)To keep water fresh and clean.
(4)To maintain the stock of water for future use.
(5)To provide a safe environment for the survival of aquatic life.

Importance of forest conservation:-
(1)To save the habitat of wild animals.
(2)To balance the forest ecosystem.
(3)For the continuity of the bio-geochemical cycle.
(4)To obtain useful substances i.e., medicine, latex, food, cloth, etc.
(5)To obtain timber for various functions such as doors, windows, tables, chairs, etc.
(6)To check soil erosion.
(7)To increase rainfall.
(8)To purify atmospheric air.
(9)To maintain the balance of O₂ and CO₂ in the atmosphere.

Question 17. Name a gas that can be directly absorbed by the plants from the air but cannot be absorbed directly by the animals. What is the normal percentage of that gas in the air? With the help of a diagram briefly describe the cycle of the said gas.
Answer:
(1) Name of the gas – Carbon dioxide.
(2)Normal percentage of carbon dioxide gas in air is 0.03% to 0.04%.
(3)Methods of carbon dioxide gas cycle The cycle of carbon dioxide gas is completed in the following three stages –
(1) Removal of carbon dioxide gas from its source,
(2) Assimilation of carbon dioxide gas,
(3) Returning of carbon dioxide gas to its source.

(1)Removal of carbon dioxide gas from its source:-
The autotrophs (green plants) intake carbon dioxide from their source to perform the process of photosynthesis.

(2)Assimilation of carbon dioxide gas:-
The carbon dioxide gas which is taken from the environment by autotrophic organisms is assimilated into complex organic molecules like glucose. The green plants can fix 4.9 x 1012 kg of carbon per year. The heterophytes and animals get their required carbon from the autotrophs.

(3)Returning of carbon dioxide gas to its source:-
The carbon dioxide gas returns to its source by the following methods
(1)Respiration:-
Every living organism performs the process of respiration to obtain energy. The carbon dioxide gas produced during respiration is returned to its source.
(2)Combustion:-
The carbon dioxide gas produced due to the burning of different types of fuels is returned to its source.
(3)Decomposition:-
The dead bodies of various plants and animals are decomposed by the action of decomposers. Carbon dioxide produced during decomposition due to their respiratory activity is returned to its source.
(4)Evaporation:-
The carbon dioxide gas which is dissolved in different sources of water returns to its source during the evaporation of water from these sources.

Question 18. Discuss briefly the role of Bacteria in releasing and fixing nitrogen in the environment.
Answer:

Role of Bacteria in releasing and fixing nitrogen in the environment:

Nitrogen is the most important constituent of the protoplasm of the living organism. Though the atmosphere contains as much as 77.17% elementary nitrogen, most living organisms cannot utilize this gaseous nitrogen to synthesize their protein. Some bacteria are capable of fixing the atmospheric nitrogen.

Some free-living bacteria like Clostridium, azotobacter, etc. can fix atmospheric nitrogen into nitrogenous compounds.

Symbiotic bacteria like Rhizobium live in the root nodules of leguminous plants and some symbiotic bacteria like Casuarina live in the root nodules of nonleguminous plants and can fix atmospheric nitrogen.

Some ammonifying bacteria like Bacillus ramosus, Bacillus vulgaris, etc. release ammonia from the protein of dead organisms.

Some nitrifying bacteria convert ammonia into nitrite ions. Nitrosomonas converts ammonium ions into nitrite ions and Nitrobacter converts nitrite into nitrate ions.

Some denitrifying bacteria like Bacillus denitrificans, pseudomonas, etc. convert nitrite and nitrate into atmospheric free nitrogen.

Question 19. What is the source of oxygen in atmospheric air? What is meant by ‘oxygen cycle? Describe the oxygen cycle in nature with the help of a line drawing.
Answer:

(1) Source of oxygen:-
Green plants supply oxygen gas to the atmosphere during the process of photosynthesis.
(2)Oxygen cycle:-
The process by which oxygen from its source enters into the living body, takes part in metabolic reaction, and in the last, returns to its source, is called the oxygen cycle.
(3)Methods of oxygen cycle:-
The cycle of oxygen is completed in three stages

(1)Removal of oxygen from its source:-
Respiration Every living organism takes in oxygen gas for respiration.
Combustion Some quantity of oxygen is utilized during the burning of different fuels.

(2)Taking part in metabolic reaction:-
Carbon dioxide and water are produced during respiration. Carbon dioxide comes out to the atmosphere but the oxygen atom present in water is assimilated to form complex organic molecules.

(3)Returning of oxygen to its source:-
Green plants produce oxygen gas during the process of photosynthesis. This gas comes out through the stomata of the leaves and is mixed with atmospheric air.

Question 20. What is an ecosystem? Explain the interrelationship among the different components of the ecosystem.
Answer:

(1) Ecosystem :
The basic structural and functional unit of ecology is called an ecosystem.
(2)Inter-relationship among the components of ecosystem :
There are two main components of an ecosystem in
(1) abiotic and
(2) biotic.

Soil, minerals, water, gases, temperature, light, etc. collectively constitute the abiotic part of the ecosystem. Living beings like, producers, consumers, and decomposers form a biotic part of the ecosystem. Green plants convert solar energy into chemical energy during photosynthesis. Plants take carbon dioxide and water from their outer sources for photosynthesis and form glucose as food.

Oxygen gas is also liberated during this process. Heterophytic plants and all animals obtain their food from the plants. Here animals are called consumers. Decomposers decompose the dead bodies of producers and consumers by secreting enzymes. Thus they help to return the materials to their respective sources.

There is a cyclic rotation of materials that occurs in an active ecosystem and the flow of energy is unidirectional. The energy flows from producer to consumer.

Question 21. What do you mean by water conservation? Mention the means of conservation of water.
Answer:

(1) Water conservation:-
The use of the proper quantity of water and to prevent the addition of harmful substances into its sources is called water conservation.

(2)Methods of water conservation:-
(1)By preventing excess cutting of trees and promoting the practice of excess tree plantation.
(2)By treating sewage and industrial wastes in water treatment plants before releasing them into rivers.
(3)By constructing dams and bunds.
(4)By preventing washing, bathing, and cleaning of animals in pond water.
(5)By forbidding testing of bombs in oceans.
(6)By checking active sedimentation in lakes, ponds, rivers, etc.
(7)By controlling the use of pesticides and insecticides.

Question 22. What do you mean by forest conservation? Mention the means of forest conservation.
Answer:

(1) Forest conservation :
To control the excessive cutting of trees for timber and set of industries and to protect it from fire and disease is called forest conservation.

(2)Means of conservation of forest:-
(1)By cutting down only matured trees.
(2)By promoting the practice of regular plantation of new sampling at specific distances.
(3)By preventing forest fires.
(4)To restrict the entrance of domestic animals.
(5)By implementing the laws formulated by the state and central government.
(6) Through mass awareness programs, people should be informed about the dangerous effects of deforestation.
(7)By protecting them from diseases and pests.
(8)By checking block cutting.

Question 23. Discuss in brief the means of conservation of tigers.
Answer:

Means of conservation of tiger:-
(1)By promulgating the laws for unnecessary killing of tigers. A person violating the law is liable to legal action.
(2)To establish National Parks, sanctuaries, Protected areas, and Reserve forests in the different parts of the country.
(3)Educate the public so that they can understand the importance of tigers in this universe. For this lectures based on the importance of tigers should be arranged in universities, colleges, and schools. To develop mass consciousness cinema shows should be arranged. Print media also may be helpful in this program.

Question 24. What are the meanings of the terms Sanctuary and Reserve Forest? Give one example of a Sanctuary in West Bengal. Mention the importance of those forests.
Answer:
(1) Sanctuary:-
A sanctuary is a protected area that is reserved for the conservation of only animals and human activities like harvesting of timbre, and collection of minor forest products, and private ownership rights are allowed so long as they do not interfere with the well-being of animals. Ex-Jaldapara, Nagarjuna sagar, Dachigam.

Reserve forest:-
It is a forest area that is protected with all its components by the India Forest Act. Entrance without permission is prohibited. Ex – Gorumara, periyar.

(2)Sanctuary in West Bengal — Jaldapara
(3)Importance of Reserve forest
(1)To save the habitat of wild animals.
(2)To balance the forest ecosystem.
(3)For the continuity of the bio-geochemical cycle.
(4)To obtain useful substances, i.e., medicine, latex, food, cloth, etc.
(5)To obtain timber for various functions such as doors, windows, tables, chairs, etc.
(6)To check soil erosion.
(7)To increase rainfall.
(8)To purify atmospheric air.

To maintain the balance of 02 and C02 in the atmosphere.

Question 25. Why is the replenishment of forests necessary? Or, What is the importance of forests in human life?
Answer:

Forest is an important natural resource that provides us with many valuable things:

(1) Atmospheric regulation:
Forest regulates 02 and CO₂ balance. The CO₂ content in the atmosphere is taken up by the plants during photosynthesis and O₂ is released. This O₂ is used by the living organisms in the process of respiration.

(2)Control soil erosion :
The branches of roots firmly bind the soil particles with the ground. The dense leaves of forests prevent raindrops from hitting the soil rich in organic matter is porous and permeable and serves as a natural filtering agent. The humus increases the adhering capacity of the soil particles and prevents soil erosion.

(3)Productive use:
Forests provide several products such as timber, fruits, seeds, cloth, furniture, medicine, building materials, papers, and one of the important sources of economy.

(4)Local use :
People living in nearby villages collect firewood from the forest. They also collect honey, timber, cotton, fur, wool, and meat and market it for money. Medicinal plants, gums, and resins were also collected from the forest.

(5)Watershed protection :
Forests help to protect an area of land that separates water flowing to different rivers or seas.

Question 26. Write the important functions of the forest.
Answer:
(1) It maintains the ratio of O₂ and CO₂.
(2)It provides a natural habitat for wildlife plants and animals.
(3)In maintains climatic conditions by rainfall.
(4)It prevents soil erosion.
(5)It is an important source of building materials.
(6)It is used by local inhabitants for different purposes involving food and shelter.
(7)It provides medicines, spices, honey, clothes, paper, furniture, and other useful substances.

Question 27. Name the major types of forest in the world.
Answer:
(1) Tropical rain forest
(2)Sub-tropical forest
(3)Mediterranean forest
(4)Temperate forest
(5)Coniferous forest
(6)Plantation forest

Question 28. What are the causes of deforestation?
Answer:

Causes of deforestation

(1) Population explosion
(2)Uncontrolled cutting of trees
(3)Development of road and railways
(4)Forest fires destroy trees and animal life
(5)Destruction of timber-yielding trees by fungal infection and by pest
(6) A water reservoir (dam) constructed across the stream used for generating power.
(7) Over-exploitation of land resources.
(8) Transformation of tropical rainforest to grassland.
(9)Forests are damaged by storms and snow.

Question 29. What are the consequences of deforestation?
Answer:

The consequences of deforestation

(1) Global warming – due to deforestation, the concentration of greenhouse gases (CO₂) increases in the atmosphere causing global warming.
(2)Decrease in groundwater level
(3)Change in soil character and erosion
(4)Wildlife extinction – forest is a natural habitat for millions of flora and fauna. Deforestation makes them homeless.
(5)Frequent floods and droughts destroy large numbers of trees.
(6)C02 consumption and oxygen production are affected adversely.
(7)Change in climatic conditions by affecting rain.
(8) Decrease in the quality and quantity of timber.
(9)Deterioration in the quality of life of the weaker section of people living in the forest.
(10)Increasing incidents of landslides.

Question 30. Define Afforestation. Write the importance of water on earth.
Answer:

Afforestation:

Process of planting trees in an area of land to form a forest. It increases the protective and productive outputs.

Water is a vital natural resource used for various purposes.
(1)Drinking purpose:
Water that is fit for drinking is called potable water and it is essential for all living organisms.

(2)Agriculture:
Plants need water to synthesize their food. A large quantity of water is used for the irrigation of crop fields.

(3)Industry:
Water is used as raw material, solvent, and washing medium in industry. The industry is very dependent on adequate water supplies. Major water users are steel, paper, textile, chemical, and petroleum refining and they account for nearly 80 percent of industrial water demand.

Question 31. Write the uses of water for different purposes.
Answer:

Uses of water for different purposes

(1) Used in agriculture for irrigation of crops.
(2)Used for cooking, washing, bathing, cleaning, etc.
(3)Used in chemical laboratories as solvent.
(4)Used for performing various chemical reactions.
(5)Used in textile and paper industry.
(6)Water can dissolve gases like O₂ and oxygen.
(7)Used in photography.
(8) Water is used in biochemical reactions and enzymatic activities.
(9)Water is used to generate electricity in hydroelectric plants.
(10) Waterways of inland streams and oceans are effective through fare.

Question 32. What is the over-utilization of water?
Answer:

Over-utilization of water

We often misuse water sources in many ways. All citizens are made aware of the proper use of water and avoid misuse of this natural resource.

During personal use, we often discard some amount of drinking water, during bathing and washing we misuse water. In some areas, tap water on streets is always open. In many areas, agricultural fields are irrigated with underground water. Wastage of water occurs in many industries.

Question 33. Define water scarcity and mention its causes.
Answer:

When the water demand is more than its occurrence, it causes scarcity.

The factors that cause scarcity of water are :
(1)due to drought – it is due to lack of rainfall for sufficient duration, severe drought, resulting in a reduction in groundwater level, and destruction of grassland and crops.
(2)due to misuse of water – improper utilization and distribution of water.
(3)Global warming – Excessive heat dries out surface water.
(4)Pollution – Disposal of sewage water in streams and lakes is a wasteful technique. So sources of fresh water are polluted and wasted.
(5)Increased human demand for water and overuse of water.
(6)Increase in human population.
(7)Lack of access to safe drinking water.

Question 34. What are the consequences of overuse of water?
Answer:

Consequences of overuse of water

(1) Reduction in agricultural productivity
(2)Extreme dryness of soil
(3)Desertification and loss of forest cover
(4)Groundwater pollution with arsenic or fluoride
(5)Gradual depletion of groundwater for drinking purposes.
(6)Affecting industrial products.

Question 35. Define water conservation. Name the various methods of water conservation.
Answer:

Conservation.

The conservation of water by proper use and save it for future use is called conservation.

To meet the water scarcity problem, water has to be conserved by the following methods:
(1)proper distribution and utilization of water
(2)proper drainage method to be implemented
(3)increase in recharging of soil with water
(4)rainwater harvesting
(5)proper maintenance of ponds and lakes
(6)avoid misuse or overuse of water in houses and industries.

Question 36. Write the steps of Rainwater Harvesting.
Answer:

Steps of Rainwater Harvesting

It is a simple and effective method of water management by which rainwater is collected, stored, and used to meet the demand for fresh water.

This form of harvesting rainfall benefits all, particularly in areas where rainfall is less.
Rooftop rainwater harvesting forms one of the best methods, a simple and low-cost technique, requiring minimum knowledge.

It consists of 3 main steps-
(1)roof surface for collection of rainwater,
(2)gutters and drain pipes are required for the transport of water from the roof to the storage reservoir,
(3)storage tanks are used to store water.

Water from the storage tank, passed through the filter, may be used as drinking water.

Question 37. What are the advantages and disadvantages of rainwater harvesting?
Answer:

Advantages:
(1) Rainwater is generally free from germs and contaminations.
(2)It is soft water with neutral PH and does not contain any salt.
(3)Rainwater does not harm water pipes and reservoirs by corrosion.

Disadvantages :
The supply of water depends on the amount of rainfall. In rooftop farms, rainwater may be contaminated with air pollutants, animal or bird droppings, insects, etc. so it needs regular cleaning and repairing.

Question 38. What are the different sources of food?
Answer:

(1) Agriculture:
The maximum quantity of food we consume is agricultural products. These include cereals, pulses, and oil seeds. Disease-resistant grains are raised and seeds are vernalised by special treatment.

(2)Horticulture :
The practice of growing flowers, fruits, and vegetables is called horticulture. Hybridization techniques and modern methods of cultivation are being used for the production of new varieties.

(3)Animal husbandry:
The breeding, feeding, and caring of domestic animals is called animal husbandry. It provides us with meat and dairy products.

(4)Fishery:
Scientific breeding and rearing of fishes. There are freshwater fishes and marine water fishes. They are rich in protein, vitamins, minerals and fats.

Question 39. What are alternative food sources?
Answer:

Alternative food sources

To meet the additional demand for food, scientists and nutrition experts have found dietary potential in some plant products, other than the common food materials.

Bacteria and fungi are used for preparing bread, alcoholic drinks, cheese, pickles, and yogurt.

Blue-green alga spirulina is used as food. Plant seeds form a good source of food for animals and humans. Animal sources of food are meat, milk, and dairy products. Honey is produced by bees and eggs by birds are used as food. Fungus used as food are mushrooms.

Yeast is used to produce yeast cake.

Some edible forms of algae are laminaria, Sargassum, and Porphyra. Chlorella is used as food. Bryophytes like mosses provided food for birds and mammals. The seeds of pinus giardiana (chilgoza) can be taken as food. Sago (sabudana) is a carbohydrate-rich matter extracted from the stem of palm trees.

Question 40. Write a note on “world food problem and its effect.”
Answer:

“World food problem and its effect.”

The United Nations report indicated that in the years 2012-2013, more than 800 million people all over the world suffered from hunger. One of the serious earliest food scarcity in the form of famine faced by the people of Bengal caused the death of many people in 1776.

The causes of world food problems are –
(1)Slow down of production of main cereal crops
(2)Damaged caused due to natural calamity •
(3)Increase in price of food.
(4)Demand of biofuel
(5)Increased population
(6)Increasing urbanization
(7)Intensive farming and irrigation system
(8) Erosion of soil.

Question 41. What are the uses of energy?
Answer:

Uses of energy

The capacity of doing work is called energy. All forms of energy are convertible.

(1)Domestic use:
In rural areas, wood, coal, and kerosene oil are utilized as sources for cooking, lighting, and other purposes. In urban areas, it is used for lighting, heating, cooling rooms, washing machines, etc.

(2)Commercial use:
Energy is used on a large scale in hotels, malls, restaurants, and shops for lighting, cooling, and other purposes.

(3)Industrial use:
Coal, oil, and natural gas are used for heating, burning, lighting, and running machines.

(4)Transport use :
Most of the vehicles in the air, water, or on the road run with petroleum products.

Question 42. What are the reasons for growing energy needs?
Answer:

Reasons for growing energy needs

The economic growth of a nation depends on energy. Just before 50 years ago, the scope of using energy was at least 10 times less than in recent days. The development of power resources in an organized manner results in the industrial development of the country.

The requirement of energy is indispensable in the fields of agriculture, transport, business, and domestic purposes. The different forms of energy in use are thermal energy, electrical energy, light energy, mechanical and chemical energy. An increase in living standards is also responsible for the increase in energy demand.

Question 43. How does the wastage of energy take place? How is energy conserved?
Answer:

Wastage of energy means, losing energy without any work. More urban use with non-stop usage, unnecessary use of vehicles, and poor road conditions are some common ways to waste energy.

Energy conservation takes place through its judicious use in the following ways –
(1)Keeping the lights and fans closed when not in use in houses & offices.
(2)Switching off the ignition of the vehicles when standing a traffic signals.
(3)Regular maintenance of machines so that power consumption may be reduced.
(4)Use of solar heater.
(5)Use of better combustion technology for fuels of the vehicles.
(6)By using renewable sources of energy.

Chapter 5 Environment And Its Resources Chart Type Questions

1. Environment And Its Resources National Parks

2. Environment And Its Resources Wild Life Sanctuaries

3. Environment And Its Resources Wildlife Reserves in India

4. Environment And Its Resources Reserve Forests

5. Environment And Its Resources Biosphere Reserves

Chapter 5 Environment And Its Resources Bio Scientist

1. In 1866 Earnest Hackel coined the term Ecology.
2. In 1927 Charles Elton stated that Ecology is the scientific natural history.
3. In 1935 A. G. Tansley gave the term Ecosystem.
4. In 1966 Odum mentioned the Abiotic and Biotic components of the ecosystem. He also defined the food chain in that year.
5. In 1972 Odum defined conservation.
6. In 1927 Elton gave the concept of an ecological pyramid.
7. In 1942 R. Lindeman denoted the model of energy flow in an ecosystem.
8. In 1993 wild classified land based on land use capabilities.

Question 1. Write a note on intraspecific and interspecific competition.
Answer:
1. Intraspecific competition :
There are two basic types of such competition—
(1)Scramble competition :
In such competition, the individuals of a community get access to resources sub-divided into small parts. Each individual obtaining a scarce amount of resources may not survive in the long run.

(2)Contest competition :
In such competition, the successful individuals of a community obtain the resources whereas the unsuccessful ones do not have any access to the resources.

An example of intraspecific competition is where resources are limited. The visiting flamingoes in South American lakes and fishes residing in the lakes compete for common Zooplankton.

2. Interspecific competition :
Competition takes place between individuals of different species of the same community for food, space, and other requirements that are limiting, each is affected by the pressure of the other. At times resources may not be limited by the feeding capacity of a species but may be reduced due to interference caused by other species.

An example of interspecific competition is where resources are not limited but the inhibitory influence of one species on another takes place.

Question 2. Classify plants and animals based on temperature control.
Answer:

Plants are divided into four categories based on their heat-tolerating capacity—

(1) Megatherms — plants that can tolerate high temperatures throughout the year for example; desert vegetation and tropical rain forests. Tropical plants require constant high temperatures for their maximum growth,
(2) Mesotherms — plants that can withstand high as well as low temperatures; for example, tropical deciduous forests, aquatic plants,
(3) Microtherms — plants growing in regions of low temperature, for example mixed coniferous forests,
(4) Hekistotherms — plants growing in regions where the temperature is very low, for example alpine vegetation. Alpine plants are adapted for short summer periods for flowering and fruiting. Plants receive energy from absorbed solar radiation and convection and they lose heat by radiation, convection, and evapotranspiration.

Based on temperature control animals are divided into three groups :
(1)Poikilothermal or Ectothermic animals or Cold-blooded animals whose body temperature changes with changes in their environmental temperature, e.g. most invertebrates.
(2)Homeothermic or Endothermic animals or Warm-blooded animals whose body temperature is independent of the temperature of their environment, e.g. birds and mammals.
(3)Heterotherms — Animals with limited power of temperature regulation respond to extreme temperatures by aestivation and hibernation, e.g. some marsupials.

Question 3. Write a note on the different types of parasites.
Answer:

Different types of parasites:

(1)Phytoparasite:
Plant parasites; for example, root nematodes, aphids, lac insects, stem borers, and wasps form galls on plants like oats, and willows. Mites from witches broom in Hackberry.

(2)Zooparasite :
Animal parasites; for example, Platyelminthes, nematodes, and arthropods.

(3)Hyperparasite:
Such parasites live on another parasite, example, Plasmodium vivax a protozoan is a hyperparasite of the female Anopheles mosquito which is a parasite of humans.

(4)Temporary parasite: Parasites like mosquitoes and bugs which suck blood from their hosts. For example, Leech (Hirudinaria) sucks the blood of cattle and man.

(5)Permanent parasite :
Entamoeba histolytica, certain platyhelminthes, nematodes, and arthropods are examples of permanent parasites.

(6)Ectoparasites:
live on the external surface of host organisms; for example, lice on humans, ticks on dogs, copepods on marine fishes, louse (Pediculus) sucks blood spreading diseases like typhus, Rat flea (Xenopsylla) — Spreads germs of plague from rat to man. Cuscuta is a rootless leafless parasite on hedge plants.

(1)Entamoeba histolytica — protozoan living in the human intestine causes amoeboic dysentery.
(2)Plasmodium vivax — a protozoan living in human blood that causes malaria.

Question 4. Define the different types of food chains with examples. What is a food web?
Answer:
Types of food chains:
There are three types of food chains — predator food chain, parasitic food chain, and saprophytic or detrital food chain.

1. Predator food chain :
A predator food chain starts from green plants and extends upto carnivores, i.e., it includes consumers only. Here the size of the living organism gradually increases, but their number gradually diminishes.

2. Parasitic food chain :
A parasitic food chain goes from larger (host) to smaller (parasite) animals.

3. A saprophytic or detrital food chain :
A saprophytic food chain goes dead organisms or organic matter into microorganisms. Such food chains are interconnected with each other to form a food web.

Examples of the food chain :
(1)Predator food chain — Grass —> Grasshopper —> Frog —> Snake —> Eagle
(2)Parasitic food chain — Plant— > Pig —> Helminth
(3)Saprophytic food chain — Dead animal —> Maggot —> Frog — Snake —> Peacock.

Food Web :
(1) Definition :
When different food chains of the same habitat are interconnected with each other to form a complicated network then the feeding relationship is known as a food web.

Question 5. Write a note on the role of animal husbandry in human welfare.
Answer:
Role of animal husbandry in human welfare :
Animal husbandry can be used to obtain a lot of benefits for mankind which are as follows —
1. Dairy products — Milk and other dairy products such as yogurt, cheese, paneer, butter, ice cream, etc. could be obtained.
2. Meat — The demand for protein is mainly covered by cattle and other animals.
3. Land management — Grazing by live stocks can be used to control the growth of weeds In the agricultural field.
4. Labour — Horses, donkeys, yaks, etc. can be used for mechanical carriers.
5. Fibre — Sheep provides fur or wool for the textile industry.
6. Fertilizer— Cow dung can be used as manure for the crop field. The blood and bones of animals are also used as fertilizer.

Question 6. Discuss the impact of light on organisms at the individual level.
Answer:
Effect of light:
(1) In green plants, chloroplasts tend to concentrate on the surface of a leaf, which gets more light,
(2) Productivity is higher in those plants that receive more and brighter light. That is why trees are more productive than submerged aquatic plants,
(3) In some plants, a span of daylight affects their growth and flowering. This phenomenon is known as Photoperiodism. Plants, such as dahlia, sugarcane, strawberry, etc. bloom in shorter daylight periods and are called Short Day Plants (SDP). The plants, such as peas, radishes, spinach, etc. bloom in longer daylight periods and are called Long Day Plants (LDP). In some plants, such as tomatoes, cucumbers, cotton, etc. daylight does not have any significant impact. These are known as Day Neutral Plants (DNP).
(4) Light enhances the pigmentation of skin,
(5) Birds and bats show circadian rhythm (daily rhythm of activities), which is controlled by light.

Question 7. Discuss the effect of temperature on organisms at the individual level.
Answer:
Effect of temperature:
(1) Plants grown in desert regions have light-colored
body hairs, acting as heat reflectors. They have fewer stomata to reduce transpiration,
(2) Plants growing in hot but humid climates of tropical regions have thick leaves to increase the rate of transpiration,
(3) In amphibians, reptiles, and fishes, body temperature varies with environmental temperature. These animals are, therefore, known as poikilothermic animals. On the other hand, birds and mammals have constant body temperature in any environment. These are known as homeothermic animals,
(4)Some animals, such as toads, house lizards, ants, etc. can withstand a wide range of temperature variations in the environment. These are called eurythermal animals. Some animals, such as fishes and other cnidarians cannot tolerate wide temperature fluctuation. These are called stenothermal animals.

Question 8. What is parasitism? Classify parasites based on their position in the host body and the duration of parasitism.
Answer:
Parasitism :
Parasitism is the most advanced type of interspecific interaction in which one species depends upon other species for food or shelter or both. Here, the dependent member (parasite) is benefited, but the helping member (host) is deprived.

Based on their position in the host body, parasites may be of two types —
(1) Ectoparasites :
These parasites draw nutrients from outside the body of the host.
Example: Louse, ticks, bedbugs.

(2) Endoparasites :
These parasites live inside the body of the host and collect nutrients from them.
Examples: Tapeworms, roundworms, Plasmodium (malarial parasite), etc.

Based on the duration of parasitism, they may be of two types —
(1) Obligatory parasites :
These species lead parasitic life throughout their life cycle.
Examples: Tapeworm, roundworm, Plasmodium, etc.

(2) Facultative parasites:
These species show parasitic behavior in certain periods of their life cycle. Example: Female mosquitoes suck blood only during egg maturation and before laying eggs.

Question 9. Write a note on the carbon cycle.
Answer:
Carbon cycle: The carbon cycle refers to the cyclic exchange of carbons in the physical and biological systems,
(1) Reservoir pool:
The carbon bed of the lithosphere acts as a reservoir pool for carbon,

(2) Cyclical pool :
Cyclical pool involves the atmosphere and the seawater

(3) Utilization of carbon from nature:
Utilization of carbon from nature involves two pathways —
(1) Biological path:
The biological path of carbon utilization involves the activities of green plants and shelled mollusks. Green plants trap carbon within cellular compounds by photosynthesis. Shelled mollusks utilize carbon of CO₂ to prepare their shell,

(2) Physicochemical path:
The physicochemical path or carbon utilization involves certain marine deposits, such as limestone, dolomite, feldspar, etc. Limestone, feldspar, etc. absorb carbon (CO₂) to prepare calcium carbonate (CaCO3).

(4) Return of carbon to nature :
Carbon is returned to the environment by two paths —
(1) Biological path :
All living forms (except a few anaerobes) release CO₂ by respiration. CO₂ is released into the nature by decomposition of organic matter. After the death of mollusks, their carbon-rich shells are decomposed to produce CO₂.

(2) Physicochemical path:
Combustion of fossil fuel, wood, etc. forest fires, and volcanic eruptions produce huge quantities of CO₂. This cyclic process of utilization and return of carbon to nature occurs at the same rate. This helps to maintain constant carbon content in the environment. Ecosystem, similar cyclic exchange also occurs in the case of other elements.

Question 10. How can energy be conserved in daily life?
Answer:
Energy conservation in daily life:
To meet our-future requirements, we need to conserve energy. By following the measures mentioned below, energy can be conserved to a large extent.

(1)Lighting :
Utilize maximum daylight by painting walls in a lighter shade. Keep lamps dust-free. Replace bulbs with CFL or LED lamps. Use electronic chokes instead of copper chokes.

(2)Fans :
Switch off the fan when you leave the room. Fit electronic regulators for ceiling as well as table fans.

(3)Electric iron :
Set the regulator at the appropriate position for ironing at medium heat. Use a sprayer to moisten clothes.

(4)Kitchen appliances :
Use mixers preferably for wet grinding. Do not the run machine in over or under-load conditions. Do not open the microwave oven’s door frequently to check food. Use flat bottom pans to get full contact with the heating plate of the induction oven.

(5)Gas oven:
Cook in regulated flame. Off it or simmer the flame during the preparation of food to save LPG. Use pressure cookers as much as possible. Cover the pans while cooking. Let items reach room temperature after taking them out of the refrigerator, before cooking.

(6)Water heater:
Install solar water heater replacing the electric water heater. Do not use the water heater for too long time.

(7)Electronic devices :
Switch off TV and audio systems when you leave the room for even short intervals.

(8) Computers:
Turn off the computer when not in use. Turn off the monitor during long downloading.

(9)Refrigerator:
Use star-rated energy-saver models. Keep it in moderate cooling mode. Do not keep the door open for a long time. Make sure that the door sealing pads are airtight. Set the refrigerator in such a position so that air can easily circulate the refrigerator.

(10)Washing machines :
Run in full load condition at optimum water level. Set a timer as recommended. Apply detergent in the right quantity. Avoid washing with hot water as much as possible. Prefer drying under the sun.

(9)Air conditioners:
Install energy saving star—rated sets. Select the set, with cooling capacity, as per the room size. Operate in moderate cooling mode. Fit the outdoor unit in a shady place. Clean filters regularly. Seal the doors and windows.

(10)Home:
Select heat-reflecting and light-shaded paints for the outside wall. Use film-coated reflecting glass in windows. Position the windows in the right place to maintain cross ventilation.

Question 11. Write a note on the abiotic components of an ecosystem.
Answer:
Abiotic Components:
Abiotic components of an ecosystem consist of nonliving factors.

These factors are of two types —
(a) Climatic and
(b) Edaphic.

The climatic factors contain temperature, light, wind, humidity, rainfall, and water whereas the edaphic factors include soil, topography, etc.

1. Temperature :
Temperature is such an important abiotic factor that it has a great influence on the distribution of organisms and their metabolism. Most organisms can survive in a temperature range of 10°—50°C.

2. Light:
It is another important abiotic factor. The intensity, quality, and duration of light have a great impact on the living world. Light provides energy to the producers for photosynthesis. The energy stored in the synthesized food by green plants is the source of energy for all types of consumers directly or indirectly.

3. Water:
Water, the most important abiotic factor, is very much essential! for life. Earth’s surface consists of 71% water. Water is one of the main raw materials of photosynthesis, which is the source of food for the living world.

4. Air:
The gases present in the atmosphere, mainly oxygen, carbon dioxide, and nitrogen have a great impact on living organisms. Oxygen is too much necessary for respiration. Carbon dioxide is used as a raw material for photosynthesis. Nitrogen is needed for synthesizing protein.

5. Soil:
It is the surface layer of land as well as it is an important edaphic factor of ecosystem. The distribution of plants like halophytes (in saline soils), lithophytes (in rocky soil), osteophytes (in acidic soils), psammophytes (in sandy soils), etc. is mainly influenced by the soil. Soil is the source of all the macro and microelements essential for living organisms.

6. Topography :
The distribution of plants and animals is influenced by different types of habitats like plains, hills, slopes, etc. Temperature decreases with altitude, so topography plays a major role in the distribution of plants and animals.

7. Minerals :
The distribution of microbes, plants, and animals depends upon the availability and concentration of minerals, which have an important role in the growth and development of the organisms.

Question 12. Define and classify the ecological pyramid.
Answer:

Ecological Pyramid:

1. Definition :
The graphical representation of the gradual reduction of the trophic levels of food chains, i.e., from producers to different types of consumers forms a conical shape known as an ecological pyramid. It was denoted by Elton (1927).

The first trophic level is the base and the successive trophic levels make up the upper tiers and apex.

2. Types :
Ecological pyramids are of three types —
(1) Pyramid of numbers,
(2) Pyramid of biomass and
(3) Pyramid of energy.

(1)Pyramid of numbers:
The numerical relationship among different trophic levels is represented by a pyramid of numbers. In this type of pyramid, the number of producers is highest and the number of different consumers is decreased in the successive levels of the pyramid from bases to apex.

(2)Pyramid of biomass :
The pyramid of biomass indicates the decrease or the gradual reduction in biomass at each trophic level from base to apex.

(3)Pyramid of energy :
The energy flow in an ecosystem and total energy at each trophic level of the food chain is represented by a pyramid of energy.

Question 13. Write a note on the major types of forests in the world.
Answer:

Major types of forests in the world :

1. Tropical rainforests:-
Year-round high temperatures and abundant rainfall make this a dense, lush forest. Tropical rainforests are found near the equator. They are vital storehouses of biodiversity on the planet, and yet face severe threats today, with much of their original extent depleted.

2. Sub-tropical forests:-
These are found to the sound and north of the tropical forests. The trees here are adapted to resist the summer drought.

3. Mediterranean forests:-
These forests are found to the south of the temperate regions around the coasts of the Mediterranean, California, Chile, and Western Australia. The growing season is short and almost all trees are evergreen, but mixed hardwood and softwood.

4. Temperate forests:-
Found in such places as Eastern North America, Northeastern Asia, and Western and Eastern Europe, temperate forests are a mixture of deciduous and coniferous evergreen trees. Usually, the broad-leaved hardwood trees shed leaves annually. There are well-defined seasons with a distinct winter and sufficient rainfall.

5. Coniferous forests:-
Coniferous forests inhabit the cold, windy regions around the poles. There are both hardwoods and conifers found in this region. The conifers are evergreen and structurally adapted to withstand the long drought-like conditions of the long winters, whereas the hardwoods are deciduous.

6. Montane forests:-
These are also known as cloud forests because they receive most of their precipitation from the mist or fog that comes up from the lowlands. Some of these montane woodlands and grasslands are found in high-elevation tropical and temperate zones. Plants and animals in these forests are adapted to withstand the cold, wet conditions and intense sunlight. Trees are mainly conifers.

7. Plantation forests:-
There are around 140 million hectares of “plantation forests” in the world, accounting for around 7% of global forest cover. The productivity of planted forests, in terms of supplying a sustainable volume of timber and fiber, is usually greater than natural forests.

Plantations produce around 40% of industrial wood. Both the plantation area and contribution to world wood production are projected to continue to increase in the foreseeable future.

Question 14. Discuss the stages of energy flow in an ecosystem.
Answer:

Stages of energy -flow:

Now energy flow in the ecosystem takes place in three successive stages :
(1) Acquisition of energy,
(2) Uses of energy and
(3) Unidirectional flow of energy.

1. Acquisition of energy :
The source of energy in the ecosystem is solar radiation. 12.3 x 1022 calories of solar energy reach the earth each year. Of which a major part is reflected in the space due to the presence of clouds, smoke, and dust particles.

According to German Scientist Rudolf Geiger, about 42% of solar energy is reflected in space due to the presence of clouds, dust particles, etc. in the atmosphere. 10% of the solar energy and ozone, oxygen, water vapor, carbonic acid, etc. are absorbed by the suspended solid particles in the air.

In the daytime 48% of the solar energy falls on the earth. Some of the light energy is also reflected from the surface of the earth. The remaining light energy is entrapped by the chlorophyll present in the palisade and spongy parenchymatous cells of the mesophyll tissue of the leaf where photosynthesis takes place. As a result, light energy is transformed into kinetic energy which is stored as potential energy in the carbohydrate food matter.

The primary production in the ecosystem is the production of glucose by green plants. The energy released during this time is called gross production. After respiration and other living processes the energy left behind is termed as net production or NP.

2. Uses of energy :
In an ecosystem, the producers transform solar energy into chemical energy and later in the presence of water and carbon dioxide prepare carbohydrates. These plants are taken in by animals and thus potential energy is acquired by them. Again when the secondary consumers feed on primary consumers they also acquire potential energy.

Thus when tertiary consumers take in secondary consumers, we see a similar flow of potential energy to occur. Thus the main source of energy of all animals is food. The amount of energy acquired from food is called gross energy intake and in short, denoted by the letter I.

When energy flows through the different trophic levels of an ecosystem we can see that some energy is dissipated as heat at each step which is of no use.

In the year 1942, Raymond Lindemann formulated the law called the 10 percent law. According to this law, about 10% of total energy is transmitted during energy flow through several trophic levels. That is why we notice a diminution in the amount of energy. Energy used up by a body to function properly is called respiratory energy (R).

For example, about 100 kg of organic food present in the grass, will make 100|10 kg. or

10 kg. biomass in the case of herbivorous animals, and of about — kg. i.e. 1 kg biomass in case of carnivores. According to Lindemann’s 10% law, in a grassland ecosystem about 100 kg of grass would increase 10 kg of flesh in the body of a deer. If this deer is taken in by a tiger its flesh would help in increasing 1 kg of flesh in the body of the tiger. Thus a gradual diminution of energy is noticed.

The formed energy is spent in digestion, metabolism, and performing other physiological functions by an animal. Some energy is also liberated as heat and thus lost to the surroundings.

3. Energy flow is unidirectional:
Producers obtain their light energy from the solar energy. This light energy once entrapped by the chlorophyll cannot retrace its path but is given out to surroundingsding. Thus, along the trophic level energy gets transmitted step by step but once given out it cannot follow its way back. Thus the energy flow is unidirectional.

 

• Chapter 1 Life and Its Diversity
• Chapter 2 The Levels of Organization of Life
• Chapter 3 Physiological Processes of Life
• Chapter 4 Biology and Human Welfare