Class 6 Science

Chapter 12 Waste Products Waste Products

Origin and Nature-The waste products of our home and their reuse :

In urban communities everywhere they are producing huge quantities of household and commercial waste. Most of you have seen heaps of rubbish or garbage dumped at the roadside or in the dustbin.

You may have noticed a dustbin in your house or on the roadside usually unused things such as plastic, packets, old bottles, parts of vegetables, damaged or unused papers, broken glass pieces, boxes, etc. are thrown in the dustbin.

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Sometimes you may have also seen your parents, to sale some old papers, plastic bottles, some pieces of metal, broken glasses, etc to some salesman or rag-pickers. These throwaway items are called waste products.

Waste are unwanted or unusable materials which is rejected after primary use or have no further use.

Make a list of things of your house which already have been discarded.

 

Articles discarded	Sources
	From house	From kitchen
1.
2.
3.
4.

 

Now the question is why we discard things. Usually, we discard things because these things occupy a lot of space and these have no further use in that format.

Moreover, organic products such as rotten vegetables and vegetable peels spoil the hygienic atmosphere of our house.

Make a list of waste products around you and complete the table.

 

List of Waste Products	Do they occupy space?	How much space they occupy?	Do they have definite weight?
1. Paper boxes
2. Plastic boxes
3. Pieces of thermocol
4. Old blades
5. Rotten fruits, vegetables
6. Old batteries
7. Electrical broken parts
8. Unused mobile parts
9.
10.

 

The traditional method of disposal of waste is by dumping the rubbish in landfill sites. such as disused quarries and grovel pits.

If you notice in a dustbin or garbage, a heap of vegetable peels, banana and other fruit peels, paper packets, jute products, straw products or other plant products decompose easily and mix with soil within a few days whereas plastic or polythene packets, bags and bottle pieces of glass, tin, cans, radio, television, electrical and computer parts remain unchanged, neither decompose nor mix with soil.

The former products are biodegradable and later products are known as non-biodegradable products. The waste products that easily decompose and get mixed with the soil are called Biodegradable products and the waste products that do not decompose even after remaining in the soil for a long time are called Non-Biodegradable.

Make a list of Biodegradable and Non-Biodegradable products around you.

 

	Throwaway products	Biodegradable	Non-Biodegradable
1.
2.
3.
4.

 

Try to keep two separate colored waste buckets or baskets in your house and in your classroom or in school and label them as Biodegradable and Non-Biodegradable. Keep degradable and non-degradable waste products separately in two bucket baskets.

Besides this, you keep another bucket of the basket to keep recyclable waste products such as paper, plastic packets, plastic, bottles, metallic substances.

 

 

Identify the biodegradable and non-biodegradable products from the above-mentioned pictures and complete the table below.

 

Products	Biodegradable	Non-biodegradable
1.
2.
3.
4.

 

Let’s see some waste products and from where they come (sources)

 

Waste products	From where they come (Sources)
1.    Broken glass parts, lamp.	Houses and public dustbin.
2.    Plastic bottles, polythene bags, etc.	Houses.
3.    Packets, wood pieces, dust.	Shops and from different commercial activities
4.    Rotten vegetables	Market places
5.    DDT, BHC, and other pesticides.	Agricultural land
6.    Broken pipes, plastic, asbestos, etc.	From construction place
7.    Syringes, cotton, used glasses, plusters, % medicine foiles, etc.	Hospitals and other health centers
8. Chemical wastes, oil, etc.	From factory

 

From the above waste materials complete the table below.

 

Products/materials	Types of waste		Remarks
	Bio-degradable	Non-bio degradable	Useful	non-useful

 

All the waste that we generate can be categorized into three types

1. Bio-degradable.
2. Non-Biodegradable and
3. Recyclable.

The Biodegradable materials can be put into deep pits in the ground and be left for natural decomposition (breakdown). Non-biodegradable waste to be disposed off.

The three R’s-reduce, reuse, and recycle-all help to cut down on the amount of waste we throw away. They conserve natural resources, landfill space, and energy.

We can use newspaper for packaging, broken plastic buckets as dustbins, carrier bags can be reused in shopping, and when possible carry goods in a bag. By this way you can reduce the use of plastic bags. Don’t ask for plastic bags, use your old bag.

 

Chapter 12 Waste Products Reusing Waste Products

Reusing Waste Products:

Many items found around the home can be used for a different purpose. So before you throw these items away think about how these things can be reused.

Reuse is the action or practice of using something again whether for its original purpose (known as conventional reuse) or to fulfill a different function (known as creative reuse).

 

Benefits Of Reuse

1. Reuse and reduce hazardous waste.
2. It reduces air, water, and land pollution.
3. Limits the need for new natural resources, such as timber, petroleum, fibers, plastic product, etc.
4. Gives economic benefits.

Since the introduction of the EPA’s Reduce, Reuse, Recycle campaign, many have adopted recyclable waste management systems.
Some home items we can save from trash and instill with new life and purpose.

 

Items We Can Reuse

1. Glass jars, containers or cans.
2. Gallon jugs, plastic soda bottles, and other plastic containers.
3. Newspapers, magazines, hard boards, paper bags, etc.
4. Clothes, towels, bedding, etc.
5. Seeds.
6. Plastic bags.
7. Bathroom items like toothbrushes or other brushes, toothpaste tubes, shop care, etc.
8.  Broken dishes
9. Old furniture.
10. Metalic substances.

You can reuse many organic waste items like egg cells, rotten vegetables, teabags, peels of fruits, leaves, scales of fish, etc. converting them into composite fertilizer. These can be used to grow plants in your garden.

Papers, plastics, glasses, etc. can be recycled and would be the raw material for new products. So don’t through all these things in the dustbin as waste.

Separate these things which can be recycled and hand over these things to the particular rag-pickers or ‘kabadiwallahs’. With these 3 ‘R’s we can refuse some items such as plastic bags for each product, and plastic bottles as containers.

In spite of these, we can use our own utensils to carry cloth or other natural fiber carry bags when we go to shopping and reuse polythene bags. Therefore, we can adapt the 4Rs (Reduce, Refuse, Reuse, and Recycle) to reduce the waste items.

Complete the table with 3 types of waste items

 

Waste items	Categories		Recyclable
	Bio-degradable	Non-biodegradable
1. Plastic bags		Yes	Yes
2. Paper	Yes		Yes
3. Rubber		Yes	Yes
4. Food wastes	Yes
5. Glass
6. Metals
7. Leather
8. Textile
9.
10.
11.
12.

 

Rejected computers, mobile, its parts, and other electronic goods are known as electronic waste or e-waste. Recycling is the only solution for the treatment of e-wastes.

 

 

 

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 11 Habits And Habitats Of Some Important Animals Behavioural Science And Behavioural Scientists

 

You may have heard the name of Arctic Tern, a small migratory seabird famous for its long-distance migration between the north pole and south pole. o you know how the male bird impresses the female?

The male bird fly over the female or around the female with a fresh fish carrying in his beak. If the male is able to please the female then she (the female) receive the fish and bonding form between them.

Later during nest building and courtship male provides the female with a steady diet of fish. Most of you have seen the spiderweb (net-like structure made up of fine thread) Have you noticed how the spider catches its prey?

Many spiders build webs with fine threads (proteinaceous spider-silk). When an insect such as a fly, mosquito or other small insect falls into the spider-web, it sticks on the sticky threads.

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The spider soon approaches the trapped insect and uses its fangs to inject venom into its body and after the death of the prey, the spider sucks the juice of the prey.

Take another example

Most of you have heard the sweet voice of the common cuckoo, especially during spring. Cuckoos are unable to build their nest. Female (a hen) Cuckoo lays its egg in the nest of other birds mainly Crow.

During the egg-laying period male cuckoo moves around the nest of the crow and emits a constant voice and disturbs the male and also female crow (or other birds).

 

 

When the crows both male and female try to drive away the male cuckoo at that appropriate moment, the hen cuckoo flies down to the host’s (crow or other birds) nest, pushes one egg out of the nest and lays its own egg and flies off.

The whole process takes about a few seconds (cuckoo layers 10-12 eggs but one egg at a time and in different nests of other birds for incubation).If you look around you may find many of such cases of animal behaviour in nature.

The behaviour of organisms allows them to interact with their own kind as well as with other kinds (species). Behaviour is the way organisms respond to their environment and other members of the same species and sometimes with other species.

The science of animal behaviour is known as ethology. Behavioural science (ethology) has a close relation to other branches of science (Ecology, Genetics, Physiology, etc.).

Activities of animals enable them to survive and to find out a favourable environment. Animals behave in a particular way in order to meet a particular need.

 

Ethology

It is the scientific and objective study of animal behaviour usually with a focus on behaviour under natural conditions.

Animal’s behaviour includes all the ways that animals interact with each other and the environment. The branch of biology that studies animal behaviour is called Ethology.

 

Chapter 11 Habits And Habitats Of Some Important Animals History Of The Study Of Animal Behaviour

People have been making detailed descriptions of the natural history of animals since the dawn of human history. The origin of the scientific study of animal behaviour lie in the works of various scientist and thinkers.

Behavioural science has its scientific roots in the work of Charles Darwin (1809-1882). Charles Darwin’s approach was a revolutionary one.

 

 

He observed animal behaviour from childhood and later his five-year voyage on HMS Beagle (the ship on which he travelled) as a geologist gave him a lot of opportunities to study animals in different parts of the world.

From his observation, he published his theory in 1958 after years of scientific investigation. The study and research of modern biology are all based on Darwin’s scientific theory.

The simple things of Darwin’s Natural selection theory are-Animals adapted themselves in different environments by changing their behaviour.

This change inherits from one generation to another, the animals or plants able to do positive changes selected by the nature and sustain and ultimately form new species, and those forms who can’t change (unable to adapt in surroundings) extinct from the earth.

From different studies, it has been found that the behaviour of animals has a genetic basis (Genes influence the development of neural and hormonal mechanisms that control behaviour) but the development of mechanisms that control behaviour is subject to environmental influences, such as practice after birth.

Jeans Henri Fabre, French Biologist (entomologist) was one of the founders of the study of insect behaviour. It was his hobby to observe the behaviour of the insects and noting all these things. He wrote many books.

 

 

Fabre had the great merit of demonstrating the importance of instinct among insects. He wrote many beautiful accounts on insects. In one experiment he showed the stubborn habit of caterpillars moving in a line.

The direction of movement of the first one follows the rest. In one of his experiments, he picked up a line of caterpillars with the help of a stick and placed them on the edge of a round pot.

Fabre noticed that the caterpillars kept on moving in a circle for hours on the circular edge of the pot. The caterpillars kept moving as the same way until they got tired and dropped from the edge.

This is an example of instinctive behaviour control by the nervous system. Modern studies of behaviour, based upon the observation of animals in their natural environment, were established by the work of Karl.

 

 

Von Fritsch, Konrad Lorenz and Niko Timbergen. They were collectively awarded the Nobel Prize in 1973. Von Fritsch studied the behaviour of honeybees for over forty years.

 

 

Von Fritsch established that bees use polarised light and magnetic fields to navigate. They can also see colours.

He showed that bees communicate to fellow workers the positions of food and sources found at distance from the hive by means of a ‘waggle dance’. After seeing the dance, worker bees rush to the source and fetch the nectar (food) to the hive.

Lorenz performed many experiments. In one of his spectacular demonstrations (experiment) with birds (Grey leg goose) he showed that the young animal (birds and mammals) forms a more or less-permanent bond with a larger, moving object that is first observed.

 

Waggle Dance

The Waggle dance of a worker honeybee is the way it communicates the location of a new food source to other workers. The dance is performed on the vertical comb surface or on the floor the hive entrance.

It is a figure of eight (‘8’) dance, performed in darkness surrounded by sister workers. The dancing worker bee emits buzzing noice, vibrates its wings and laterally vibrates its body.

 

 

When the dance is performed more rapidly it indicates that the food source is close to the hive (shorter distance). In the mid-20th century, Dutch scientist Niko Timbergen studied the nesting of Herring Gulls (a type of bird).

He noticed that nearly hatched gull chicks were fed by their parents only after they picked the red spot on the side of its parent’s beaks, near the tip (The adult bill is yellow with a prominent red spot).

 

 

Timbergen tested the hypothesis that it is this spot that stimulates the chick to the peak. In his study, he presented to very young chicks in the nest, two models of a gull’s head one in natural colours with a red spot and the other identical shape that red spot was absent.

The model with the red spot received all the pecks. Niko Timbergen In another experiment Timbergen noticed the foolish behaviour of birds. Herring gulls hatch eggs on the ground.

He placed a bigger and more glossy fake egg near the real eggs. He found that the parents come hurriedly to warm that fake egg, leaving behind the real eggs.

Jane Goodall was the first woman who spent many days in the jungles of Tanzania (Africa) and ventured into the little-known world of wild Chimpanzees. She studied their behaviour and she discovered that Chimpanzees make tools, eat and hunt for meat, and have similar social behaviour to humans.

 

 

She was the first person who tell us that chimpanzees used sticks as tools to dig out termites and they insert the stick inside the termite hive and collect termites. They can use tools for catching fish.

 

Chapter 11 Habits And Habitats Of Some Important Animals Some Famous Indian Ethologists

There are many Indian ethologists (scientists) who became famous for their studying the habits and behaviour of animals. Among Indians Ratanlal Brahmachary is widely known for his research in pheromones, (the biochemical messengers in a living organism).

Brahmacharya made a significant contribution in tiger behavioural studies. He studied the animal for over 50 years. He was among the first scientists to observe the scent-marking behaviour of tigers, where the animals spray urine on tree branches to mark their territories and communicate via biochemical messengers (pheromones).

 

 

He wrote several books in ‘Bangla’ to promote the cause of wildlife protection and scientific observation of animal behaviour.

Salim Ali is the another famous naturalist and Ornithologist (scientist works on birds) of India. He is known as the “Birdman of India”. He was a great bird-watcher. He wrote many books on birds and their behaviour.

 

 

In his book “the Book of Indian birds” (1941) he discussed the kinds and habits of Indian birds. He was honoured by Padmabhushan and Padma Vibhusan awards. Raghavendra Gadagkar is also a famous naturalist who studied the working cycle of Bumblebees.

M. K. Chandrasekharan, a famous zoologist studied the working cycle in the body of various animals, including bats.

 

 

Gopal Chandra Bhattacharya, one of the famous naturalists of Bengal spent his entire life in studying the behaviour and habits of the insects found in Bengal. He wrote many books and papers both in Bengali and English in a very simple language.

His writing are so simple that common people can easily understand these. His famous book in Bengali “Banglar kitpatango”. If you get a chance you must read the book.

 

Cultural Transmission Of Behaviour

One advantage of living in groups is that animals gain information from one another. Young animals like mammals and birds learn skill from their parents by watching and observing.

Macaque Monkeys of the Japanese island of Kohima learned to wash sweet potatoes originally provided for them by researchers in the early 1950s.

This behaviour was passed on from parents to offspring and was observed by other members of the troop. After a few months, researchers observed that all the monkeys were washing their potatoes in the sea.

Nearly fifty years later, this colony of monkeys still wash their potatoes even though they are not provided with dirty potatoes any more. Scientists think they like the salty taste.

From the above discussion, you may have felt behavioural science is interesting one. It is really an interesting branch of science.

From today onwards you also start observing the behaviour of animals (mainly birds, insects, common mammals, etc), all around you like the famous scientists you have just learned.

Not only start watching, note down the events with data, time and place and analyse the data from time to time. Who knows one day you might be a great Ethologist (behavioural scientist) like Darwin, Frisch, Goodall, Salim Ali, or Gopal Chandra Bhattacharya.

Of course, you will need to study hard and research a lot for that.

Complete the table:

Some behavioural incident	Describe by
1.    Behaviour of chimpanzees	1. Jane Goodall
2.    ……………	2.    ……………
3.    ……………	3.      …………….
4.    ……………	4.       …………….

 

Chapter 11 Habits And Habitats Of Some Important Animals The habits And Behaviour Of Some Animals

The surrounding conditions in which an organism lives and with which it interacts is called its environment. The place where an organism lives is known as its habitat.  An organism gets shelter, food and the right climatic condition in a specific habitat.

Habitat constitutes a part of the total environment. The way organisms respond to their environment and to another member of the same species is known as behaviour. The habit of an organism refers to a usual way of behaving.

Let us know the habits and behaviour of some animals.

1. Ants:

All of you have seen ants. Ants are social insects. They live in colonies that may reach as many as a few million members. They are of various colours and types. Scientists are not yet able to describe all of the types.

Many types yet to be discovered. Their total number is nearly half of the total organisms. Ants work together to gather food and care for the young, and their behaviour is surprisingly coordinated and methodical.

In fact, most ant colonies are so united towards the common purposes of survival, growth and reproduction that they behave like a single organism. This social behaviour gives ants a major advantage over solitary insects and other animals.

Ants perform many strange and interesting activities. According to scientists red ants are masters and the black ants are their workers. Red ants are good in fighting in comparison to black ants. But black ants are a more intelligent and first movers. They are hard. workers as well.

 

 

The colour Most ant’s live in nests which may be located in the ground or under a rock or built above ground and made of twigs, sand, grovel, mud etc.

Many species produce winged males and queens (female) that fly into the air, where they mate. Queen ants have wings which they shed when they start a new nest.

There are three kinds of ants in a colony. The queen, the female workers and the males. The queen and the males have wings, while the workers don’t have wings. The queen shed the wings when they start a new colony after mating.

The queen is the only ant that can lay eggs. The male ant’s job is to mate with the future queen ant and they do not live very long. Once the queen grows to adulthood, she spends the rest of her life laying eggs.

Depending on the species, a colony may have one queen or many queens. A division of labour (work) exists among worker ants, for example, the bigger ones with very large heads or with powerful jaws are called soldiers.

Soldier ants protect the queen, defend the colony, gather or kill (other insects or organisms) and attack an enemy in search of food and nesting space.

If they defeat another ant colony, they take away eggs of the defeated ant colony to their own nests and when the egg hatch, the new ants become the ‘slave’ ants for the colony.

Do you know how the soldier ants protect the colony? The soldiers like our army barrack stand in the anthill at each exit and block it with their heads.

When a returning worker approaches the closed entrance, it knocks with its antennae on the head of the soldier, who lets him in after receiving this sign.

Some other jobs of the colony include taking care of the eggs and babies, gathering food for the colony and building the anthills or mounds are performed by workers.

Workers with swollen abdomen devour (consume) the nectar of flowers and honey from honey beehives. They regurgitate the honey and feed other workers.

Some species of ants farm Aphids (a tiny plant sap-sucking insect), protecting them on the plants where they are feeding and consuming the honeydew aphids release from their body.

This is a mutualistic relationship with these dairying ants milking the aphids by stroking them with their antennae. The aphids are then called the “Cow of ants”.

You may have seen the nest of ants, known as anthills. Anthills are cupola-shaped (dome-shaped) nests of ants. The population of a large anthill may reach several million individuals.

The anthills (nest) have numerous passages, where in the young develop. Ants live in groups of numerous families for many years, consisting of females, males and workers.

 

 

An ant has a mobile head with well-developed biting upper jaws. The head bears compound eyes and bent antennae, legs are well-developed. The abdomen is very narrow.

Some species (Red imported fire ants have sting) of ants have a string at the posterior end of the abdomen to discharge poison. Some form of ants make their home in wood, they are often called wood ants.

 

 

 

Ants live in the nest which are located underground, in ground-level mounds, or in trees. Carpenter ants are large ants, they form nests in wood.

Ants typically eat nectar, seeds, fungus or insects. Ants spend winter in the underground part of the anthill. (Where the temperature is not as low as on the surface).

Gathering into a tight cluster they stay there until spring and feed on stored food. In hot countries, Nomadic ants are found. They keep changing their nest from time to time.

Worker ants of some tropical species cultivate mushrooms and moulds under the ground surface and use them to feed the larvae.
Ants feed mainly on insects.

It has been calculated that an ant family brings about 1 (one) kg of insects every day to the anthill, including caterpillars, butterflies, and beetle larvae.

The majority of these insects are pests (damage beneficial plants) of the forest and cultivated crops. Ants are useful in eliminating these pests.

Your work:

Try to observe ant’s behaviour along with their morphology in different localities. You may find many interesting behaviours of ants.

 

SI. No.	Location	Name of Ants /Sample	Colour of ants	Size of ants	Structure of ants	Habitat	Behaviour any speciality
1.
2.
3.
4.
5.

 

Do it yourself:

Try to find Habitats of different types of ants.

Take some necessary things like-pen, a pencil, a notebook, a watch glass, gloves, pins, needles, a small brush, a small glass tube, a little amount of alcohol, forceps, some polybags or glass jars etc.

Observations:

1. Find an ant’s nest.
2. Follow the line of ants from where to where they are moving.
3. Whether they have anything in their mouth or not?
4. Whether they are carrying large food and what type of this food?
5. What is the colour of these ants?
6. Have you seen any mixture of ants?
7. Take samples of one / two ants and put them into alcohol for further studies. (8) Try to follow the nest pattern.
8. Whether see any other interesting events?
9. Follow the mutual understanding of ants with other animals.
10. Whether the ants eating their food on the spot or carrying it to their nest?
11. Whether the ants are carrying food alone or eating alone?
12. How speedy the ants are?
13. How they communicate with each other?

Fill up the tables :

1.

Size of ants	large	Medium	Small	Remarks

 

2.

Colour of ants	Red	Black	Brown	Other	Remarks

 

3.

Body shape	Head	Thorax	Abdomen	Other Parts	Remarks

 

4.

Types of carrying substance	Insects	larva	Fungus	eggs	Other	Remarks

 

5.

Types of food	Vegetarian	Reaction	Non-veg	Reaction	Remarks

 

6.

Attitude of ants	Aggressive	Quiet	Normal	Other	Remarks

 

7.

Seasonal activity	Summer	Winter	Spring	Other season	Remarks

 

8.

Nature of Ant’s nest (anthills)	In the ground with mud/ sands etc.	In tree	In wood	In leaks	Others	Remarks

 

9.

Special behaviour you watch if any	During movement	Meeting with other ants	Fighting among them	Carrying food	Carrying egg	During flight	Anthill making	Remarks

 

Synchronise all the matter and write a paper on your observation. (You may use the following hints) Take help from your teacher.

1. Type
2. Colour
3. Structural Specification
4. Food
5. Colony
6. Association with other animals
7. Social behaviour
8. Works of different forms
9. Seasonal appearance
10. Any interesting observation
11. Sample collection
12. Drawing figures of different forms
13. Communication
14. Draw figures of anthills
15. Conclusion
16. Acknowledgement.

 

Chapter 11 Habits And Habitats Of Some Important Animals Termites

You may have seen tunnels in the frames of doors, windows even in walls by termites. Termites, popularly known as ‘white ants’ are also social insects like ants and honeybees.

Termites live in large colonies. They form their nest in soil or wood. Sometimes they form their nest (termitaria) which often rises to a height of 2.5 metres or above.

 

 

Termites have four distinct castes-Queen (female), King (male), these are fully-winged reproductive forms, Workers which are small, wingless, sterile forms responsible for building and maintaining the nest and all other works of the nest.

The last cast is Soldiers which are also wingless and sterile and are responsible for defending the colony. Soldiers have large heads with powerful jaws (some forms have a snout-like projection from which they discharge a sticky secretion that immobilises enemies (usually ants).

Four from (castes) of termites are-Male, Female (reproductive forms) workers, and soldiers. The termitaria (nests) of termites is made up of many chambers, underground channels, and covered tunnels above ground, through which food is carried are constructed by using saliva to cement particles of sand together and are very strong.

 

 

The queen of termites is very bulky and whitish or creamy coloured. The abdomen is usually the only visible part. Termites don’t have a hard covering around the body.

Their body colour except for some soldiers’ form (they are pigmented) are whitish, or pale and have no pigment, so they are called white ants. They expose very little to sunlight.

If they are too exposed to sunlight the water in their bodies dries up. Termites maintain humidity and temperature in their nest and the tunnels of their passages.

Termites have a special feature, they can digest. cellulose, a component of carbohydrates (found in plant food products), with the help of microorganisms (Tryconympha-a protozoa) present in their (termites) intestines.

 

 

Other animals do not have this ability. Though termites damage a lot of wooden substances of our society but it helps to clean the environment by removing leaves, dead vegetation, and wood from the environment.

Reproductive forms like Queen (female) and King (male) are winged forms. They have functional eyes and are pigmented. Soon after a heavy shower of rain, young reproductive forms fly out of nests and undergo a flight (nuptial flight).

Mating occurs during this flight. After that, they fall to the ground and lose their wings. After some of them have been eaten by birds, lizards, toads or frogs or other insects.

Surviving pairs of males and females are ready to start a new nest and form a new colony. You can easily observe this incident during the rainy season. Try to observe termites and related facts, note down these and then analyse your observation.

 

Do It yourself

Observe the following things and note them down. Then fill up the tables.

1. Collect different types of termites.
2. Try to find their nests.
3. If possible with the help of the teacher try to observe the constructional peculiarities of their nest.
4. Try to find out the living places of termites.
5. Draw pictures of different forms of termites-Reproductive forms, workers, soldiers. Try to observe their functions (different forms of termites).
6. Try to observe their movement.
7. Observe detailed morphology such as shape, size, colour, jaws, wings, abdomen, etc.
8.  Insert a stick through one of the holes in the termites’ nest, and observe their movement. Find some termite mounds. Measure their height, and how hard they are; look for the entry of exit points. Draw pictures.

Ants and termites are sometimes mistaken for each other, however, they are very different groups.

Difference between Termites and Ants :

 

	Termites	Ants
1. Body	1. Differentiation of the body into the head, thorax and abdomen is not so distinct. The waist is broad, the abdomen is broad at the end.	1. Three distinct parts of the body, distinct narrow waist, abdomen pointed at the end.
2. Antenna	2. Antennae almost straight beadlike.	2. Segmented elbowed antennae.
3. Food	3. Eat the cellulose inside the wood.	3. Eats sugar and proteins.
4. Visibility	4. They are not usually visible unless swarming.	4. Frequently visible around us.
5. Body colour	5. Except the soldier’s colour of body is pale whitish.	5. Usually not white, red, black, or brown.
6. Wings	6. In winged forms—both wings are equal.	6. Wings of winged form are not equal; the front wing are larger than the hind (back) wings.
7. Eyes	7. Usually workers have no eyes.	7. Compound eyes present.
8. Sex of the worker	8. Sexually undeveloped males and females.	8. Sexually undeveloped females.

 

1. Ant wings do not break off easily. Termite wings break of easily with just a touch. Termite wings are twice as long as the body.
2. Can you identify a flying ant with a winged termite?

Similarities between ants and termites

1. Both ants and termites can have a winged stage in their reproductive cycle.
2. Both are social insects-division of labour in different castes.
3. Both have jointed appendages so both are arthropods.

 

Chapter 11 Habits And Habitats Of Some Important Animals Honey Bees

Honey Bees:

All of you have tested honey. Do you know from where this honey is extracted? We get honey from beehives. The nest of honeybee are called a beehive. Honeybees are social animals. They live in big colonies.

Each honeybee colony includes one big female, who is the queen, several hundred males, drones and many thousand workers. The workers are underdeveloped females, who are incapable of reproduction.

 

 

A drone is larger than a worker and the end of its abdomen is blunt. Whereas the abdomen of a worker is more pointed. The queen has a relatively much larger and longer body than either the drone or the worker.

 

 

The queen and workers possess sting whereas the drone do not. The honeybee has mouthparts modified for sucking, manipulating wax, and collecting nectar. The legs of the worker are adapted to collect pollen and to build cells in the combs.

How can you differ a honeybee from a fly?

1. Honeybee has two pairs of wings but fly has one pair.
2. The worker and queen bee have a string at the end of the abdomen and the fly has not.
3. The abdomen of a honeybee possesses many hairs.

The nector, sucked from a flower by a bee is drawn into a bulky crop and mixed with the secretion of the crop glands (crop = stomach). Then bees put the nector into comb cells, wherein it transforms into honey.

The queen lays all the eggs of the colony when drones do nothing in the colony only to mate with the queen during the marriage flight.

 

The Workers Do All The Work

1. Gather nector and pollen from flowers, defend the colony, take care of the queen, eggs, and larva, and build beehives.
2. If the cells of beehives get warm, workers fan it with their wings, they also fan very fast to dry the hive after heavy rain.
3. They ventilate and regulate the temperature of the hive.
4. Keep the hive clean and carry away debris and the bodies of any dead bees.
5. They secrete the wax with which they build the combs.
6. They incubate the eggs and also feed all other members of the community, including the larvae.

The worker bees defend the colony aggressively-if an enemy comes nearby they attack by pricking it with their sting. That sting is fixed with the abdomen in such a way that when it pricks the enemy’s body, it tears the abdomen, gets detached from the abdomen and sticks to the enemy As a result, the worker bee dies.

Bee-bread:

It is a mixture of honey and pollen, all members of the honeybee colony feed this.

1. All larvae feed rich food for three days; this is known as bee milk which vomits out by worker bees.
2. The larva which is marked to be queen feeds royal jelly for five to six days. Other larvae after three days feed with bee bread.

Honey is tasty and beneficial. Honey is a good food with more or less all the components of food. Humans have learnt the art of honey extraction from beehives from the wild and also knew the artificial culture of honey bees.

 

 

In India 3-4 types of honey-bee species are common.

1. Apis indica (Common Indian bee)
2. Apis florea (Little bee)
3. Apis dorsata (Rock bee)

 

 

Do It yourself

1. Observe carefully beehives and bees in the garden.
2. Take help from your teacher, collect an old beehive and observe its cells.
3. Try to observe different types of bees from the artificial culture site.

Fill up the table

SI. No.	Type of Beehives	Location of beehive	Draw a figure of it	Observe different chambers

Try to collect different type of bees and observe it and write their features:

Type of bee	Length	Presence of sting or not	Body structure	Drawing
1.
2.
3.
4.

 

Try to observe:

1. Time of beehive formation.
2. Place of beehive formation.
3. Type of the bees who form the beehive.
4. Follow (if possible) from which plant they usually pick nectar.
5. Keep some sugar solution and other solution where the bees visit. How many times in an hour?
6. How do bees help in pollination?

 

Chapter 11 Habits And Habitats Of Some Important Animals Elephant

Elephants are the largest living land animals of the world. Elephants are broadly divided into two groups such as Indian Elephant or Asiatic elephant (Elephas maximus) and African Elephant (Loxodonta africana).

Indian or Asiatic elephant is relatively smaller than the African with relatively small ears and tusks. Size and weight are the most striking characteristics of elephants.

 

 

The elephants found in India each weigh about two thousand kilograms (kg) (range 2000 to 5000 thousand kg) in average and their height is around eleven feet from head to toe (African elephants are even more tall and heavy).

In general male elephants are larger than females. Indian elephants can live 70 years. Whereas African elephant lives 50 years approximately. Age can be judged from ears and teeth. The nose and the upper lip of the elephant are joined to form the trunk.

The trunk is very useful. It functions for grasping something, breathing, help in feeding, dusting and watering his body, smelling (sometimes it raises high to smell), drinking, lifting something, sound production/communication, it also helps in defence and protection.

Another peculiar structure of elephants is its tusks. Tusks are elongated continuously growing front teeth usually but not always in pairs. The average length of tusks of an adult African elephant is 5-8 feet weight around 23-45 kg.

The Tusk of an Indian female elephant is relatively short and its weight is also less than African.

1. The second incisors of the elephant are modified into huge tusks but in the case of tiger, dog, etc. canine teeth is elongated. Nearly a good number of elephants (30,000 approx in Africa) are killed for their tusks by poachers (hunters who kill elephants and other animals illegally) every year.
2. A group of elephants is called a ‘herd’.

Elephants live in herds (in groups). Each group actually is a family. A herd is always led by the oldest and largest female elephant, other. members of the herd are daughter, granddaughter, grandson etc.

 

 

The herd usually is made up of 8-100 elephants. Female elephants are called cows. They have a gestation period of 22 months and produce one offspring at a time. The baby is called a calf.

When a calf is born it is raised and protected by the whole matriarchal herd. Males leave the family unit between the ages of 12-15 years and may lead solitary lives or live temporarily with other males.

Like a human being elephants also keep an eye out for their offspring when in danger elephant raises its trunk and trumpets to call for help and the other elephants of the group come to fight against danger unitedly.

Matriarchy is a social system in which females (in mammals) hold the primary power positions in roles of political leadership.

Touching is an important form of communication among elephants. Individuals greet each other by stroking or wrapping their trunks, older elephants use trunks to slap, kick and shove to discipline the younger ones.

You may have heard that sometimes elephant gets hurt by getting hit by trains while they are crossing the railway track (lines). In such cases, elephants gathered around the wounded elephant.

 

 

A peculiar phenomenon is found among the elephant herds. If an elephant calf gets lost while walking in the forest, the herd tries to search it out. But if they found that lost calf under the shelter of humans, they never accept it back.

Elephants eat a lot. Each elephant can eat up to 150 kg of grass, leaves, branches of plants, fruits etc. in a day. Elephants love to stay in the forest. The forest does not always offer them sufficient food.

Then they enter fields of crops in the villages in search of food. When villagers try to stop them they attack human beings and destroy huts and houses. Every year many acres of paddy fields in the North Bengal and Jangalmohol areas are lost by them.

When wounded or cornered the elephant really becomes dangerous. Migration of elephants usually takes place in the rainy season when they are relatively safe and they travel long distances in search of new feeding grounds.

 

Threats To The Elephant Population

1. Habitat loss is one of the key threats to elephants.
2. Many climatic changes also affecting elephant populations.

Increasing conflict with human populations taking over more and more elephant habitats and poaching for ivory are additional threats that are placing the elephant’s future at risk.

Asian elephants have been very important to Asian culture for thousands of years. They have been domesticated and are used for religious festivals, transportation, tourism and moving heavy objects.

Try to gather knowledge by visiting any forest ranger’s office and talking to the people who are in touch of forest animals. If you found any Mahut ask him about the different behaviour of elephants.

 

Chapter 11 Habits And Habitats Of Some Important Animals Chimpanzees

1. Most probably all of you have seen chimpanzees either in zoos or in TV. Observe their activities.
2. Anthropoid apes (apes-like animals) are Gibbons, Orang-utans, Gorillas and Chimpanzees.
3. Chief similarities between the chimpanzee and humans are- the absence of a tail, more or less upright posture and a high degree of development of the brain.

The Chimpanzee one of the ape-like animals is very close to humans. Human and these ape-like animals, ancestor was the same. Many years ago (Miocene era) human line (evolutionary line) had been separated from the ape-group.

 

 

Chimpanzees are usually found in the deep forests of equatorial Africa. They usually live in groups with a single male as head and have a harem of several females. The male protects the family. Chimpanzees possess excellent memory and quickness of wit.

Experiments on chimpanzees have demonstrated that they can apply acquired habits under varied conditions. In nature they break off a twig, remove the leaves and use it to extract insects (termites) and their larva from the narrow passage, they use straws as toothpicks.

Chimpanzees have learnt to imitate closely a number of operations performed by humans such as putting on clothes, eating and drinking at tables, sweeping, washing up, using keys, hammers and other tools, to ride bicycles, and smoking. They easily become friends with humans.

 

Chapter 11 Habits And Habitats Of Some Important Animals Migratory Birds

You may have seen migratory birds in Alipur Zoo or Santragachi Jheel (lake), Howrah or Kulik Bird Sanctuary, Raiganj or many other places. They usually come to this area during winter.

Migration is a natural process. It is the regular seasonal movement (fly) of birds from one place to another (between breeding and wintering grounds). Migration is also occur in other types of animals such as fish, mammals, reptiles etc.

Migratory birds are these birds which fly to warm areas (countries) from cold areas (countries) during winter and return to their homes once winter is over.

They unite in flocks numbering hundreds and thousands of individuals (some may travel solitarily). Some fly in the daytime, while others fly at night. The birds feed on the route, rest and fly further to their habitual winter grounds.

India is a winter home for most of the Siberian birds such as Siberian cranes, Greater Flamingo, and Demoiselle cranes. Many birds from other regions of the world also migrate to India every year during winter and summer (few cases) for food, breeding and nesting.

There are many birds migrate to India during the late autumn or winter months, fly from Tibet, Bhutan, Ladakh, high mountainous regions of the Himalayas and the Siberian region, where winter is very cold, snow covers the land and water bodies are the main source of food for them start to freeze and it becomes hard to get food and they come down to the plain lands for their food, sometimes for breeding.

Winter in India is moderate and less cold than in their original home place of that birds. At that time a lot of food is available here.

At the onset of summer when the cold decreases and snow melt and trees bear leaves and flowers begin to appear, insects, molluscs and other foods available they return to their home again.

During migration, the birds keep permanent routes that they follow every year to the winter and in spring they return to breed.

 

Few Migratory Birds Who Visited India

1. Amur Falcon (North East India, Nagaland)
2. Siberian Cranes (Bharatpur National Park)
3. Great Flamingo during winter [Gujarat, Chillca lake (Orissa)]
4. Demoiselle Crane (Rajasthan)
5. Bluethroat (Nilkantha pakhi)
6. Coloured birds, Black-winged stilt
7. Bar-headed goose-they migrates over the Himalayas and spend their winter in India (Assam, Tamilnadu)
8.  Rosy starling.
9. Great white Pelican (You may find them in Alipur Zoo during winter)
10. Jacobin Cuckoo (coming to India in the summer season).

These birds come to India from South-East Asia and the Siberian region during the winter and summer seasons. The migratory birds mainly arriving at the wetland spots of the national park, also seen in parts of the lakes and settle down in shallow or water ponds, Jheels etc.

Siberian species come to India only during winter and prefer swampy lands for nesting. You may find migratory birds if you visit Chupirchor (Purba Bardhaman), Santragachi Jheel (Howrah), Alipore Zoo, Rabindra Sarobor (lake), Sajnekhali (Sundarban), Sahebbandh jheel, Purulia.

Arctic tern are small migratory birds which cover the maximum distance. It migrates from the Arctic to Antarctica and back. If you are in Sundarban, Mandarmoni or Dadanpatra (East Midnapur) during Nov-Dec.

You will see wild ducks, geese, cranes, storks and other large migratory birds passing overhead. You may observe this in other parts also where large water lands are present. Besides birds, very few other animals make such long and regular migratory journeys.  Such as-Eels, and salmon (migratory fish).

1. Decrease in the amount of habitual food, and shortened day time which are the signals for migrating from the areas.
2. Migration is an instinctive action of birds and it developed several million years ago under the effect of seasonal change.

In Santragachi Jheel (lake) you may see many migratory birds during winter (November- February). Different types of duck, Gadwall, and Northern Pintail usually come there.

In the Botanical garden (Acharya Jagadish Chandra Bose Indian Botanical Garden) Shibpur, Howrah is also a place where you may see some migratory birds (Brown Hawk, Owl, Booted eagle, some wood peakers and Kingfishers).

In the Eco-urban village, New town, Kolkata also hosts a few rare migratory birds in the winter (Amur falcons, Bluethroats, Open billed strokes, Strawberry Finch, Egrets, etc.)

Besides these places migratory birds like wild ducks are seen is many lakes, ponds and wetlands of rural Bengal, Wagtail (Khanjana bird) with long tail, grey coloured kajal bird (black lining in its eyes) are found in the fields and fruit trees of Bengal.

These birds are also the winter guest which comes from the Himalayas. Birds are normally selective in their food, and with their high degree of mobility, they can fly to where the kind of food they require is available.

As a general rule, species whose range of food is limited, make the longest journeys. Birds during their long journey they face many problems such as adverse weather, the direction of winds, storms and overall disturbance created by humans.

Scientists are trying to know how these migratory birds calculate the direction, and distance and get their necessary energy during flight. Still, scientists have to get answers of many such questions.

Do it yourself:

1. Visit the places where migratory birds appear each year.
2. Observe their behaviour.
3. Note down when they come and when leaving the place.
4. Look around your residence or locality to watch birds, if you find any new birds, note it. How many days do birds stay there.
5. What type of food the bird eat.
6. Gather some information from different sources regarding migratory birds.

 

Chapter 11 Habits And Habitats Of Some Important Animals Crow

Crow:

The crow is one of the most familiar birds and is found around humans. Crows are found all over the world. In India two types of crow are common-

The house crow (Corvus splendens) are common in India and Srilanka. It is an expert thief that will steal everything. There are around 40 species of crows in the world.

House crow (Pati kak) or Indian grey necked or Colombo crow and Raven (Dhar kak). In the house crow’s forehead, crown, throat and upper breast are glossy black, while the neck and breast are lightly grey in colour.

The wings are tall and the legs are black. The entire body of the raven is jet black in colour and they are bigger than a house crow. Crows eat small animals such as mammals (rats, moles, etc), amphibians (frogs, toads etc), reptiles (lizards, house lizards) and other small birds and their eggs.

They also eat insects, seed grains, nuts, fruits, non-insect arthropods, molluscs, and worms (earthworms). They also pick up their food from the garbage.

 

 

Many scientists think that crows are the most intelligent among the birds and also like the chimpanzee, based on their ability to solve problems, make tools and apparently consider both possible future events and other individuals’ states of mind.

Crows can hide food, they can use sticks as tools. Crows sit in a council, and hundreds of crows gather in certain events like human beings.

Crows can make their nest but they are not at all experts in this matter. Both members of a breeding pair help to build the nest. They prefer to nest in evergreens but can make a nest in deciduous trees when evergreens are less available.

The nest is made largely of medium-sized twigs with inner cups lined with pine needles, grass, weeds, soft bark or animal hair. Crows are social birds too. They call other members in the time of any danger and death of any member.

In the event of the death of a crow other living members call to each other, gathering around and paying attention to the dead one. They are likely trying to find out if there’s a threat where the death occurred so they can avoid it in the future.

Do it yourself:

Observe the crow around you and try to answer the following questions : . How are the structural difference between the two types of common crows?

1. What are their nature?
2. What type of food they eat?
3. How they make their nest and with which type of plant?
4. Give some examples of crow’s intelligence.

 

Chapter 11 Habits And Habitats Of Some Important Animals Mosquito

Mosquito

Most probably all of you have an experience of mosquito bites. Mosquito bites along with the ‘song of mosquito’ (the sound due to the beating of their wings produced during flight) are one of the most irritating matters to human beings.

Mosquitoes are found all over the world, but they are abundant in the tropics. You have heard the name of three main types of mosquitos such as-Anopheles, Culex and Aedes.

 

 

These three types of mosquitos transmitted diseases like malaria, filariasis or elephantiasis and dengue fever respectively. It is only the female mosquitoes that suck human blood (other vertebrates are also mainly warm-blooded animals) but males are harmless, they do not bite, and they only suck plant juice.

The disease is transmitted by the mosquito biting and sucking blood from an infected person (carrying blood with germs) and giving the germs later to another (healthy) person through another bite.

Females of most mosquito species require a blood meal in order to ripen their eggs. Actually, the germs (microorganisms) of diseases are sucked by the female mosquito pass some time within the mosquito’s body and then is transmitted to another person through saliva (containing germs) which is secreted by the mosquito after each bite to the person before starting bloodsucking.

Germs of disease pass into the bloodstream along with the mosquito’s saliva. The female mosquito lays eggs in standing waters of small pools, drains, water tanks, and other containers (where water is stored) near the house. Anopheles and Aedes mosquitoes lay eggs in clean water whereas Culex in dirty water.

Mosquitoes’ saliva contains a substance that prevents the blood from clotting and this chemical evokes a response that causes localized redness, swelling and itching.

This is due to the immune system response of the body. The swelling is caused by histamine which is produced by the body’s immune system.

Histamine increases blood flow and WBC (White blood corpuscles) count around the affected area, which causes swelling (inflammation). Mosquito bites itch because histamine also sends a signal to the nerves around the bite.

The larva hatches out of the egg and moves in rapid Jerks. They are usually stick-like bodies and with many hairs. They either float horizontally (Anopheles larva) or hang from the surface (Culex larva).

At that stage, they eat microorganisms and insects present in the water. After a few days, larva change into a pupa (the resting stage). Pupa is coma (») like and doesn’t takes any food.

After a short period, a full-grown mosquito (imago) comes out breaking the pupal cover. Shortly after emergence, the wings harden and expand and the mosquito fly out of the water.

If you carefully look the mosquitos and follow when they appear (their appearing time like day, evening night, early night, late night) you can get some idea about the type of mosquito.

 

Anopheles

They are slender, greyish bodies with delicate legs. Black spots on the wings, when they seat on a surface they form a 45° angle to the surface (inclined appearance). They make sounds during flight. Come out in the late evening and at midnight.

Transmit the germs of malaria disease (Plasmodium-microscopic protozoa).

 

Culex

No spots on the wings, larger than anopheles with shorter legs, sit nearly parallel with the surface. Make no sound during the flight. Come out at night, may appear in day time also in the evening and early morning.

Transmit the germs of Filariasis (microscopic stages of helminth).

 

Aedes

Comparatively large body, with black and white bands on the body (abdomen and legs). They rest almost parallel to the sitting surface and make no sound during flight. Come out in day time.

Transmit the virus of Dengue fever.

Mosquitoes are known to transmit a variety of viruses (Dengue, Chikungunya etc.) and other pathogens (Pathogens disease-causing microorganisms) like protozoans (malaria) and helminth (filariasis).

However, not all species of mosquitoes can become infected with and transmit all pathogens. Prevention is better than cure, so we have to take preventive measures against mosquitoes.

The most important is the destruction of breeding places of mosquitoes and different development stages. We have also to be careful against adult mosquitoes that are never able to bite us, regular use of mosquito nets and other devices should be taken to avoid mosquito bites.

 

Chapter 11 Habits And Habitats Of Some Important Animals Fish

Fishes are vertebrates and all of them live in water (aquatic). Their primary respiratory organ is the gill, present under the operculum on either side of the head. Very few fishes like Kai, Magur, and Singhi have accessory respiratory organs besides gills; so they can live some time outside the water.

Fishes gulp water through their mouths and pass it out through the gills. Gills with the help of blood capillaries, (fine blood contains vessels) absorb oxygen (O₂ ) from the surrounding water and release carbon dioxide (CO₂ ) to it.

Gill is the respiratory or breathing organ of fish which exclusively work in water. So fishes are not able to live outside of water. They die soon when they are kept out of the water (except some jeol fishes already mentioned).

Operculum is the large flap with a free lower edge on either side of the head. It covers the gill. Gills have many comb-like structures with many blood capillaries. For this reason, the gills are red (If you lift the hard operculum you can see the gills.)

Fishes can live in three types of water-salty water, sweet water and mix-water (salt and sweet water). Fishes that live in salty water (sea- water) are called marine fishes (Salman, Pomfret, Shark, Ray fish, etc.)

And those who live in the sweet water of lakes, rivers, ponds, canals etc. are called freshwater fishes (e.g. Bata, Ruhu, Catla, Punti, Tilapia, etc) and some fishes live in the semi-salty water of Sundarban and the areas in which freshwater (river, canals) meets salt water are called brackish water fishes (Bhetki, Parse, etc.).

Skeletons of some fishes are soft and more flexible, these are called Cartilaginous (skeletons made of cartilage) fishes such as Shark, Dogfish, Pomfret, and Ray-fish. Many marine fishes are cartilaginous fishes.

On the other hand, the skeleton of another group of fish’s skeleton is hard and less flexible (skeleton made of bone) are called Bony fishes such as Ruhu, Katla, Punti, Tilapia, etc.

Fishes move in the water by swimming with the aid of the powerful muscles (myotome) of the tail, tail-fin and other fins. Fins help in movement and balance in the water. The tail fin is like the helm of a boat.

It takes the fish to the direction in which the fish wants to move. The tail muscles and other muscles of the trunk of fish contract alternately on the two sides and thus cause a wave-like movement of the tail and the tail fin, which push the fish forward in a straight line.

Fish eat small algae of water, small insects and their larvae, warm, underwater plants and their parts, some large fishes eat small fishes too.

Give different types of foods to the fish of an aquarium separately or keep some fish in a jar to observe the activities of fish, what type of food they like most, what type of food they reject which fish take which type of food. Make a table of your observation.

Some fishes can move or migrate from salt water to fresh water and fresh water to salt water which no apparent discomfort e.g. Eel (fresh water to sea) and Salmon and Hilsa (sea to freshwater).

 

Care Of The young

Many fishes do not show any parental care to their offspring. Usually, they lay large numbers of eggs (millions of eggs). But some fishes show parental care to their offspring.

Fish species that take care of their young (usually spawn) are a very small number. Fishes like- Tilapia, Shol, Chitol Gojal etc take care of their young till the eggs hatch and grow into adults.

When the female (mother) lays eggs in the nest (usually form with algae) the male (father) fish stands guard all the time. If he finds any enemy he chases it away to a particular distance.

After the hatching of young fish (fry) both males and females jointly guard them for several days preventing them to swim far away from the nest. Tilapia shows an excellent type of parental care. They build a nest before the female lays eggs.

They make many long furrows on the underwater soft floor of the earth and are covered with algae. Fertilization of eggs occurs in these nests. The female carries the fertilized eggs in their mouth until the eggs hatch into young.

After that, the young do not disperse but stay near the mother. When there is the danger she allows them to enter her mouth again for protection. In some forms of Tilapia males also do the same work.

Because of the care given by the parents of Tilapia a high proportion of their young survive than in most other fishes, which give no such care.

Sea-horse, a type of sea fish that are named for the shape of its head which looks like the head of a tiny horse. In males have a broad pouch into which the female lays eggs and fertilization occurs inside the pouch.

The eggs hatch in the pouch of the male (father). During the development of eggs (gestation), his mate (mother) visits him daily. The young fish after hatching remained in the pouch for a period of time.

After leaving the breeding pouch, the youngs swim by the sides of the males. In case there happen anything dangerous, then the male will open the pouch at once. The young will swim quickly into it and the pouch is closed afterwards.

Many of you have seen fish in aquariums. One of the aquarium fish is, Paradise fish, which male or father fish uses saliva to form bubbles. With this, form a bubble nest.

The female (mother) paradise fish use this bubble nest and lay eggs with this form of bubble nest. Fertilised eggs are much lighter than the eggs under the nest. The male fish guard the nest and take care of the babies.

A floating mat of saliva-coated air bubbles often incorporates plant matter. The shark takes great care to its offspring. In general, they do not lay eggs in water the fertilized eggs developed in the body cavity, hatched into the young and then separated from their mother.

They take nourishment from egg falls. Mother fish is only for protection and hatching. Fish live in the most varied aquatic habitats-in seas and freshwater bodies, near the upper surface and in the deep at high and low temperatures etc.

The living conditions, food, rivals and enemies are different everywhere, which influences great variety in the structure and behaviour of fish.

Sometimes the oxygen level in the water decreases, sometimes water starts to evaporate quickly and sometimes they face dangerous chemical substance gets mixed in the water. When in danger, fishes generate a strange smell from their bodies.

Other fishes after sensing this smell takes guard and swim around very fast in the water. Fish living in the upper strata (level) of the water and at the surface usually have a stream-lined body shape and a well-developed caudal fin, making it possible for them to swim at high speed.

Bottom-dwelling fish usually swim slowly. Their flattened body is barely (hardly) visible to prey and enemies. Fishes of coral reefs are usually brightly coloured.

Fish use their bright colour for camouflage, blending in with the corals and plants of the habitat and they are able to ambush their prey as well as protect themselves against predators.

Colourless fish inhabit water caves or in the deep sea where they live under conditions of entire darkness. The colour of some catfishes are blackish which helps them to camouflage.

Some deep-sea fishes have luminescent organs (light-producing organs). About 32,000 types of Indian fishes have been identified, but still, a lot of fishes are to be identified.

Your work:

1. Try to observe fishes in the aquarium, observe their movement breathing technique, food intake, and types of food they take.
2. Try to observe jeol fish (fishes with accessory respiratory organs) like Shol, and Singhi. Try to observe how mother Shol protects their offsprings.
3. Observe Tilapia carefully in a small tank, and follow their behaviour.

 

Chapter 11 Habits And Habitats Of Some Important Animals Snake

All of you have seen snakes either them in natural conditions or at a zoo or in the buskets of snake-charmer (Bedye). Snakes are slender cylindrical long, legless reptiles. Snakes are carnivorous (flesh eaters) and hunt other animals.

Snakes have a fairly restricted diet some feeding on rodents (rats, moles) others on birds, frogs, toads, fish or insects. Some feed other reptiles as well as other snakes.

Wheather snakes are able to hear or not?

Snakes are unable to hear because they have no external (outer) ear. But they feel vibrations very well. During the snake charmer’s play with snakes, they (snakes) follow the pungi (the sound-producing instrument Been use before, the snake) that the snake charmer holds with his hands.

The snake considers the person a threat and responds to it as if it were a predator. Remember that snakes never eat bananas or drink milk etc. as we have a common myth.

Eating by these animals snake balance nature and maintains the food chain and also save our food crops from the rodents like rat, mole and insects. Some snakes are highly specialised as egg-eater.

Except for the extremely cold areas, snakes are found all over the world. Snakes are abundant in tropical regions. In India there are around 300 species of snakes, out of them few are (around 60 species) venomous (poisonous).

Snakes live in the branches and holes of trees, in the ground, in the holes (made by rodents usually) in the undisturbed moist dark corners of a broken walls, rubbish, woods, breaks, etc. Some snakes live in the water.

The skin of the snake is covered with scales which are smooth and slightly overlap one another. In most cases, there is a series of transversely enlarged plates beneath the belly. In land, snakes move with the help of their abdominal scales.

 

Shedding Of Scales

Snakes periodically moult (shedding) or change their scaly skins (outer layer of skin with scale) and acquire new ones. Before shedding, snake stops eating and often hides or removes to a safe place.

All snakes swallow their prey-whale. They have the remarkable power of swallowing animals several times of their own diameter. The bones in the skull of the snake and the ligaments are so arranged that they can expand their jaws and open their mouth widely.

Teeth are angled backwards and solid (except the two poisonous teeth) for smooth capturing of prey (to grip with prey). Less than one-third of snakes are venomous (poisonous) and of them perhaps one-third kill their prey by injecting poison.

Other preys kill by constriction or biting and swallowing. Poisonous (venomous) snakes have two tubular fangs (poison teeth) in the anterior (front part) of the upper jaw.

These fangs are connected with the poison gland (they are modified salivary glands) through narrow tubules. The teeth of Boas and pythons are solid. They are non-poisonous snakes.

They fangs are used to inject poison into the organism of prey or enemy when biting it. Venom is primarily used to paralyse the prey. It also helps in digestion (it is a salivary secretion)

Snakes have a long tongue that is forked at the tip. The tongue is continuously flickering in and out through a groove in the upper lip. This is not at all related to the poisonous equipment.

This is simply an organ of touches and feels the surrounding environment (olfactory function) such as can feel the temperature, and presence of some chemicals in the air (they only can feel all these when this information passes to the brain via a special organ present in the upper part of the mouth), moisture etc.

The eyelids of the snake are fused together, become transparent and cover the eyes like a watch crystal. We have already learned that most snakes are non-poisonous, and few are poisonous to human beings.

The common poisonous snakes are :

1. Common krait (Kalach or Domna-chilli)
2. Cobra (Keute), King Cobra (Sankhachur)
3. Russel’s viper (Chandrabora) saw-scaled viper
4. Indian cobra or spectacled cobra (Gokhra)
5. Malabar pit viper (usually found in the western ghat area)
6. Banded krait (Shakhamuti).

So far the largest snake is the giant anaconda reaching up to 11 metres in length. It lives in South America. Banded Seakrait is among the most toxic and venomous snakes in the world lives in the coral reef of India and spent most of its time underwater.

Python, Boa, Jaldhora, Indian Rat snake (Dhamna snake), common Sand Boa, etc. are non-venomous. Snake venoms are a complex cocktail of proteins and enzymes.

Some snakes’ venom (poison) affects the nervous system (Neurotoxic venom) while some affect the blood circulatory system (Hemotoxic venom). Besides these types, some venom affects specific sites or muscle groups (cytotoxic venom).

There are nearly 3000 different species of snakes in the world. Nearly 10% of these are venomous. Of that (10%) 10-15% snake venom is the most dangerous. A very small portion of it is fatal to humans.

Snakes never target a person to bite, as well as a human is not at all the food of a snake. They are very fearful. When a snake finds itself in front of a human it thinks itself to be in danger and shows some symptoms against human-like a hissing sound (due to rapid breath) or lift its head and expanding the neck portion (in some cases) and turning its tail.

In extreme cases they bite a person, they bite to protect themselves or if they are facing any obstacle by a man. Snakes usually do not want to waste its poison except to catch prey.

Why does snake venom kill humans but not the snake that is filled with venom?

It is a complex matter but you just know the simple fact that the poison used by the snake to paralyse or kill the prey, that poison breaks down in its stomach into harmless products and also they have developed antibodies (natural body defence protein) to protect itself from their own venom.

More over the poison gland is well protected in the snake’s body. So the own poison does not affect the snake.

If one is bitten by a snake, the victim should be taken to a physician as fast as possible. Not to bring him to an Ojha for any type of unscientific treatment.

It is most effective to treat the victim with a special antivenom and if necessary perform a blood transfusion. Snakes even poisonous ones, should not be killed.

All snakes, including poisonous ones, are beneficial for exterminating harmful rodents. The poison of snakes is used in medicine in various drugs.

Your work:

1. Gather more information about poisonous and non-poisonous snakes.
2. Try to understand their bite spot (take help from your teacher/parents).
3. Explain the truth against the non-scientific myths of society.

 

Chapter 11 Habits And Habitats Of Some Important Animals Tiger

All of you have seen tigers from childhood either in pictures or in the cinema or in the circus or in the forest or in the zoo. When a visitor goes for a visit to Sundarban, he or she always expects to see a tiger in natural condition.

Tiger is the most fascinating and powerful animal of the cat family (the cat family includes the cat, tiger, and lion). Tiger is the king of the forest (Jungle) and easily hunts animals bigger than its own size. Tigers live solitary lives (live alone), except during mating season and when females bear young.

Tigers are usually territorial (living in a particular area) and mark their large home (area) ranges by creating stretch marks in the tree’s bark, emitting liquid from its urine which it spread by urination in trees and ground.

The tigress and tiger find each other by smell. Tigers also excrete waste at a particular place to mark their presence. The eyesight of the tiger is exceptionally (very) good, particularly at night.

The eye has been designed to see very well in the dark. In normal daytime, they can see more or less like us. But at night their vision is about six times better than of a human being.

This is due to the presence of Tapetum Lucidium in the retina of the tiger’s eyes which makes it possible. Tigers have a well-developed sense of touch that they use to navigate in the darkness, detect danger and attack prey.

The tiger’s sense of hearing is also very good. Their ears are capable of detecting the origin and direction of various sounds produced by prey in dense forests. The sense of smell is poor in tigers.

Tigers take extremely strong jaws and sharp canine teeth on them. The teeth of tigers are very strong and are built for gripping and tearing flesh. Tiger’s hind legs are longer than its front legs.

They can cover 20-30 feet in one jump. Tigers have large padded feet so they can move silently towards their prey. The claws (retractable) of the tiger are up to 4 inches in length and are used to grasp and hold on to prey.

A tiger cannot only jump and hunt its prey but also climb a tree and swim in the water if necessary. Tigers of Sundarban is known as the Royal Bengal Tiger (Panthera tigris tigris) is world famous due to its special features.

They have light yellow or reddish yellow coloured skin with black stripes. This is the only tiger group which inhabits mangrove forests. These features help them to hide easily in the mangrove forests.

Now-a-day it is threatened by poaching loss of habitat and fragmentation of habitat. They are born killers. They allow the prey to get near and make a sudden leap (jump).

At it with their slippy and strong body (inflicting) deep wounds with their sharp claws). They know the exact point to attack. They usually hold the neck of the animal. Usually tiger hunt between dawn to dusk (mainly evening to early night).

Royal Bengal tigers are caring towards the females and children, therefore when the killing of prey happens, male tigers eat after the female and children complete their feast.

They like to hunt animals like deer, pig, water buffalo, badger, and wild boar. They have also peculiar food habits, they even eat crabs, fish, iguanas, tortoises or other reptiles.

During the day it remains hidden in the forest. Active during the evening and early part of the night to stalk its prey lying in wait by paths to forest or water, or along the banks of rivers.

If the prey is too large to be taken at a single meal is dragged away into a thicket (a dense group of bushes and trees) to which the tiger returns on successive days,. They can carry double their body weight.

When the tigers become old or injured they often come near to human settlement or (villages) to get easy prey like cattle, sometimes it becomes man-eater as well. Tigers prepare clean spots before giving birth of a cub.

Mothers never leave the place after giving birth of cubs and remain to sit with them all the time. It can go without eating only to guard the cubs. If anyone finds out its den or location, then the tigress immediately moves away to find another spot (new spot).

Both male and female tigers are ferrous. They kill anyone who comes near the den or during changing den. Many woodcutters and honey collectors fall victim to the tigress. By nature, tiger cubs are playful and rather active.

When the cubs grow up a little, the tigress teaches them to hunt, how to tear and how to eat meat with teeth. Tigress also teaches the cubs how to swim. After six or seven months tiger cubs become adults.

Your work :

1. Gather information about the distribution of tigers.
2. Make a chart mentioning its role in the food chain.
3. Gather information about the nature of the tiger.
4. Try to campaign against tiger killing.

 

Chapter 11 Habits And Habitats Of Some Important Animals Whales

Whales are large-sized aquatic mammals. Whales have streamlined body shapes, well adapted to swimming. The body is completely hairless except for some hair on the top of the head, near its nasal area.

Blubber, the thick layer of fat under the skin of a whale which is the Auxiliary source of energy and conserves body heat.

Whales have a thick layer of fat under their skin which is known as Blubber. Blubber serves to conserve body heat (whales, like mammals, is a warm-blooded animal) and provide energy for movement.

They have no external ears or projecting nostrils like us. This arrangement helps them to move smoothly in the water. In some forms, hairs are modified as whalebone (not true bone) which acts as a filter for the food, for example, right whales.

Whales move in water by means of the extended tail which have two horizontal labeo (flulees) projecting on each side (this is totally different from the tail of fish) that act as propellers and a pair of forelimbs that have been modified into flippers.

Hind limbs have become last (two small bones attached in the pelvis indicate that their ancestors had hind limbs too). In some forms have a dorsal fin (this is little more than a fold of skin and not supported by a skeleton or fin rays).

These indicate that whales are descended from four-footed terrestrial mammals.

 

Flipper

The extended and modified forelimb of the whale. Its bones have similarities with the forelimbs of other terrestrial animals. The flippers can only move up and down. They are not propellent. It is a balancing organ. The blue whale is the largest living animal (largest mammals also) of the earth.

The length of a Blue Whale reaches up to 30 metres and its weight is 150 tons. They feed on small aquatic animals mainly krills [a small prawn-like (crustacean) animal]. A blue whale eats from 2-4 tons of food daily.

Though whales is totally aquatic animal their respiratory organ is the lung. It breathes when it comes to the surface of the water. Whales dive to depths of 100 to as much as 1200 metres and some like sperm whales can stay below for an hour.

Before driving, the whale takes in a large volume of air and after coming back to the surface it exhales deeply through the blowhole (nasal opening) present on the top of the head.

They exhale air in such speed that the released air goes (spout) straight up to a height of 10-40 feet. The exhaled air is spout usually warmer than the surrounding air so the surrounding atmospheric air gets transformed to water droplets.

Thus when a whale come to the surface after a deep dive, a white stream is seen from a distance almost like a fountain. Many of you may see this picture in TV or in video. It is an amazing sight.

 

Different Types Of Whales

Few of them are

1. Blue whale (30 m. long)-a largest animal on the earth
2. Greenland right whale (16-20 m long)
3. Pigmy right whale (6 m)-a smallest whale (the whale has dorsal fin)
4. Bottlenose whale (10 m)
5. Humpback whale (13-16m)
6. The sperm whale (tooth whale)-23 m long square head and the snout tooth is 20 cm long and approximately 3 kg is weight. They are the most aggressive in nature.

Your work:

1. Try to collect pictures of different types of whales.
2. Draw a picture of a whale and mark its parts.
3. Compare a whale with a shark.
4. Gather information about whale killing and campaign against it.

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 10 Biodiversity And Its Classification

 

Would you face any problem if you are asked to write the names of some living organisms such as plants or animals around you?

I am sure you wouldn’t face any problems. You can write many pages without any hesitation. There are several life forms in our earth. Living forms are a little bit to a great different from each other.

This variability is known as biological diversity or biodiversity. Biodiversity is the term used to describe the variety of life in the earth. It includes every plant and animal as well as microorganisms such as bacteria and viruses.

Viruses are between living and non-living forms. Viruses are living when they are inside living organisms. But you cannot get all the living forms in a particular place or location. Biological diversity is not evenly distributed over the earth’s surface.

Read and Learn More WBBSE Notes For Class 6 General Science and Environment

 

Chapter 10 Biodiversity And Its Classification Simply Biodiversity Is The Number And Variety Of Living Forms In A Particular Place.

You can study the biodiversity of plants and animals in your locality. Make a table of different plants and animals of your locality. How many varieties of plants and animals are there and their number in a particular place. Simply that is the biodiversity of that place.

 

 

Complete the table

Organisms	Number	Varieties	Remarks
1. Plants
2. Animals
3. Other organisms

 

Now the question is how many species exist on our earth? Exactly how many species of life exist on earth is not known. However, it estimates range from 20 to 50 million (2 to 5 crores) or more than that.

Among the vast number of living forms (species) nearly 1.9 million (Nineteen lacks) species are identified all over the world. They are given scientific names. A large number of species are yet to be identified.

Now let us see what is species.

You have seen tigers, different types of dogs, pigeons, crows, cows, cats as well as different types of mango trees, ornamental plants, etc.

Among them, some animals or plants have similar features but some have different ones. Living forms or organisms having the same features are known as species.

1. The term ‘Biodiversity’ was coined by Walter G. Rosen, in 1985.
2. E. O. Wilson popularized this word. Wilson is often called the father of Biodiversity.
3. Members of a species have close similarities (same features) and more or less have the same type of gene and they reproduce within themselves only.
4. All humans are single species Homo sapiens.

Such as Rohu fish is Labeo rohita. Bata fish is Labeo bata. A common mango plant is Mangifera indica. Pea plant is Pisum sativum.

 

 

If you follow crows in your locality you may find some have a grey part around the neck region but some have not so and totally black in color. There are two different species of crow, the former is Corvus splendens (Pati kak), and the latter is (raven) Corvus corax.

 

 

Such as Tiger-Panthera tigris, Cat-Felis catus. These are the scientific name of these organisms. Now the question what is the necessity of giving a scientific name to a living organism?

Most of the animals and plants have a local name, such as Tiger, (English name) is known as ‘Bagh’ in Bengali, ‘Sher’ in Hindi, ‘hu’ in Chinese, and ‘Huli’ and ‘Puli’ in somewhere. So it creates confusion to identify the actual animal.

To solve this problem scientists consider the features of that organism (animals, plants or microorganisms), and a scientific name is given to that particular organism.

For example, the scientific name of the Tiger is Panthera tigris. This animal or Tiger is known as Panthera tigris all over the world. The scientific name of the Tiger is Panthera tigris.

 

 

 

Like this all human beings of our earth whatever their religions and race, color, and height belong to the same species-Homo sapiens. This is the scientific name of humans.

1. The scientific name has two parts-first word is known as ‘genus’ and the second word is known as ‘species’.
2. Such as in Panthera tigris
3. ‘Panthera’ is genus and ‘tigris’ is species.
4. Scientist Carolus Linnaeus introduced this naming procedure. This is known as Binomial nomenclature.

So far scientists have identified nearly 1.9 million (nineteen lacks) species. Still, a lot to be identified. But now the question arises of how these vast numbers of species to be kept properly in an organism table.

To avoid confusion, Taxonomists (Scientists that deal with this part of biological science) have classified these organisms in scientific methods. Biological classification is the way biologists use to categorize and organize all the life in earth.

 

Have you Noticed How Medicines Are Kept In Medicine Shop And Books In The Library

If you notice carefully that the medicine shopkeeper and librarian keep medicine and books respectively in a definite order. Librarians arrange books in different racks in a particular order-subjectwise, classwise, and sometimes alphabetically like A-Z.

 

 

Medicine shopkeepers also arrange different medicine in racks or boxes alphabetically from ‘A’ to ‘Z’. So they are able to deliver books or medicines as soon as the demand is placed.

 

Similarly, all living organisms are classified into groups based on very basic shared characteristics. Organisms within such groups are then further divided into small groups.

Scientists have arranged this living forms in definite order or rule on the basis of similarities and dissimilarities. The scientific arrangement of different living forms (species) on the basis of similarities is known as classification.

Classification of living forms has many steps. The major first step of classification is the kingdom. Though some Taxonomists introduce a category (rank) over the kingdom is known as the Eight levels of modern classification

Steps are-

1. Domain
2. Kingdom
3. Phylum
4. Class
5. Order
6. Family
7. Genus
8. Species

‘Domain’. They placed all organisms under three domains. Under these domains, six kingdoms are placed. More or less acceptable six kingdoms are

1. Bacteria
2. Protozoa
3. Chromista
4. Fungi
5. Plantae
6. Animalia.

In some other type of popular classification (R. H. Whittaker, 1969) organisms are placed under five kingdoms.

They are

1. Monera
2. Protista
3. Fungi
4. Plantae and
5. Animalia.

In some recent classification, organisms are placed under three domains, the first rank of classification.

3 domains are

1. Archaea
2. Bacteria.
3. Eukarya(by Carl Woese)

 

Kingdoms

1. Monera-Prokaryotes (have no true or typical nucleus)
2. Protista-Unicellular eukaryotes (which have typical nucleus)
3. Fungi-Including all fungi.
4. Plantae-All photosynthetic plants.
5. Animalia-All animals.

 

 

Viruses are not placed in any type of classification because they are not truly living organisms. They are treated in between living and non-living forms.

They only grow (reproduce) when they are enter into a living organism’s body. But outside the living body virus is non-living (no sign of a living organism).

 

Chapter 10 Biodiversity And Its Classification History Of Classification

From the dawn of civilization, many attempts have been made to classify living organisms. The biological classification of plants and animals was first introduced by Aristotle Linnaeus and later classified all living organisms into two kingdoms (Two kingdom classification).

1. Plantae (Plants) and
2. Animalia (animals) that include all plants and animals respectively.

Classification of organisms into plants and animals was easy to understand, but a large number of organisms did not fall into either category. After many attempts, R. H. Whittaker (1969) proposed a five kingdom classification, which is very popular.

Later Cavalier-Smith’s and others classified organisms into six kingdom.

 

Kingdom Bacteria

They are single-celled prokaryotic microscopic organisms. They have the simple primitive type of nucleus. In five kingdom classific- action Bacteria are placed within the kingdom Monera.

Some members of this kingdom are harmful to humans as well as other plants and animals. Bacteria are responsible for many human diseases such as tuberculosis (TB), Typhoid, Cholera, Diarrhea, etc. But some are beneficial too.

Example-Salmonella typhi, Vibrio cholera, Rhizobium, etc.

 

 

Kingdom Protozoa

Protozoans are single-celled eukaryotes (having typical nuclei) either free-living or parasitic. Which feed on organic matter such as other microorganisms or organic tissues and debris.

Examples-Amoeba, Entamoeba (germ of amebiosis), Plasmodium (germ of Malaria), etc.

Thomas Cavalier-Smith et. al 1981, has ranked protozoa as a kingdom. In the five kingdom classification, they are placed within the kingdom Protista.

 

 

Kingdom Chromista

This is an eukaryotic kingdom. They include the group of colored algae as well as various colorless forms that are closely related to plants. Details of this kingdom are not yet known.

Example-Macrocytis kelp, Diano-flagellates, Foraminifera, some marine algae etc.

 

 

Chloroplast contains chlorophylls ‘a’ and ‘c’. Photosynthetic chemists often carry various pigments in addition to chlorophyll which are not found in plants. Kingdom chloroma is distinguished from plants because of the more complex chloroplast.

 

Kingdom Fungi

Mushrooms, Yeast, Mucor, and other pigment less forms which are unable to produce their own food. They absorb nutrition from (heterotrophs) other organism’s body.

Some fungi are harmful some are beneficial. Some mushrooms are edible. Some are not. Some fungi help in alcohol and bread formation.

Example-Toadstools, Penicillium, Yeast, Mucor, etc.

 

 

Kingdom Plantae

All plants belong to this kingdom. Chlorophyll present in their body. They can produce their own food with the help of chlorophyll.

Example-All green plants.

 

 

Kingdom Animalia

All animals from sponges to man. are placed within this kingdom. They have sense organs. Animals are unable to produce their own food.

Example-Sponge to humans, all animals.

 

 

 

Five Kingdom Classification

 

 

All of you may have seen earthworms, ants, cockroaches, snails, jellyfish, prawns, crabs, etc. in nature. Have you seen any backbone or internal spine or hard internal structure of these animals?

On the other hand, you have seen fish, toads, snakes, tortoises, birds, cows, goats, etc. The animal of the first group have no internal hard structure, some may have external hard structures (shells of snails) or covering (cockroaches, ants,s, etc).

But the animals of the second group possess a hard internal structure. The first group of animals who have no hard internal supporting structure are known as invertebrate animals and the animals of the last group who have hard internal bony structures are known as vertebrate animals.

Make a list of vertebrate and invertebrate animals in your locality.

 

Complete The Table

Locality	Date/year	Invertebrates	Vertebrates
		1.	1.
		2.	2.
		3.	3.
		4.	4.

 

Now all of you have understood that vertebrates have a hard internal bony structure which is known as the vertebral column. Whereas invertebrates have no vertebral column.

The animals of the animal kingdom are placed under some phylum (rank below the kingdom) on the basis of the simple to complex nature of the body construction of the animals.

If you examine the legs and antennae of prawns, crabs, cockroaches you will see these organs are made up of many small parts. If you pull two ends of these organs parts will be separated easily.

 

 

Therefore, the appendages of these animals are joined. So these animals are placed under phylum Arthopoda (Artho = jointed, poda = leg). Body of these animals are covered with a hard covering that contains a specialized nitrogenous substance known as a cuticle.

If you carefully observe their eyes you may see these are made up of many small eyes. These eyes are called compound eyes. Insects like fly, mosquitoes, moths, and butterflies are also included in this group (Arthopoda).

Many of you may have seen snails, and oysters and some of you may also have seen octopuses, and squids (in sea or aquarium). Octopus, sepia, and Loligo have no outer hard covering. Sepia and Loligo have calcareous internal hard plate-like structures.

 

 

All these soft-bodied, unsegmented animals are placed under the phylum (group) Mollusca (phylum-Mollusca). Snails, and oysters have hard outer shells (coverings) made of calcarious materials.

Mollusks have a soft ventral muscular leg for their movement (in some forms legs are modified into other forms).

 

Insect

Insects are arthopodes. This is the largest animal group (class) among the animal kingdom. They are found in land, air, and water. The most successful group of animals appeared in the earth nearly 40 crores years ago.

Insects have three pairs of legs and usually with two pairs of wings. Their body is divided into three parts-Head, thorax, and abdomen.

Example:

Dragonflies, grasshoppers, ants, beetles, wasps, aphids, butterflies, mosquitoes, flies, cockroaches, etc.

A large number of animals inhabit the earth today. These animals vary in shape and size, habit and habitat, colors, weight as well as in their distribution.

Kingdom Animalia is broadly divided into two major groups-Non-chordates (groups of lower and simple animals) and chordates (groups of higher and complex animals).

The majority of chordates have hard internal bony structures, and vertebral columns. These animals are placed under the rank (group) vertebrate.

The chordates who have no vertebral column are called lower chordates or invertebrate-chordates (e.g. Balanoglossus, Amphioxus, etc.) Lets see some important animal groups (phylum) and their salient features habitats and common examples.

 

 

1. Invertebrates have no notochord. In all chordates, the notochord is present either throughout life or early (developmental) stages of development.
2. In vertebrates, the notochord is replaced by the bony vertebral column.

All vertebrates possess notochord in their developmental stages but are replaced later by the bony vertebral column. But in a few chordate members notochord remain as notochord throughout life or for a certain period but no replacement occurs.

These chordates are known as lower chordates or invertebrate chordates. Examples are Balanoglosus, Amphioxus, Acidia, etc. Vertebrates are divided into six classes. You can separate them externally observing their features. Let’s see some important features of them.

 

Chapter 10 Biodiversity And Its Classification Vertebrates

 

Arrange the following animals in their respective groups (phylum/class) and write/remark why you placed them to that group (Phylum/class).

 

Chapter 10 Biodiversity And Its Classification Animals

Human, shark, toad, leech, earthworm, frog, monitor-lizard, crocodile, cockroach, cobra, whale, tortoise, vulture, owl, pea-cock, fox, lion, rat, cat, koi fish, ray fish, snail, octopus, corals, tapeworm, roundworm, mosquito, fly, spider, starfish, sea-urchin, salamander, orangutang.

 

Animals	Group Phylum/class	Remarks (Why they are kept in this group)
Example: 1. Human	Phylum—Chordata	1. Body covered with hairs
	Class—Mammalia	2. Presence of mammary glands
		3.
2.
3.
4. Leech	Phylum—Annelida (invertebrate)	1. Soft segmented body sucker present
5.
6.
7.
8.
9.
10.

 

Fill in table

Features of vertebrate animals	Types of vertebrate (class)
1. Live early stages of life (larval stages) in water, adult in the land.	1
2. Body covered by feathers.	2
3. Have a vertebral column (bony) and gill is the respiratory organ.	3
4. Body is covered by hair.	4
5. Give birth young one who doesn’t lay eggs.	5
6. Body covers with dry scales.	6
7.    Presence of fin with fin-rays.	7
8.    Vertebral column made of cartilage.	8
9.    4 legs with claws.	9

 

Complete the table

Features	Group	Example
Example: 1. Presence of tube-feet	1. Echinodermata (Phylum)	1. Starfish
2. Flat body head with hooks and suckers.	2.	2.
3.    Round body tapering at both ends present in the human intestine.
4.    Soft segmented body
5.    Body with jointed appendages
6.    Presence of ventral muscular foot.	6. Mollusca	6. Snail
7.    Skin with calcareous spines
8.    Soft, cylindrical body with single aperture
9.    Body covered by hard calcareous shell
10.    Simple body with many pores, mainly marine
11.    Presence of compound eyes.
12.    Invertebrate body with internal calcareous skeleton

 

Complete the table

From the following examples (animals) pick the animals of the same group and put them in a Box

 

Chapter 10 Biodiversity And Its Classification Animals

1. Dog
2. Koi fish
3. Shark
4. Corals
5. Dolphin
6. Penguin
7. Poller Bear
8. Magur
9. Sponges
10. Hydra
11. Octopus
12. Tortoise
13. Crocodile
14. Toad
15. Butterfly
16. Whale
17. Cobra snake
18. Owl
19. Kite
20. Fox
21. Sparrow
22.  Crow
23. Rat
24. Ray-fish
25. Salamander
26. Lizard
27. Tapeworm
28. Starfish
29. Filaria worm
30. Leech
31.  Sea-urchin
32. Earthworm
33. Spider
34. Vulture
35. Sea lily
36. Jellyfish
37. Scorpion
38. Pigeon
39. Roundworm
40. Deer
41. Rhinoceros
42. Kangaroo
43. Oyster
44. Lion
45.  Sepia
46. Man
47. Monkey
48. Whale
49. Dolphin

 

 

Complete The Table

From the above examples select invertebrate and vertebrate animals and put them in their respective box.

 

Invertebrates		Vertebrates
Example	Phylum/class	Example	Phylum/class
Sponges (9)		Dog 1
Put the animals (from the figure) to their respective phylum/class)

 

Kingdom Plantae

All of you have seen plants of different types, some are long, some are medium and some are small to very small. Some plants can’t stand erect some are not, they creep along the soil or climb up with the help of support.

Plant kingdom-Plantae :

Most plants are green. They possess green pigments and chlorophyll in their body. Plant makes its own food by photosynthesis (a process by which plant makes their food with the help of sunlight, chlorophyll, water, and carbon dioxide).

There are various plants in nature. Some of them are long-lived and some are short-lived. There are usually three types of plants besides very small plants like algae.

 

Chapter 10 Biodiversity And Its Classification Phylum Class Plants

 

Try to collect different types of plants and try to understand the difference between them (Take help from your teacher):

Points/Questions	Herbs	Shrubs	Trees
1. Have any woody stem	1. No	1. Yes	1. Yes
2. Have any trunk	2. No	2. No	2. Yes
3. Height of the plant	3. ……..	3. ……..	3. ……..
4. Branches	4. ……….	4. ……….	4. ……….
5. Life span	5. ……….	5. ……….	5. ……….
6.
7.
8.

 

Complete The Table

Pick up the plant from the list (below) and place it to its proper place.

1. Potato
2. Pumkin
3. Bitter melon
4. Water melon
5. Paddy
6. Banana
7. Mango
8. Hibiscus
9. Palm
10. Rose
11. Ginger
12. Maize
13. Coconut
14. Amlaki
15. Mint
16. Bael
17. Neem
18. Garlic
19. Sundari
20. Shal
21. Water hyacinth
22. Grass.

 

Herbs	Shrubs	Trees
1.	1.	1.
2.	2.	2.

 

In the summer or rainy season when we swim in ponds or rivers, we often meet some water weeds. Some are floating, some are underwater like ribbons. Many of you have experienced how to walk on a slippery surface in the bathroom, pond side ‘ghat’ etc.

If you carefully observe the surface you may find some greenish or brownish surfaces. These are the algae. Algae are a type of plant. They have no roots, stems or leaves.

They do not have flowers (non-flowering plants) but they can make their own food in their bodies because they have chlorophyll. Algae often float freely in lakes, ponds, and oceans.

 

 

Sometimes they fix themselves with some objects. You can see some ribbon-like or thread-like algae in the pond. These long ribbon-like slippery algae are known as water silk (Spirogyra).

 

 

Most of the algae are simple thallus-like and without any root, stem or leaves. They are aquatic or grow in a moist places. Algae are placed under the group Thallophyta.

 

 

Algae

(singular. Alga) Algae are mainly aquatic, non-flowering, photosynthetic (can produce their own food) having chlorophyll and other pigments but lack of true root, stem, and leaves.

 

Thallophyta

A group of plants or plant-like organisms, whose body is thallus like have no root, stem or leaves. Algae and some fungi are examples of Thallophyta.

During monsoon or autumn, many of you have seen a thick green mat that grows on the surface seen mostly in the lawns, moist old boundary walls of your school or home, or in rocky surfaces in forests, tree trunks, etc.

These are moss-like plants (See picture). These moss-like plants are placed under the group Bryophyta. They include liverworts, hornworts, and mosses.

Bryophytes live in humid (moist) and shaded places. Bryophytes are non-flowering plants. The main body of bryophytes is more or less thallus-like (Ricca) plants. They do not have true roots, stems, and leaves.

They generally have something similar to a root, which is known as rhizoids. Which absorbs water from the substratum (the place to which the plant is attached).

But some bryophytes have leafy (not true leaf) erect structures which bear capsule-like spore-bearing sacs when the capsule dies off, spores (powder-like small grains) come out and fall on the moist surface.

New plants grow from these spores. example Moss, Liverwort, Pogonatum, etc. Bryophytes are called the amphibians of the plant kingdom. Though they grow in terrestrial environments (land area) they are dependent on water for the reproduction process.

 

 

Many of you have seen Fern as an ornamental plant in some gardens or roadside. You may have eaten Shushnishak, Dhekishak, etc., and attending a height of up to six Tree ferns have full trunks meters.

All these plants are placed under the group Fern-like plant or Pteridophyta. They are generally terrestrial in habitat occurring in moist shady places over the soil. Sometimes they also grow on other trees.

Pteridophytes have leaves, roots, and sometimes true stems. Stems are usually covered by brown scaly leaves (ramenta). Pteridophytes are non-flowering plants.

They have feather-like leaves (compound). Young leaves of fern is coiled at the tip (look like dog tail). If you look underside of mature fern leaf you will fine brown or blackish dot-like or sac like hard structures.

It bears spores. Now plants grow from these spores through some stages. intermediate position between Pteridophytes occupies the intermediate position between Bryophytes and Phanerogams (flowering plants).

 

 

Fern and moss have two stages in their life cycle sporophytes stage (bear spore) and gametophytes (bear games) From the above discussion you have learned three types of plant groups under the non-flowering group (Cryptogam, seedless plants).

They are Thallophyta (alga), Bryophyta (moss-like plant), and Pteridophyta (fern-like plants). Besides these, there is a large group of seed-bearing plants (mainly flowering plants or phanérogamae or Spermatophyta) around us.

The main plant body has true root, stem, and leaves. If you compare a Pine (pinus) tree with a Mango tree you can see the difference between their leaves, their fruits, and seeds.

Seeds produced by Pine (pinus) are naked and are not enclosed within fruits, but the seed of the Mango plant is enclosed within the fruit. You may also find differences in their leaves. The leaves of Pinus is needle like whereas the leaves of Mango is flat.

Pine (gymnosperms) have no flowers or fruits and have ‘naked’ seeds on the lower surface of leaves. The seeds are arranged together in a circle (forming a cone). Whereas Mango’ plant is a flowering plant and has a seed that is enclosed within the fruit.

 

 

The former plant (Pinus) group is known as Gymnosperm and the later plant group (Mango) is known as Angiosperm.

 

 

Both Gymnosperms and Angiosperms are included under Spermatophyta or Phanerogamae (seed-bearing plants)

 

Gymnosperm

These are the seed-bearing plant group having no flowers and fruit seeds are naked (uncovered).

Example Cycys, Pinus, Casarina.

Angiosperm

These are the seed-bearing flowering plant group where seeds are enclosed within the fruits.

Example Mango, Neem, Apple, etc.

Angiosperms are seed plants, they have flowers and seeds and are produced inside fruits. They occur in all types of habitats dry, wet, and temperate areas.

Difference between Gymnosperm and Angiosperm

Question	Gymnosperm	Angisosperm
1. have any flowers?	1.	1.
2. Have any fruit?	2.	2.
3. Location of seeds.	3.	3.
4. Example	4.	4.

 

Make a list of Gymnosperm plants and Angiosperm plants

Gymnosperm plant	Angiosperm plant
1.	1.
2.	2.
3.	3.

 

Take some seeds of Pea (motor) or Bengal Gram (Chola) and Paddy (Dhan). Then remove their outer cover (dry cover), and give little pressure to both type of seed [Pea seed and Paddy (rice)] you may see.

Pea seed has two semicircular halves but Paddy (rice) has one long portion with little whitish mark at the end. Then two halves of pea seed and a single part of paddy is known as cotyledons.

Pea (and gram) is dicotyledon seed (having two cotyledons) and paddy (rice) is a monocotyledon seed (having one cotyledon). Dicotyledon seed-bearing plants are known as dicotyledons and monocotyledon seed-bearing plants are known as Monocotyledons.

 

 

Monocotyledons bear seeds that have a single cotyledon or seed leaf.

Example: Rice, Grass, Sugarcane, Wheat, Bamboos, Maize, etc.

Dicotyledons bear seeds that have two cotyledons or seed leaves.

Example: Grams, Peas, Beans, Sunflower, rose etc.

Place the plants in the box below. Ginger, Banana, Wheat, Rose, Ground nut, Potato, Plam, Maize, Tomato, Pea, Garlic, Onion, Hibiscus, Eucalyptus

Monocotyledons (monocots)	Dicotyledons (dicots)
1.	1.
2.	2.
3.	3.
4.	4.

 

1. Take one leaf of the banana plant and one mango leaf. Look carefully.
2. Do you notice any difference of the colour of the two surfaces?
3. What are the arrangement of veins in two leaves? Is it the same?

 

Question	Banana leaf	Mango leaf
1. How many veins in the middle?	Single midvein	Single midvein
2. Types of arrangement of veins in the leaf blade?	Side branches run paralleled from mid-vein without meeting each other.	Side branches coming from the mid vein meet with each other and form a network of veins.
3.    Meeting of side branches of veins occur	No	Yes
4.    Type of venation	Parallel venation	Reticulate venation
	The arrangement of veins in a leaf blade is called venation.

 

Now you have an idea about venation. Monocots have parallel venation while dicots have reticulate venation. Try to collect different leaves and examine their venation.

 

Complete The Table

Plant leaf	Type of venation Parallel / Reticulate	Type of plant Monocots / dicots
1.
2.
3.
4.

 

 

Try To Summarise your Understanding

1. Mango is a (Angiosperm / Gymnosperm) plant.
2. The venation of sugarcane leaf is (parallel/reticulate).
3. Banana is a _______________ (Dicotyledonous / monocotyledonous) plant.
4. You are given a leaf that has the reticulate type of venation; the plant is _______________ (Monocotyledonous / Dicotyledonous).
5. Pinus bears fruit (yes/no).
6. Plants have no root, stem, and leaf are ________________ (algae/bryophytes/ pteridophytes).
7. Rizoids present in ________________  (algae / bryophytes / pteridophytes).
8. Body divisible into root, stem, and leaves but has no flower the plant is ________________ (Bryophytes /Pteridophyts/Gymnosperms).
9. Water-silk, Spirogyra is a _____________ (algae / Moss/Fern).
10. ‘Sorus’ is found in (Spirogyra / Moss / Fern).
11. A parallel type of venation is usually found in (Monocotyledonous / Dicotyledonous/plants).
12. Pea seeds have (one / two) cotyledons.
13.  The plant usually found in seashore Casurina is (a seed-bearing / seedless plant).
14.  New leaves of fern are (straight/curly).
15.  (Algae/Brophytes / Pteridophytes) are amphibious plants.
16.  Naked seed-bearing plants are called ___________ (Gymnosperms/Angiosperms).

Besides two major kingdoms Plantae (plant kingdom) and Animalia (Animal kingdom), there are some other kingdoms. Though we have already learned a little bit of these kingdoms. Under the popular 5-kingdom classification Bacteria are placed under Monera.

Members of these kingdoms are simple, single-called (prokaryotic) organisms (though in some recent classifications, Bacterias are placed under the kingdom Bacteria).

Bacteria is present in most of places of the earth. They are not visible normally (not visible to our naked eyes) they are visible only under Microscope (the instrument through which we can see very small organisms/particles).

You may have seen curd formation in your home. Usually, a little amount of old curd are added to the milk and after a few hours, this milk turns into curd. Small Bacteria (Lactobacillus) present in curd is responsible for the formation of curd.

Some Bacteria are beneficial some are harmful. We obtained antibiotic drugs from some bacteria. Some bacteria make the soil fertile and help in crop production.

Again you must have heard about many bacterial diseases like Cholera, Typhoid, Diarrhoea, Tuberculosis (TB), Plague, Leprosy, etc. Many bacterial species cause food processing also.

All organisms are made of the smallest unit. This structural and functional unit of life is known as a cell. These are the building block of living organisms as the bricks of a brick wall.

Bodies of organisms like plants, animals, bacteria, etc are made up of cells. Normally each cell contains a round-shaped structure known as a nucleus.

Bacteria (members of the Monera kingdom under 5 kingdom classification) have single cells and have no typical nuclei in their bodies. All of you have heard the name of the disease Malaria, Dysentery.

1. Malaria is caused by the protozoa- Plasmodium. Dysentery by-Entamoeba
2. The main symptoms of malaria are pe- periodic attacks of shivering followed by high fever, headache, and muscular pain.
3. Dysentery-Gastrointestinal trouble.

These diseases are caused by a type of small unicellular (single-celled) organism, known as Protozoa. Protozoa is placed under the kingdom Protista (in the five-kingdom classification, though in some recent classifications, protozoa is treated as a separate kingdom).

Members of the kingdom Protista are unicellular (single-celled) with typical nuclei (eukaryotic). Euglena, Paramecium, etc. tiny (small) organisms are placed under the kingdom Protista other examples of Protista are Amoeba, Diatom, etc.

All of you have seen toadstools around your house usually in moist places. Many of you have eaten mushrooms as food. Though some mushrooms are poisonous and not suitable for eating.

Many of you have seen blackish-green mould in old bread and rotten lemon. All these are fungi (singular-fungus). Sometimes many of us suffer from different types of fungal diseases. Fungi are unable to produce their own food.

They have no chlorophyll. Fungi are heterotrophic. They collect food from dead, decaying organic substances. Some fungi are parasitic in nature. All fungi are placed under the kingdom of Fungi.

Lichens: Fungus live in symbiotic association (mutual inter-relationship) with algae.

Collect some samples from a pond/playground and surrounding area and placed them under the following kingdom:

If possible use a hand lense or microscope (take help from your teacher)

Sample	Plantae	Animalia	Fungi	Protista	Monera
1.
2.
3.
4.
5.

 

Place these collected animals into the following box.

Sample	Invertebrates	Vertebrates
1.
2.
3.
4.
5.

 

In this way select any environment (take help from your teacher) and make the following list

Environment

Plant Group	Plants	Sample
Thallophytes
Bryophytes
Pteridophytes
Gymnosperms
Angiosperms

 

Environment

Plant	Plant Group	Animal	Animal group
1. Aquarium
2. Forest
3. Sea
4. Desert
5. Mountain area
6. Grassland
7. Pond

 

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 9 Common Machines Introduction To Machines

Machines:

We do different types of work in our daily life in homes, schools, colleges, offices, etc. You know that to do work, you need to apply some force. Some work needs less force and some work needs a large force.

When you push down the handle of a tubewell, water comes out from its mouth; you use a pair of scissors to cut a piece of paper or cloth; you drive a nail into a wooden block by hammering it with a hammer; to open the lid of a soft drink bottle you use a bottle- opener.

To dug soil you use a shovel; you use a pen or pencil for writing or drawing on paper; labourers use an inclined wooden plank to load heavy barrels upon a truck; a pulley is used to lift a load up, etc.

The underlined things are nothing but machines. Note that in each of these things you apply force on one part and the work is done at another part.

Read and Learn More WBBSE Notes For Class 6 General Science and Environment

Chapter 9 Common Machines Simple Machines

A simple machine is a mechanical device which is used to multiply the amount of applied force or to change the direction of force or both.

Simple machines make a job easier to do.

Types of simple machines

These are six types of simple machines:

1. Lever.
2. Inclined plane.
3. Screw.
4. Pulley.
5. Wheel and axle.
6. Wedge.

 

Chapter 9 Common Machines Complex Machines

A complex machine is made up from two or more simple machines. With the advent of civilization, various types of complex machines have been devised so far.

For example:

Sewing machines, bicycles, buses, taxis, tractors, printing machines, computers, etc.

Let us look at the following chart :

 

Purpose of use	Simple machine	Complex machine
Sewing	Needle	Sewing machine
Writing	Pen or Pencil	Printing machine or Type Machine
Cutting paper	Blade, Knife, Scissors	Electric cutting machine
Cutting wood	Saw	Electric-cutter
Cutting soil	Spade	Tractor
Making holes in walls or in wood	Chisel	Drilling machine

 

General terms related with simple machines :

1. The force applied on a machine is called the effort (E).
2. The force against which a machine works is called the load (L) or resistance.
3. A fixed point situated on the body of a machine about which the machine turns while doing mechanical work is called the fulcrum (F).
4. The shortest distance of the effort from the fulcrum is called the effort arm.
5. The shortest distance of the load from the fulcrum is called the load arm.

 

Chapter 9 Common Machines Lever

A lever is the simplest machine that we are familiar with. It is a rigid rod which is capable of turning about a fixed point (or axis) called a fulcrum.

Types of levers :

Based upon the position of the fulcrum, load and the point of application of the effort, levers are classified into three groups:

Class, I lever: The fulcrum is in between the effort and the load.

 

 

Class II lever: The load is in between the fulcrum and the effort.

 

 

Class III lever: The effort is in between the fulcrum and the load.

 

 

Examples of class I lever :

A see-saw, a crowbar, a pair of scissors, a wire cutter, the handle of a tubewell, a spade, a beam balance, etc.

 

 

Examples of class II lever :

A nutcracker, a bottle opener, a wheelbarrow, a lemon squeezer, etc.

 

 

Examples of class III lever :

Forceps, a pair of tongs, a fishing rod, a broom, a human forearm, a bread-cutting knife, etc.

 

 

Chapter 9 Common Machines Concept Of Inclined Plane

An inclined plane is a slanted surface which is used to lift heavy loads by applying relatively little effort. See the shown alongside. It is easier to lift a load along an inclined plane than to lift it vertically.

 

 

It has many applications in real life. A staircase, a ramp, a leaning ladder, a hilly road, a bridge or a flyover, etc. are examples of an inclined plane.

 

Chapter 9 Common Machines Screw

A screw generally looks like a nail having spiral grooves on the surface of a metal rod. The spiral ridges so-formed are called threads of the screw. These spiral ridges actually make an inclined plane.

 

 

A screw is a combination of an inclined plane and a cylinder. It is easier to drive a screw into a wooden plank with a screwdriver than by hammering. That’s why it takes less force to drive a screw into wood than to drive a nail.

 

Chapter 9 Common Machines Pulley

A pulley is a simple machine to lift a load by applying an effort in a convenient and suitable direction. You have seen that a bucket of water from a well can easily be raised with a pulley by applying the effort in the downward direction.

A picture of it is shown in. It is nothing but a grooved wheel through which a rope runs.

 

 

Note: A pulley is used for lifting a load up.

 

Chapter 9 Common Machines Wheel And Axle

Take a circular wheel having a hole at its centre. Through the centre, attach a pen/pencil/anything like this firmly to it. This forms a wheel and axle arrangement.

Thus, the arrangement consists of a big cylinder joined with a small cylinder, The big cylinder is called the wheel and the small cylinder is called the axle.

 

 

If you rotate the wheel, you see the axle (pen/pencil) also rotate. Ropes are wound around the wheel and the axle in opposite directions.

In general, the rope round over the axle is tied to the load, while at the other end of the rope round over the wheel the effort is applied. It is clear that the wheel and axle arrangement takes less effort to move something.

 

 

There are many applications of this arrangement. In a screwdriver, the thick handle works as a wheel, while the metal rod attached to it functions as an axle. Similarly, a water tap, a door nob, a steering wheel, wheels of a car, etc. are other examples.

 

 

Chapter 9 Common Machines Maintenance Of Machines

A machine needs to be properly maintained for its trouble-free, efficient and longer use.

We can take the following ways:

1. Most of the parts of a machine are made of iron. To protect these parts from rusting they should be painted.
2. Moving parts of a machine suffer wear and tear due to friction. Such parts should be lubricated with good-quality of lubricating oil to reduce friction.
3. When a machine is not in use, it should be covered to protect it from dirt and dust.
4. A machine should be cleaned at regular intervals.
   Following these ways, we can increase the life of a machine.

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 8 The Human Body Heart

Have you observed where Doctor places his stethoscope on the chest of a patient to hear the heart sound?

If you put your hand on the chest of your friend who has just completed a running events in school sports. What you will feel if you place your ear in his chest, you will hear ‘lub-doub’ sounds of the heart (heart sounds) and it comes more or less from the left side of the chest.

 

This active organ is one of the most vital organs of our body is called ‘the heart’. It is the main organ of blood circulation of our body. Make a hand-made stethoscope or you may get it from your school laboratory (Biology Department).

Try to understand the location of the heart in the human body and complete the table. If necessary take help from your teacher.

Read and Learn More WBBSE Notes For Class 6 General Science and Environment

Tick in the proper place :

 

 

Chapter 8 The Human Body Location Of Heart

Location Of Heart:

The heart is well covered in our body. It is protected by rib cage by the sternum (the middle place where ribs meet together) from the side and front and back by the vertebral column (made-up of hard bony vertebrae).

 

 

The heart is located in a thoracic cage (cavity) in between the sternum and vertebral column. The largest part of the heart is situated in the left half of the thoracic cavity.

What is the heart?

The heart is the pumping mechanism of the body. It is a hollow, muscular cone-shaped organ. It is the main organ of blood circulation. The weight of the heart is about 300 grams.

It may compare with a two-storied house with two rooms in the ground floor and two in the first floor. The first floor or the upper part of the heart (apex or anterior part) has two chambers (rooms) and the ground floor or lower part (base or posterior part) also has two chambers (rooms).

Therefore, the human heart has four (4) chambers, two in the upper part and two in the lower. The upper chambers are called the atrium or auricle and the lower chambers are called the ventricles. The walls of the ventricles are thick than the auricles.

The blood continuously moves through the organs. This movement is called blood circulation.

 

Chapter 8 The Human Body Blood

The blood is red fluid salty in taste, and alkaline in reaction.

The heart is enveloped (covered by) in a membranous sac called the pericardium. (the outer membrane of the heart) The blood flows through a narrow elastic tube-like structure, these are called blood vessels.

Blood vessels are of three types-

1. Arteries
2. Veins and
3. Capillaries.

Arteries:

These are blood vessels through which blood flows from the heart to organs.

Veins:

These are the blood vessels through which blood flows from organs to the heart.

Capillaries:

Are minute blood vessels. They are actually found between small arteries and veins.

 

 

 

 

1. Blood purifies in the lungs.
2. Impure blood reaches the lung through the pulmonary artery. After purification pure blood
3. Again come to the heart (left auricle) through the pulmonary vein.
4. Blood flows from right ventricle to the lungs through the pulmonary artery.

Usually, the artery carries pure blood (more oxygenated blood) and the vein carries impure blood (less oxygenated blood). But the pulmonary artery carries impure blood and the pulmonary veins carry pure blood.

 

 

The left ventricle of the human heart is the largest chamber and it is the most powerful chamber too. This is to exert more pressure which helps to send pure blood to the aorta.

All these events which you have just read not happen one by one. Blood enters simultaneously to the right and left auricles and similarly, blood passes to the right and left ventricle simultaneously from the right auricle and left auricle respectively.

Similarly, blood flows out from the right and left ventricles to the lungs and body respectively simultaneously. The work of the heart consists of rhythmic contractions (reduce size) and relaxations (expands) of auricles and ventricles.

The contraction of the heart is called systole and the relaxation is called diastole. The contractions and relaxations of the different parts of the heart take place in a definite order.

1. In the simultaneous contraction of both auricles, blood passes from the auricle to the ventricle.
2. Simultaneous contraction of both ventricles → blood flows out of the heart.
3. During the relaxation of auricles and ventricles → blood enters into these chambers.

The work of the heart gives rise to sounds known as heart sounds. They may be heard by putting an ear directly to the chest or by means of a special instrument, stethoscope or phonendoscope.

 

Heartbeat

Heart always in move it. expands and contracts. Each expansion (diastole) and contraction (systole) consists the heartbeat.

Heartbeat:

Pulsation of the heart including one complete systole and diastole.

Pulse are the result of the rhythmic contractions of the heart.

 

Pulse And Pulse Rate

Pulse rate is the number of times a person’s heart beats per minute.

The normal pulse rate may vary from 60 to 80 beats per minute in rest. In children, the pulse rate is faster. The average pulse rate of an adult is 72 per minute (72 beats/minute).

Try to check your pulse rate and your friends or family members’ and make a table. The pulse rate depends on various conditions. A person’s pulse is often felt through the arteries (radial artery) on the wrist.

You can measure the pulse rate by pressing the radial artery (superficial artery underlying bones) with two fingers (fore and middle) by your opposite hand.

Besides the wrist, you can take your pulse inside the elbow, at the side of your neck (cardiac pulse) or on the top of your foot. You can also take your pulse at your groin behind your knee and on the temple.

Complete the Worksheet

Examine the pulse of different persons:

 

Name	sex	age	Pulsebeats per minute		Remark on condition resting/working
			Pluse beat	per minute
1.
2.
3.

 

Pulse checking points of the body	Pluse per minute	Remarks
1. Wrist
2. Neck
3.
4.
5.

 

Chapter 8 The Human Body Measure your Pulse

Tracking your pulse is easy. You can do it at your wrist or neck. Little press with (lay) your index (2nd) and middle finger (3rd) on the inside of your wrist below the base of your thumb (between the bone and the tendon on the radial artery).

 

 

The spot over the radial artery. When you feel the beat, count the beat for 15 seconds (with a watch or stopwatch). Multiply the count by four to calculate the number of beats per minute.

Calculation :

Suppose you count the number of beats in 15 seconds is 18 then the pulse rate per minute is (pulse rate)

18 x 4 = 72 beats per minute.

Pulse rate depends on the physical condition of the person concerned. Take the pulse rate of your friends in different conditions and compare it.

 

Name	Age	Sex	Physical condition	Remarks
1.			1. Sitting in the School bench
			2. After working such as stair Brealey
			3. After running
			4.  Lying in bed.
			5.  After a sports event

 

Don’t do this if your friend or the person is not fit or ill

 

Chapter 8 The Human Body Problem Of Heart

You will find some people who are suffering from heart disease. You may head some students who has a hole in their heart. Let’s see some of the common heart problems.

Sometimes there are defects (problems) in the walls of the heart like holes in the heart or to the valves (valves may be too narrow or partially or completely blocked) which means either blue (venous) blood or red blood (oxygenated) gets mixed up or the heart may not pump very well.

These show some symptoms like-

1. Blue baby-blue skin and blue around the lip.
2. Difficulty in feeding.
3. Shortness of breath.

These symptoms usually due to a reduced supply of oxygen to the body. If you find someone around you with this problem you must convey the message to your parent, teacher, and doctor you know.

Sometimes you may hear pacemaker has been fitted to some person’s heart. It is an artificial treatment of irregular heartbeat. Sometimes blood flow in heart muscles (cardiac muscles) are hampered.

In some cases, heart muscles not work properly, and the person feels chest pain, breathing problems, and sweating profusely. This a serious problem of the heart. In this case, the patient must be hospitalized.

There are many different types of heart diseases. Some are congenital (people born with heart problems) but the majority of heart diseases develop over the course of time and affect people later in life.

Some Heart diseases are

1. Coronary artery disease
2. Silent ischemia
3. Angina
4. Arrhythmia

Some common symptoms of different types of heart disease:

1. Discomfort.
2. Chest pain that radiates to the shoulders, neck or arms.
3. Shortness of breath.
4. Profuse sweating.
5. Nausea and vomiting.
6. Rapid heartbeat.
7. Severe weakness.

You should advise a person who is facing a few of these symptoms should go to a doctor or health center for a check-up.

 

Chapter 8 The Human Body Blood Pressure

It is the pressure of circulating blood on the walls of blood vessels. Normal human blood pressure is 120/80 mm Hg. (systolic pressure 120 mm /Hg, diastolic pressure 80 mm/Hg)

Blood pressure is measured by a special instrument known as Sphygmomanometer.

 

 

All of you have seen blood. Many of you may have tested it. You have already learned that blood is a red-coloured fluid salty in taste and alkaline in nature. Blood is one of the most important fluids of the body.

It is a connective tissue that delivers necessary substances such as nutrients (food substances) and oxygen to the cells and brings back carbon dioxide from cells.

It transports metabolic waste (waste products) from the cells and transfers these into the liver and kidney.

 

Chapter 8 The Human Body Composition Of The Blood

The major constituent of blood is water, the watery part of blood is known as plasma. Plasma is viscous, slightly yellowish fluid, 55% of blood is plasma. Plasma consists of 90- 92% water and 8-10% organic and inorganic substances.

The greater part of organic substances are protein-like albumins, globulin, and fibrinogen. It also contains glucose, fat, and waste products like urea, and uric acid. Plasma also contains different mineral salts, vitamins, etc.

Other components of blood are different types of blood cells (45%). As the plasma is a watery substance it helps the blood to move through the thick and thin channels (blood vessels) from one part to another.

Most of the carbon dioxide is carried by the blood plasma.

 

 

1. Red blood cells or Red blood corpuscles (RBC) :

They are flattened disc-like structures, transport oxygen (O₂) to different parts of the body. RBCs are not visible to the naked eye (microscopic).

They are red in color due to the presence of the pigment hemoglobin, it helps to carry O₂ and CO₂. blood plasma. Most of the O₂ carried by Most of the CO₂ is carried by the hemoglobin of RBC.

2. White blood cells or white blood corpuscles (WBC) :

WBC are white and have a nucleus. They are also not visible to the naked eye. They are also very important. They perform a protective function. WBC fight with the microbes that attack our body and in most cases they engulf (eat) and destroy bacteria and other microbes.

3. Blood platelets or thrombocytes :

Besides RBC and WBC there are some very small irregularly shaped particles in the blood, these are called platelets or thrombocytes. They help the blood to coagulate (blood clotting) when there is a cut in the body.

 

 

Besides this blood contains many other things such as hormones, enzymes, different foreign bodies, toxins, etc. Blood try to balance its components but when it does not work the imbalance will cause problems. Then we may have to go to the doctor for a check-up.

Make a table with different components of blood

 

Component of blood	Function
1. Plasma
2. RBC
3. WBC
4. Platelets
5. Other components of plasma

 

Why does blood clot?

When you cut your finger, it starts to bleed, but after some time, the bleeding stops. This is because your blood contains special substances that make the blood clot.

Platelets, fibrinogen (a protein present in plasma), and some chemicals take part in blood clotting. After some chain chemical reaction platelets dump together and form a plug which reduces bleeding.

 

Chapter 8 The Human Body Effects Of Fight Of Blood With Microbes

Every day various types of disease-causing microbes enter our bodies. But they are always not able to cause diseases.

Why all time we not get sick ?

Because the body has its own defense mechanism which destroys many microbes once they enter into the body. Body defense includes physical and chemical barriers that are always ready and prepared to defend the body from infections.

The first line of body defense includes our skin, tears, mucous, cilia, stomach acid (HCI), urine flow, friendly bacteria, and WBC. Natural barriers and the immune system of the body defend against organisms (microbes) entering in to our body.

When our eyes are infected by microbes, (bacteria or viruses) such as conjunctivitis (by a virus) thick white fluid or puss comes out of our eyes.

You may have noticed eyes discharge at the corner of your eyes or in the eyelids. Eye discharge is usually thicker and pus-like yellow, green or even grey in colour.

Personal hygiene, thorough washing of eyes with clean water. Not to touch your eyes without cleaning your hands and with contaminated clothes. It is to necessary to take the advice of a doctor as soon as possible.

You may have noticed that yellowish or whitish or brown-yellow pus (liquor purine) discharges from old wounds or boils pus is a protein-rich fluid filled with dead WBC (leucocytes) that fight against microbes.

When the buildup is on or near the surface of the skin it is called a pustule or pimple. An accumulation of pus is on enclosed tissue space is called an abscess.

Thick discharge of mucus may be an indication of infection of fungus or other microbes. Besides blood, some other substances are present or secreted in different parts of the body which also protect the body from harmful microbes.

When bacteria (microbes) enter the body through the eyes, nose, mouth, cut or bruise or even with food there are different mechanisms like blood to kill the microbes.

Different things besides blood help to kill microbes

 

 

To improve body defense against germs we need to follow the following guidelines

1. Maintain healthy diet
2. Maintain cleanliness of body and dresses.
3. Maintain regular exercise.
4. Skin care because the skin is one of the most important first lines of defense against microbes.
5. Behavioral change according to need.

 

Complete The Table

Make a list of entry points of germs in our body.

 

Organ/things	Place / Location / Cause
1. Head and face	1. Mouth (Mouth aperture)
	2. Nose (Nasal apperture)
	3. Ear
2. Skin	1. Cut
	2.  Dirty skin
	3. Damage skin.
3. Mouth	Through food and water
4.
5.
6.

 

Make a list of preventive measures of the body (defense mechanisms)

 

Name	Place	Role
1.    Hydrochloric acid
2.    Mucus discharges
3.    Saliva
4.
5.
6.

 

You may have faced some breathing problems in a crowded bus or train or in a less airy place. This is due to the inadequate amount of oxygen in air. There is a continuous interchange of gases between humans and the external environment (breathing).

We breathe approximately fifteen thousand liters of fresh air in a day. We have special apparatus for this purpose, that is, for respiration. The main respiratory organ of humans is the lung.

Other important associated organs are the trachea, bronchi, and bronchioles. The air (oxygen-mixed air) enters our body either through the nose or mouth and travels to the lungs through the windpipe (trachea) bronchi and bronchioles.

Lungs have about three hundred million tiny air sacs (alveoli) which are surrounded by fine blood vessels. Blood vessels absorb oxygen (O₂) from air sacs and transfer oxygen to the blood.

At the same time, carbon dioxide (CO₂) leaves the blood and enters into alveoli or air sacs and is thrown out through the same route during exhale. All of you know that oxygen is necessary for our survival.

 

 

The air we breathe consists of oxygen with other gases. Atmospheric air contains nearly 21% (or 1/5) oxygen.’ After entering our body through respiratory organs oxygen reach different parts of the body (every cell) and burns the food there and releases energy from food.

We use this energy for our activities. The lung is the main respiratory organ of humans. Human has two lungs-right and left. The human lung is a bag-like structure, blackish pink in color. The right lung has 3 lobes and is bigger in size.

The left one is comparatively smaller and has two lobes only. Lungs are situated in the thoracic cavity. The windpipe or trachea divides into two parts. Each part is called bronchus (bronchi- pleural)

Two bronchi enter separately into two lungs. The branches of bronchi after entering the lung divide into numerous branches and sub-branches. These smaller branches of bronchi are called bronchioles.

Bronchioles ultimately end in small air sacs (balloon-like structure), alveoli. Each alveolus is covered with small blood vessels (capillaries).

Trachea is internally supported by a half ring of cartilage (soft bone cartilage ring) that prevent the trachea and bronchi to being collapse completely during low air pressure.

Respiration is a physiological (biochemical) process in which food substances are broken down with the aid of oxygen and as a result carbon dioxide and water are produced and energy is released.

Normal respiration rate (breathing rate) for an adult person at rest range from 12 to 16 breaths per minute. In a relaxed state a man breathes approximately fifteen times per minute.

In both lungs of an adult, there are about 300 million alveoli (30 core)

The path-way of air passing in the human respiratory system.

Environment:

 

Chapter 8 The Human Body Breathing

Breathing is a mechanical process. It consists of two processes

1. Inspiration-Taking in of air (oxygen) from the environment.
2.  Expiration-Giving out of carbon dioxide to the air.

Organ of Breathing:

Organs concerned with the process of breathing (external respiration) are wind-pipe (trachea) bronchi (branches from trachea), ribs and muscles between the ribs (intercostal muscles), and the diaphragm.

Diaphragm is a muscular membrane present between the lungs and stomach (between the thoracic and abdominal cavities)

Mechanism-How do we inhale and exhale?

1. During inhalation or inspiration rib muscles and diaphragm contract, increasing the area of the thoracic cavity the cage in which the lung is placed with the increase of the thoracic cage lung expands, as a result, the atmospheric air enters in to the lungs.
2. During exhalation or expiration, reverse cases happen. Rib muscles and diaphragm relax. The area of the thoracic cage (chest) decreases. As a result, lungs become compressed and air comes out from the lungs.

 

 

Chapter 8 The Human Body Lung Problems

Lung disease refers to disorders that affect the lungs.

Asthma:

Asthma is a disease that affects the breathing passages of the lungs. This makes breathing troubles.

COPD:

It is a type of obstructive lung disease characterized by long-term breathing problems.

Pneumonia:

the bacterial disease affects the lung.

Common symptoms of lung disorders include shortness of breath, coughing, noisy breathing, and chest pain, blood in the cough, etc.

1. In some lung diseases like TB (Tuberculosis) blood comes with a cough.
2. It is a bacterial disease. Lung cancer is also a dreadful disorder of the lung.
3. If you find any such problem you should inform your parent, teacher, and physician.

Signs and symptoms of Lung disease TB (TB may occur in another organ too) Coughing that lasts for three or more weeks

1. Cough with blood (blood in cough)
2. Chest pain or pain with breathing or coughing. Weight loss, fever, night sweating, etc.
3. In the later stage blood in coughed at regular basis.
4. Asthma: Asthma is also a lung-related problem in which difficulty in breathing.
5. Chest pain
6. Cough and wheezing
7. Rapid breathing.

 

 

Chapter 8 The Human Body Bones Bone Joints And Muscles

Bones:

Have you ever observed any human skeletons? The human skeleton is composed of many short and long bones of different types. We can stand erect and walk straight because of the presence of bones.

At the time of birth, a baby has more than three hundred bones (approx 300) inside the body. (So their body is so flexible). With the passage of time as one grows some of the bones join together.

 

 

A fully grown adult has 206 bones. Nearly half of the total number of bones in a human body are located in the hands and legs (30 in each hand and leg). The thigh bone, which is known femur is the longest bone and the smallest bone is step is present in the ear (middle ear)

Touch and feel different bones of your classmate or try to see any pressure bone and complete the table-

 

Parts of the body	No. of bones	Structure / How they look like	Position of the bones
1. Finger
2. Palm
3. Wrist
4. Hand
5. Arm
6. Legs 1. Thigh 2. Ankles 3. Feet 4. Finger of leg

 

If you follow the central axis of (the 22 bones in the brain box) the skeleton (middle part) and skull is at the top made up of many differently shaped (22 bones) hard bones.

The skull ends with the upper Jaw, and lower Jaw attached separately below the skull Jaws bear the Position of the eye, Cranium (brain) teeth. Below the skull is the vertebral column or backbone. It consists of vertebrae short hard knob-like bones known as vertebrae.

 

 

These are the bones that permit you to bend and twist your back. It also protects the inner spinal cord. Vertebrae of different regions of the vertebral column have some structural differences. In the chest region ribs (12 pairs) are present.

 

 

Ribs from both sides joint in the front side with the sternum and form the rib cage which protects many vital organs of the body like lungs, heart, etc.

1. The skeleton performs functions of support, movement, and protection.
2. Bone marrow is present inside the bones it produces blood cells.

Bones are called long, short, flat, and mixed according to their shapes. Long bones are found in the limbs-such as upper arm bone forearm bones, thigh bone, and shin bone.

Short bones are found in the wrist, ankles, and fingers. Flat bones are found in pectoral and pelvic girdles. eg. ribs, scapula. Mixed bones are present in the head.

 

 

Make a list of different bones as their shape and size and mention their location

 

Bones’ shape and size	Location	Remark
1.
2.
3.

 

How Are Bones Held Together

The bones are held together by means of tough strip-like structures known as ligaments.

Ligaments stretch across the joint and prevent bone from moving too far away in the wrong direction.

Tendon is a tough band of fibrous (connective) tissue that usually connects muscle to bone. A ligament is a fibrous connective tissue which attaches bone to bone.

The gymnasts exercise to stretch their ligaments for easy movements of their bones.

 

Orthopedic Problems

Dislocation of the bones:

Sometimes bone loses its location, this is called the dislocation of bone. For example, in the event of an accident, the head of the arm bone (humerus) which normally fits into the shoulder blade might be knocked out of its socket.

This knocking out of the humerus is a dislocation of the bone. The same case may happen in the femur and other joints also.

 

 

How are bones joints?

Bones joined with each other in various ways. The point at which two bones are joined together is known as the bone joint.

 

Type Of Joints

1.  Bone joints present in the skull are not movable. These are called immovable joints.
2. Some bone joints are less mobile and have only a limited range of movement. These are called partly movable joints or slight movable joints. Example-Joints between vertebrae, hip joints, etc.
3. Movable joint (or synovial joint) This is the type of bone joint in which some degree of free movement of bone is possible.

In this type of joint opposing bony surfaces are covered by cartilage (a type of elastic bone) and bones are held together by surrounding tubes like capsules. Ligaments are present on the outside of the capsule and synovial membrane inside.

Within the synovial cavity a liquid, synovial fluid is present which makes the movement of bones easy.

 

Chapter 8 The Human Body Types Of Movable Joints

Pivot Joint (= rotary joint)

The joint between the first (atlas) and second vertebra (axis) of the vertebral column in our body. A truly movable joint that allows only rotary movement around a single axis. In this type of joint, the moving bone rotates within a ring that is formed from a second bone.

 

 

Ball And Socket Joint

A joint in which a ball (head of a bone) moves within a socket so as to allow rotary motion in every direction within certain limits.

For example hip and shoulder bones have this type of joint. Rotation of the head of humorous and femur within their respective cavities of joints.

Ligament: They attach one bone to another.

Tendon: Attach muscles to bone.

 

 

Hinge Joint

The wrists, ankles knee, and elbow joints have hinge joints. Hinge joints are formed between two or more bones where the bones can only move along one axis like the hinge of a door.

 

 

Saddle Joint

In a saddle joint, you can slide and hinge the bone in any direction (biaxial) allowing movement in sagittal and frontal planes. The joint at the base of the thumb is a saddle joint.

 

 

 

 

Complete The Table

Different bone joints their location and functions

 

 

Bone joints	Type of joint	Nature of joint
1. between 1st and 2nd vertebrae	1. Pivot	1. Synovial or movable
2. Rotation of the head of the femur in pelvic girdle	2.
3. Joint in the skull	3. immovable	3. immovable
4. Wrist joint	4.	4.
5. Finger joints	5.	5.
6. Joint between vertebrae	6.	6.

 

Different Movements

 

 

Chapter 8 The Human Body Problem Of Bone Joints

Calcium makes our bones hard. If our body does not get enough calcium and vitamin ‘D’ to support important body functions it takes calcium from our bones. This is called losing bone mass.

 

 

This increases the risk of bone disease and Osteoporosis (bones are weak and porous). Another common bone-related disease is Osteoarthritis. It is a degenerative disease of the joints usually accompanied by pain and stiffness. This degenerative disorder develops with age and affects walking.

Gout:

When excessive uric acid, a type of waste product deposited in joints. Joints become swollen, reddish, and very painful situations arise.

 

 

Back pains:

Back pain may be caused by a slipped disk or it may be associated with some disease of bones and joints.

Rheumatoid arthritis:

It is a chronic inflammatory disease affecting the connective tissue of the joints, pain, and stiffness in the joints. It usually begins with the joints in the finger spreading to the wrist, and elbows.

How do broken bones heal?

Although bone is a hard body part but during an accident or injury bone breaks. But the broken bone has the power to repair itself. Gradually new bone starts growing across the gap eventually.

 

 

This new bone part hardens and unites the two broken ends. The doctor make plaster because the damaged part should not be moved. This helps to grow new bones without any difficulties and are united in the correct position.

 

Chapter 8 The Human Body Muscles

You may have seen a bodybuilder and may have seen a weight-lifter at least in Television. If you observe their body you may find different prominent muscles. Muscles grow bigger and better by exercise.

There are approximately six hundred and fifty muscles in the body. Each one of these muscles performs a particular task. For example, while walking, there are over two hundred muscles in action.

The muscle controls the bone to which direction it moves. The muscles are made up of packages of stretchable fibre-like material (myofibrils). These fibers are extremely slender (thin).

Each fiber is commanded by a nerve which makes it to contract. When muscles contract they do work.

Functionally all muscles are divided into two groups

1.  Voluntary (=striated) muscles-It contract by the w.I of man, example skeletal muscle.
2.  Involuntary (smooth) muscles-It’s contractions are not controlled by man.

 

 

For example, muscles are found in the walls of internal organs, and blood vessels.

Muscles attached with the bones (hands, legs, etc.) are called skeletal muscles. Muscles attached with the stomach and other internal organs are known as visceral muscles. (viscera internal organs).

Muscles of the heart are known as cardiac muscles. It is a special type of muscle. It is branched, involuntary, and usually never gets fatigued.

How do muscles work?

A tendon joins the muscle to a bone. The muscles can only perform one action and that is they can pull (contraction). In order to move a joint at least two separate muscles are required.

For example, the lower arm is raised when the bicep muscle (muscle present on the upper side of the arm) is contracted. In this state, the tricep muscles (muscles of the lower side of the arm) relaxed.

 

 

The arm can not be strengthened again by the biceps alone. It is done when the triceps pull the ulna down the biceps and then relax.

Ask your friend to fold his arm from the elbow. What you will see? Biceps muscle over the humorous swell. Press this part. You will feel hard then ask your friend to relax and lower his arm. Then see the length of the biceps muscle.

Make a table of your observation :

The shape of muscle (working muscle)	muscles at the time of elbow folding	muscles at the time of  relaxation
Length	increase/decrease	increase/decrease
Width	increase/decrease	increase/decrease
Stiffness	increase/decrease	increase/decrease

 

Nature of Job	The nature of muscles involve
1.    Movement of Jaw
2.    Peristalsis movement or movement of the Alimentary canal.
3.    Movement of the tongue
4.    Holding somethings
5.    Climbing
6.    Swimming
7.    Talking.
8.    Opening and closing of eyes
9.    Rhythmic contraction of the heart

 

What is a muscle cramp?

You may often hear the case of muscle cramps of players. A cramp is an involuntary action that is a painful contraction of a muscle. It occurs when a muscle suddenly contracts unexpectedly.

It is usually a very painful state and remains for several minutes. Muscle cramps usually occur in the feet and hands. Sometimes it occurs in leg near the knee (calf muscle).

 

Problems Of The Muscles

You may have seen some people who is unable to move his/her lower body parts since birth. Legs and hands are slender. Many of you and your friend and family members who use computers often face some problems in fingers and neck.

During old age, people can not walk properly, and sometimes may not be able to stand erect, due to weakness of muscles. You may have found many office workers who has been having neck and back pains.

These area-related muscles are not working properly due to overaction. After proper exercise, this pain can be relieved.

 

The Growth And Development Of The Human Body

Most of you have noticed a newborn baby and a four-month-old baby. (1 to 3-month baby). You must have also observed that they have soft, small, slender arms and legs, fingers are short, slender, and have no or little strength.

All of us have passed this phase during starting of our life but as the advancement of age, our body gradually develops and gain strength. With the advancement of age, height and weight increase. Let’s see some examples and complete the table.

 

Name of the organs /Parts of the body	Functions
1. Hand and Finger	1. To hold something, used during swimming, most of the work such as writing, throwing, etc.
2. Legs	2.
3. Knee	3.
4. Teeth	4.
5. Shoulder	5.
6. Ankle	6.
7. Lips	7.
8. Tongue	8.

 

Every living organism requires food. We also require it for our survival maintenance of health, growth, and development. You have noticed with the advancement of age, a person’s body develops.

Proportionate development of different parts (organs) of the body occurs. Diet is the kind of food on which a person or a group lives. There are various components of food such as carbohydrates, fat, proteins, minerals, vitamin, and water.

Each of these components has a specific role in body formation. Good dietary habit gives us sound health and good mental development.

 

 

If you do not get sufficient food in day or day after day your body would not grow as well as the development of mental growth would also be hampered.

 

Chapter 8 The Human Body Work To Do

Complete the list by taking measurements of a different person as mentioned below. Some data has been provided. You have to complete the list.

From this table, you will get a picture of the measurement of different parts of our body (organs).

 

Age of the person	Height (cm)	Weight (kg)	Name of different parts/organs of body Measurement (cm)		Proportionate measurement of the head, hand body, leg.
3-years	94-95	14	Head	46-7-50-7
			Head	15-17
			Body	12—13
			Leg	20-23
6-years	112-113	20-22	Head	49-50
			Head	50-51
			Body	40-41
			Leg	65
9-years	132	31	Head	51
			Head	59
			Body	51
			Leg	72
12-years	149-150	40-41	Head	51
			Head	66
			Body	56
			Leg	93

 

Name of the student	Class	Sex	Weight	Height
1.
2.
3.
4.
5.
6.
7.
8.
9.

 

Categorization of Weight of different student

 

Number of Students	Less than 30 kg	30.5-32.5 (30-32 kg)	32.6-34.5 (32-34 kg)	34.6-36.5 (34-36 kg)	36.6-38.5 (36-38 kg)	38.6-40.5 (38-40 kg)	40.5-above  (40-above)

 

From this table, you would get the average weight and height of students of your class. You may notice some has abnormal length and weight. They may be shorter or longer than average as well as some may be underweight and some are over weighted.

 

Normal Height		Short height (dwarfism)	Long to very long (Gigantism)
Male	Female

 

No. of students	Normal Weight		Under Weight	Over weight (Obese)
	Male	Female

 

Chapter 8 The Human Body Abnormal Development

In the human beings, abnormal development can occur due to some chemical factor (hormone), hereditary or disease-related causes.

 

Three major functioning groups of food.

1. Energy-producing food- carbohydrates,-Fat
2. Bodybuilding Food of balanced diet
3. Protective Food Minerals, vitamins, water

Some Deficiency Diseases

 

 

Before the start of puberty at the age of 10 there is not much difference between in growth ratio between boys & girls. (about 5 cm per year). Growth rate changes during puberty. In the onset of puberty in girls usually starts at around the age of 10.

Girls on average start their growth between the age of 10 and 14, about a year before boys. The average boy starts his growth at the age 12. Besides the above-mentioned deficiency disorder some other types of illnesses you may notice among students.

In the following table, a few of them and their probable reason are mentioned.

 

	Name of Illness	Cause of reason of illness
1.	Broken corner of the nail	Deficiency of calcium and some toxic effects of fluoride.
2.	White mark on teeth	Toxicity of fluoride.
3.	Fadeness of the corner of the eye	Deficiency of iron, vitamin B, and protein.
4.	Color of skin	Malnutrition and deficiency of protein.
5.	Ulcer at the corner of the lips and tongue	Deficiency of vitamin B.
6.	Swollen gum and profuse bleeding	Deficiency of vitamin C.
7.	Change of shape of the bone	Deficiency of calcium, protein, and vitamin D.
8.	Frequent breaking of bone	Deficiency of calcium.
9.
10.

 

Chapter 8 The Human Body Work To Do

After careful observation, you make of table (considering all these disorders) of your classmates.

 

SI. No.	Name of the ‘ students	Class	Sex	Observation	Remark
1.	R. Das	VI	M	Swollen gum relish blood appears sometime	Vitamin ‘C’ deficiency, need to take citrus fruits
2.	…………	…………	…………	…………	…………
3.	…………	…………	…………	…………	…………

 

Body Mass Index

The Body Mass Index (BMI) ( Quetelet index) is a value derived from the body mass (weight) and height of an individual. BMI can be measured by dividing the body mass (weight) by the square of the body height.

Its value indicates a health condition either person is under-weight, or mal or overweight or obese. Body mass index is a simple calculation using a person’s weight and height the formula is

Simply divide your weight in kilograms (kg) by your height in square meters. Example-Suppose the height of a student is 1.2 metres and weight is 38 kg. How can you calculate the body mass index (BMI) of that student?

Now check the scale of BMI and make remarks

 

Importance Of BMI

It is an indicator of whether a person’s weight is low, normal or over normal. Being overweight causes different physiological problems such as disease of the heart, bones, and liver. A person can be cautious about BMI and can take steps accordingly.

Scale of BMI
BMI less than
15 =excessively low weight
16-18.5 = low weight
18.5-25 = Normal
25-30 = Heavy weight
30-40 = Excessively heavy
40 above = Obesity

The growth rates of girls and boys are slightly different. The growth rate of the girls increases in the age group of eight to twelve or thirteen.

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 4 Rocks And Minerals The Earths Crust Rocks

Do you know?

1. Our planet earth is more than 5000 million years old.
2. The earth comprises of three main regions-the lithosphere (which is solid), the hydrosphere (which is the liquid portion) and the atmosphere (or gaseous portion).
3. The outermost surface of the earth is made up of hard soil, sand, silt, clay and rocks like granite, etc.
4. The pressure and temperature under the earth’s surface are extremely high.
5. Within the earth the temperature increases with depth at the rate of 1°C for every 32 m of depth, giving an average temperature of about 5000°C at the centre. At such high temperatures, the rocks remain in a molten state which is known as magma.
6. During volcanic eruptions, such molten magma erupts on the surface of the earth and flows down the slope of the surface. Then it is called lava.
7. Outside the crater of a volcano, the lava gets solidified by cooling and in this way, primary rocks are formed.
8. Rocks differ from one another in colour and texture.

Read and Learn More WBBSE Notes For Class 6 General Science and Environment

Chapter 4 Rocks And Minerals Different Types Of Rocks

Different Types Of Rocks

On the basis of the mode of formation.

The rocks are classified as

1.  Igneous rocks.
2. Sedimentary rocks and
3. Metamorphic rocks.

Igneous Rocks

The word ‘igneous’ means ‘fire’, derived from the Latin word ‘ignis’ or its Sanskrit word ‘Agni’. Igneous rocks are formed by the process of solidification of hot molten lava.

They are referred to as primary rocks. Basalt, Granite and Pumice are three common examples of igneous rocks. The black-coloured stones you see near railway tracks or stone chips that are used for the construction of asphalt roads are nothing but pieces of granite.

Note that no holes are seen in a granite rock. But in a pumice stone, you can see many holes. Usually, pumice is formed by the process of quick cooling and solidification of bubbling foam from the upper portion of molten magma.

When the bubbles escape into the air, the holes are formed in the solid pumice.

Sedimentary Rock

The word ‘sedimentary’ is derived from a Latin word which means ‘settling down’. Sediments of sand, gravel, slit and clay are deposited in water bodies like seas, rivers and lakes over millions of years.

Due to the high pressure and temperature of the interior layers of the earth, these sediments get consolidated (or hardened) into rocks which are known as sedimentary rocks. These are also called secondary rocks.

Sometimes fossilized remains of plants and animals are found between the layers of sediments. As shown in Sandstone, Shale and Limestone are three common examples of sedimentary rocks.

Sandstone is formed by the consolidation of the deposits of sand, whereas deposits of clay get hardened to form shale.

Metamorphic Rocks

The word ‘metamorphism’ means ‘change of form’. Metamorphic rocks are rocks which are formed by the process of metamorphism of pre-existing igneous and sedimentary rocks.

During the process of metamorphism, the original structure of pre-existing rocks gets altered into new minerals which combine together to form metamorphic rocks.

Metamorphic rocks are harder and more resistant than the original rocks.

Marble, Slate, Gneiss, Quartzite, Schist, etc. are examples of metamorphic rocks.

For example:

Limestone gets metamorphosed to form marble. Shale gets altered to form Slate. Granite gets metamorphosed into Gneiss. Quartzite is the metamorphosed form of Sandstone.

Chapter 4 Rocks And Minerals Minerals And Ores

The earth’s crust is made up of rocks of various types. Do you know that a rock is a mixture of various minerals in different combinations. About 2000 minerals are known to exist in the earth’s crust.

However, minerals are made up of some chemical elements. Among these elements, in the earth’s crust oxygen is the most abundant, and silicon is the second most abundant element.

Other elements are aluminium, iron, calcium, sodium, copper, magnesium, zinc, etc. You must have an idea about some objects made from metals that we use in our everyday life.

Follow this chart:

Metal	Uses
Aluminium	To make utensils, furniture, electrical wires, picture frames, and the body of planes.
Iron	For making machines, rods, rail lines, utensils, lamp posts, and railings.
Copper	In the manufacture of electrical wires, cables, electrotyping, electric motors, electric cells, coins.
Zinc	In galvanizing iron and steel, to prepare a painted zinc white, in a dry cell.
Silver	Utensils, ornament manufacturing.
Gold	In manufacturing valuable ornaments.

Most of the metals are found to occur in nature in combination with other elements forming compounds mixed with soil and sand. These compounds are known as minerals.

Example:

Aluminium is found as different compounds, namely, Bauxite, Cryolite, Felspar, and Diaspore-which are minerals of aluminium. The minerals of iron are Haematite, Magnetite, Copper has the minerals Copper glance, Copper pyrites, and Cuprite.

Metal extraction is the process by which a metal is extracted from its minerals.

The particular mineral from which a metal can be extracted conveniently and economically is called the ore of that metal.

Example:

1. The ore of Aluminium is Bauxite, of Iron it is Haematite, of Copper it is a Copper glance.
2. All ores are minerals but all minerals are not ores for a metal.

A metal may have more than one mineral, but one or two ores from which the metal can be extracted conveniently and economically.

For example:

Aluminium has the minerals Bauxite, Cryolite, Felspar, and Diaspore but its ore is only Bauxite. Because Aluminium is extracted economically from Bauxite.

Chapter 4 Rocks And Minerals Alloys

You are familiar with some solid substances like bronze, brass, steel, stainless steel, bell- metal, etc. These are not pure metals, but rather, a mixture of metals. These are called alloys.

Definition Of Alloys :

An alloy is a mixture of two or more metals as a solid solution.

Why do we prefer alloys than pure metals?

1. Alloys are harder than pure metals.
   For example, a bridge built of pure iron cannot withstand heavy load but a bridge built of steel (an alloy of iron and carbon) can do that easily.
2. Alloys are used to protect the metal from corrosion by air or moisture.
   For example, an iron spoon gets rusty easily but a spoon made of stainless steel (an alloy of iron and chromium) never rusts.
3. The purpose of alloying is to lower the melting point.
   For example, an alloy of lead and tin, called solder has a melting point lower than lead or tin. An electric fuse is also made out of the alloy of lead and tin in a 3:1 ratio.
4. An alloy is used for superior casting.
   For example, statues, and medals are made out of brass (an alloy of copper and zinc), and bronze (an alloy of copper and tin).

Chapter 4 Rocks And Minerals Fossils

A fossil is a skeletal impression (or trace) of once-living plants and animals from the past geological age. These skeletal impressions get preserved in between the layers of sedimentary rocks.

Formation of fossils :

When a plant or animal died in a watery environment (one day which were alive) and got buried in mud and slit, their body parts underwent a lot of changes over millions of years. First of all their soft tissues had been decomposed.

For animals, only hard bones or shells were left behind and for plants, traces of leaves were left behind. Over time many chemical changes also took place and the organic remains got preserved over the top and hardened into rocks.

These rock-like traces are called fossils. Fossils help us in fixing the relative ages of rocks. Besides this, the footprints of extinct animals help us to study about them.

Chapter 4 Rocks And Minerals Fossil Fuel

Fuels are the substances which produce heat on burning. Our domestic use fuels include cow-dung cakes, matchstick, wood, hay, paper, etc. We also use fossil fuels like coal, petroleum and natural gas.

These are called fossil fuels because they are formed by the chemical decomposition of dead remains of plants and animals over millions of years which got buried underneath the earth.

Coal :

Coal is found deep under the earth’s surface. Coal was formed when huge forest areas got buried under the earth’s surface about 200 million of years ago.

Due to the very high pressure and temperature of the interior layers of the earth and chemical decomposition reactions, the remains of plants got compacted to form a stony residue, called coal.

Different varieties of coal, e.g. peat, lignite, and bituminous are formed. They differ in their carbon content and volatile compounds.

Uses of coal :

Coal is the most common fossil fuel that we use. On burning coal, heat energy is produced. This heat energy is used to generate electricity in thermal power stations.

When coal is burnt in absence of air, the volatile impurities are expelled, leaving behind a liquid residue (called tar) and a porous residue (called coke).

The coke contains 98% of free carbon and does not produce any smoke on burning. So, coke is a better fuel than coal. Coal is also used as a source of some organic compounds such as benzene, toluene, naphthalene, etc.

Chapter 4 Rocks And Minerals Petroleum And Natural Gas

Millions of years ago, the dead bodies of extremely small sea animals and plants got covered by mud and sand. Due to intense heat and pressure under the earth, the sediments changed into sedimentary rocks.

After a lot of chemical decomposition, the bodies of dead animals and plants decayed into a product of petroleum and natural gas.

Petroleum occurs at depths 500-2000 m between two layers of impervious rocks and the natural gas always remains above petroleum trapped in between the rock cap and the petroleum layer.

Uses of petroleum :

Crude petroleum is refined by the process of fractional distillation at different temperatures. The products of refining of petroleum are kerosene, petrol, diesel, LPG, paraffin wax, lubricating oil, asphalt, petroleum gas, naphtha, etc.

1. Kerosene is used as a household fuel in wick stoves.
2. Petrol is used as fuel for light vehicles like cars, scooters, etc.
3. Diesel is used to running heavy vehicles like buses, trucks, tractors, etc.
4. LPG (Liquid Petroleum Gas) is used as a household fuel.

Uses of natural gas :

Natural gas contains 95% methane. Under high pressure, natural gas is stored in cylinders. It is commonly called Compressed Natural Gas (or CNG) and is used as fuel for homes, transports and industries.

Natural gas can be piped from production wells to homes in the same way as water supply. Natural gas causes less pollution on burning, than vehicles run on diesel. So, natural gas is a very clean and efficient fuel.

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 1 Interdependence Of Organisms And The Environment Man And Other Animals Depend On Plants

Our family and our society:

Human beings are the most intelligent organism in earth. Yet we can not live alone. Not only we but no animal or plant or any other organism can also live alone.

An organism (Animal, plant, or microbes) lives in a group or a single (solitary), or whether the organism form a society or not, all the organisms have to depend on others directly or indirectly.

You must have noticed that your father or some other person calls a doctor when someone of your family member is ill, call a plumber to repair water pipe connections, or call an electrician. For any electrical problem in the house. Different persons are engaged for different types of jobs.

Read and Learn More WBBSE Notes For Class 6 General Science and Environment

Where you go when your cycle do not work properly?

Moreover, you have also noticed that in your family mother or any elderly woman or any other person does the work of cooking. Father, uncle, mother or grandfather performs the work of daily marketing.

Therefore, it is clear that all of us to depend on others for our existence in the family and in society. It is also clear that we can not do all these works ourselves alone.

In the living world, animals depend on other animals and plants for their food, shelter, oxygen, reproduction, body defense, development, etc. Plants also depend on animals too for carbon dioxide (CO₂ ), pollination, dispersal of fruits and seeds, reproduction, growth, etc.

So in the living world animals and plants are interdependent :

Prepare Two Table-

1. For which work we need help from family members and
2. From other members of our society.

Family Work:

Type off work	Whom to depend upon/performer
1.    Daily household cooking	1.    Mother, aunt, or some other person
2.    Washing and cleaning	2.    Mother or any person keep for this work
3.  Looking after children	3.    Mother, grandmother
4…………………………	4…………………………
5…………………………	5…………………………
6…………………………	6…………………………

 

Help from others Outside the family

Type of work	Whom to depend upon/performer
1.    Electrical repairing	1. Electrician
2.    Plumbing problem	2………………..
3.    Sweeping and cleaning	3………………..
4……………..	4.    Physician./ Doctor
5	5

 

How do we depend upon plants for our survival?

If you carefully observe around, you will find so many things that we depend upon come from plants.

Complete the table mentioning the plant products/objects:

Column l	Column-ll
Products	Plant/Plant parts
For Food
1. Rice	1. Paddy/ seed and fruit
2. Wheat	2. ………..
3. Bazra	3. ………..
4. …………	4. ………..
Household goods (wooden)
1. Furniture	1. Wood from trees
2.	2. ……………….
3.	3.
Building materials
1. Cori / Borga	1. ………..
2. Pillar	2. ………..
3.	3. ………..
Cloths
1. Fibres	1. Cotton
2.	2. ………..
Medicine
1. Quinine	1. Bark of Cinchona Tree
2.	2.
3.	3.

 

Not only man but other animals also depend upon plants in nature. Observe your surrounding and complete the table-

How Do Human Beings And Other Animals Depend Upon Plants

Dependence of animals upon plants.

From the above discussion, it has been more or less clear that human beings as well as other animals depend upon plants. But it is true that all the food products of animals are not directly come from plants.

Human beings and some other animals also get food from other sources-like other animals or their derivatives, such as we get milk from goats, cows, buffalo, camels, etc.,

Eggs from different birds, meat from different animals such as goat, sheep, cow, chicken, goose, etc. The source of food of Carnivores (like tiger, lion, etc.) are animal. They do not take directly the plant or plant products.

They use other animals as their food who are usually depend upon the plant directly (herbivorous), such as deer, cow, goat, etc.

Carnivorous

The animals that feed on other animals Example Tiger, Lion, etc.

Herbivorous

The animals eat only plants example cows, Buffalo, Deer They, etc.

Herbivorous animals like cows, deer, goats, sheep, elephants, etc. depend upon plants directly for their food. For example, when we take guava as food, we take plant products directly.

But when we take a boiled egg or a glass of milk or a piece of meat as the food we are indirectly taking plant products as the hen (for egg) or cow (for milk) or goat or sheep (for meat). respectively who collect their food directly from plants.

Therefore, all animals depend on plants for food either directly (herbivores) or indirectly (carnivores)

 

Make a list of animals who depend upon plant/plant products directly. (Complete the table.)

Name of the animal	Plant/ plant parts	Other sources (animals)	Nature
1. Cow	grass, different plant parts leaf, stem, fruit, flower, etc.	not taking animals’ food	totally depend upon plants (herbivorous)
2. Goat	………………..	………………..	………………..
3. Hen	Grass, young leaves	small insects earthworm etc.	depend on both plant and animal (omnivorous)
4. Snail	………………..	………………..	………………..
5. Monkey	………………..	………………..	………………..
6. Deer	………………..	………………..	………………..
7. Lion	………………..	………………..	(Carnivorous)

 

Make a list of animals who take plant/ plant products indirectly.

Animals	Animal food sources	Plant food sources of consumed animals	Nature
1. Tiger	Dear, cow, hare, goat, etc.	Grass, different plant part	Carnivorous
2. Kite	–	–	–
3. Fox
4. Pea-cock

Insectivorous plants

Pitcher plants, trap insects and use them as external sources of food of animal origin.

 

Human Beings depended a lot upon plants. let’s complete the table below. Here different plant parts have been mentioned.

Chapter 1 Interdependence Of Organisms And The Environment Use Of Plant Parts Other Than Food By Animals

Dependence of animals on plants to build their homes:

Mostly birds build their nests on the trees, but some other animals such as mammals, arthropods, and reptiles also use trees as their home. Weaver birds (such as Baya weaver) are specialized to use leaves and twigs and build fine nests.

But all of the birds are not able to do so efficiently, they build nests with plant parts like twigs, dry grass leaves, and with other substances (e.g. crow). Some birds like parrots, wood pickers, and owls live inside the cavity or holes of trees.

Nest:

A bird nest is a place in which a bird lays and incubates its eggs and raises its young.

Some birds are unable to build their nest in trees but build nests in the rooks and corners of houses, in the cornices or many places using different plant parts. (e.g. Sparrow) Herrons and some sea birds build platform nests.

Platform nests are large flat nests built in the tree top. Vulture builds their nest high on the branches of Banyan (Bath), Peepal, and Raintree. Some tree dwellers are Spider, Monkeys, Tree kangaroos, Orangutans, Sloth, etc.

Squirrels, Spiders, Ants, and many other insects, also live on trees. Bats hang from the branches of trees. Many birds also stay, their night and resting period on the plant.

Observe your locality, school, playground, park, bushes, and forest (if you have a chance to visit).

Complete this table on how birds and other tree-dwellers build their nest using different plant parts.

Different plant parts	Animals	Nature of nest	Tree
Example 1. Twigs, leaves	Weaver Bird (Babui) Baya weaver	Hollow fine flask-shaped narrow tube-like nest	Palm, Coconut
2. Dry twigs, grass leaves, and other substances	Crow	Pot-like, irregular build-in horizontal branches	Mango, Jam, etc.
3.
4.
5.
6.

 

Chapter 1 Interdependence Of Organisms And The Environment Use Of Plant Parts For Building Our House

Have you seen any wooden houses? If you go to any hilly areas or earthquake-prone areas you will find this type of house. The frame of the house, floor, roof, beams, and side walls all are made of wood. You may also notice heavy wooden frames in the ceiling.

Farmers are habituated to use wooden equipment from ancient times during cultivation, such as Plough, Mai (ladder), etc. Boats, traditional ships (in ancient times) wheels of bullock carts, and chariots, (two-wheeled vehicles pulled by horses) are also made up of wood.

Most of our household furniture such as chairs, tables, beds, and almirah are also made up of wood. In some remote places, temporary bridges are also prepared with bamboo and wood.

Make a list of wooden articles and their sources (plant parts) and uses.

Wooden articles	Source/plant/ plant parts	Uses
1. Boat	1.    Tree trunk-wood	1. Use as a vehicle In the water.
2. …….	2.  Tree Trunk	2. ……
3. …….	3. …….	3. a Sitting arrangement of students in classroom.
4. …….	4. ……	4. ……
5. …….	5. ……	5. ……

 

Use of Plant Parts:

Plant Parts	Name/Type of plant	Use of the part	Remarks
Example
1. Fruit	Bel-tree	Food, as well as medicine	Other parts are also used, such as leaves, twigs wood.
2. Leaf	Palm-tree	Hand fan	Other uses chatai (Mat)
3. Seeds
4. Trunk
5. Flower
6. Gum (Latex)	Rubber	Eraser, car tires	Prepare from an excretory product of plant (latex).
7.

Chapter 1 Interdependence Of Organisms And The Environment Our Dependence On Plants For Our Clothes

Most of you have seen a charka printed in Indian currency. Do you know what its use is? If you observe it carefully you will see charka pullar making fine threads from the cotton balls (karpas).

These threads are used to prepare clothes. If you visit any handloom weavers’ house you will find how these threads are used to form a piece of cloth. If you carefully observe a thread you will see threads are made up of fibers.

There are many fibers yielding plants in nature, such as karpas, simul, Jute, etc. Cotton fibers are used to make cloths from which we make our dress materials.

Though nowadays artificial fibers are also used to prepare dress materials but dress-materials made up of cotton are comfortable and health-friendly.

Karpas threads are also used to prepare bags, ropes, and many other household goods, simul cotton (silk cotton) are used to prepare pillow, and mattresses and also use in medical purpose.

Jute and Coconut fibers are also used to prepare sacs, rope, and other goods. Nowadays use of jute and coconut fibers has been declined. Artificial fibers are used in place of that, these increase the chance of pollution.

Complete the table.

Name of the fibre-yielding plants	Parts of the plant used is fiber	Use of it	Remarks
1. Karpas	Fibers around the seed	Cloth, dress-material preparation	Comfortable and health-friendly dresses
2. Shimul	………	………	………
3. Jute	………	………	………
4.  Coconut	………	………
5.	………	………
6.

Chapter 1 Interdependence Of Organisms And The Environment Other Products Of Plants Which We Often Use

So far from the discussion, it has been found that we depend upon plants for food, clothes, shelter, and many other different objects used in everyday life.

But this is not the end there are so many other things we get from plants. The book you are now reading, and the paper on which you write all are plant products. The glue (gum) you use are also a plant product(though nowadays synthetic glue are also used).

Excretory products:

Waste matters produce during metabolism in the body example resin, latex, tannin (plant) urea, and uric acid (animal).

Alkaloid:

Nitrogenous excretory products of plant e.g. quinine, reserpine.

Resin:

Excretory products of plants are used to polish wooden furniture. It makes our furniture glossy and beautiful, as well as protects wooden furniture from water (water proof).

Most of you have heard the name of Quinine, it is also an excretory product (alkaloid) of the Cinchona plant used as effective medicine of Malaria. Many such plant products are used as medicine, such as products of Tulsi, Swarpagandha, Basak, etc.

List of plant products used as medicine

Plant products	Parts of Plant	Use
1. Quinine	The bark of the plant Cinchona	Effective medicine of Malaria
2. ……..	……..	……..
3 ……..	……..	……..
4 ……..	……..	……..

Chapter 1 Interdependence Of Organisms And The Environment We Get Oxygen From Plant

You have learned already that man as well as other animals inhale oxygen (O₂ ) and exhale carbon dioxide (CO₂ ) during respiration. Plants consume carbon dioxide (CO₂ ) of the atmosphere during food preparation (photosynthesis).

The process of food preparation of green plants (chlorophyll-containing) with carbon dioxide and water in the presence of sunlight is called Photosynthesis.

During this process, plants give off (liberate) oxygen.

So these two processes photosynthesis (by plants) and respiration (by all organisms) balance atmospheric oxygen and carbon dioxide.

 

 

From plants, only oxygen (O₂ ) is liberated during day time though plants to take oxygen (O₂ ) for respiration. But the amount of O_{2 produced} during photosynthesis is higher.

So, the green plants get their necessary oxygen for respiration from their own system and liberate excess O₂ to the atmosphere during the daytime.

The amount of CO₂ liberated during respiration also use by plants for photosynthesis, but not during the night (because photosynthesis does not occur during the night.)

Chapter 1 Interdependence Of Organisms And The Environment Dependence of Plants On Animals

Pollination:

While moving in the park or in the garden you may have seen bees, butterflies bumble bees or some other insects who are moving from one flower to another (fluttering among flowers). Are they playing? No, they are in search of their food (honey or nectar).

Their movement from flower to flower benefited plants. These insects transfer pollen grains which are attached with their legs, wings, and mouth parts from one flower to another. They act as a vehicle.

This process of transfer of pollen grains from flower to flower is known as pollination. Pollination leads to fertilization. The process of union or fusion of pollen grain (male gamete) and ovum (female gamete) starts the production if seeds. It is essential for the creation of new plants.

Pollination:

It is the process of transfer of pollen grains from the anther (male part) to the stigma (female part) of a flower. When the pollen grain are transferred within the same flower or other flowers of the same plant is called self-pollination.

The pollen grains can be transferred from the flower of one plant to the flower of different plants of the same type. This is called cross-pollination.

Agents of pollination:

Those who help in pollination are known as agents of pollination these are insects (bees, butterflies, ants, etc.), birds, reptiles, bats, man (biotic agents), wind, water (abiotic agents), etc.

 

Complete the table

Pollinating agents	Examples
1. Wind	1. Paddy, Maize
2. Water	2. Vallisnarla
3. Bee	3  ……………
4. Birds	4  ……………
5 ……………	5  ……………
6 ……………	6  ……………
7 ……………	7  ……………
8 ……………	8  ……………

 

Chapter 1 Interdependence Of Organisms And The Environment Dispersal Of Fruits And Seeds

Many of you have noticed that Banyan or Peepal trees grow in the narrow fold of concrete walls or in the carnies or in the corner of the roof.

How does this happen?

This is due to the dispersal of fruit and seeds of these plants. Seeds of these plants are brought to this unusual location (where no or little soil content) may be by wind, water or most cases by birds.

Birds often fly with fruit or seed in their breaks, sometimes these fall to the ground or other places. Sometimes birds drop partly eaten fruit, seeds may also be transferred through the feces of birds.

Bats and some other mammals (dogs, foxes, etc.), also transfer seeds through feces. Undigested or partly digested seeds of feces germinate in favorable conditions.

Many of you after coming from the playground or park pick some sharp stick-like things from your dress, which are attached with your dress, and threw it outside. You may have also noticed your mother or sister also doing this after Coming from the park.

These are seeds of grass or other plants. This is one of the ways of dispersal of seeds. Many fruits and seeds have some adhesive substance or some plants have sticky seeds or some fruits and seeds have special devices like hooks and thorns by which are attached with animals’ bodies and transfer from one place to another.

Some seeds are so light and have a wing or fiber-like structure that helps them to float in air for a long time and can move from. one place to another by air.

Fruits and seeds after ripening usually go away from their parent plants to be distributed so as to develop their families in a larger scale with the least competition.

There are a variety of ways to disperse of seeds in nature-wind, water, animals, and sometimes special devices such as utilizing explosive force to spread their seeds away (e.g. Dopati).

Humans consciously or unconsciously take part in the dispersal of fruits and seeds. Such as when you through a mango or Jamun seed after eating its soft food part to ground.

Complete the table

Agents that help in the dispersal of fruits and seeds	How this happens
(A) By animal	(A)
1. Rat	1. ………….
2. crow	2. ………….
3. Fox	3. ………….
4. Wild cat	4. ………….
5. Man	5. ………….
(B) Wind	(B) ………….
(C) Water	(C) ………….
(D) Plant, Own device	(D) ………….

 

Chapter 1 Interdependence Of Organisms And The Environment Nature Of Relationship Between Different Organisms

You may have noticed the presence of many red ants in ‘Jam’ (Black plum) and ‘Jamrul’ (water rose apple) trees especially during summer when’ these plants bear fruits (Jam and Jamrul).

It will be difficult for you to collect fruits without experiencing any bites of the ants. These ants protect the plant and fruits in exchange they get food and shelter from the trees.

Different organisms of different populations do not live in isolation from one another. They are dependent on one another for food, reproduction, dispersal, space, and protection.

In nature, we can often see relationships between two organisms. Sometimes both are dependent on each other for their survival such as in Lichen, an organism which is an association of blue-green algae and fungus.

The fungus helps in the absorption of water and minerals and the algal partner manufactures food. Both of them share this food.

In some relationship, one organism of two different types of organisms (species) is benefits, while the other remains unaffected. The organism which is benefited is called commensal and this incident is known as commensalism.

Example:

Arctic fox follows seal while Jackals follow Lion and Tiger they feed on the leftovers.

Symbiosis (or Mutualism):

When two or more organisms survive and benefited in nature by helping one another. This type of beneficial relationship is called symbiosis.

Example of Symbiosis :

Rhizobium, nitrogen-fixing bacteria form nodules in the root of leguminous plants such as peas, grams, beams, etc. Rhizobium fixed nitrogen and forms a nitrogenous compound which are shared by both. Plants give shelter and allow the Rhizobium to form nodules.

Some of you may have seen during the cultivation of paddy farmers use a reddish-green small plant, Azola in the field. This plant helps to increase production.

Azola a tiny aquatic plant (Fern) reddish-green in colour whose leaves contain nitrogen-fixing cyanobacteria (Anabaena azollae). This is a symbiotic association between them. Anabaena can capture atmospheric nitrogen.

Azola gives them shelter. Azola is used in the paddy fields as a biofertilizer (natural manure). Therefore, no need to add additional nitrogenous manure in the field.

Chapter 1 Interdependence Of Organisms And The Environment Few Examples Of Symbiotic Relationships

Chapter 1 Interdependence Of Organisms And The Environment Animals Eat And Being Eaten Who Eats Whom

If you are asked what things cows, goats, deer, and buffalo use as food-all of you have the ready answer. They eat plant materials. The animals who eat only plants are called herbivores (herbivores) on the other hand the animals who eat other animals are called carnivores (carnivores).

Herbivorous herbivores :

Herbivores are animals who eat only plants example cows, Deer, goats, etc.

Carnivorous/carnivores:

The animals mostly eat meat or the flesh of animals example tigers, lions, etc.

Omnivorous (omnivores):

Omnivore is an animal that eats either animals or plants or both example pigs, bears, men, etc.

If you observe carefully in nature one animal eats another and himself becomes the prey for some other animals.

Predator and Prey:

Tiger eats deer. Here tiger is called the Predator and the deer is called the Prey. The organism which does the act of capturing, killing, and eating another organism (animal) is called a predator.

On the other hand, the organism which is being killed and eaten is called the prey. See another example- A toad eats insects. They (toads) are being eaten by snakes. The snakes become the food of eagles or peacocks.

Predator and Prey (relationship):

Examples:

 

Make a list of animals of herbivores, and carnivores :

Prey and Predator

Animal	Nature	Where you have seen	What docs it cat (Prey)	Predator
1. Deer	Herbivorous	Forest, sanctuary or zoological garden	Grass, plant-parts	Tiger, Lion (carnivores)
2. Monitor Lizard	Carnivorous	Grass-land  near pond, Lake, river, forest, bushes	Snake, “crocodiles gg, fib., rat, ground birds, and  their eggs	Big animals like Python etc.
3  ……………	3  ……………	3  ……………	3  ……………	3  ……………

 

Chapter 1 Interdependence Of Organisms And The Environment Parasitism

Living on others and taking food from it.

Have you seen Leech attach with the body of a cow or buffalo? Have you seen lice, tiny brownish insects present in the hairs of a human head. Leech and lice both suck blood from which organisms they attack, these animals are called parasites.

 

The organism that feeds on another living organism without killing it (doing harm to the host) is called a parasite (for example. a bed bug). The parasite is harmful to the host (from which the parasite collects food).

Host:

The host is the organism from which the parasite obtains nourishment.

Parasite:

The organism (usually smaller than the host) obtains nourishment from a larger organism called the host and spends a part or whole of its life on or inside the body of the host is called a parasite. example Lice (animal), Swarnalata (plant).

Temporary parasite	Mosquito (Anopheles, Culex)
Permanent Parasite	Human louse (external) Tapeworm (Taenia) (internal)
Ectoparasite	Leech, Bed bug.
Endoparaslte	Plasmodium. Taenia

 

Complete the table :

List of a few parasites and their location and the harm they cause.

Parasitic Organisms	Host	Location (Where it lives)	Harmfulncss (How It harms the host)
1. Tuberculosis bacteria (TB) [Mycobacterium tuberculosis)	Man and some other mammals	Lung, Bones, Lymph nodes, etc	Causing Tuberculosis (TB) —fever, cough, weakness, weight loss, late-stage blood in the cough.
2. Tape worm [Taenia solium)	Man, pig, cow, etc	Intestine, stomach, brain, muscle cells	Weakness, seizure, anemia.
3. Malarian Parasite (Plasmodium)	Man	RBC, (Blood cell), Liver	Fever, weakness, anemia enlargement of liver and spleen.’.
4. Amoeblosis [Entamoeba histolytica) Protozoan microbes	Man	Human intestine	Diarrhea, dehydration, (loss of body water) pain in the lower intestine, mucus in the stool (mucousy stool)
5. Typhoid
6. Dengue

 

Swarnalata (Cuscuta)

A yellowish filamentous (wire-like) creeper plant that surrounds different areal parts of plants and sucks the juice from the host plant (by haustoria).

Dependence Of Man On Animals 

Many of you have experience of taking the juice of ‘tulsi’ or ‘Basak’ or ‘kalmegh’ leaves mixed with honey as ayurvedic medicine. Honey is a sweet viscous fluid obtained from a honeycomb prepared by the honey bees.

Chapter 1 Interdependence Of Organisms And The Environment Honey Is A Mixture Of Nectar Pollen And Saliva Of A Honey Bee.

Like honey we use many products of plants and animals as food, medicine, dress material, and other purposes, Humans are benefited from the animal world in many ways since the dawn of civilization.

 

On the basis of utility animals can be grouped in the following types

1. For food

1. We get milk from cows, buffalo, goats, sheep, etc.
2. We get meat from fowl, ducks, goats, sheep, cows, buffalo, pigs, etc., and eggs from birds.
3. We also get some bi-products from animals such as butter, ghee, panir, loss, etc.

Products	The animal from which we get it
1. Milk
2. Meat
3. Honey
4. Egg
5.
6.

2. Animals used in preparing to clothe

Many of our dress materials like ‘sari’, shart, ‘dhuti’, and many others are made up of silk beside plant products- cotton. Silk is a hard, shiny, fine thread extracted from the cocoons of silk-moth. Silk moth is a tiny insect (Bombyx mori).

We get laksha from insects, and silk from silk moths (insects). Warm clothes are prepared from wool. Wool prepare from the body hairs of sheep and some other animals.

Dress material- animal sources

3. Animals are used in producing medicine

You may have seen cod liver oil. It is used to massage the whole body of a baby and adult. This is good for skin and bone as it contains a good amount of vitamins A and D.

Sometimes Doctor (physician) prescribes some tablets (medicine) made up of liver oil extracts (Fish like shark, cod, Halibert liver oil) which are rich with vitamins A and D. These vitamins make our bones and teeth strong.

Vitamins are components of our diet present in very small amount though it has no calorie value but it protects our body and maintains growth. Deficiencies of vitamins cause many problems of our bodies.

Vitamins are A, D, C, E, and B-complex. We eat ‘mate’ of meat. This is the liver of that animal.

Name of the medicine of animal origin	Animal from which its obtained	Use of it
1. Cold-liver oil capsule	1.	1.
2. Antivenom (antivenin)	2.	2.  Used to treat Venomous snake bites
3.	3.	3.
4.	4.	4.

 

4. Role of Animal in pollution control/Animals that help in reducing pollution

All of you have noticed that crows eat dead and decaying substances from the roadside or uncleaned dustbins where waste materials are dumped. You may have also seen vultures (birds with ugly long hair and fewer necks) that eat dead and decaying animals.

 

 

These birds keep clean our environment. Crow is called a sweeper bird as it cleans our environment.

 

Name of the Animals reducing pollution	How the animals work	Remarks
1. Vulture	1.    Tree trunk-wood	1.
2. Crow	2.	2.
3. Owl	3.	3.

 

5. Animals that help in transportation

Some of you may have the experience to ride on bullock carts. From the old ages bulls, buffalo, camels, and horses are used to pull carts in remote places as well as in some urban areas.

These carts are used to carry passengers as well as goods from one place to another. Donkeys, horses, camels, and elephants are also used to carry people as well as goods where regular vehicles are usually not available.

Rain Deer (in Scandinavian countries), dogs are used in the polar regions particularly in the Arctic circle to pull the ‘Sleigh carts’, which carry goods and polar people. Horses are used since the ancient period for the speedy transport of persons, especially to send messages in the battlefield.

Name of the animals that help in transport	Types of Carriage	Nature of carriages
1. Horse
2. Bullock-carts
3
4

6. Animals that help in Agriculture

If you go to the village side during the rainy season you may find some small farmers are still using bullocks for plowing. Though nowadays tractors or other new machines are used in a large scale.

Bullock, camel, buffalo, horse, and donkey are also used to separate grains from crop plants.

Name of the animal	How the animals are used in agriculture	Remark
1. Bullock (Ox)	Plowing, pulling leveler to leveling the uneven agricultural field.	Small farmers use them to cultivate small areas, (nowadays tractors are usually used in this purpose)
2. Horse	–	–
3. Camel	–	–
4. Donkey	–	–

Chapter 1 Interdependence Of Organisms And The Environment Use Of Microbes In Human Welfare

Microbes we depend upon :

If you follow the process of curd preparation at home or in the sweet shop you will see a small amount of card as inoculum (saja) are added to milk during the preparation of new curd and under a suitable temperature this curd-mixing milk turns into curd.

Why does this happen? A type of microbes known as Lactobacillus is responsible for curd formation. With the transfer of old curd millions of Lactobacillus, microbes transfer to milk. These microbes (LAB) grow in milk and convert it into curd.

Lactobacillus is commonly called lactic acid bacteria or LAB. The organisms which are not visible with the naked eye are viewed under a microscope only and are called microbes.

Like curd, the dough which is used for making ‘dosa’ and ‘idli’ is also fermented by microbes (bacteria). A number of traditional drinks (‘hanria’, mohua, etc) and food are also made by fermentation.

Fermentation is the process in which a substance mainly sugar (carbohydrates) breaks down into simpler substances (alcohol or any organic acid) Microorganisms (microbes) like yeast (fungus), and bacteria usually play role in the process.

Yeast :

Single-cell fungus Scientific name-Saccharomyces cerevisiae

Steps of making curd (Complete the table)

Preparation of bread :

Most probably all of you have seen bread and experienced its test. Do you know how this soft, porous food prepare? Bread is made up of flour, water, and a little bit of sugar.

During its preparation ‘yeast’, a kind of single-cell fungus is mixed with the dough (flour, water, and sugar mixture). Yeast helps to ferment the dough. During fermentation carbon dioxide (CO₂ ) and alcohol are produced.

CO₂ helps in swelling dough. During breaking CO₂ comes out, thus pore is formed in the bread.

Preparation of medicines :

Nowadays many of you are familiar with the term antibiotics. If you go to a medicine shop you will find different types of antibiotics. Sometimes doctors prescribe antibiotic medicines to cure certain diseases.

Antibiotics are chemical substances that are produced by some microbes (bacteria, fungus) which can kill or retard the growth of other disease-causing microbes. Many of you are familiar with the drug penicillin, a commonly used antibiotic. Penicillin is prepared from penicillium-a fungus

Nowadays scientists are able to prepare many antibiotic medicines (antibiotics) from different microbes. Streptomyces is the largest antibiotic medicine-producing microbes (bacteria) (antibacterial, antifungal, antiparasitic medicine).

Many of its products are applied in humans and are used as veterinary medicine, agriculture, as well as antiparasitic agents. Erythromycin and Streptomycin have commonly used antibiotics derived from streptomyces.

Complete the Table :

Chapter 3 Element Compound And Mixture Matter

Matter:

All of us have an idea that we live in an environment full of different kinds of matter having varied properties. Air, water, oil, milk, book, chair, table, gold, silver, pen, pencil, sugar, etc. are all examples of matter.

The matter around us generally exists in three different states-solid, liquid, and gas.

For example:

Ice, iron, salt, etc. are solid; water, mercury, oil, bromine, etc. are liquid; air, oxygen, carbon dioxide, nitrogen, etc. are gas.

Chapter 3 Element Compound And Mixture Classification Of Matter

Of the varieties of matter that we see around us some are pure and some are impure. A pure substance is one which contains one kind of material throughout its body.

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The substances that contain more than one kind of pure substance are necessarily impure substances or mixtures.

Types of pure substances:

The result of elaborate investigations show that pure substances are of two types:

1. Element and
2. Compound.

Chapter 3 Element Compound And Mixture Element

An element is a pure substance that can not be broken or decomposed into a new substance by any chemical means.

For example:

Breaking down a piece of iron we get tiny particles which contain all the properties of iron like attraction by a magnet and no new particles having different properties are obtained.

This means that iron contains nothing other than iron. Similar results will be found for aluminium or copper.

More examples:

Gold, copper, iron, zinc, silver, mercury, carbon, sulphur, phosphorus, chlorine, bromine, iodine, hydrogen, oxygen, nitrogen, etc.

Do you know that till date 116 elements have been discovered, of which 92 elements are found in nature and they are called natural elements. The rest 24 elements have been discovered by scientists artificially, so they are called artificial elements.

Elements can be solid, liquid or gas:

 

Solid elements	Liquid elements	Gaseous elements
Gold, copper, iron, zinc, carbon, etc.	Mercury, bromine, etc.	Hydrogen, oxygen, nitrogen, chlorine, etc.

Chapter 3 Element Compound And Mixture Study Of Metals And Non Metals

Based on physical and chemical properties, the elements are further classified into three groups:

1. Metal
2. Non-metal and
3. Metalloid.

1. Metals:

The elements which are in general hard solids at room temperature with high melting and boiling points, lustrous (shiny), heavy, malleable, ductile, good conductors of heat and electricity, reflect light and produce a characteristic sound when struck (i.e. sonorous) are called metals.

Physical properties are exhibited by a substance externally without any change of its composition.

Chemical properties are exhibited by a substance when it undergoes a complete change of its initial composition due to the action of some other substances or by heat or electricity or sound.

In general, metals are solids. But, mercury is an exception-It is found in a liquid state at room temperature.

More example:

Gold, iron, tin, silver, copper, lead, aluminium, zinc, mercury, sodium, potassium, calcium, magnesium, etc. About 70 metals are found in nature.

Exceptions:

1. Mercury is liquid though it is a metal.
2. Sodium is soft and light though it is a metal. Sodium can be cut with a knife.

2.  Non-metals:

The elements which are in general soft with low melting and boiling points, non-lustrous (non-shiny), brittle, non-conductor of heat and electricity, which do not reflect light and do not produce sound when struck (not sonorous) are called non-metals.

Non-metals can be solid, liquid or gas.

1. Solid non-metal: Carbon, sulphur, boron, iodine, phosphorus, silicon, etc.
2. Liquid non-metal: Bromine.
3. Gaseous non-metal: Hydrogen, oxygen, nitrogen, chlorine, etc.

Malleability:

It is the ability of a substance due to which it can be hammered into sheets. Gold and silver are highly malleable. Non-met- als are transformed into powder when hammered hard.

Ductility:

It is the ability of a substance due to which it can be drawn into wires. Gold can be drawn into a very thin wire.

 

Exceptions:

1. Graphite (a form of carbon) is a good conductor of electricity though it is non-metal.
2. Diamond (a form of carbon) is a very good conductor of heat though it is a non-metal. Diamond is hard.
3.  Lodine is solid. It is lustrous though it is a non-metal.

Chapter 3 Element Compound And Mixture Compound

In ancient times, Indian philosophers thought water, air, and soil are the main constituents of the earth. Scientist Henry Cavendish first proved that water is not the main substance-it can be decomposed into two simpler substances, namely, hydrogen and oxygen.

Activity:

Take a beaker and pour a little water in it. Add a little acid in the water. Take a medium-sized rubber cork and two iron nails. Fix the nails on the cork with a little gap between them and dip the cork into the water as shown in inCombining 3-4 electric cells make a battery.

Join two copper wires at two opposite ends of the battery. Join the wires with the nails through a switch. Then, switch on and allow current to pass through the arrangement.

You will observe that gas bubbles are evolving at the two nails. To know the nature of the evolved gases, you are to hold two inverted gas jars filled with water over the nails.

Gases will be collected in the gas jars by downward displacement of water. When the gases become filled completely, the mouth of the gas jars are covered with a glass lid and kept erect.

The two gases are hydrogen and oxygen.

1.  When a lighted splinter is inserted into the gas jar filled with hydrogen, it is put off but the gas burns with a blue flame.
2. On introducing a glowing splinter into the gas jar containing oxygen, the glowing splinter rekindles but the gas does not burn itself.

Also, it can be verified that hydrogen and oxygen are present in water in the ratio of 1: 8 by weight.

Chapter 3 Element Compound And Mixture Learning Outcome

Water on electrolysis gives hydrogen and oxygen. Water is liquid but hydrogen and oxygen are gases. Hydrogen is combustible and oxygen supports combustion.

Water, on the other hand, is neither combustible nor a supporter of combustion-rather if it is used to put out a fire. So, there is no resemblance in properties between hydrogen and oxygen, each of which differs from water.

Evidently, water is a complex substance compared to hydrogen and oxygen. Here, the complex substance water is a compound. In a compound, the properties of the constituents are lost and new properties appear instead.

Similarly, ammonia is a compound of two elements-nitrogen and hydrogen, carbon dioxide is a compound containing carbon and oxygen.

More examples of compounds :

State	Name of compound	Constituent elements
Solid	Table salt	Sodium + Chlorine
	Glucose	Carbon + Hydrogen + Oxygen
	Soda	Sodium + Carbon + Oxygen
Liquid	Kerosene	Carbon + Hydrogen
	Alcohol	Carbon + Hydrogen + Oxygen
	Sulphuric acid	Hydrogen + Sulphur + Oxygen.
Gas	Methane	Carbon + Hydrogen
	Hydrogen chloride	Hydrogen + Chlorine
	Hydrogen sulphide	Hydrogen + Sulphur

 

Definition:

A compound is a pure substance which can be disintegrated by chemical means into two or more elements.

Alternatively, When two or more elements combine in a definite ratio by weight to produce a substance with new properties then the substance produced is called a compound.

Characteristic properties of compounds :

1. A compound is formed by a chemical combination of two or more elements in a fixed proportion by weight.
2. The composition and properties of all portions of a compound must be the same, i.e., it must be homogeneous.
3. The constituents of a compound can not be separated by simple physical means.

Chapter 3 Element Compound And Mixture Mixture

A mixture is an impure substance.

Two or more elements or compounds may remain blended together in any proportion by weight so that the individual properties of the ingredients are retained.

For example:

On mixing one or two tablespoons of sugar in water taken in a glass and stirred thoroughly by a spoon, the sugar dissolves in the water and a mixture is formed.

Any portion of the mixture tastes equally sweet. The properties of both sugar and water remain unchanged in it, so it is a mixture.

Mixtures	Name of the constituents
Air	Oxygen + Nitrogen + Water vapour + Inert gases
Sea water	Water + Salt
Smoke	Air + Fine carbon particles
Soda water	Water + Carbon dioxide
Lemonade	Water + Sugar + Carbon dioxide
Beverage	Water + Sugar + Lemon

 

Characteristic properties of mixtures:

1. The constituents of a mixture remain side by side.
2. The constituents are blended in any proportion by weight.
3. The constituents of a mixture can be separated easily by physical means.

Chapter 3 Element Compound And Mixture Concept Of Atoms And Molecules

In the 19th century, the famous British scientist John Dalton first developed a scientific theory regarding the structure of matter. He proposed that all matter is made up of very minute, indivisible particles called the ‘atoms’ which can neither be created nor destroyed.

 

 

An element is made up of one type of atom only. Later Amedeo Avogadro suggested that the atoms of gaseous elements like hydrogen, oxygen, nitrogen, etc.

cannot exist in nature freely-rather they are present as particles joining two atoms together. He called these particles as ‘molecules’. Atoms of the same or different elements combine to form a molecule.

Chapter 3 Element Compound And Mixture Symbol Formula And Valency

Symbol:

There are so many elements that it is not easy to represent an element by writing its full name. Conveniently it is done by symbols. The symbol is the short form or abbreviated name of an atom of an element.

Scientists follow a different procedure for shortening the names of the elements. John Jacob Berzelius used the first letter (in the capital) of the name of the element as its symbol.

For example:

Name of element	Symbol
Hydrogen	H
Oxygen	O
Boron	B
Fluorine	F
Nitrogen	N
Sulphur	S
Carbon	C
Iodine	I

 

It has been found out that two or more elements have the same first letter. In those cases, the second letter (in small) is added to the first letter (in the capital).

For example:

 

Name of element	Symbol
Calcium	Ca
Helium	He
Aluminium	Al
Bromine	Br
Cobalt	Co
Lithium	Li
Beryllium	Be
Nickel	Ni

 

In some cases, second prominent letter (in small) is added to the first letter (in the capital).

For example:

Name of element	Symbol
Chlorine	Cl
Magnesium	Mg
Chromium	Cr
Manganese	Mn

 

In some cases, symbols are derived by taking a single letter or two letters from the Latin name of some elements.

For example:

Name of element	Latin name	Symbol
Sodium	Natrum	Na
Copper	Cuprum	Cu
Gold	Aurum	Au
Potassium	Kalium	K
Iron	Ferrum	Fe
Silver	Argentum	Ag

 

Formula:

The formula is the shortcut way to express the molecule of a compound. It expresses the number of atoms of each element present in the compound.

For example:

One molecule of hydrogen, oxygen and nitrogen consists of two atoms and their formula are written as H₂, O₂, and N₂ respectively. Here, the number 2 represents the number of atoms.

So, ‘P’ refers to a molecule of phosphorus which contains 4 atoms, ‘O₃ ‘ refers to one molecule of ozone which contains 3 atoms of oxygen, etc. A molecule of water contains 1 atom of hydrogen and 2 atoms of oxygen, so the formula of water is H₂ O1 or simply H₂ O.

Atomicity is the number of atoms present in a molecule. H₂ , O₂ , N₂ have atomicity = 2; atomicity of P₄ = 4; atomicity of O₃ = 3, atomicity of H₂ O = 3, etc.

More Examples

Name of compound	Formula	Number of atoms	Atomicity	Meanings
Carbon monoxide	CO	C = 1, O = 1	2	Mono-1
Nitrogen dioxide	NO2	N = 1, 0 = 2	3	Di-1
Phosphorus trichloride	PCI3	P = 1, Cl = 3	4	Tri-1
Carbon tetrachloride	CCI4	C = 1, Cl = 4	5	Tetra-4
Phosphorus pentachloride	PCI5	P = 1, Cl = 5	6	Penta-5

 

Valency

In general, the valency of an element is expressed by the number of hydrogen atoms which can combine with one atom of an element to form a compound.

Name of compound	Formula	Number of atoms	Valency of another element = Number of combined H-atoms
Water	H2 O	H = 2, 0 = 1	Valency of O = 2
Hydrogen chloride	HCI	H = 1, Cl = 1	Valency of Cl = 1
Ammonia	NH3	N = 1, H = 3	Valency of N = 3
Methane	CH4	C = 1, H = 4	Valency of C = 4

 

Chapter 3 Element Compound And Mixture Various Mixtures Solution

You already got the idea that a mixture contains more than one type of substance mixed in any proportion. Already it is told that solution is a mixture.

The solution of sugar or salt in water is a homogeneous mixture as the proportion of sugar or salt and water in every part of the mixture is the same.

In a solution, the substance whose proportion is less than the other is called the solute and whose proportion is comparatively larger. then the other is called solvent.

Generally, in a solution of sugar or salt in water, the solid substance (sugar or salt) is the solute and the liquid substance (water) is the solvent.

Thus, Solution = Solvent + Solute

In general, the colour of a solution is the same as that of the solute.

Solute	Solvent	Solution	Type of the solution
Copper sulphate	Water	Copper sulphate solution	Solid-liquid solution
Glycerine	Water	Glycerine solution	Liquid-liquid solution
Carbon dioxide	Water	Soda-water	Gas-liquid solution

 

Chapter 3 Element Compound And Mixture Process Of Separating Components Of A Mixture

The constituents of a mixture can be separated by a simple physical process. A single particular process can not be applied to all types of mixtures. Any process suitable for a particular mixture may not be applicable in the case of another mixture.

Filtration:

Perhaps you know that muddy water (a mixture of water, mud, sand, etc.) looks turbid. If it is kept in a vessel undisturbed for some time you might have noticed that mud, sand, etc.

Settle at the bottom of the vessel and the water above these settled solid matters appears more transparent. The settled solid is called sediment. The clear water (or supernatant liquid) at the top may be poured off without disturbing the sediment.

 

 

This process of separating mud from water is called decantation. The supernatant water is apparently clear but still contains tiny particles. So by decantation complete separation is not possible.

Then, a better process called filtration is employed. A special type of porous paper called filter paper is generally used in laboratories for the separation of an insoluble solid like sand or chalk dust from a liquid (water).

A mixture of sand and water is taken in a beaker. A circular (dry) filter paper is folded two times and opened in the form of a cone such that three folds remain on one side and a single fold on the other.

The cone is fitted in a funnel and the filter paper is made wet with a few drops of water so that it sticks to the sides of the funnel. The mixture is then poured slowly into the filter paper down a glass rod.

Water passes through the pores of the filter paper while sand is retained in the filter paper. Water collected in a receiver looks transparent; it contains no suspended solid particles.

This clear water is called filtrate, and the solid left on the filter paper is called the residue. The total process is called filtration.

Crystallization

By filtration, a solution of sugar can not be separated into its constituents, because sugar disappears completely in water. In that case, crystallization is a suitable process.

Take a solution of sugar and water in a beaker. Heat the solution gently and go on heating with constant stirring with a glass rod. The solution will become more and more concentrated. Then allow the solution to cool down at room temperature.

Some granular crystals of sugar separate out from the mixture. Such little grains have a geometric shape. There are called crystals. The process of separating solid crystals from a solution is called crystallization.

Separation by using a magnet:

You know that a magnet attracts magnetic substances like iron. Take a mixture of iron fillings and sand. Spread the mixture over the clean paper. Place a magnet over the mixture and pull it back and forth through the mixture.

Iron fillings are attracted by the magnet, but the sand particles remain unattracted. Repeat the process several times. The magnet is taken outside and by jerking, iron fillings are separated out from the sand.

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 5 Measurement Necessity Of Measurement In Our Daily Life

Measurement is the basis of science. In our daily life, we need to measure different things for different purposes.

See the following purposes:

1. How far is your school from your house?
2. When your school starts ?
3. When your school close?
4. How do you buy vegetables, fruits, rice, fish, etc. from the market?
5. How do you buy packet milk, mustard oil or rice bran oil?
6. How do you know that your friend has a fever?
7. Which one is longer-door or the window of your study room?
8. Which contains more milk-a cup of milk or a glass of milk?
9. Which has a more area-your bedroom or your bathroom?
   ….. and so on.

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To answer all these questions, you need to measure something. Sometimes it may be the length, mass, time, volume, area, temperature, etc.

Now the question arises-how can you measure these things?

You need some instruments to measure length, time, etc.

For example, when we buy sugar or wheat, the grocer measures its mass (usually we call it weight) using a common balance. Sometimes an electronic balance is used for the same purpose for more accurate measurement.

When we fall sick, the doctor measures our body temperature by using a clinical thermometer.

Chapter 5 Measurement Physical Quantities

Anything that can be measured with certain instruments is called a physical quantity. Some of examples of physical quantities are length, breadth, height, area, volume, mass, weight, density, time, temperature, etc.

The number of physical quantities that can be measured are very large. All physical quantities are classified as fundamental and derived quantities.

Fundamental and Derived quantities :

Suppose you want to measure the floor area of your study room. Using a measuring tape, you will record the ‘length’ and ‘breadth’ of the floor and then multiply these two to get the actual floor area, i.e., Area = length and breadth.

Again, if you want to measure the volume of the room, by the same way you are to record the ‘height’ of the room and use the formula Volume = length x breadth x height.

Note that, while measuring ‘area’ you used the physical quantity ‘length’ for twice and while measuring ‘volume’ the physical quantity ‘length’ is used thrice.

So, you understand that the physical quantity ‘length’ does not depend on other quantities whereas area, volume or density (Density = mass + volume) depend on other physical quantities.

Definition:

The physical quantities which do not depend on other quantities (i.e. which cannot be simplified further) are called fundamental quantities. Length, mass and time are examples of fundamental quantities.

The physical quantities which are expressed in terms of two or more fundamental quantities are called derived quantities. Area, volume, density, speed, force, momentum, etc. are examples of derived quantities.

Chapter 5 Measurement Units Of Measurement

All measurements are based on the comparison.

How?

Usually, the thing which to be measured is compared with a known constant quantity of the same nature as a ‘standard’. This standard quantity is nothing but a standard unit. Let us try to understand the meaning of this statement.

Earlier, to measure the length the ancient men used various kinds of standards such as a footstep (a pace), an arms length (a cubit), a hand span, a foot or width of four fingers, etc.

Suppose, you measure the length of your study room with the help of your foot. If it is equal to twenty feet, you may say that the length of your study room is equal to twenty foots.

In this case, the foot is taken as the unit of length and twenty is the numerical value of the measurement. See the following where some earlier units of measurement of length are shown.

However, all these units vary from person to person and led to a lot of confusion.

You see that any measurement involves two things:

A number and a unit. No measurement is complete unless both the number and the unit are mentioned.

For example:

If your height is 1.5 metres, then 1-5 is the number and the metre is the standard unit. Your mass of 45 kg means that your mass is 45 times the standard mass of 1 kg. Here 45 is the number and kg is the standard unit.

So, if we say that the mass of a body is 20-it is totally meaningless, rather we are to say 20 grams or 10 kilograms.

What is a unit?

Unit:

For the measurement of any physical quantity, some convenient and definite quantity of the same nature is chosen as a standard and the physical quantity is expressed by a numerical value to represent how many times the standard quantity is contained in the given physical quantity.

This standard quantity is called a standard unit. The units used to measure fundamental quantities such as length, mass, time are called fundamental units and the units used to measure derived quantities like area, volume, density, etc. are called derived units.

Chapter 5 Measurement System Of Units

In ancient days, different systems of units were used. In France in 1791, the metric system for standard units was first adopted. In this system, metre-kilogram-second (MKS) were taken as the base units.

Of length, mass and time respectively; And for measuring smaller physical quantities centimetre-gram-second (CGS) were taken as the base units of length, mass and time respectively.

To make measurement more scientific, convenient and uniform, scientists accepted a system of units called the SI units or International system of units in the year 1960.

It is used in science and technology all over the world in a uniform pattern. In this system, there are seven fundamental quantities.

Physical Quantity	Unit	Symbol
Length	metre	m
Mass	kilogram	kg
Time	second	s
Electric current	ampere	A
Temperature	kelvin	K
Intensity of light	candela	cd
Amount of substance	mole	mol

 

Multiples And Sub Multiples Of Metres

It is the fact that for the measurement of long lengths or distances, we require larger units of metre and for measuring smaller lengths, we require smaller units of the metre. For example, the distance from Howrah to Puri is 499000 m or 499 thousand metres.

To express such a long distance in metres is not practical. Therefore to measure larger lengths, we need different multiples of metres. Similarly, to measure the length of a small object like a pencil, pen or eraser, the metre is too big.

Therefore, to measure lengths smaller than a metre we need different sub-multiples (or fractions) of the metre. And see the tables.

Multiples of metre

Multiples	Symbol	Relation
1 decametre	dam	10 metre
1 hectometre	hm	100 metre
1 kilometre	km	1000 metre

 

Sub-multiples of metre

Sub-multiples	Symbol	Relation
1 decimetre	dm	1/100 metre
1 centimetre	cm	1/100 metre
1 millimetre	mm	1/1000 metre

 

Chapter 5 Measurement Measurement Of Different Physical Quantities

Measure of length

In general, the shortest distance between two ends of an object is called its length. Breadth, depth, height, thickness, radius, diameter, etc. are different physical quantities but all these are lengths.

The practical units of length are metre, centimetre, inch, foot, etc. for everyday use.

Definition of international standard metre:

A cylindrical bar made of an alloy of platinum (90%) and iridium (10%) was kept at the International Bureau of Weights and Measures in Paris, France.

The distance between two fine marks engraved on the platinum-iridium bar maintained at 0°C (or.273K) temperature is called the International Prototype of a metre.

You know that 1 centimetre = 1/100th part of 1 metre
1 inch (symbol”) = 2.54 centimetre
1 foot (symbol) = 12 inches or 0.3048 cm

Common instruments we use to measure length are rulers, metre scales and measuring tapes. Look at your ruler (15 cm long) and find that it is marked with centimetres on one side and inches on the other side.

To measure the length of a pencil, the zero mark of the scale is made to coincide with one of the ends of the pencil and the scale reading coinciding with the other end of the block is taken.

To reduce error in this measurement, the eye must be positioned at vertically above the point whose measurement is to be taken.

Measurement Of Area

In general, area means the space occupied by a flat shape or the surface of an object. Its SI unit is m².

Suppose you are asked to measure the area of your science book. Place the book on a table and measure its length and breadth with an ordinary scale and then apply the formula: Area = length and breadth.

If you are said to measure the area of a spherical object like a football, you are to measure its diameter first. and like this, held the sphere in between two books or rectangular blocks.

Measure the distance between the inner edges of the blocks by an ordinary scale. This distance is the diameter of the sphere. Then apply the formula: Area = π × diameter x diameter. [π (pi) is a constant number whose value is 22/7 or 3.14].

The SI unit of area is square metre (symbol m²) where 1 m² = 1 m x 1m = 100 cm x 100 cm = 10,000 cm².

Measurement Of Volume

In general, volume is the quantity of space occupied by the closed surface of any shape of a substance (solid, liquid or gas). Its SI unit is cubic metre or m³ where 1m³= 1m x 1m x 1 m = 100 cm x 100 cm x 100 cm = 1000000 cm³.

If the length, breadth and height of a cube are of 1 m then the volume of the cube will be 1 m³. The volume of a liquid is expressed by the unit litre (symbol L).

Sometimes smaller unit of litre like millilitre (symbol ml) is used where 1 litre = 1000 millilitre.

There are different instruments used to measure the volume of a liquid. A measuring cylinder is one of these. In the three measuring cylinders of different sizes (or volumes) are shown. They are graduated in ml from bottom to upwards.

Measuring cylinders are made of glass or plastic and availability of different sizes such as 50 ml, 100 ml, 200 ml, etc.

Suppose you are said to measure the volume of tea in a cup or some milk, you are to pour the total amount of that liquid into an empty measuring cylinder.

Take the scale reading where the uppermost surface of the liquid touches the measuring cylinder. This is how you can know the required volume of some liquid.

Measurement Of Time

What is the meaning of ‘time’?

‘Time’

The interval between any two instances (or incidents or events) is called ‘time’.

If you are asked to say what is the time duration of your tiffin break?

Here, two events are the ‘starting of tiffin break’ and the ‘ending of tiffin break’. The interval between these two events is the actual required time.

The standard unit of time is second (s). It is actually measured in terms of a mean solar day. A mean solar day is a time taken by the earth to complete one rotation about its own axis. Its value is 24 hours.

That is, 1 mean solar day = 24 hours (24 x 60 x 60) seconds = 86400 s
Thus, 1s = 1/86400 part of 1 mean solar day

To measure the time of larger events, larger units like minutes, hours, days, months, years, decades, and centuries are used. For example, you express your age in years, months and days.

1 min = 60s
1h = 60 min
1 day = 24 h
1 year = 365¼ days
1 leap year = 366 days.
1 decade = 10 years
1 century = 10 decades

How To Measure Time

The instrument used to measure time is a clock or watch. The earlier people used to estimate time by looking at the visible position of the sun in the sky.

Then came the early clocks like sundial clocks, sand clocks, simple water clocks, etc. (see the shown below). The sundial clock has a flat plate called the dial and a metal rod which casts a shadow on the dial at different hour lines when the sun appears to move at different positions in the sky.

 

Nowadays, time is measured with the help of modern advanced clocks and watches like pendulum clocks, table clocks, wristwatches, digital clocks, stopwatches, modern atomic (quartz) clocks, etc.

Our watches record time in seconds, minutes and hours. The minimum time it can measure is one second, i.e., by it less than a second cannot be measured. But in certain activities, there is a need to measure even a 1/100th fraction of a second accurately.

A digital clock is used for such purposes. For example, to measure the time taken by an athlete to finish a 100-metre race, the knob is to be pressed at the starting point and then at the finishing point.

 

The time interval gives the accurate time in seconds. For re-use, the knob is to be pressed once again to bring both the minute’s hand and the second’s hand to the initial position.

Stopwatch can measure 1/10th of a second accurately. Nowadays digital stopwatch is preferably used as it can measure 1/100th of a second.

Measurement Of Mass

The mass of a body is the amount of material substance contained in it. It can be measured by using a beam balance or physical balance. To measure the mass of rice, wheat, pulses, sugar and others, a shopkeeper usually uses standard weights like 1 kg, 500 g, 100 g, 50 g, etc.

The body whose mass is to be measured is placed on the left pan and standard weights are placed on the right pan till the beam comes in a horizontal position.

To measure small masses to a precision of 1 mg or even less, a physical balance is mainly used in laboratories and in jeweller shops.

Chapter 5 Measurement Importance Of Estimation In Measurement

In our daily activities, we do not always do work with accurate measurements using instruments. In cases where actual measurement is practically not possible, we often make estimations or approximations.

For example:

1. We add sugar to a cup of tea by estimation only.
2. You may take 10 minutes to reach your school by walking. If you walk fast, you may take 9 minutes or if there is a jam on the road, the time maybe 11 minutes.
3. For cooking food, if the amount of salt is slightly less or more, it does not make much difference.
4. When we buy vegetables or groceries, the measurement may not be accurate. But when we buy gold, the measurement should be precise.

Note: Estimation is a skill that one learns by practice.

However, while dealing with some devices like computers, rockets, etc. accurate measurement of various parameters is a must. The errors that come in readings can be reduced by taking the average of a large number of measurements of the same quantity.

Measurement Of Plant Growth

You must know that plant growth means the process by which a plant grows in size. Apparently simply by looking you can estimate about the growth of a plant but to know the actual growth you must need an apparatus.

An auxanometer or arc-auxanometer is such an apparatus. See shown alongside. In this apparatus, there is a flexible wire attached with the plant apex at one end and a weight attached at its other end.

This wire passes over a pulley or a wheel. A pointer (or indicator) is attached with this wire. The pointed end of the indicator lies on a scale like an arc of a circle.

The indicator initially rests at ‘0’. When the height of the plant increases, the pulley rotates and accordingly the indicator moves over the scale. The scale reading gives the magnitude of plant growth over a certain period of time.

The rate of plant growth can be calculated by diving the increase in plant height by time.

Measurement Of Animal Growth

Using a centimetre scale we can measure the growth of man and other animals. In your physical education class, you must have seen the centimetre scale.

You are to stand straight in front of it and you are to note the point where your head touches the indicator. This length gives the measurement of your height in centimetres.

To measure the average height of all students in your class measure the height of all. Add all the values. Divide the total height by the number of students. You will get the average height of the students in your class.

You can also find which height is maximum and which height is minimum. Taking the difference of these two values, you can also find the range of height of the students in your class.

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products

Chapter 6 Primary Concept Of Force And Energy Concept Of Rest And Motion

In our surroundings, we see some objects which do not change their positions with respect to time. They are called stationary objects or they are said to be at rest. Examples are our house, school, bank, post office, hills, trees, etc.

But moving vehicles, flying birds, walking people, falling raindrops, throwing balls, etc. occupy different positions at different instants of time in their immediate surroundings. The objects which change their positions with time are called moving objects or they are all in a state of motion.

Do you know that the rest and motion of something is always measured relative to a stationary second object in its immediate surroundings. Here, the position of the second object is known as a reference point.

Suppose you are traveling in a train. If you consider the reference point inside the train, you will see other passengers, walls or floors of the train at rest.

But if the reference point is considered to be outside the train like a platform or ground, everything inside the train compartment appears to be moving along with the train.

Read and Learn More WBBSE Notes For Class 6 General Science and Environment

This is the reason why looking outside the window, the passengers observe that the trees, buildings, etc. are moving backward.

Chapter 6 Primary Concept Of Force And Energy Concept Of Force

Can you say why does a football moves when kicked? What makes a moving ball on the ground to stop on its own? What makes a spring to elongate or contract? What makes a sponge or ballon to get deformed? How does a body change its speed or its direction of motion?……..

It is our common experience that an external force is a basic cause for all cases. For example-to run a cycle you are to apply a force by your leg on the pedal, you pull your drawer to open, you push your drawer to close, you push a heavy box to displace, you pull a box for displacing it across the ground, in a car the engine supplies a force by which the car moves, etc.

Chapter 6 Primary Concept Of Force And Energy Effect Of Force

A force can be realized only by the effects that it can produce on an object.

Let us see the following examples:

1. Force produces motion in an object or stops motion.

By pushing a car or by pulling a trolley, the car or trolley starts to move. But a moving object can be brought to rest when a force is applied in the opposite direction of its motion.
For example-a, a moving cycle can be stopped by applying brakes.

Sometimes, the applied force is not enough to produce motion in a stationary object. If you push a wall of your classroom, it will not move.

2. Force can increase or decrease the speed of a moving object.

If you push a moving cycle from behind, it moves faster. But if you push the moving cycle from the opposite side, the cycle would start to slow down.

3. Force can change the direction of motion of a moving object.

A player can change the direction of a football by kicking or pushing. A batsman can also change the direction of a cricket ball by hitting with the bat.

4. Force can change the shape and size of an object.

A sponge or ballon or dough (flour mixed with water) or a tube of toothpaste when pressed a little gets deformed. The shape of a toothpaste tube changes on squeezing. The size of the spring gets elongated on pulling and contracted on squeezing.

So, force is the external cause acting on a body that changes or tends to change the state of rest or of motion, the direction of motion or the shape and size of the body.

In fact, force is the basic cause of motion.

Units of force :

The commonly used unit of force is kilogram-force (symbol kg).
The SI unit of force is newton (symbol, N).
In the CGS system, the unit of force is dyne (symbol dyn).

Chapter 6 Primary Concept Of Force And Energy Force Without Touch

In our daily life, we come across with several cases of forces.

Basically, all forces are categorized into two groups:

1. Contact forces and
2. Non-contact forces or forces acting at a distance.

1. A force that is applied on an object by another object due to actual contact between the objects is termed as a contact force.

For example-kicking, a football, hitting a cricket ball with a bat, hammering a nail, writing with a pen, etc. are contact forces.

2. Non-contact forces come into play without any physical contact between the objects. This type of force act from a distance.

Examples are:

1. Gravitational force.
2.  Electrical (or electrostatic) force.
3. Magnetic force.

1. Gravitational force:

If you drop a stone from a certain height, it falls down. You know that the earth exerts pull (force) on the stone without touching it. In fact, the earth attracts everything towards its center.

This force is called gravitational force. We call this force as the weight of the object. So, the SI unit of weight is the newton.

Do you know that the weight of an object can be measured with a spring balance?

2. Electrostatic force:

Suppose you rub a plastic comb on your dry hair. Bring the comb near small pieces of paper. You will see that the papers are pulled towards the comb. Here also there is no actual contact between the comb and the papers.

 

3. Magnetic force:

When you bring a bar magnet near some iron nails, then the nails are pulled toward the magnet. Here, the magnet itself applies a force on the nails.

 

Chapter 6 Primary Concept Of Force And Energy Concept Of Energy And Its Different Forms

After playing football for one half you get tired and take some rest. You are asked to say the reason of such tiredness. You will say that energy is spent from your body while doing work.

Do you feel the same tiredness if you do not work hard for a long time ?-Certainly not. When energy is spent from your body you lose the ability of doing work. So, it is rightly said that energy is the ability to do work.

We get energy from the food that we eat daily. A body which is able to do some work is said to possess some energy. This means that work and energy are closely related to each other.

Types of energy:

In nature, energy can be found in different forms.

The different forms are:

1. Mechanical energy
2. Heat energy
3. Light energy
4. Electrical energy
5. Chemical energy
6. Magnetic energy
7. Sound energy
8. Nuclear energy.

Do you know that this energy can neither be created nor destroyed? Only one form of energy can be transformed into other forms.

Chapter 6 Primary Concept Of Force And Energy Mechanical Energy

It is the energy possessed by an object due to its state of rest or of motion.

This energy is of two types:

1. Kinetic energy and
2.  Potential energy.

You must have an idea that an object in motion gains some ability to do work, and it is called its kinetic energy. On the other hand, an object by virtue of its position, configuration, and shape gains some ability to do work, and it is called its potential energy.

Let us explain the idea with some examples:

1. You see that before taking a long jump (or high jump), an athlete brings his body in a state of motion by running for some distance. If he jumps standing at a point, he could not jump long. Actually, when the athlete runs, he gains an ability to jump by which he can jump a long distance due to his kinetic energy.
2. A cricket ball at rest possesses no kinetic energy. But, a moving ball possesses kinetic energy due to its motion and blows the stationary stumps away.
3. A bullet fired from a gun possesses kinetic energy due to its tremendous motion.
4. Moving wind gains the ability to do work due to its motion. A boat with a sail moves forward due to the kinetic energy of the wind. Moving wind can run a windmill due to its kinetic energy.
5.  A hammer while coming down from a height acquires an ability to do work. Due to this ability, the hammer possesses kinetic energy and drives a nail into the wood on striking.
6. See A book kept on a table at rest possesses potential energy due to its position. Here, ‘position’ refers to the height of the table top from the floor.
7. see the normal state of the spring coil in a watch. When the coil is wound up, then potential energy is stored in it due to the change in its configuration.
8.  In the dotted line shows the normal position of a bow. When the bow is bent, then due to the change of shape of its different parts, potential energy is stored in it.

 

 

Chapter 6 Primary Concept Of Force And Energy Transformation Of Energy

There are many examples of the transformation of energy.

1. A ball lifted from the ground to a certain height has only potential energy due to its position. When the ball falls down, its potential energy decreases and kinetic energy increases by the same amount. So it is an example of the transformation of potential energy into kinetic energy.
2. A hammer raised at a certain height possesses potential energy. To drive a nail, when it is brought down then the potential energy is converted into kinetic energy.
3. When a stretched bow is released as shown in the potential energy of the bow imparts kinetic energy to the arrow by which the arrow can move forward with high speed. So, this is an example of the conversion of potential energy into kinetic energy.
4. As shown in a ball is placed on a spring and the ball kept at rest ball remains initially at rest. If the spring is compressed and released immediately, it is seen that the compressed, spring has acquired the ability to push the ball.

 

 

 

Here, the spring on compression gains potential energy which on being released is converted into the kinetic energy of the ball.

More examples:

1.  When you rub your palms, you feel hot. If you rub for a long time, you feel hotter. In this occasion, mechanical energy is converted into heat energy.
2. When you play tabla or hit the drum with sticks, the sound is produced. So mechanical energy is converted into sound energy.
3. Bring a magnet near a nail. You see the nail to move toward the magnet. In this case, magnetic energy (of the magnet) is converted into mechanical energy (or kinetic energy of the nail).
4. 1. Switch on a bulb. 2. Switch on a fan. 3. Switch on an electric iron.
5. In the first case, the bulb gives light. So electrical energy is transformed into light
   energy.
6. In the second case, the fan starts moving, Here, electrical energy is transformed into mechanical energy.
7. In the third case, the iron becomes hot. So in this occasion, electrical energy is transformed into heat energy.
8. In an electric bell, when the switch is pressed current flows and electrical energy is converted into sound energy.
9. In the explosion of crackers, its chemical energy is converted into light, sound, and heat energies.
10. When you pour water into some quicklime taken in a pot, you watch that heat is produced. Here, the chemical energy of quicklime is transformed into heat energy.
11. When coal burns, the chemical energy changes into heat energy.
12. In a microphone, sound energy is transformed into electrical energy.
13.  In an electric cell, chemical energy is transformed into electrical energy.

 

Chapter 6 Primary Concept Of Force And Energy Sources Of Energy

It is a common fact that from food we get energy for our daily activities. Broadly speaking, these food come from both plants and animals.

Plant sources: Rice, Dal, Vegetables, Fruits, etc.

Animal sources: Fish, Meat, eggs, Milk, etc.

We know that sun is the main source of energy on earth.

Green plants absorb solar energy and prepare food by the process of photosynthesis. So, plants convert solar energy into chemical energy in food. Animals get food from plants. As a whole, both plants and animals directly or indirectly depend on solar energy.

Coal, mineral, petroleum, etc. are produced by the conversion of plants and animals of an earlier age which remained buried for thousands of years under the earth. So, the chemical energy stored in coal or mineral is actually solar energy.

Water from ponds, rivers, and lakes is evaporated by means of solar heat and forms the clouds which provide rainfall on earth.
Accumulated rainwater in the mountain comes down with high speed by which the water turbine is rotated and in this way, hydroelectric power can be generated.

Chapter 6 Primary Concept Of Force And Energy Concept Of Energy Flow

Green plants are able to prepare food. So, they are called producers. It is a fact that green plants maintain the ecosystem.

The organisms which feed on plants and plant products e.g. animals are called consumers.

The animals which live directly upon green plants are called primary consumers.

Example: Goat, Rabbit, Deer, Cow, etc. Primary consumers are herbivores.

Man is omnivores-because man eats both plants and animals and their products. The animals which eat primary consumers or herbivores are called secondary consumers.

Example: Frog (eats insects), Tiger (eats deer), etc.

The animals which eat secondary consumers are called tertiary consumers.

Example: Snake.

Food chain:

In nature, there is a predator-prey relationship of plants and animals in a chain-like structure. It is called a food chain.

 

Food web:

A food web consists of many food chains. It shows how different consumers are connected through different food chains. So, the food web can be considered as the natural interconnection of different food chains.

 

Examples of a food web

Food pyramid: 

A food pyramid is a triangular diagram representing an arrangement of plants and animals of a food chain step by step from bottom to top. Each step in a food pyramid is known as the trophic level.

In general, the producers occupy the first step and gradually the next upper steps are occupied by the primary consumers, secondary consumers, and tertiary consumers respectively.

In regard of energy transfer from one step to another, Lindermann’s law of ten percent is very important.

According to this law:

About 10% of energy assimilated at each trophic level is needed for the building of body mass and the rest 90% of energy is consumed for metabolic activities.

Chapter 6 Primary Concept Of Force And Energy Energy Crisis

Most of our energy requirements are met by the burning of fossil fuels like coal, petroleum, and natural gas. These are known as non-renewable sources of energy. These are being done so widely that in the coming days, we will face a crisis of energy.

Scientists have named such scarcity of energy sources as ‘energy crisis’. Do you know that 150 years ago the world population was approximately 100 crores; And, now it has become near about 600 crores? To fulfill the demands of such a huge population, we are using underground fossil fuels.

But their stock is limited. To overcome this situation, we are to be alert in using natural energies, side-by-side, to think about the use of non-conventional (or alternate) sources of energy such as solar energy, wind energy, tidal energy, co-thermal energy, biomass energy, etc. These are renewable sources of energy.

Chapter 6 Primary Concept Of Force And Energy Frictional Force In Our Daily Life

We see that a ball moving on the grass gradually slows down and stops on its own after moving through a distance.

Why?

Certainly, there is an external force that opposes the motion of the moving ball occurring between two surfaces (One of the ball and another of grass) which are in contact with each other. This force is called the force of friction or simply frictional force. It is a contact force.

Does the ball travel more distance on the floor than over the grass?

Actually, the ball faces more obstruction while moving over the grass. That is, the frictional force depends on the smoothness or roughness of the two surfaces which are in contact with one another.

Any surface, however rough or smooth, has a lot of irregularities like hills and valleys when viewed through a microscope. When two such surfaces slide (or tend to slide) over one another, the irregularities are interlocked with each other.

This is the reason why frictional force acts in a direction opposite to the direction of motion.

WBBSE Notes For Class 6 General Science and Environment

• • Chapter 1 Interdependence of Organisms and the Environment
  • Chapter 2 Phenomena Around Us
  • Chapter 3 Element, Compound and Mixture
  • Chapter 4 Rocks and Minerals
  • Chapter 5 Measurement
  • Chapter 6 Primary Concept of Force and Energy
  • Chapter 7 Statics and Dynamics of Fluid
  • Chapter 8 The Human BodyChapter 9 Common Machines
  • Chapter 10 Biodiversity and its Classification
  • Chapter 11 Habits and Habitats of Some Important Animals
  • Chapter 12 Waste Products