Class 6 Science Chapter 2: Diversity in the Living World

A Morning After Rain

It has rained in the night and the morning is cool. Madam Sulekha has asked two visitors to take her class out. One is Dr Raghu, a scientist from the research laboratory nearby. The other is Maniram chacha, an older man from the neighbourhood who can copy the call of almost any bird. The class is going on a nature walk, and they have been told to bring a notebook, a pen and water.

Two Guides, Two Ways of Knowing

It is worth noticing who is leading this walk. One guide trained in a laboratory. The other learnt by living beside these trees and listening for years. Neither knows everything the other knows. A child who thinks knowledge lives only in laboratories, or only in books, is going to miss half of what is out there this morning.

The Rule Before You Start

Dr Raghu sets one rule at the gate. Observe without disturbing. No plucking of leaves, no pulling of flowers, no chasing anything that moves. You may pick up leaves that have already fallen and keep them in a scrapbook. Everything else stays exactly where it is. The park is somebody's home, and you are a visitor in it.

Listen As Well As Look

Maniram chacha adds a second instruction, and it surprises them. Do not only look. Stop and listen. Birds are calling all round the park, and each kind of bird has its own call. He copies a few and the children try to copy him. Most of them are bad at it and all of them start hearing more than they did.

What They Actually Find

Within an hour the class has found grasses underfoot, bushes at the edges and large trees overhead. There are birds on the branches. Butterflies move between flowers. Monkeys cross from one tree to the next without touching the ground. None of this was arranged for them. It was all there yesterday too, unwatched.

A Word for All of It

The whole variety of living things in a place has a name. It is called biodiversity. It counts how many kinds there are and how different they are from each other. A forest has a great deal of it. A single cricket field has much less. India, taken as a whole, has more than almost any other country.

Variety Between, and Variety Within

There are two kinds of variety here, and children usually notice only the first. Between kinds is obvious: a monkey is not a butterfly. Within one kind is quieter. Two grasses side by side may be different kinds. Every bird species has its own call. Listening is what makes the second kind of variety show up.

Looking at a Plant Properly

A glance tells you almost nothing, so look in an order. Start with the stem. Is it thick or thin, hard or soft, upright or creeping? Then the leaves: their shape, their size, and how they sit on the stem. Then the flowers, if there are any, and their colour. Stem, leaves, flowers. Three things, every time.

Looking at an Animal Properly

Animals will not wait while you study them, so ask three quick questions instead. Where was it, on the ground, in the water, in the air? How did it move, by walking, flying, crawling or swimming? What was it doing? Those three answers, caught in a moment, are worth more than a long look you never write down.

Write It, Do Not Trust It

Record what you find as you find it, in a table with a row for each plant or animal. This feels slow and it is the part that matters. By evening, memory has blurred one bush into another and lost half the birds. A written row can also be compared with a classmate's, which a memory can never be.

The Notebook Beats the Camera

A photograph catches what a thing looked like. It does not catch the smell of the park after rain, the sound overhead, or the fact that the butterfly kept returning to one flower and ignoring the rest. Writing forces you to decide what was worth noticing, and deciding is the skill you are practising.

Why Anybody Should Care

Naming the variety is not the point of it. The point is that the variety is useful and it can be lost. Plants feed us and give medicines. Insects move pollen between flowers so that fruit forms. When a kind of living thing goes, nothing replaces it, and what it did for the rest stops being done.

From Noticing to Grouping

By the end of the walk the class has pages of observations and a problem. There are far too many plants and animals to hold in the head one at a time. The next topic is about what to do with a long list like that: sort it into groups, using features you have already recorded.

Scenario:

A class marks out a square of ground one metre on each side in a corner of the school. They agree to count every different kind of living thing inside it. Meera expects two or three. The count runs to eleven, including three grasses, a creeper, ants, a beetle and a spider. The class then marks a second square on the bare path. That one yields four. Rohit asks why the two squares differ so much. The children look at what each square has. The first is shaded and damp and the second is trodden and dry. They see that the number is not luck but a result of the conditions.

Analysis:

Biodiversity is countable, and counting it in two places at once shows what it depends on. The shaded damp square held nearly three times what the dry path did.

Activity:

Mark a square of one metre in two different places near your school. Count the kinds of living thing in each and write one reason for the difference.

Title:

Ten steps, one square metre

Safety:

Do not put your hands into holes, under stones or into thick undergrowth, and do not touch or taste any plant you cannot name. Take an adult who knows the area with you.

What You Notice:

One square metre holds far more kinds than anybody expects, and the two-minute wait is what makes them appear. Comparing a morning list with an evening list usually shows different animals in the same square, which is why one visit is never enough to describe a place.

Each kind of bird has its own call, so a practised listener can name birds without seeing one.

People who have lived beside a forest for years often know its plants better than any book does.

India is one of the most biodiverse countries on Earth, which is why this chapter starts at home.

What to note about a plant — SLF - Stem, Leaves, Flowers — Three things to look at on every plant, in that order, before anything else.

What to note about an animal — Where, How, What — Where was it? How did it move? What was it doing? Three questions, one animal.

Thirty Plants and One Table

The class comes back from the walk with thirty rows in the plant table and no idea what to do with them. Reading thirty rows one after another teaches nobody anything. Madam Sulekha asks a better question. Can you put them into piles, so that everything in a pile is alike in some way? That is grouping, and the rest of this topic is about choosing what to group by.

Why Bother Grouping?

Thirty separate plants must be remembered one at a time. Four groups of plants can be held in the head at once, and anything new can be placed into one of them. Grouping does not change the plants. It changes what you can do with what you know about them, which is why every science does it sooner or later.

The First Cut: Height and Stem

The easiest feature to use is the one you can see from a distance: how tall the plant is, and what its stem is like. Is the stem soft and green, or hard and woody? If it is woody, is it one thick trunk, or several stems starting low down? Those two questions sort most plants you will meet.

Trees

Some plants stand well above your head on a hard, thick, woody trunk. Their branches usually begin high up, well away from the ground, which is why you can walk underneath one. A mango is a tree. So is the neem in most school compounds. The single thick trunk is the giveaway.

Shrubs

Shrubs are not as tall. They often have several brown woody stems, and those stems start branching very close to the ground, so a shrub looks bushy from the bottom up. Those stems are hard, though thinner than a tree trunk. A rose plant is a shrub. Note that the flower had nothing to do with deciding it.

Herbs

Herbs are typically small, with soft green stems that you could bend between your fingers. A tomato plant is a herb. So is most of what grows in a vegetable patch. The word has nothing to do with cooking here: in this chapter a herb is simply a plant with a short soft stem.

Climbers and Creepers

Two more kinds are worth naming because their stems are weak. A climber has a weak stem and needs something to hold on to, so it climbs a wall, a stick or another plant. A creeper also has a weak stem, but instead of climbing it spreads along the ground. Money plant climbs. Pumpkin creeps.

The Lines on a Leaf

Hold a leaf up to the light and you will see thin lines running through it. Those are veins. The pattern they make has its own name: venation. Every leaf has one, most people never look at it, and it turns out to tell you a surprising amount about the plant it came from.

Net or Lines?

There are two patterns to know. In some leaves the veins spread out on both off a thick central vein and join into a net. That is reticulate venation, and hibiscus shows it well. In other leaves the veins simply run alongside each other without making a net. That is parallel venation, seen in banana and in every grass.

What Is Under the Ground

Roots are harder to study, because looking means digging. A mustard plant has one main root going down with smaller side roots along it. The main one is called a taproot. Common grass has no main root at all: it has a bunch of thin roots of similar size springing from the base of the stem, called fibrous roots.

A Pattern Nobody Arranged

Now put two of those features together, and something odd appears. Plants with net-veined leaves generally have taproots. Plants with parallel-veined leaves generally have fibrous roots. Sadabahar has a taproot and net veins. Lemongrass has fibrous roots and parallel veins. Nobody designed this. It is simply what is found, over and over.

Splitting a Seed

Soak a chickpea for two or three days and peel off its coat, and the seed comes apart into two halves. Each half is a cotyledon, a store of food for the young plant. Seeds with two are called dicotyledons, or dicots. Soak a maize grain and you will find one thin cotyledon instead. Those are monocotyledons, or monocots.

Three Clues That Agree

Here is the whole thing in one line. Dicots have two cotyledons, reticulate venation and a taproot. Monocots have one cotyledon, parallel venation and fibrous roots. Chickpea is a dicot, wheat is a monocot. Any one of the three clues lets you predict the other two, which is a useful trick and, as the next section warns, not a perfect one.

Scenario:

A class sorts twenty plants from the school grounds into trees, shrubs and herbs. The first attempt produces an argument. Three children call one plant a shrub and two call it a tree. Their teacher asks what the disagreement is about. It turns out one group judged by height and the other by the stem. They measure instead. The plant stands waist high and has several hard stems branching close to the ground. That settles it as a shrub. The class rewrites the rule it will use. Height alone is unreliable because a young tree is short, so the stem decides the group every time.

Analysis:

Both groups were looking carefully and still disagreed, because they were using different rules. Agreeing the rule before sorting is what makes a sort repeatable.

Activity:

Sort ten plants near you into trees, shrubs and herbs. Write the rule you used, then swap with a partner and see whether you agree.

Title:

Read the leaf, then check the root

Safety:

Ask an adult before lifting any plant, and never lift one from a garden or field that is not yours. Do not taste any seed or leaf, and wash your hands after handling soil.

What You Notice:

Most of your predictions come out right, and that is the point of the exercise. If one does not, you have found the reason the book says generally rather than always. The chickpea comes apart into two neat halves; the maize does not, and the difference is easy to feel with a fingernail.

Wheat has fibrous roots and parallel venation, which makes it a monocot like maize.

Chickpea has a taproot and net-veined leaves, and its soaked seed splits neatly in two.

Banana leaves show parallel venation clearly enough to see from across a courtyard.

Herb, shrub, tree by stem — Soft, several, sky — Herb has a soft stem. Shrub has several hard stems low down. A tree reaches the sky.

The three clues that agree — Two-Net-Tap — Two cotyledons, net venation, taproot. One goes with the others; flip all three for monocots.

The Poster Problem

The class is asked to make a poster of every animal they saw on the walk, plus any others they know. Within ten minutes the sheet is a mess. Ants, a goat, pigeons, houseflies, a fish from the pond, monkeys. Somebody says it would look better if the animals that belong together were drawn together. Which is a fine idea until you ask what belongs together means.

Start With What You Can Watch

For plants, the first cut was height and stem, because you can see those from a distance. For animals the equivalent is movement. You need not catch an animal or measure it to see how it gets about. You have already recorded that on the walk, in the column headed how it moved.

Six Ways of Getting About

Sort the poster by movement and most animals fall into place quickly. Some walk. Some run. Some fly. Some crawl. Some hop or jump. Some swim. Those six cover nearly everything a Class 6 child will meet, and the odd ones that do not fit are usually the interesting ones.

And the Part That Does It

Movement is only half the answer. The other half is which body part does the moving. An ant walks on legs. A goat walks and jumps, also on legs. A fish swims with fins. A pigeon walks on legs and flies with wings. Recording both the movement and the part is what makes the grouping useful.

An Animal in Two Groups

Look again at the pigeon. It walks and it flies, so it lands in the walking group and the flying group at once. Children often think this means they have made a mistake. They have not. A grouping is a tool for thinking, and an animal is allowed to appear in two places if it genuinely does two things.

A Housefly Does It Too

The housefly is the second example worth holding on to. It walks on legs and it flies with wings, exactly like the pigeon, and nothing else about the two animals is remotely alike. That is a useful warning. Sharing one feature does not make two animals close relatives.

Other Ways to Cut the Same Pack

Movement is not the only feature available. Animals differ in shape, in size, in the way their bodies are built, and in colour. Any of these can be used to sort the same set of animals, and each one produces a different arrangement of the poster.

So Which Grouping Is Correct?

None of them, and all of them. There is no single right way to group animals. The feature you pick depends on what you are trying to find out. Sorting by movement tells you about getting around. Sorting by size tells you nothing about that, and something else instead.

Why Anyone Bothers

This can feel like tidying for its own sake. It is not. Grouping and recording what lives in a place is how anybody can later say what has been lost, or argue that a place is worth keeping. Without records, an argument about a forest is just two people disagreeing loudly.

Janaki Ammal

Janaki Ammal, who lived from 1897 to 1984, was an Indian botanist who spent her working life on exactly this. She became head of the Botanical Survey of India and set up programmes to record the variety of plants growing here. She also played a key part in a campaign to save a particular forest.

Ten Years for Silent Valley

Silent Valley is a moist evergreen forest in the Palakkad district of Kerala. A hydroelectric dam was proposed across the Kunthipuzha river that runs through it. The battle against that dam went on for ten years, and most of the people leading it did not live anywhere near the forest.

How an Argument Gets Won

They used what was available to them. Seminars. Letters to the editors of newspapers. Articles. Programmes to make people aware. Petitions, and appeals in court. None of that is dramatic and all of it took years. The movement succeeded and the forest is still standing, which is why it is worth knowing about.

Back to the Poster

So the poster can be arranged several ways, and each arrangement answers a different question. Before you sort anything, decide what you want the sorting to show you. The next topic turns to a question the poster cannot answer: why a camel and a fish are built so differently in the first place.

Scenario:

A class makes a table of twelve animals and how each one moves. Walking, flying, crawling, hopping and swimming all appear. Then Imran notices a problem. A duck walks, flies and swims, so it belongs in three columns at once. The class tries a second table instead, listing the body part used for each kind of movement. Legs, wings and fins now sort cleanly, and the duck simply has all three. Sana counts the animals with more than one way of moving and finds five of the twelve. The class decides a single column was the wrong shape for the question.

Analysis:

The first table failed because it assumed one animal has one answer. Sorting by body part instead let an animal appear wherever it truly belongs.

Activity:

List eight animals you know. Mark every way each one moves and the body part it uses. Count how many have more than one.

Title:

The two-column animal table

Safety:

Watch from where you are. Do not follow, touch or feed any animal, and do not lean out of a window or over a balcony rail to see better.

What You Notice:

Legs turn up far more often than anything else, which is worth noticing before anyone tells you. The second sorting by size splits animals that the first sorting had put together, and that is the whole point: the feature you pick decides the groups you get.

Janaki Ammal lived from 1897 to 1984 and headed the Botanical Survey of India.

The Silent Valley campaign lasted ten years and was led largely by people who lived nowhere near the forest.

A pigeon belongs in the walking group and the flying group at the same time, and that is not a mistake.

Ways animals move — Walk, Run, Fly, Crawl, Hop, Swim — Six ways to cover the animals a child will meet. Then ask which body part does it.

Features for grouping animals — MSSC - Movement, Shape, Size, Colour — Movement first, because it is easiest to watch. Then shape, size and colour.

Same Country, Different Living Things

Fill in a table of what grows and lives in a desert, a mountain, a pond and your own surroundings, and one thing jumps out. The lists barely overlap. A cactus is not found on a snowy mountain. A deodar is not found in the sand. The obvious question follows: why not?

The Cactus and the Deodar

Alex has seen cactus plants in the deserts of Rajasthan, with thick fleshy stems. Maya has seen deodar trees up in Himachal Pradesh, in the Himalayas, conical in shape with flexible sloping branches. Two plants, two regions, and nothing much alike between them.

What a Desert Is Like

Start with the place rather than the plant. A desert has very little water. A hot desert is very hot through the day and very cold at night. Anything living there has to manage both extremes, and has to manage them without much water.

Why a Cactus Is Fleshy

That explains the fleshy stem. It stores water, which lets the plant tolerate the hot conditions of the place. The thickness is not decoration. It is a water tank, filled when water is available and drawn on when it is not.

Why a Deodar Is Conical

Mountains in very cold regions get frequent snowfall, and snow piling on a tree is a heavy load. A deodar is conical with sloping branches, so the snow slides off easily instead of settling. Some trees have this ability and some do not.

Two Camels, Two Deserts

Now put the camel of the hot desert of Rajasthan beside the camel of the cold desert of Ladakh and look for differences. There are several, and each one turns out to match the place. This is worth doing slowly, because it is the clearest example in the chapter.

Legs and Hooves

The hot-desert camel has long legs with wide hooves. Alex heard from his grandmother why: the long legs and wide hooves let it walk on sandy desert without sinking in. The cold-desert camel is shorter in height and leg, and short legs are easier to walk on in mountains.

One Hump or Two

Food is not easily available in a desert, so camels store it in their humps. The hot-desert camel has one hump, which carries it through times when food is scarce. The cold-desert camel has two. Those two shrink in late winter, because the food inside is being used.

Long Hair for Ladakh

The cold-desert camel has one more feature the other does not need. It grows long hair from head to neck. The winters of Ladakh are severe, and the hair is what gets the animal through them.

How a Camel Keeps Water

Kashi from Rajasthan adds what he has noticed at home. A camel passes very little urine. Its dung comes out dry. It does not sweat at all. Put those three together and very little water leaves the body, which is why a camel can go many days without drinking.

The Same Plant, Twice

Maya has seen rhododendrons with bright flowers in the Shola forests of the Nilgiris. There they are short and their leaves are small, which helps them survive the heavy winds on mountain tops. Pema from Sikkim says the ones near her are taller. Same plant, different regions, different features.

A Shape That Slips Through Water

Sagar went to the Andaman and Nicobar Islands and saw huge whales and colourful fish. His father explained the shape of the fish. A streamlined body, narrow at the ends, lets water slip past, and that is what makes swimming possible.

The Word for All of It

Six examples, one idea. Whatever lives in a region turns out to be built in a way that suits it. Such a feature has a name: an adaptation. The cone of the deodar and the low growth of the Nilgiri rhododendron are both adaptations to mountains.

Reading a Feature Backwards

Once you have the word, you can use it in reverse. See a feature and ask what condition it answers. Wide hooves answer sand. Fleshy stems answer drought. Small leaves answer wind. The next topic asks what happens when the place itself is taken away.

Scenario:

Two pupils argue about why a cactus cannot grow in their town. Nita says it is too cold. Arjun says the problem is the rain. Their teacher puts the question another way. What does a cactus body do? The class lists its features: thick fleshy stems that store water, and spines instead of broad leaves. Then they look at their own rainfall figures, which show heavy rain for four months. A plant built to hoard water has no advantage where water arrives in quantity, and its roots sit in wet soil for months. Arjun's answer holds. The class sees that an adaptation fits a place, and in the wrong place it is a disadvantage.

Analysis:

An adaptation is not a general improvement. Thick water-storing stems are an advantage in a desert and a liability where the soil stays wet.

Activity:

Find out your district's rainfall by month. Name one plant that grows well there and say which of its features suits that pattern.

Title:

Feature, then condition

Safety:

Look, do not pick. Some plants have thorns, stinging hairs or sap that irritates skin, so keep your hands off leaves and stems you do not know.

What You Notice:

Some guesses will be wrong, and those are the useful ones. A thick leaf may turn out to be about water, or about heat, or about being eaten. Naming a feature is easy. Working out which condition it answers is the actual science, and it usually needs more than one look.

The two humps of a cold-desert camel shrink in late winter, because the stored food inside them is being used up.

Rhododendrons in the Shola forests of the Nilgiris are shorter and have smaller leaves than those in Sikkim.

A camel does not sweat at all, which is one of three ways it keeps water inside its body.

What the two camels differ in — LHH - Legs, Hooves, Humps — Long legs and wide hooves and one hump for the hot desert. Short legs and two humps for the cold.

How a camel saves water — Little urine, Dry dung, No sweat — Three ways of not losing water, which is why it can go many days without drinking.

Where Does It Live?

Ask where a sea turtle lives and the answer comes easily: the sea, or the ocean. A camel lives in a desert, hot or cold. A rhododendron lives in the mountains. That place has a name. The place a living thing lives in is its habitat.

What a Habitat Hands Over

A habitat is not merely an address. It provides food, water, air, shelter and the other needs for survival. Hold on to that list, because it explains why losing a habitat is a serious matter and not just a change of scenery.

Sharing One Place

Many different kinds of plants and animals may live in the same habitat. A pond holds fish, insects, frogs and water plants at once. This is why habitat matters so much to biodiversity: the variety of a region is shaped by the places it contains.

Land or Water

Habitat gives another way to group living things, and the simplest cut is land against water. Whatever lives on dry ground is said to have a terrestrial habitat. Forests, deserts, grasslands and mountains are all terrestrial.

The Water Half

Whatever lives in water is said to have an aquatic habitat. Ponds, lakes, rivers and oceans are the examples worth remembering. Notice that a pond and an ocean are both aquatic, although almost nothing else about them is the same.

The Animals in Both

Some animals do not fit either box. A frog lives in water and on land, and it is far from alone. Such animals are called amphibians. This is the two-groups idea from earlier in the chapter turning up again, now about habitat instead of movement.

What If the Place Goes?

Now the hard question. What happens if the habitat of a plant or animal is damaged? What happens to a goat when the grass is gone? Could a fish live on without any water? Go back to the list of four things a habitat provides, and the answers are already there.

Ask Somebody Older

There is a way to check this yourself. Ask your parents, grandparents or neighbours which plants, birds and insects they saw often as children and rarely see now. The lists are usually longer than anybody expects, and they are evidence of habitats that have been damaged.

From Lost Homes to Lost Variety

Damage to a habitat takes away homes, food and other resources. Animals and plants cannot simply move elsewhere, because elsewhere suits something else. So the numbers fall, and this leads to the loss of biodiversity. That chain is the whole argument in one line.

Three Indian Examples

The populations of the Bengal Tiger, the Cheetah and the Great Indian Bustard have declined in India, because human activities have taken away their natural habitats. These are not distant examples. All three are Indian animals, and all three were losing ground.

What Was Done About It

The Government of India has started several projects to conserve biodiversity. Project Tiger was begun in 1973 for the declining Bengal Tiger. The Cheetah Reintroduction Project was begun in 2022. Habitats of Great Indian Bustards have been declared Protected areas in Gujarat, Rajasthan and Maharashtra.

The Birdman of India

Salim Ali, who lived from 1896 to 1987, travelled across India to observe the diversity of its birds. He drew up a list of them and wrote down where each one travelled and where it lived. He noted the regions where bird diversity was high, then took steps to conserve those regions.

Two Places He Preserved

Two of the regions he preserved are Keoladeo National Park, at Bharatpur in Rajasthan, and the Ranganathittu Bird Sanctuary, at Mandya in Karnataka. He also wrote a landmark series of ten books on the birds of the Indian Subcontinent, and was awarded the Padma Vibhushan in 1976.

Protected Without a Government

Not all protection comes from above. Sacred groves are undisturbed patches of forest, some small and some very large, found all over India. They hold many plants and animals, including numerous medicinal plants. The local community protects them, and nobody may cut a tree, harm an animal or disturb the area.

Scenario:

Behind Bhanwarpura in western Rajasthan lies a stretch of open grassland. The village has always called it the waste. Nothing is grown on it. Two Great Indian Bustards were seen there last winter. The forest department now wants the stretch declared a protected area. At the same meeting a company offers to lease the land for a solar farm. There would be rent for the panchayat and work for twelve families. A third group points to the grove of old trees by the village pond. That grove has been left untouched for generations by agreement alone, with no order from anybody. The sarpanch asks the Class 6 children to set out what is at stake before the village votes.

Analysis:

Calling the grassland waste is the whole problem. It produces no crop, so it looks empty, and that is exactly the habitat the Bustard needs. The village is really choosing between two kinds of value and two ways of protecting a place.

Activity:

Find one piece of open, uncultivated land near you: a field edge, a roadside strip, a patch behind a building. Visit it twice, once early and once late in the day, and list every living thing you see. Then ask two adults what they think the land is for, and compare their answers with your list.

Title:

What the elders remember

Safety:

Talk to people you and your family know. Do not go to unfamiliar houses or ponds alone, and tell an adult at home where you are going.

What You Notice:

The lists are usually longer than anybody expects. What the older person treats as ordinary is often something you have never seen at all. That gap is not nostalgia. It is a record of habitats that have changed, collected the only way it can be collected now.

Salim Ali, who lived from 1896 to 1987, wrote a landmark series of ten books on the birds of the Indian Subcontinent.

Salim Ali helped preserve Keoladeo National Park, at Bharatpur, and the Ranganathittu Bird Sanctuary, at Mandya.

Sacred groves hold numerous medicinal plants, and the community around them allows nobody to cut a tree.

What a habitat provides — FWAS - Food, Water, Air, Shelter — Four things, and the reason losing a habitat is not merely losing a view.

Three conservation efforts — Tiger 73, Cheetah 22, Bustard protected — Project Tiger in 1973, Cheetah Reintroduction in 2022, and protected areas in three states.