Living Creatures: Exploring their Characteristics

Why This Matters

Look around you right now.

Some things are alive. A dog, a sparrow, a tulsi plant, the friend next to you. Other things are not alive. A pencil, a chair, a stone, your phone.

This sounds easy. A dog is alive, a stone is not. We all just know it.

But do we really? Let us try a tricky one.

A car moves on the road. A river flows. A flame on a candle moves and even seems to grow. Are these alive? Most people pause here. They are not so sure any more.

So “alive or not alive” is not as simple as it feels. We need clear rules. In this chapter you will learn the exact signs that tell a living thing from a non-living thing. Once you know them, you will never be confused again — not even by a moving car or a flowing river.

The Big Idea

Every living thing — a tiny ant, a tall tree, a whale, you — does the same set of special jobs. Living things take in food, they grow, they breathe (respire), they sense things and react, they throw out waste, and they make young ones of their own kind. Non-living things do none of these. So to check if something is alive, we do not ask “does it move?” We ask “does it do these jobs of life?” If it does, it is living. If it does not, it is non-living.

Let’s Break It Down

What makes something “alive”?

A living thing is also called a living being or an organism. (Organism just means any single living thing — one plant, one animal, one tiny germ.)

All living things share a small set of common signs. Scientists found that every living thing does these jobs:

1. Needs food — to get energy.
2. Grows — gets bigger over time.
3. Respires — breathes; takes in air to make energy from food.
4. Responds to stimuli — senses the world and reacts to it.
5. Excretes — throws out the waste its body makes.
6. Reproduces — makes new young ones of its own kind.
7. Moves on its own — can move some part of itself by itself.

And one more thing happens to every living being in the end: it dies. A non-living thing cannot die, because it was never alive.

Here is the key idea. A thing is living only if it does all of these jobs. One job alone is not enough. (A car moves, but that is the only sign it shows — so it is not alive. More on this soon.)

Figure 10.1 below shows the seven signs as a wheel around living things. Keep coming back to it.

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Now let us look at each sign, one by one, slowly.

Living things need food

Think about yourself. If you do not eat for a long time, you feel weak and tired. That is because your body runs on food. Food gives you energy — the power to move, play, think and grow.

Every living thing needs food. A cow eats grass. A lion eats meat. You eat roti and dal. Even a plant makes its own food using sunlight, water and air. (You will study how plants make food in a later class.) The way a living thing takes in and uses food is called nutrition.

A non-living thing never needs food. A chair sits in the same spot for years and never gets hungry. A stone never eats.

They grow

Look at a photo of yourself as a baby. You were tiny. Now you are much bigger. Can you fit into the clothes you wore four years ago? No — because you have grown.

To grow means to get bigger in size over time. All living things grow. A kitten grows into a cat. A small seed grows into a tall plant. A chick grows into a hen.

Growth is slow. You cannot see it happening minute by minute. But over weeks and months, it is clear.

Figure 10.2 below shows a seed growing into a plant, step by step. Watch it get bigger at each stage.

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A non-living thing does not grow on its own. A toy car you bought last year is exactly the same size today. A rock does not become a bigger rock by itself.

They respire (breathe)

Put your hand on your chest. Feel it move up and down. You are breathing. You take air in, and you push air out, all day and all night, without even thinking about it.

Why do we breathe? Here is the part the textbook often skips. Food alone does not give you energy. Your body has to “burn” the food slowly, like a tiny safe fire inside your cells. And just like a real fire needs air to keep burning, your body needs air (the oxygen in it) to release energy from food. This whole job — using air to get energy out of food — is called respiration.

So:

Breathing means taking air in and pushing air out.

Respiration is the bigger job: using that air to release energy from food.

Breathing is one part of respiration. When we inhale, air moves from outside into our body. When we exhale, air moves from inside our body to outside.

Do plants breathe too? Yes — but they have no nose. Plant leaves have tiny holes called stomata (say it as “STOH-ma-ta”). Air goes in and out of the leaf through these little holes. So plants respire as well.

Every single living thing respires. A non-living thing never does. A chair does not need air to release energy, because it has no food and no energy to release.

They respond to stimuli (the touch-me-not and our senses)

Imagine you step on a sharp thorn with a bare foot. What happens? You pull your foot back at once — fast, before you even think.

The thorn is a stimulus (say it as “STIM-yoo-lus”). A stimulus is anything that makes a living thing react. Pulling your foot back is your response. (The plural of stimulus is stimuli, said “STIM-yoo-lie”.)

You sense the world using your sense organs — eyes, ears, nose, tongue and skin. A loud sound, a bright light, a bad smell, a hot cup — all are stimuli, and your body reacts to each one. This sensing and reacting is called responding to stimuli.

Here is a surprise. Plants respond too, even though they have no eyes or ears.

The best example is the touch-me-not plant (also called chhui-mui, lajjalu or mimosa). When you touch its leaves, they quickly fold up and droop. Leave it alone, and after some time the leaves open again. The touch is the stimulus. The folding is the response.

Figure 10.3 below shows this. See how the open leaves close after a finger touches them.

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Some plants even fold their leaves at night, after the sun sets — like the amla (Indian gooseberry) tree. The change from light to dark is the stimulus. So responding to stimuli is a sure sign of life. Non-living things ignore everything. Pour water on a stone, shout at it, push it — it does not care, because it is not alive.

They excrete

Your body uses food and air to make energy. But this also makes some waste — stuff the body does not want. Keeping waste inside would harm you. So your body throws it out.

Throwing out the waste made by the body is called excretion.

You can see this every day. On a hot afternoon you sweat. Sweat is mostly water and salt that your body removes through the skin. That is why white patches sometimes form on a shirt near the armpits — they are dried salt from sweat. Urine (pee) is another way animals throw out waste.

Plants excrete too. Look closely at the very edges and tips of the leaves — plants push out extra water there as tiny droplets. You can spot these droplets on grass and rose plants early in the morning. (This is different from dew, which you met in Chapter 8. Dew settles all over a cold surface from the air; these droplets come from inside the plant and sit right at the leaf edges.)

Every living thing excretes. A non-living thing makes no waste, because it does no jobs inside. A pencil never sweats and never makes urine.

They reproduce & move on their own

Have you seen puppies, kittens or chicks? These are the young ones of dogs, cats and hens. Living things make new young ones of their own kind. A dog makes puppies. A mango tree makes seeds that grow into new mango trees.

Making new young ones of one’s own kind is called reproduction.

Why does reproduction matter so much? Because every living thing dies one day. If living things did not make new young ones, life would simply end. Reproduction keeps life going — one generation after another, forever. That is its whole purpose.

Now, the last sign: movement. Most living things can move some part of themselves by themselves. You can walk and wave your hand. A fish swims. A bird flies.

But what about plants? A plant cannot get up and walk to another place. Does that make it non-living? No! Plants do show movement — just smaller, slower movement. A touch-me-not folds its leaves. Many flowers open in the morning and close at night. A climber plant winds its stem around a stick. Some plants, like Drosera, even trap insects by moving tiny hairs on their leaves. So plants move too, in their own way.

The key word is “on its own”. A living thing moves itself. A football also moves — but only when you kick it. By itself, it just lies there. That difference matters a lot, as we will now see.

Living vs non-living — the tricky cases

Now for the puzzles from the start of the chapter. A car moves. A river flows. So why are they still non-living?

The trap is this: we feel that “anything that moves must be alive”. But movement is only one of the seven signs. A thing is alive only if it shows all the signs of life. Let us test the car against every sign.

Figure 10.4 below puts a living dog next to a non-living toy car. A tick means it shows that sign; a cross means it does not.

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See the difference? The dog passes every test. The car passes only one and fails all the others. So the car is non-living. The same is true for a river. It flows, but it never eats, grows, breathes or makes baby rivers. A candle flame seems to “grow” and “move”, but it does not eat, breathe or reproduce either. So all of these are non-living.

Let us reason through one example carefully.

Here is a clean side-by-side list of how living and non-living things compare.

One more idea before we move on. What about a seed? It just sits there. Is it living? A seed looks still and lifeless, but inside it is a tiny baby plant waiting. Given the right conditions, it will grow into a plant. So a seed is living. It is just resting.

What does a seed need to wake up and grow? When a seed turns into a tiny sprout, we say it has germinated. A bean seed needs the right amount of water and air. Too little water and it stays dry — no growth. Too much water and air cannot reach it — again no growth. Most seeds do not even need light to germinate; they can sprout in the dark. (But after sprouting, the young plant does need sunlight to grow well.)

Figure 10.5 below shows four pots from a real experiment. Notice which seeds grow and which do not.

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Common Mistakes

Some ideas about living things feel right but are wrong. Let us clear them up.

Quick Check

Time for some quick questions to test the ideas.

Practice Problems

Try each one yourself first. Then tap to check.

Easy

Medium

Challenge

Summary

• A living thing (also called an organism) does a special set of jobs that non-living things cannot.
• The seven signs of life are: it needs food, it grows, it respires (breathes), it responds to stimuli, it excretes (removes waste), it reproduces (makes young ones), and it moves on its own. Every living thing also dies one day.
• A thing is alive only if it shows all these signs — not just one.
• Movement alone does not mean alive. A car, a river and a flame all move, but they fail the other signs, so they are non-living.
• Plants are living. They may not walk from place to place, but they grow, respire, respond (like the touch-me-not folding its leaves), excrete and reproduce — and they do move parts of themselves.
• A stimulus is anything that makes a living thing react; the reaction is its response.
• A seed is living — a tiny resting plant inside. It needs the right amount of water and air (not light) to germinate, which means to sprout and start growing.

What’s Next

Now you can tell any living thing from a non-living thing, and you know why each sign matters. Living things do not survive alone — they depend on the air, water, soil, sunlight and plants around them. These gifts of nature are precious. The next chapter is Nature’s Treasures. There you will explore the natural resources all living things need to stay alive, and why we must use them with care. See you there!