Characteristics of Living Things

Look around you right now. A potted plant on the windowsill, a gecko on the wall, your own hand turning the page — these are all living things. But the fan spinning above you, the phone buzzing in your bag, the bus rumbling past outside? Those are non-living. How can you tell the difference for sure, every single time? It is not a guess. Scientists use a small checklist of signs, and in this note you will learn all of them — and the exact word your PSLE marker is waiting to read.

Parents: let your child tap through the sorting game and the "Predict first" boxes before they reveal the answer — guessing first makes the science stick. The blue dotted words are tappable definitions, and the "Teacher's tip" boxes name the precise keyword the PSLE marker awards. Fifteen minutes of doing it together beats an hour of reading.

By the end you'll be able to look at anything and decide if it is alive — and explain why. All living things share four signs: they grow, they need air, food and water, they reproduce, and they respond to changes around them. Let's meet each one.

Living things grow

A tiny chick hatches from an egg. Feed it, give it water, and over months it gets bigger and bigger until it becomes a full-grown hen. A small seedling pushes out of the soil and, year after year, becomes a tall tree. You did the same — you were once a baby, and now you are a P5 or P6 student who is taller, stronger and cleverer.

This is the first sign of life. Living things . They do not just get bigger — they also develop, which means their bodies change and become more complete. A tadpole grows legs and becomes a frog. That is growing and developing.

Be careful, though. Some non-living things can seem to "get bigger" by accident. A fire spreads and gets bigger, and a balloon gets bigger when you blow into it. But that is not the same as living growth, because a fire and a balloon do not develop or change into a grown-up version of themselves — and as you'll see, they fail the other signs of life too.

The exact PSLE keyword here is grow.

Living things need air, food and water

Try holding your breath. Within seconds your body is begging you to breathe again. Skip your meals all day and you feel weak and grumpy. Forget to drink water on a hot Singapore afternoon and you feel dizzy. Your body is telling you something important: it needs three things to stay alive — air, food and water.

Every living thing needs them. A goldfish takes in air that is dissolved in its tank water, eats fish food, and of course lives in water. A potted plant takes in air through its leaves, makes its own food using sunlight, and drinks water through its roots. The reason living things need food is to get to grow, move and stay alive.

Here is a thinking trap to watch for. A car "needs" petrol and "needs" air to run — but a car is not alive. Needing fuel by itself does not make something living. A living thing must show all the signs of life, not just one — and we'll test that idea soon.

The exact PSLE keyword here is that living things need air, food and water.

Try the experiment yourself — set the conditions for a seed and watch what it needs to sprout.

What does a seed need to grow?

Predict first: Which jar will the seed sprout in?

Living things reproduce

A pair of birds builds a nest and lays eggs, and soon there are baby birds. A cat gives birth to kittens. A mango tree drops seeds, and from those seeds grow new mango trees. In every case, the living thing makes a new young one of its own kind — birds make birds, cats make cats, mango trees make mango trees.

This is the third sign of life. Living things can . Reproducing is how a kind of living thing keeps going instead of dying out. Animals do it by laying eggs or giving birth; plants do it by making seeds (or sometimes by growing new plants from a part of themselves).

This is often the sign that catches out the tricky non-living examples. A fire can "grow" and "needs air" — but a fire cannot reproduce. It cannot make a baby fire of its own. Only living things can make more of their own kind.

The exact PSLE keyword here is reproduce.

Living things respond to changes

Reach out and gently touch the leaves of a Mimosa plant — the touch-me-not you sometimes see on grassy verges — and the leaves fold up right in front of you. Poke a snail and it pulls back into its shell. Shine a bright light into your own eyes and you blink. In each case, something in the surroundings changed, and the living thing reacted to it.

This is the fourth sign of life. Living things in their surroundings. A change in the surroundings that a living thing reacts to is called a (more than one are called stimuli). The touch is the stimulus; the Mimosa folding is the response.

You respond to stimuli all day without thinking: you sweat when it gets hot, you turn towards a loud sound, your eyes adjust when you walk from a dark cinema into bright sunshine. A rock does none of this. Kick a rock and it just sits there — it cannot respond, because it is not alive.

The exact PSLE keyword here is respond to changes (and the change is called a stimulus).

How do we KNOW something is alive?

Here is the most important idea in this whole topic, so read it twice.

Something is a living thing only if it shows ALL four signs of life: it grows, it needs air, food and water, it reproduces, and it responds to changes. A non-living thing might show one or two of these by accident — but it can never show all four.

This is exactly how the classic traps work. A fire grows bigger and "needs air" to burn — that is two signs. But a fire cannot reproduce and cannot respond to changes, so it fails the test. A fire is non-living. A car moves and "drinks" petrol, but it cannot grow into a bigger car, cannot make baby cars, and cannot respond to a stimulus. A car is non-living too.

So never decide from just one sign. Run the whole checklist. Only a thing that ticks every box is alive.

Try it yourself. Tap each item to sort it into living or non-living, and read why.

Living or non-living?

Predict first: Before you start — is a fire a living thing?

🤔 Predict first: A car moves on the road and drinks petrol to run. Is a car a living thing?

Watch out — these are easily mixed up

A few traps catch students every year. Learn them now and you'll grab easy marks.

Quick recap

🎯 Mastery check

Answer all 7 — your progress is saved on this device.

A small chick is fed and watered, and after a few months it becomes a full-grown hen. Which characteristic of living things does this show?
You touch a Mimosa (touch-me-not) plant and its leaves fold up. Which characteristic of living things is the plant showing?
A mango tree drops seeds, and from those seeds new mango trees grow. Which characteristic does this show?
A fire spreads and gets bigger, and it needs air to keep burning. Why is a fire still NOT a living thing?
Which list shows three things that ALL living things need to survive?
A car moves on the road and uses petrol to run. A student says the car must be alive because it moves and needs fuel. Why is the student wrong?
A wooden table was made from a tree that was cut down. How should we classify the wooden table now?