What Plants and Animals Need to Live
PrimaryEvery living thing has a short list of basic needs. Miss even one, and it cannot survive for long. Let's find out what those needs are — and prove it with a real experiment.
The basic needs of life
| Need | Animals | Plants |
|---|---|---|
| Air | Oxygen to breathe | Carbon dioxide (and oxygen too) |
| Water | To drink | Absorbed through roots |
| Food | Must eat other living things | Makes its own food using sunlight |
| Light | Not required to live | Essential — powers food-making |
| Space/shelter | Somewhere safe to live and rest | Room to grow roots and reach light |
Why plants and animals get their food so differently
The biggest difference between plants and animals is how they get food. A plant is like a tiny solar-powered food factory: using sunlight, water and air, it makes its own sugar inside its leaves. An animal cannot do this trick, so it must go out and find food by eating plants or other animals. That is why a plant can stay rooted in one spot its whole life, while animals must move around to find their next meal. Take away any one need — no water, no light for a plant, no food for an animal — and the living thing weakens and eventually dies, because its "factory" or "engine" cannot keep running.
A need is something that is essential for survival — without it, the living thing will die. A want (like a toy, or a treat) is nice to have, but you could still live without it.
Experiment: does a bean seed really need light?
- Set up two cups. Plant a bean seed in damp soil in each of two identical cups.
- Water both the same. Give both cups the same small amount of water every two days — this keeps water a fair, controlled condition.
- Change only one thing. Put Cup A on a sunny windowsill. Put Cup B inside a dark cupboard. Light is now the only difference between them.
- Observe and record. Once a day for two weeks, check both cups and write down what you see (has it sprouted? how tall? what colour are the leaves?).
- Compare. After two weeks, look at your table. The sunlit plant should be green and growing steadily; the dark plant will likely be pale, weak, or barely growing.
- Conclude. Because water and everything else was kept the same, any difference between the two plants must be caused by light — proving light is a real need for plants, not just a "nice to have."
Test yourself
Q1 Why can a cactus survive for months in the dry desert with almost no rain?
A cactus still needs water like every plant, but it is specially built to store water in its thick, fleshy stem after a rare rainfall, and to lose very little water afterward (it has a waxy skin and tiny spines instead of big leaves). It doesn't need water less — it is just very good at saving what little it gets.
Q2 A goldfish is in a sealed jar with no air holes. What will eventually happen, and why?
The goldfish will eventually struggle and die, because the oxygen dissolved in the water will run out and cannot be replaced without contact with fresh air. Air (oxygen) is a basic need for every animal, including fish.
Q3 Is sunlight a need for animals the same way it is for plants? Explain.
Not directly — an animal like a mole can live its whole life underground in the dark and survive fine, because it gets its energy by eating food, not from sunlight. But animals still depend on sunlight indirectly, because the plants (or the animals that ate plants) they eat were grown using sunlight in the first place.
How the ideas connect
Every key idea in this chapter, branching from the core concept — use it to see the whole picture at a glance.
The key facts, visualised
Worked problems, step by step
Follow each solution line by line, then try to reproduce it on paper before moving on.
Example 1A bean plant is kept in a dark cupboard. What will happen?
- Plants need light to make food
- Without light it cannot make food
Example 2Why can a lion not make its own food like grass can?
- Only plants have the parts to catch sunlight
- Animals lack this ability
Now you try
Work each one out first, then tap to reveal the worked answer.