KS2 Science — Food Chains, Habitats & Interdependence

Taught through what our animals eat, and what eats them

Approx. 50 minutes · KS2 · Teaching-led

Before you start

This lesson is mostly explaining. There are questions at the end, but the point is to understand how living things depend on each other well enough that the questions answer themselves.

Take as long as you like. Nothing is timed.

What you'll learn to do

• Build a food chain and use the right words for each part.
• Explain where the energy in a food chain comes from.
• Explain what happens to a whole habitat when one thing changes.
• Explain what a habitat is and why animals are suited to theirs.

Part 1 — Everything starts with the Sun

Here is something surprising. Every meal you have ever eaten started as sunlight.

Follow it backwards and you will see why.

Say you eat a chicken. The chicken ate grain. The grain is a plant, and the plant made itself out of sunlight, air and water. So the energy in your dinner came from the Sun, passed along through a plant and then a chicken.

Try it with a hedgehog. Gary eats a beetle. The beetle ate a leaf. The leaf was made by a plant using sunlight.

Try it with anything at all. You always end up at a plant, and then at the Sun.

This is because plants are the only living things that can make their own food. They use sunlight to do it. Animals cannot. Every animal has to eat something else, and if you keep following the chain backwards you always arrive at a plant.

That is why the Sun is the start of every food chain on Earth.

Part 2 — The words for each part

Scientists have proper names for the parts of a food chain.

Producer. A plant. It produces its own food using sunlight. Every food chain begins with one.

Consumer. An animal. It has to consume — eat — something else.

Consumers come in order:

• Primary consumer — eats the producer. Primary means first.
• Secondary consumer — eats the primary consumer. Second along.
• Tertiary consumer — eats the secondary consumer. Third along.

Predator and prey. A predator hunts and eats another animal. The animal it eats is the prey. An animal can be both — a frog is a predator when it eats a fly and prey when a heron eats it.

A chain with our animals

leaf → beetle → hedgehog → badger

• leaf = producer
• beetle = primary consumer
• hedgehog = secondary consumer
• badger = tertiary consumer

The hedgehog is a predator when it hunts the beetle, and prey when the badger hunts it. Both at once, depending on which way you look.

Which way do the arrows go?

This trips up almost everyone, so it is worth getting right now.

The arrow means "is eaten by." It points in the direction the energy travels.

So we write leaf → beetle, because the leaf is eaten by the beetle and the energy moves from the leaf into the beetle.

People often want to draw the arrow the other way, from the eater to the thing eaten, because that is the direction the animal moves when it goes to eat. But food chains are about energy, not about who moved. The energy goes from the eaten to the eater, and so does the arrow.

Arrows always point at the eater.

Part 3 — Habitats

A habitat is the place where a living thing lives. Not just a spot on a map — everything about that place: how warm it is, how wet, what grows there, what else lives there.

Every habitat gives its animals what they need, and the animals are suited to it.

• A hedgerow gives a hedgehog leaves to hide in, insects to eat and somewhere to nest.
• A rainforest is warm and wet all year, with tall trees. A chameleon is built for exactly this — gripping feet for branches, and skin that needs high humidity.
• A pond holds water all year, which is what a frog needs for its eggs and its skin.

Move an animal to the wrong habitat and it will not manage, because it is built for somewhere else. A chameleon in a hedgerow would be too cold and would not find the right food. A hedgehog in a rainforest would be too hot and too wet.

This is why zoos and keepers work so hard to recreate a habitat indoors. Getting the heat, the humidity, the plants and the food right is copying a habitat that the animal cannot be taken to.

Part 4 — When one thing changes, everything changes

This is the most important idea in the lesson.

Living things in a habitat depend on each other. That is called interdependence. And because they depend on each other, changing one thing changes lots of others.

Go back to our chain:

leaf → beetle → hedgehog → badger

Now imagine the beetles disappear. Perhaps a chemical was sprayed on the field.

Think through what happens next, one step at a time:

• The hedgehogs have lost their food. Some go hungry. Some move away. Some do not survive. There are fewer hedgehogs.
• The badgers have lost some of their food too, because there are fewer hedgehogs. There are fewer badgers, or they must find something else.
• The leaves are now being eaten less, because the beetles that ate them have gone. There may be more plants than before.

One change. Effects going all the way up the chain and all the way down it.

It works the other way too

Now imagine the badgers disappear instead.

• Hedgehogs are no longer hunted by badgers, so there may be more of them.
• Beetles are eaten more, because there are more hedgehogs. There may be fewer beetles.
• Leaves are eaten more by the remaining beetles, or less, depending on how the numbers settle.

Remove a predator and the numbers below it do not simply grow forever — they wobble and settle somewhere new. But everything shifts.

Part 5 — Food webs

Real life is more complicated than a single chain, because most animals eat more than one thing.

A hedgehog eats beetles, but also worms, caterpillars and slugs. A food web shows all of these chains joined together.

Food webs matter because they show why some habitats cope with change better than others. If a hedgehog only ate beetles, losing the beetles would be a disaster. Because it eats five different things, losing one is survivable.

More connections means a habitat is more able to cope. A habitat with only a few kinds of living thing is fragile. A habitat with many is tougher.

Part 6 — Questions

1. What is a producer, and why does every food chain start with one? (2 marks)

2. In the chain grass → rabbit → fox, name the primary consumer and the tertiary level if there is one. (2 marks)

3. Which way do the arrows point in a food chain, and why? (2 marks)

4. A gardener removes all the slugs from a garden. Explain two things that might happen as a result. (2 marks)

5. Explain why a habitat with many different living things copes better with change than one with only a few. (2 marks)

6. Explain why a chameleon would not survive in a British hedgerow. (2 marks)

Try this

• Draw the food chain for your own dinner tonight, backwards, all the way to the Sun.
• Watch our animal cams and see if you can work out one food chain from what you see.
• Related lessons: Life Cycles · Adaptation · KS3 Science — Classification & Variation.

Notes for the adult

Curriculum: KS2 Science — constructing and interpreting food chains, identifying producers, predators and prey; recognising that living things are suited to and depend on their habitat.

Deliberately teaching-led. Five parts of explanation to one short question set. The arrow direction and the interdependence idea both need building rather than stating, and both are commonly taught as facts to memorise.

The arrow misconception is addressed in Part 2 by explaining why the wrong answer is tempting, not just asserting the right one. Children who have drawn it the wrong way need the reason, or they will revert.

Part 4 is the heart of the lesson. Work through it aloud one step at a time rather than reading it straight. The moment a child realises the hedgehog was harmed by something two steps away is the moment interdependence lands.

Access: read-aloud, dyslexia-friendly font, enlarged text, high contrast and calm mode. Chains are written on their own lines and print clearly.

No timing, no scoring.

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