AQA Biology 4.7.2.1 · Combined and Triple

Food chains and food webs

Which way the arrow points, who starts every chain, and what happens along the web when one population changes.

Combined Science · Foundation tier

Start here

No more foxes.

Every fox in a field disappears.

If you had to guess, would there be more rabbits or fewer?

Food chains

Producer first, arrow to the eater.

Feeding relationships within a community can be represented by food chains. All food chains begin with a producer which synthesises molecules. This is usually a green plant or alga which makes glucose by photosynthesis. Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers and then tertiary consumers.

What does the arrow between the rabbit and the fox mean?

Pick one.

Consumers that kill and eat other animals are predators, and those eaten are prey.

Food webs

Change one population.

Most animals eat more than one thing, so chains join into a web. Pick a change and follow the arrows.

Grass feeds rabbits and grasshoppers. Rabbits are eaten by foxes; grasshoppers by shrews; shrews by owls and foxes.

In this web the grasshoppers die out. What happens to the owls?

Pick one.

Think again · which way?

“The arrow means ‘eats’.”

Your call

Choose

In the chain grass, rabbit, fox, which way does the arrow between grass and rabbit point?

Sort

Which role?

Place each organism from the pond chain: algae, pond snail, small fish, heron.

Tap a card, then tap the box it belongs in. Tap a placed card to take it back.

Command words in this lesson

Draw: A food chain with arrows from food to eater.
Explain: What happens to one population when another changes.
Name: The producer, primary, secondary and tertiary consumers.

Key fact

All food chains begin with a producer, usually a green plant or alga. Arrows point from the food to the eater. In a web, change one population and the ones linked to it change too.

Key note · AQA 4.7.2.1

Food chains and food webs

Feeding relationships within a community can be represented by food chains. All food chains begin with a producer which synthesises molecules, usually a green plant or alga which makes glucose by photosynthesis.
Producers are eaten by primary consumers, which in turn may be eaten by secondary consumers and then tertiary consumers. Consumers that kill and eat other animals are predators; those eaten are prey.
Arrows point from the food to the eater: the direction biomass is transferred.
In a food web, follow the arrows to predict what happens to other populations when one changes.

Photograph this card. Tomorrow, cover it and say each line first.

Previous and next

Connects to

Ask MrBadmus

Still drawing the arrow towards the food?

The field web is a made-up example.