KS3 · Biology

Food webs

Remove the cats from a garden and the lavender might suffer. Food webs explain why.

Biology · A web of effects

What happens when the cats disappear?

Two food chains from one garden share an organism: lettuce → snail → thrush → hawk, and lavender → bee → thrush → cat. (Each arrow means 'is eaten by'.) Now every cat is removed. Add an arrow for each 'a change here changes that'. Start at the cats and follow the effect as far as it will go — then check your web against ours.

  1. Cats
  2. Thrushes
  3. Bees
  4. Lavender
  5. Snails
  6. Lettuce
  7. Hawks
Add a link

No links yet.

Biology · Words for living together

Habitat, population, community — or interdependence?

Pick an example, then choose the word that describes it.

Still to sort

Habitat (0)

The place an organism lives. It gives food, shelter and somewhere to reproduce.

Where the line is: A habitat is a PLACE, not a group of living things.

Population (0)

All the organisms of ONE type living in the same place.

Where the line is: One type only. Several types together make a community.

Community (0)

All the populations of different organisms living in the same habitat.

Where the line is: Many types of organism — but only the living things, not the place.

Interdependence (0)

Organisms in a community interacting and depending on each other.

Where the line is: Something organisms DO for or to each other — not a place and not a group.

7 of 7 still to sort.

Four words, four different sizes of idea. Sort each example into the one that fits.

Watch out: Easy mistake: a community is only the living things. The habitat is the place they share.

Biology · Reading a food chain

Which way do the arrows point?

A food chain from a garden: lettuce → snail → thrush → hawk

Which idea is closest to what you think right now?
How sure are you?

Two models of who eats whom

Food chainvsFood web

A food chain is a good start. But real feeding is messier — which is why biologists use food webs.

Focus

What it shows

Food chain

One feeding relationship after another, in a single line

Food web

Many food chains, linked together

The insight

This is the big one. A chain is one line of feeding; a web is a set of interconnected chains.

A consumer that eats several foods

Food chain

Can't show it — each consumer seems to eat just one thing

Food web

Shows every food it eats

A producer or primary consumer with several predators

Food chain

Looks as if only one organism eats it

Food web

Shows everything that eats it

How it's built

Food chain

One producer, then the consumers that feed on it in turn

Food web

Chains that share organisms, joined at those shared organisms

How realistic?

Food chain

Too simple

Food web

A better, more realistic model

Biology · Reading a food web

The garden food web
HawkCatThrushSnailBeeLettuceLavender

View: Whole web. Showing 1 layer: Food web

View

Explore

Tap an organism to read it, or pick a chain to trace it out from its producer.

Every arrow points the way the food passes: from the organism eaten to the one that eats it.

Two chains, joined at the thrush. Tap any organism to read what it eats and what eats it.

A newcomer arrives

?

Reason it through

How did rats arriving on ships put the kiwi in danger?

Link 1 of 4

First link · your turn

Rats weren't always part of New Zealand's food webs. How did they get there?

2
Locked — reveal the link above first
3
Locked — reveal the link above first
4
Locked — reveal the link above first

WHAT YOU'VE LEARNED

A quick recap of today's lesson.

Pull one thread of a food web and the whole thing moves.

What you need to know

  • A habitat is where an organism lives; a population is one type of organism in a place; a community is all the populations in a habitat.
  • Food chain arrows point the way food passes: from the organism eaten to the organism that eats it.
  • Every food chain begins with a producer, which makes its own food. Consumers eat other organisms.
  • A food web is a set of linked food chains — a better, more realistic model than one chain.
  • A change in one population can affect populations in every part of a food web, not just its own chain.

The big picture

Organisms in a community depend on each other. A food chain shows one line of feeding, with arrows pointing the way the food passes, and it always starts with a producer. A food web links many food chains together, so it's a more realistic model. Because each organism can sit in several chains, a change in one population can spread right across the web.

Key points

1Interdependence: organisms rely on each other — for food, for pollination, even for cleaning.
2Read every arrow as 'is eaten by'.
3Most consumers eat more than one food, so a single chain is too simple.
4An apex predator is at the top of its food chains — nothing in the web eats it.
5Removing an apex predator can reach all the way down to the producers.
6Introducing a new organism can be harmful: rats in New Zealand ate the eggs of ground-nesting birds.

Worked example

Problem

In the garden web, snails and bees are eaten by thrushes, and thrushes are eaten by hawks and cats. The thrush population falls. Predict what happens to the snails, the bees, the lettuce and the hawks.

⚠ Watch out

Thinking a change only affects its own food chain. Fewer thrushes means more snails AND more bees, because the thrush is in several chains at once.

🧠

Memory hook

Arrows follow the food; webs wobble. Pull one thread and every strand joined to it moves.

✓

Check yourself

In the garden web, every snail disappears. Which organism has lost one of its foods — and why might life get harder for the bees?

Flashcards

(15)
What is a habitat?
The place where an organism lives. It gives food, shelter and a place to reproduce. Habitats range from the ocean (the largest) to microhabitats like under a log.
What is a population?
All the organisms of the same type living in the same place.
What is a community?
All the populations of different organisms living in the same habitat.
What does interdependence mean?
Organisms in a community interact and depend on each other — e.g. a bee pollinates a flower, an oxpecker cleans a buffalo, a heron eats a fish.
Which way does an arrow point in a food chain?
The way the food passes: from the organism that is eaten to the organism that eats it.
What is a producer?
An organism that makes its own food. Every food chain begins with one, and it provides the food for the whole chain.
What is a consumer?
An organism that gets its food by eating other organisms. Consumers rely on producers.
Why is a food chain too simple a model?
It shows only one feeding relationship, but most consumers eat more than one type of food, and producers and primary consumers are usually eaten by more than one organism.
What is a food web?
A set of interconnected food chains in a community — a better, more realistic model of feeding in a habitat.
How do you trace one food chain out of a food web?
Start at a producer and follow the arrows from organism to organism until you reach one that nothing eats.
In a food web, what are an organism's prey and its predators?
Its prey are the organisms it eats (arrows coming in). Its predators are the organisms that eat it (arrows going out).
What is an apex predator?
An animal at the top of its food chains — nothing in the web eats it, like a fox in a woodland web.
Why can one population change affect a whole food web?
Each organism can be in several food chains, so the change travels along all of them — not just one chain.
Removing cats from lavender → bee → thrush → cat could mean fewer lavender plants. Why?
More thrushes survive and eat more bees. Fewer bees pollinate the lavender, so there may be fewer lavender plants.
Why did birds such as the kiwi become endangered in New Zealand?
Rats arrived on ships in the late 1700s and ate the eggs of ground-nesting birds, which had few egg predators. Bird populations fell.

Tap any card to flip it, or use Study as deck to go through them one at a time. In the full lesson these run as a spaced-repetition deck — you rate each card Hard, Good or Easy and the tricky ones keep coming back until they stick.

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How this lesson was checked. This KS3 Biologylesson was published through Lightbulb Learning's human-designed editorial process — the educational standards, accuracy rules and publication checks it must pass were authored and approved by Philip Halpin. It passed subject-specific assessment, automated educational checks and technical publication verification before going live (publication checks completed 30 September 2026). Published pages are monitored, human spot-checking is ongoing across the lesson library, and anything found wrong is corrected or withdrawn. How our lessons are made and checked. Spotted a mistake? Email hello@lightbulblearning.co and we'll review it.