Science · Year 4 · Animals, including humans · Summer Term

The Impact of Change on Food Chains

Explore what happens to all the animals and plants in a food chain when one part of it is changed or removed, either by nature or by human actions.

TL;DR:This topic uncovers the hidden connections in nature, showing pupils how every single plant and animal plays a vital role in its habitat.

• National Curriculum Attainment Targets
• National Curriculum for England: Science Year 4: Animals, including humans

About This Topic

This topic aligns with the Year 4 science programme of study within the National Curriculum for England, which requires pupils to recognise that environments can change and that this can pose dangers to living things. Building upon their prior knowledge of simple food chains from Key Stage 1, pupils will now delve deeper into the concept of interdependence. The focus shifts from simply identifying producers, predators, and prey to analysing the complex, dynamic relationships within an ecosystem. Pupils will explore the ripple effects caused by changes to a single population within a food chain. These changes can be natural, such as disease or unusual weather patterns, or human-induced, such as pollution, habitat destruction, or the introduction of invasive species. The core learning objective is for pupils to understand that ecosystems are delicately balanced and that the removal or addition of one element can have significant and often unforeseen consequences for all other organisms involved.

Key Questions

1. Analyse the effect on a food chain if the producer is removed.
2. Explain what might happen to the population of prey if a predator is removed.
3. Evaluate the impact of human activity, like pollution, on a local food chain.

Learning Objectives

• Describe the interdependence of organisms within a food chain and a simple food web.
• Predict the consequences for a food chain if a specific producer or consumer is removed or its population changes.
• Explain how human activities, such as pollution and habitat destruction, can negatively affect food chains.
• Construct a simple food web to show how different food chains are connected.

Key Vocabulary

Producer	An organism, usually a plant, that produces its own food using energy from sunlight.
Consumer	An organism that gets its energy by eating other organisms. They can be primary (eats producers), secondary (eats primary consumers), or tertiary (eats secondary consumers).
Interdependence	The way in which living organisms in an ecosystem depend on each other for survival.
Food Web	A system of interconnected food chains in an ecosystem.
Population	The total number of one type of organism living in a particular area.

Watch Out for These Misconceptions

Common Misconception

Removing an animal only affects the one directly above it in the food chain.

What to Teach Instead

The effects ripple both up and down the food chain. For example, removing a predator can lead to an overpopulation of its prey, which in turn can decimate the producers they feed on.

Common Misconception

Food chains are rigid, linear paths.

What to Teach Instead

Most animals eat more than one type of food, so they are part of a more complex 'food web' with many interconnected chains. A change in one chain can therefore affect many others.

Common Misconception

Humans are not part of food chains.

What to Teach Instead

Humans are consumers at the top of many food chains. Furthermore, human activities like farming, fishing, and pollution have a massive impact on nearly every ecosystem on Earth.

Active Learning Ideas

Simulation Game

Food Chain Jenga

Build a Jenga tower where each block is labelled with an organism from a specific food web (e.g., woodland or pond). As pupils remove a block, they must explain the impact on the ecosystem, noting how removing one piece can make the entire structure unstable.

30 min·Small Groups

Simulation Game

Domino Effect Diagram

Pupils create a large diagram of a food web on paper or using string and cards. They then 'remove' one organism and draw arrows or lines to trace all the potential knock-on effects throughout the web, demonstrating the chain reaction.

45 min·Pairs

Simulation Game

Local Habitat Impact Report

Pupils research a food chain from a local habitat, such as a park, canal, or school field. They then write a short report or create a presentation on how a specific human activity, like littering or construction, could disrupt that chain.

60 min·Individual

Real-World Connections

• Discussing the decline of bee populations and the impact on the pollination of flowers and food crops.
• Investigating the effects of plastic pollution in our oceans on marine life, from plankton to whales.
• Learning about the reintroduction of beavers in the UK and how they change river habitats, affecting fish, insects, and birds.
• Examining how overfishing of cod in the North Sea has affected populations of seals and seabirds.
• Understanding why building new roads or houses can fragment habitats and disrupt the food chains of local wildlife like hedgehogs and foxes.

Assessment Ideas

Quick Check

Use 'what if' scenarios. Present a simple food chain and ask pupils to write on mini-whiteboards what would happen to the other organisms if one was removed.

Peer Assessment

Pupils create a poster or a short comic strip that tells the story of a food chain being disrupted by a specific event, either natural or human-caused, showing the consequences for each organism.

Quick Check

Provide pupils with a 'confidence ladder' where they can mark how well they understand key concepts like 'producer', 'interdependence', and 'food web'.

Frequently Asked Questions

What happens if you remove the producer from a food chain?

If the producer (like grass or algae) is removed, the entire food chain will collapse. Producers are the source of all energy, so the primary consumers that eat them would have no food, and this would lead to the starvation of all the animals further up the chain.

Can an animal be both a predator and prey?

Yes, many animals are. For example, a blackbird is a predator to a worm, but it is prey for a cat. This is very common in most food webs.

Is a change in a food chain always bad?

Not necessarily, but it always causes disruption. For example, reintroducing a top predator like a wolf to an area can help control an overpopulated deer population, which in turn allows plants and trees to recover, benefiting many other species. However, the initial change can be difficult for the ecosystem to adapt to.