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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
The key difference
A food chain shows a single linear feeding pathway (producer → primary consumer → secondary consumer). A food web shows multiple interconnected food chains in an ecosystem, giving a more realistic picture of feeding relationships.
Food chains and food webs both model feeding relationships in ecosystems, but they differ in complexity and realism. Examiners expect you to interpret both, predict the effects of removing an organism, and explain why food webs are more useful than individual food chains.
Feature
Food Chain
Food Web
Definition
A single linear sequence showing what eats what
Multiple interconnected food chains in an ecosystem
Complexity
Simple: one pathway
Complex: many pathways
Realism
Oversimplified: most organisms eat more than one food source
More realistic: shows that organisms have multiple food sources
Arrows show
Direction of energy transfer (from prey to predator)
Direction of energy transfer across multiple feeding relationships
Predicting effects of change
Limited: can only trace one pathway
More accurate: can see alternative food sources and cascading effects
Starting point
Always begins with a producer (green plant)
Contains many producers and multiple trophic levels
Arrow Direction Matters
A very common exam error is drawing arrows in the wrong direction. The arrow in a food chain or food web points from the organism being eaten TO the organism eating it. This is because the arrow shows the direction of energy transfer, not "what eats what". So: grass → rabbit → fox means "energy flows from grass to rabbit to fox."
Predicting Effects of Population Changes
A typical exam question gives you a food web and asks: "What would happen if organism X were removed?" To answer:
Identify all organisms that eat X: their population may decrease (less food available), unless they have alternative food sources shown in the web
Identify all organisms eaten by X: their population may increase (fewer predators)
Trace any knock-on effects through the web: for example, if a predator declines, its own prey may increase, and so on
Always state whether the affected organism has alternative food sources in the web: this determines whether the effect is severe or buffered.
Try a comparison question (3 marks)
In a food web, owls eat mice and voles. Mice eat seeds and insects. Voles eat seeds. If the vole population decreased due to disease, predict and explain the effect on the mouse population. [3]
Show the answer and marking guidance
Owls would eat more mice because there are fewer voles available as prey
So the mouse population would decrease due to increased predation
However, mice might also face less competition for seeds (since fewer voles are eating seeds), which could partially offset the effect
Original Cambridge-style practice written for this site.
Common comparison mistakes
When answering a compare question, write matched pairs rather than two separate descriptions.
Drawing arrows the wrong way: arrows show energy transfer FROM prey TO predator
Ignoring alternative food sources when predicting effects of removing an organism
Saying a food chain starts with a consumer: it always starts with a producer
Treating food chains and food webs as equally accurate: food webs are more realistic