# Explain how predator–prey interactions can produce cyclical fluctuations in the population sizes of both species within a community.

> IB DP Biology Higher Level (2023 syllabus) — C4.1 Populations and communities · Explain · 4 marks

## Mark scheme (4 marks)

1. An increase in prey population size provides more food/resources for predators, so predator numbers increase (with a time lag).
2. Rising predator numbers increase predation pressure, causing prey population size to decline.
3. As prey numbers fall, food becomes scarce for predators, so predator population declines due to starvation/reduced reproduction.
4. Reduced predation pressure allows prey population to recover/increase again, restarting the cycle.

## Key terms

- [predator–prey interaction](https://www.gradenine.co.uk/glossary/predator-prey-interaction)

## Related

- [Revision notes for IB DP Biology Higher Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-predator-prey-interactions-can-produce-2e82f2e2) · Published by Druglandscape Ltd.