# Explain how the predator–prey relationship between two species maintains a cyclical pattern of population fluctuation in a community.

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

> In many ecosystems, population sizes of predators and their prey oscillate over time in a repeating cycle. The Canadian lynx and snowshoe hare are a well-documented example of this phenomenon.

## Mark scheme (4 marks)

1. An increase in prey population provides more food for predators, causing predator numbers to increase.
2. The increased predator population causes greater predation pressure, leading to a decline in prey numbers.
3. As prey numbers decline, food becomes scarce for predators, so predator numbers subsequently decrease.
4. With fewer predators, prey population recovers/increases again, restarting the cycle.

## Key terms

- [predator–prey relationship](https://www.gradenine.co.uk/glossary/predator-prey-relationship)
- [population fluctuation](https://www.gradenine.co.uk/glossary/population-fluctuation)
- [cyclical pattern](https://www.gradenine.co.uk/glossary/cyclical-pattern)
- [community](https://www.gradenine.co.uk/glossary/community)

## Related

- [Revision notes for IB DP Biology Standard Level (2023 syllabus)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-the-predator-prey-relationship-between-9d5f49aa) · Published by Druglandscape Ltd.