# Explain how the presence of a keystone species can affect the structure of a community, including the impact on other species and ecosystem processes.

> OCR GCSE Biology A: Gateway Science (J247) — B4 Community level systems · Explain · 4 marks

## Mark scheme (4 marks)

1. definition of a keystone species
2. impact on other species in the community
3. effect on ecosystem processes
4. example or illustration of a keystone species in action

## Related

- [Revision notes for OCR GCSE Biology A: Gateway Science (J247)](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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