# Explain why the removal of a top predator from an ecosystem can lead to a reduction in the overall biodiversity of that ecosystem.

> OCR A-Level Biology A (H420) — 6.6 Populations and sustainability · Explain · 4 marks

> In some coastal ecosystems, sea otters are the only significant predator of sea urchins. When sea otter populations declined sharply due to hunting, sea urchin populations increased dramatically. Sea urchins graze heavily on kelp, a large brown alga that forms complex underwater forests providing habitat for hundreds of species.

## Mark scheme (4 marks)

1. Removal of the top predator allows its prey population to increase without regulation
2. The unregulated prey population over-exploits a key resource / habitat-forming species
3. Loss of the habitat-forming species reduces the number of ecological niches available
4. Fewer niches / resources leads to fewer species being able to survive, so species richness / biodiversity decreases

## Key terms

- [top predator](https://www.gradenine.co.uk/glossary/top-predator)
- [biodiversity](https://www.gradenine.co.uk/glossary/biodiversity)
- [ecosystem](https://www.gradenine.co.uk/glossary/ecosystem)

## Related

- [Revision notes for OCR A-Level Biology A (H420)](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-why-the-removal-of-a-e590ee8b) · Published by Druglandscape Ltd.