# Explain how habitat fragmentation reduces biodiversity, referring to the effects on population size and gene flow.

> IB DP Biology Higher Level (2023 syllabus) — A4.2 Conservation of biodiversity · Explain · 4 marks

## Mark scheme (4 marks)

1. Habitat fragmentation divides continuous habitat into smaller, isolated patches, reducing the total area available to species.
2. Smaller habitat patches support smaller population sizes, increasing the risk of local extinction due to stochastic events / reduced resources.
3. Isolation of fragments reduces gene flow between populations, as individuals cannot migrate between patches.
4. Reduced gene flow leads to inbreeding within fragments, decreasing genetic diversity and increasing the expression of deleterious alleles / reducing adaptability, further threatening species survival.

## Key terms

- [habitat fragmentation](https://www.gradenine.co.uk/glossary/habitat-fragmentation)
- [gene flow](https://www.gradenine.co.uk/glossary/gene-flow)

## 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)
- [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-habitat-fragmentation-reduces-biodiversity-2ca497c0) · Published by Druglandscape Ltd.