# Explain how competitive exclusion can lead to character displacement in two closely related species occupying the same habitat.

> IB DP Biology Higher Level (2023 syllabus) — B4.2 Ecological niches · Explain · 4 marks

## Mark scheme (4 marks)

1. Competitive exclusion occurs when two species compete for the same limiting resource, with one species outcompeting the other
2. Where the niches of two species overlap significantly, individuals whose phenotype differs most from the competitor gain a selective advantage because they experience less competition
3. Over generations, natural selection drives the two populations to diverge in the traits associated with resource use (e.g. beak size, body size), a process called character displacement
4. Character displacement effectively partitions the resource/niche so that the two species can coexist, reducing the pressure of competitive exclusion

## Key terms

- [competitive exclusion](https://www.gradenine.co.uk/glossary/competitive-exclusion)
- [character displacement](https://www.gradenine.co.uk/glossary/character-displacement)

## 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-competitive-exclusion-can-lead-b628f559) · Published by Druglandscape Ltd.