# Explain how resource partitioning allows closely related species to coexist within the same habitat without violating the competitive exclusion principle.

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

## Mark scheme (4 marks)

1. The competitive exclusion principle states that two species occupying the same ecological niche cannot coexist indefinitely, as one will outcompete the other to local extinction.
2. Resource partitioning occurs when closely related species divide or differentiate their use of resources (e.g. food, space, time) so that their realised niches only partially overlap.
3. By subdividing resources, each species occupies a distinct realised niche, reducing interspecific competition sufficiently to allow stable coexistence.
4. A named or described example illustrating resource partitioning, such as MacArthur's warblers feeding at different heights/zones within the same tree, or anole lizards using different perch heights/microhabitats.

## Key terms

- [competitive exclusion principle](https://www.gradenine.co.uk/glossary/competitive-exclusion-principle)
- [resource partitioning](https://www.gradenine.co.uk/glossary/resource-partitioning)

## 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-resource-partitioning-allows-closely-f4bd91de) · Published by Druglandscape Ltd.