# Explain how the ecological niche of a species can change over evolutionary time as a result of interspecific competition.

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

> Darwin's finches on the Galápagos Islands show differences in beak morphology that are thought to have arisen partly through character displacement, a process in which competing species evolve to use different resources.

## Mark scheme (4 marks)

1. Interspecific competition occurs when two species require the same or overlapping resources, reducing the fitness of both.
2. Natural selection favours individuals whose niche / resource use differs from that of the competing species, as they experience less competition.
3. Over generations, heritable variation in resource-use traits (e.g. beak size / morphology) is selected, leading to character displacement and a shift in the realised niche.
4. The result is niche divergence / niche partitioning, allowing the two species to coexist by reducing overlap in their realised niches.

## Key terms

- [ecological niche](https://www.gradenine.co.uk/glossary/ecological-niche)
- [interspecific competition](https://www.gradenine.co.uk/glossary/interspecific-competition)

## Related

- [Revision notes for IB DP Biology Standard 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-the-ecological-niche-of-f91707d3) · Published by Druglandscape Ltd.