# Explain how interspecific competition between two species occupying similar niches can affect the population sizes of both species over time.

> IB DP Biology Standard Level (2023 syllabus) — C4.1 Populations and communities · Explain · 4 marks

## Mark scheme (4 marks)

1. Interspecific competition occurs when two species compete for the same limited resource(s), such as food, space, or light.
2. The species with a competitive advantage uses resources more efficiently, allowing it to survive and reproduce at a higher rate.
3. The less competitive species experiences reduced resource availability, leading to a decline in its population size.
4. In extreme cases, the less competitive species may be excluded from the habitat entirely (competitive exclusion), whereas the dominant species' population may stabilise or increase.

## Key terms

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

## 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-interspecific-competition-between-two-87f4572a) · Published by Druglandscape Ltd.