# Explain how the introduction of an invasive species into a new community can affect the population size of a native species occupying a similar niche.

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

## Mark scheme (4 marks)

1. The invasive and native species compete for the same or overlapping resources (e.g. food, shelter, nesting sites) because they occupy similar niches.
2. The invasive species is not limited by the natural predators, parasites, or pathogens present in the native community, giving it a competitive advantage.
3. Increased competition reduces the availability of resources for the native species, leading to a decrease in its birth rate and/or an increase in its death rate.
4. As a result, the native species population size declines and, if the competitive exclusion is complete, the native species may be locally eliminated / driven to extinction in that community.

## Key terms

- [invasive species](https://www.gradenine.co.uk/glossary/invasive-species)
- [niche](https://www.gradenine.co.uk/glossary/niche)
- [native species](https://www.gradenine.co.uk/glossary/native-species)

## 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-introduction-of-an-25bfc639) · Published by Druglandscape Ltd.