# Explain the difference between the fundamental niche and the realised niche of a species, and explain why a species may not always occupy its fundamental niche.

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

## Mark scheme (4 marks)

1. The fundamental niche is the full range of conditions and resources a species is theoretically capable of exploiting in the absence of interacting species.
2. The realised niche is the actual, reduced range of conditions and resources a species occupies when interacting with other species (e.g. competitors, predators).
3. Interspecific competition excludes a species from parts of its fundamental niche because a competitor is better adapted to exploit those resources or conditions.
4. Predation, parasitism, or other biotic pressures can also restrict a species to a smaller realised niche by making certain environments or times of resource use too costly.

## Key terms

- [fundamental niche](https://www.gradenine.co.uk/glossary/fundamental-niche)
- [realised niche](https://www.gradenine.co.uk/glossary/realised-niche)

## 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-the-difference-between-the-fundamental-52afd0ca) · Published by Druglandscape Ltd.