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.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The fundamental niche is the full range of environmental conditions and resources a species could use if no other species were present. The realised niche is the smaller, actual range that the species occupies when other organisms are present.
A species may not occupy its full fundamental niche because interspecific competition can exclude it from parts of that range; a competitor may be better adapted to those conditions. Predation, parasitism or other biotic pressures can also restrict the species, making some environments or times of use too costly, so the realised niche is reduced.
A species may not occupy its full fundamental niche because interspecific competition can exclude it from parts of that range; a competitor may be better adapted to those conditions. Predation, parasitism or other biotic pressures can also restrict the species, making some environments or times of use too costly, so the realised niche is reduced.
Examiner tips
- Define both niches first, then give a clear example of a limiting factor (competition or predation).
- Use the words "full" and "reduced" to show the difference.
- Mention that the restriction is due to biotic interactions.
Common mistakes
- Confusing the terms or using the same definition for both niches.
- Failing to mention that competition or predation are the main reasons for the reduction.
Mark scheme (4 marks)
- The fundamental niche is the full range of conditions and resources a species is theoretically capable of exploiting in the absence of interacting species.
- The realised niche is the actual, reduced range of conditions and resources a species occupies when interacting with other species (e.g. competitors, predators).
- Interspecific competition excludes a species from parts of its fundamental niche because a competitor is better adapted to exploit those resources or conditions.
- 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 in this question
fundamental niche · realised niche
Related
- All IB DP Biology Standard Level (2023 syllabus) revision notes →
- How to answer a "Explain" question →
- Decode the mark scheme abbreviations →
More Ecological niches questions
- Explain how the competitive exclusion principle relates to the concept of ecolog…
- Explain how the concept of resource partitioning allows multiple species of clos…
- Explain how niche differentiation can arise between two populations of the same …
- Explain how character displacement can occur when two species with overlapping e…
- Explain how the ecological niche of a specialist species makes it more vulnerabl…
- Explain how the ecological niche of a species can change over evolutionary time …