B4.2.1—Ecological niche
An ecological niche is a species role in a community, including habitat, feeding, activity, reproduction, interactions and tolerance ranges across ecosystems.
- Syllabus
- First assessment 2025
- Objective
- B4.2.1
- Level
- HL
A Niche Describes How a Species Makes a Living
An ecological niche is the full role of a species: the conditions it tolerates, resources it uses and interactions that affect its survival and reproduction.
A niche includes both abiotic requirements and biotic relationships such as competition, predation and mutualism. Two species can share a habitat yet occupy different niches.
Describe a niche with: physical limits; food or resource use; timing or location; interactions with other species.
Two birds may nest in the same forest but feed at different heights and times, reducing direct competition.
Niche is not just habitat. Habitat is where a species lives; niche explains how it lives there.
Ecological niche
Assessment in practice
2–3 marksHow it is assessed
This objective is assessed through structured response, commonly using Explain / Identify.
Command terms
Explain / Identify
What earns marks
Build the answer around this relationship: A niche is the ecological role or mode of existence of a species.
Watch for
Treating niche as only the place where an organism lives.
Representative question
Question 1
[Maximum number: 3]
Explain the niche concept.
G2. (a) niche is an organism's ecological role/mode of existence;
niche is how organism uses abiotic and biotic resources;
depends on where organism lives/habitat;
depends on organism's nutrition/feeding activities;
depends on interactions (competition/herbivory/predation/mutualism) with other organisms;
Niches, Nutrition, And Competition
A niche is the role of a species in a community, including habitat, abiotic tolerances, nutrition, activity, reproduction, and interactions. The evidence should match the question: nutrition mode, oxygen tolerance, feeding adaptation, predator-prey interaction, plant light strategy, fundamental versus realized niche, or competitive exclusion.
- Definition answers should include role plus habitat/resources/interactions, not only place.
- Nutrition modes explain how organisms obtain carbon, energy, or organic matter.
- Adaptation examples should be linked to feeding, defence, light harvesting, or competition.
- Fundamental versus realized niche and competitive exclusion are tested together because interactions narrow where species actually live.
Concept essentials
- A niche is the ecological role or mode of existence of a species.
- Niche includes habitat, feeding, activity, reproduction and interactions.
- Species in similar habitats can have different niches.
- Abiotic tolerance ranges contribute to a species niche.