An ecological niche is a combination of where an organism lives (its habitat) and how the organism lives in that environment (for example, its adaptations to cope with the environment, its life cycle, etc.).
An ecological niche reflects the role that a particular organism plays within its biological community.
- Fundamental niche: This terms is used to describe the niche that a particular organism would be likely to occupy if all the environmental factors it needed were present. The boundaries of the fundamental niche are set by abiotic factors the organism can tolerate, such as temperature, salinity and nutrient availability.
- Realised niche: This is the niche that the particular organism actually lives in. The boundaries of a realised niche are determined by the biotic factors, such as competition for resources and predation.
In ecological theory, it is posited that no two species can occupy exactly the same niche, for where this happens, one species would outcompete the other.