Niche
The Environment
• Environment: All the factors in a habitat which affect an organism; these may be biotic or abiotic.
• Habitat: The geographical area occupied by an ecosystem.
• Biotic: Factors referring to the living organisms in the ecosystem.
o E.g. Predation, competition, disease, parasites, mates.
• Abiotic: Factors referring to non-living physical and chemical elements in the ecosystem.
o E.g. Humidity, nutrient availability, temperature, light intensity, wind speed, oxygen concentrations,
water availability, soil pH.
Niche
• Niche: The role of a species within an ecosystem.
• This includes its relationship with living organisms and the non-living environment.
• Every species has its own niche – a niche can only be occupied by one species.
• If two species try to occupy the same niche, they will compete with each other; one species will be more
successful than the other and the other will struggle to survive.
(Extra) Fundamental Niche Vs. Realised Niche
• Fundamental Niche: The full range of environmental conditions (biological and physical) under which an
organism can exist.
• Realised Niche: The limited range of environmental conditions that a species is forced to occupy due to direct
and indirect interactions with other species.
Competition
• Interspecific Competition: Competition between individuals of different species.
• Intraspecific Competition: Competition between individuals of the same species.
• Competition forces species to occupy a narrower (realised) niche than their full (fundamental) niche.
(Extra) Effect of Competition on Realised Niche
Interspecific Competition
• Interspecific competition is between different species, and different species will have different niches.
• However there may be some overlap of resources between these niches and there will be competition between
the species for these resources.
• As a result, the species will be forced to specialise towards the resources within their niche that are not apart
of the overlap.
• Hence interspecific competition makes niches narrower.
Intraspecific Competition
• Intraspecific competition is between the same species, and the same species will have the same niche.
• As such these species will be competing for exactly the same resources, which there will likely not be enough
of.
• As a result, the species will be forced to move outside of their optimum range and specialise towards new
resources.
• Hence intraspecific competition makes broadens niches.
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