What is a niche?

• A. An organism's role in its ecosystem, including resource use and environmental conditions it requires.
• B. The physical space an organism occupies.
• C. The set of organisms living in a habitat.
• D. The average size of individuals in a population.

Answer: (A)

A niche is the organism’s role in its ecosystem, including what resources it uses and the environmental conditions it requires. It covers how an organism obtains food and energy, where and when it lives and feeds, and how it interacts with other species. All of these factors together describe how a species fits into its environment and how it avoids direct competition with others — for example, a species that forages at a different time of day or in a different part of the habitat occupies a different niche than others with similar needs. The physical space an organism occupies is its habitat, not its niche. The set of organisms living in a habitat is a community, and the average size of individuals in a population is a demographic detail, not about the organism’s ecological role.