This combination of a species’ physical habitat and its ecological role in that habitat defines its niche, though the meaning of this term has changed over the years. Nearly a century ago, the American ecologist Joseph Grinnell defined the niche as the sum of the habitat requirements needed for a species’ survival and reproduction. Later, ecologist Charles Elton redefined the niche as the role a species plays in a community, switching emphasis from the habitat to the species itself. By the middle of the twentieth century, ecologist G. Evelyn Hutchinson had combined these ideas, popularizing the concept of the niche as a multidimensional habitat that allows a species to practice its way of life.

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The niche is therefore determined by both physical (abiotic) factors such as climate and soil chemistry, and biological (biotic) factors based on interactions with other species. These factors lead to adaptations, the products of natural selection. Adaptations in turn enable different species to coexist by exploiting different combinations of resources. At the same time, species affect the resources and other species around them.

Species are commonly associated with a specific habitat, but “niche” and “habitat” are not interchangeable. Niches have a dual nature: They reflect both where organisms occur and what they do there. Furthermore, the niche refers to the ways that organisms respond to, and also affect, the resources and other species found in the habitat.