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How do ecologists determine the boundaries of a population of organisms?
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population
Graph of the world's estimated human population from 1700 until 2000, with population projections extending until 2100.
In population ecology, a population is defined as a group of individuals of the same species occupying a specific geographic area that, in sexually reproducing organisms, interbreed.1
Ecologists determine population boundaries based on the degree of geographic isolation and connectivity:
- Clear Boundaries: For species inhabiting isolated environments, such as islands, the geographic range is naturally defined by the physical perimeter of the habitat.1
- Complex Boundaries: For species dispersed across vast or continuous landscapes, defining boundaries is more challenging. Ecologists must assess the level of gene flow—the exchange of genetic material through interbreeding—to distinguish between local populations.12
Ultimately, populations exist on a continuum ranging from "closed" populations, which are geographically isolated with no exchange of individuals, to "open" populations that maintain varying degrees of connectedness with others of the same species.1