In biology, a deme is a term for a local population of organisms of one species, that actively interbreed with one another and share a distinct gene pool. When demes are isolated for a very long time they can become distinct subspecies or species. The term 'deme' is mainly used in evolutionary biology and is often used as a synonym for population. In evolutionary computation a "deme" often refers to any isolated subpopulation subjected to selection as a unit rather than as individuals.