Within biological communities, some species are important in determining the ability of a large number of other species to persist in the community. Such species are called

1. The question describes species within biological communities whose presence or activities significantly influence the structure, function, and persistence of many other species in the community, often disproportionately to their own abundance. 2. This ecological role is the definition of a Keystone species (A). Examples include sea otters in kelp forests or certain predators that control herbivore populations. 3. Allopatric species (B) live in different geographic areas. Sympatric species (C) live in the same area. Threatened species (D) are categorized based on their risk of extinction.