Species

A classification of related organisms that can freely interbreed.

A class of individuals capable of interbreeding, but which is reproductively isolated from other such groups having many characteristics in common. A somewhat arbitrary and sometimes blurred classification; but still quite useful in many situations.

Organisms in the same genus that have similar characteristics.

A biological classification of plants and animals.

Basic category of biological classification intended to designate a single kind of animal or plant. See candidate species, endangered species, exotic species, extirpated species, obligate riparian species, sensitive species, and threatened species.