Species Concept and Taxonomic Hierarchy

Species Concept and Taxonomic Hierarchy

A species is the basic unit of biological classification, generally defined as a group of natural populations whose members can actually or potentially interbreed with one another under natural conditions, produce fertile offspring, and are reproductively isolated from other such groups. Members of a species also typically share a common set of morphological, physiological and genetic features that distinguish them from members of other species.

Classification arranges species into a nested hierarchy of ranks, each broader category containing one or more of the rank below it. The standard taxonomic hierarchy, from the broadest to the narrowest, is:

Kingdom → Phylum → Class → Order → Family → Genus → Species

Each higher rank groups together taxa that share progressively fewer, but more fundamental, characters — e.g. all animals sharing the basic chordate body plan are placed in phylum Chordata, while within that phylum, only those additionally sharing mammalian characters (like hair and mammary glands) are placed in class Mammalia, and so on down to genus and species, which share the most specific and numerous characters. …