A taxonomic category of living forms that are phenotypically similar based upon reproductive isolation under natural conditions from other populations, and capable of interbreeding and producing fertile offspring. This is the biospecies concept. As such, it fails to take account of a historical perspective that species are genealogically unique. This, and other problems, means that there is no unified biospecies concept. Thus, species are best regarded not as natural kinds, but as individuals, each with a unique history and irreplaceable once extinct. Being a sub-division of genus, species may contain one or more sub-species, varieties (or micro species) or races.
See Clades, General theory of biological classification, Metazoan, Ontogenetic development, Ontogeny, Phyletic, Phylogeny, Race-ethnicity