A species is a population of individual organisms that can interbreed in nature, mating and producing fertile offspring in a natural setting. Species are organisms that share the same gene pool, and therefore genetic and morphological similarities.

All organisms are given two names (a binomial name); the first is the genus name and the second is the species name, for example Homo sapiens, the name for humans. The Linnaean classification system places all organisms into a hierarchy of ranked groups. The genus includes one or more related species, while a group of similar genera are placed in the same family. Similar families are grouped into the same order, similar orders in the same class, and similar classes in the same phylum.

Organisms are assigned to the higher ranks of the Linnaean classification scheme largely on the basis of shared similarities (syna pomorphisus). Species are identified on the basis...