Taxonomy

Taxonomy is the classification of all living things into groups. There are an enormous number of kinds of organisms described, and their study requires organization. Historically, animals were classified according to their structure. Those with certain characteristics were put into one group, and those with different characteristics placed into another. These groups were divided and subdivided. The result is a system of categories, each with structural characteristics associated with them. However, recent efforts have been made to reorganize some parts of the system based on the phylogeny of an organism-- that is, its relation to other organisms based on its evolutionary history.

The animal kingdom is divided into subgroups called phyla. Each phylum is divided into classes, each class into orders, and each order into families, and each family into genera. Each genus is divided into species. In groups where there are many organisms, sometimes there are additional layers of classification: subclasses, suborders, superfamilies, subfamilies, and tribes. The species is the most basic category, the kind of animal. The category of subspecies is sometimes used, often where the species doesn't satisfy the biological definition of species. That is, subspecies are usually organisms that have mostly identical characteristics and can interbreed, but live in different geographic locations.