Biological classification

Scientific classification is a means used by biologists to organize each of the organisms on the planet, based primarily on evolutionary similarity. The system works by placing each organism into a seven-layer hierarchy of groups. Each group at a given layer is composed of a set of groups from the layer directly below. Therefore, in theory, one needs know only the lowest layer (species) of a particular organism in order to uniquely determine the other six layers. In practice, however, many species actually have the same species designation, so when specifiying a species, scientists use the bottom two layers - a system called binomial nomenclature. The seven layers are as follows:

Kingdom
Phylum (animals) or Division (plants)
Class
Order
Family
Genus
Species

Additional classification is possible:

In Horticulture, species modified by selective breeding are frequently called varieties. An example of a variety is the Peace Rose, a hybrid Tea Rose.

In the classification of Homo sapiens, minor morphological differences below the significance of Species are known as Subspecies, Races, and Subraces. Examples are the Capoid or Khoisanid Subspecies of southern Africa, containing the Sanid (Bushmen) race; and the Lappish subrace of arctic Europe.

While there are only five kingdoms, there are millions of species.

Taxa above the genus level are often given names derived from the type genus. The suffixes used to form these names depend on the kingdom, and sometimes the phylum and class, as follows:

	Plants	Algae	Fungi	Animals
Division/Phylum	-phyta	-phyta	-mycota
Subdivision/Subphylum	-phytina	-phytina	-mycotina
Class	-opsida	-phyceae	-mycetes
Subclass	-idae	-phycidae	-mycetidae
Order	-ales	-ales	-ales	-formes (birds, fish)
Suborder	-ineae	-ineae	-ineae	(plural of the genus, e.g. Lari)
Family	-aceae	-aceae	-aceae	-idae
Subfamily	-oideae	-oideae	-oideae	-inae
Tribe	-eae	-eae	-eae	-ini
Subtribe	-inae	-inae	-inae	-ina