Taxonomic Groups

Organisms are classified into a hierarchy of groups. Each group is called a taxon (plural taxa). There are eight main taxonomic ranks, from largest to smallest:domain → kingdom → phylum → class → order → family → genus → speciesA mnemonic helps: 'Dear King Philip Came Over For Good Soup'.Each taxon is contained within the one above it. Moving down the hierarchy from domain to species:
• the number of organisms in each group decreases
• the organisms in each group share more features
• they are more closely related, sharing a more recent common ancestor.Worked example: the classification of humans and wolves.

Rank	Human	Grey wolf
Domain	Eukarya	Eukarya
Kingdom	Animalia	Animalia
Phylum	Chordata	Chordata
Class	Mammalia	Mammalia
Order	Primates	Carnivora
Family	Hominidae	Canidae
Genus	Homo	Canis
Species	sapiens	lupus

Humans and wolves share every taxon down to class, but are in different orders. This shows they are both mammals but are not closely related.Two organisms that share a family are more closely related than two that share only an order.