The seven taxa, or units of biological classification, from largest to smallest, are kingdom, phylum, class, order, family, genus and species. The second taxon is called phylum for animals, but for plants, it is called a division.
The wolf, for example, is of the kingdom animalia, the philum chordata, the class mammalia, the order carnivora, the family canidae, the genus canis and the species canis lupus. The domestic dog has exactly the same taxa as the wolf except the species, which is canis familiaris. A house cat has the same top four taxa as wolves and dogs, but the last three are the family felidae, the genus felis and the species felis catus. When organisms are given scientific names, only genus and species are used. For example, the wolf is referred to as canis lupus, the dog as canis familiaris, the house cat as felis catus and humans as homo sapiens.
The seven broad major categories of taxa can be broken down into further intermediate categories, such as subphylum, subclass, suborder, subfamily, subgenus and subspecies. Taxonomists, or biologists who specialize in taxonomy, are particularly important in the fields of biodiversity and conservation. Taxonomy enables the classification of species in specific locations, giving precision to decisions concerning conservation.