Taxonomy is the theory and practice of biological classification.
Biologists have so far described approximately one million species of living plants and animals, and perhaps a further quarter million extinct fossil species. There may be between 10 and 35 million species which exist but have yet to be described.
Describing a species is a formalized activity, in which the taxonomist has to compare specimens from the new species and other, similar species, and then explain how the new species can be distinguished; the description also has to be published.
Describing species is the most important task of taxonomists, but it has no particular connexion with evolutionary biology. The evolutionary interest of classification begins at the next stage with taxonomic hierarchy.
The image opposite shows a collection of beetles from a museum collection. It has been estimated that almost a quarter of all the identified species in the world today have been classified as beetles.