Taxonomy (noun, “tax-ON-uh-mee”)
Taxonomy is the science of grouping living things into categories.
This field involves two major tasks. One is to develop categories for living things. These categories are called taxa. Scientists develop taxa by looking at the similarities between life forms. The other part of this field is sorting living things into those groups.
Scientists use a few methods to decide how to classify a living thing. One approach is comparing its features to those of life forms in different categories. Before technology existed to study DNA, biologists relied heavily on physical traits to make such calls. But today, DNA analysis allows for a more refined approach.
The main taxonomic system used by scientists has eight levels. These levels are domain, kingdom, phylum, class, order, family, genus and species.
Domain is the broadest group. All life on Earth belongs to one of three domains. Those are Eukarya, Bacteria and Archaea. Life forms within each of the three domains belong to different kingdoms. Within each of those kingdoms, living things belong to different phyla, and so on. The most specific level of classification is species. Scientists have described millions of species that live today. And they expect that many more remain undiscovered.
Taxonomy describes most species with a two-part name. This name is called a scientific name. The scientific name for humans is Homo sapiens. The first part — Homo — refers to our genus. No other living species belong to this genus. But some extinct species did. Homo erectus, for example, was an early human ancestor. Neandertals (Homo neanderthalensis) were also ancient human relatives.
Taxonomy does more than just organize what we know about living things. It’s also meant to reflect how life has evolved. Over time, different groups of living things have evolved from common ancestors. In that process, they split off into different branches in the tree of life. The more recently two groups of living things split off from each other, the more closely related they are. More closely related species share more taxa.
In a sentence
Taxonomy experts have begun to update parts of the 250-year-old naming system for Earth’s species.
