Linnaean Classification System: Classification of the Human Species. This chart shows the taxa of the Linnaean classification system. Each taxon is a subdivision of the taxon below it in the chart. For example, a species is a subdivision of a genus. The classification of humans is given in the chart as an example.
Perhaps the single greatest contribution Linnaeus made to science was his method of naming species. This method, called binomial nomenclature, gives each species a unique, two-word Latin name consisting of the genus name and the species name. An example is Homo sapiens, the two-word Latin name for humans. It literally means “wise human.” This is a reference to our big brains. Why is having two names so important? It is similar to people having a first and a last name. You may know several people with the first name Michael, but adding Michael’s last name usually pins down exactly whom you mean. In the same way, having two names uniquely identifies a species.
Linnaeus published his classification system in the 1700s. Since then, many new species have been discovered. The biochemistry of organisms has also become known. Eventually, scientists realized that Linnaeus’s system of classification needed revision. A major change to the Linnaean system was the addition of a new taxon called the domain. A domain is a taxon that is larger and more inclusive than the kingdom. Most biologists agree there are three domains of life on Earth: Bacteria, Archaea, and Eukaryota (see Figure below). Both Bacteria and Archaea consist of single-celled prokaryotes. Eukaryota consists of all eukaryotes, from single-celled protists to humans. This domain includes the Animalia (animals), Plantae (plants), Fungi (fungi) and Protista (protists) kingdoms.
Three-Domain Classification. This diagram shows the three domains of organisms that currently live on Earth.