Systematics and Taxonomy
To understand the binomial nomenclature of scientific names, it helps to have at least a general understanding of how scientists categorize living things. The science of taxonomy and systematics involves the classification of organisms according to evolutionary relationships; how closely related they are to each other.
Before scientists were able to use DNA sequencing to examine evolutionary relationships, organisms were classified based on physical similarities and differences. Modern systematics combines data from many sources, including: the fossil record, comparative homologies (similarity of structures due to shared ancestry), and comparative sequencing of nucleic acids (DNA and RNA) among organisms.
Taxonomic Categories
Through this system, organisms are hierarchically classified into increasingly specific groupings. The seven basic taxonomic categories are: Kingdom, Phylum, Class, Order, Family, Genus and Species; kingdom being the broadest category, and species being the most specific.
Beginning students of biology often use a simple mnemonic device to remember the identity and order of these taxonomic categories. The sentence "King Philip came over for green soup" represents the order of taxonomic categories, from the most general to the most specific.
Carolus Linnaeus
Linnaeus (1707-1778), a Swedish physician and botanist, was the founder of modern systematics. He originated the system of binomial nomenclature used for naming plants and animals and grouping similar organisms into increasingly general categories. Today, biologists still use this basic system of classification, but advances in the fields of genetics and evolutionary theory has resulted in some of Linnaeus’ original categories being changed to better reflect the relationships among organisms.
Binomial Nomenclature
Also called binary nomenclature, this formal system of naming organisms consists of two Latinized names, the genus and the species. All living things, and even some viruses, have a scientific name.
The binomial aspect of this system means that each organism is given two names, a ‘generic name,’ which is called the genus (pl. genera) and a ‘specific name,’ the species. Having a universal system of binomial nomenclature allows scientists to, in essence, speak the same language when referring to living things, and avoids the confusion of multiple common names that may differ based on region, culture or native language.
When written, a scientific name is always either italicized, or if hand-written, underlined. The genus is capitalized and the species name is lower case. For example, the proper format for the scientific name of humans is Homo sapiens.
What Is a Genus?
In biology, ‘genus’ is the taxonomic classification lower than ‘family’ and higher than ‘species’. In other words, genus is a more general taxonomic category than is species. For example, the wolf belongs to the same genus as the coyote, Canis. Although in the same biological family (Canidae) as wolves and dogs, foxes belong to a different genus (Vulpes). This reflects a closer evolutionary relationship between the wolf and the domestic dog than between either and the fox.
What is a Species?
The species name, also called specific epithet, is the second part of a scientific name, and refers to one species within a genus. A species is a group of organisms that typically have similar anatomical characteristics and that can successfully interbreed to produce viable offspring. Canis lupus, the Timber Wolf, and Canis lupus familiaris, the domestic dog, belong to the same species, of which the domestic dog is a subspecies (the third italicized name). Wolves and dogs can interbreed, producing fertile offspring. A mule, for example, is not a distinct species. It is an infertile hybrid of a male donkey (Equus asinus) and a female horse (Equus caballus).
Natural History Information
There are many interesting on-line and in-print resources on taxonomy, systematics and natural history, including Science Prof Online and the American Museum of Natural History. Also see other interesting systematics articles on Suite101.com, including Invertebrate Classification.
Additional Binomial Nomenclature Sources
Campbell, N. and Reece, J. (2005) Biology, Seventh Edition. Pearson, Benjamin Cummings.
Tami Port - Tami Port is a college professor of cell and microbiology and creator of ScienceProfOnline.com, a free science education website.
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