by Whit Gibbons

December 9, 2007

Have you ever seen a Daucus carota? This is not a new Italian car, and not only have you seen one, you have probably eaten one. Daucus carota is the scientific name for a carrot. Why, you might ask, don't we just call it a carrot?

Contrary to what a college teacher friend of mine jokingly tells his first-year biology students, scientific names were not invented in a 19th-century tavern by a frolicking group of biology professors who thought students needed more to learn. The names have a uniformity that provides a partial taxonomic map to the evolutionary relationships among species of plants and animals. The chosen names confirm our understanding of the origins and levels of kinship among different species.

The system is not perfect, but scientific names provide consistency and a level of accuracy in biology that are often lacking when only the common names are used for organisms. For example, for an ecologist writing about the primitive fish variously called bowfin, cypress bass, or dog fish, the name Amia calva unmistakably identifies the species. By the "rules of scientific nomenclature" only one species in the world can be given that name. Scientists known as taxonomists spend a lot of time making sure the rules are not broken. Some refer to them as biological lawyers.

Every species of animal or plant has two scientific names. The first name, the genus, is always capitalized; the second, which identifies the species within the genus, is not. Both names are underlined or italicized. A genus may comprise several closely related species. Thus many large hawks are placed in the genus Buteo. The genus Anopheles includes the only species of mosquitoes that transmit malaria.

The names are usually of Latin or Greek origin or at least are made to look like they are. And the name generally is chosen to represent some definitive feature of the organism. For example, the Sonoran mountain kingsnake, a beautiful red-, white-, and black-ringed creature, is called Lampropeltis pyromelana. The genus name means "beautiful shield" in Greek, and the species epithet means "black fire." Not all species names are quite as well chosen, as observed in the black racer (Coluber constrictor), which was named in the 1700s in Europe from a museum specimen collected in North America. Racers are not constrictors, but the name cannot be changed.

How closely we are associated with a species can determine what we call it. Surely no one refers to the household pet as Canis familiaris (dog) or Felis domesticus (cat). Most professional ornithologists use the common names of birds rather than the scientific names. In fact, the American Ornithologists' Union publishes the checklist of North American birds, which includes accepted common names for all species.

In contrast, an ichthyologist who studies the dozens of species of freshwater fishes called darters generally refers to each by its scientific name. However, the use of a common name may begin to take precedent when a species achieves some level of popularity or notoriety with the general public, as did the snail darter, Percina tanasi. Some species become generally known by their scientific name, such as Boa constrictor, Iris, and Gorilla gorilla.

Some scientific names are used to designate where a species was first discovered or to honor someone. The genus name for milkweeds is Asclepias, after the Greco-Roman god of medicine. The species name of the threatened species known as the Alabama red-bellied turtle is Pseudemys alabamensis.

Just as species that are closely related are placed in the same genus, closely related genera (the plural of "genus") are grouped into a family. Jaguars, tigers, and house cats, all belonging to the same genus, are in the family Felidae. The civet cat, on the other hand, is a type of skunk and in the family Mustelidae with otters and badgers. Family names are not italicized or underlined.

The order achieved by adhering to the rules of scientific nomenclature is important in biology. The names are intended to tell us something based on our knowledge of ecology and evolution. And acquiring knowledge is certainly an appropriate endeavor for Homo sapiens, whose species name, derived from Latin, means "knowing, wise."

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