Unit Four. The Evolution and Diversity of Life


15. How We Name Living Things


15.2. Species Names


A group of organisms at a particular level in a classification system is called a taxon (plural, taxa), and the branch of biology that identifies and names such groups of organisms is called taxonomy. Taxonomists are in a real sense detectives, biologists who must use clues of appearance and behavior to identify and assign names to organisms.

By formal agreement among taxonomists throughout the world, no two organisms can have the same name. So that no one country is favored, a language spoken by no country— Latin—is used for the names. Because the scientific name of an organism is the same anywhere in the world, this system provides a standard and precise way of communicating, whether the language of a particular biologist is Chinese, Arabic, Spanish, or English. This is a great improvement over the use of common names, which often vary from one place to the next. As you can see in figure 15.2, in America corn refers to the plant in the upper photo on the left, but in Europe it refers to the plant Americans call wheat, the lower photo on the left. A bear is a large placental omnivore in the United States (the upper middle photo), but in Australia it is a koala, a vegetarian marsupial (the lower middle photo). A robin in North America (the upper right photo) is a very different bird in Europe (the lower right photo).



Figure 15.2. Common names make poor labels.

The common names corn (a), bear (b), and robin (c) bring clear images to our minds (photos on top), but the images would be very different to someone living in Europe or Australia (photos on bottom). There, the same common names are used to label very different species.


By convention, the first word of the binomial name is the genus to which the organism belongs. This word is always capitalized. The second word, called the specific epithet, refers to the particular species and is not capitalized. The two words together are called the scientific name, or species name, and are written in italics. The system of naming animals, plants, and other organisms established by Linnaeus has served the science of biology well for nearly 250 years.


Key Learning Outcome 15.2. By convention, the first part of a binomial species name identifies the genus to which the species belongs, and the second part distinguishes that particular species from other species in the genus.