An Education on Binomial Nomenclature

Scientists use a very specific system to classify and name organisms. This system allows scientists around the world to identify precisely which animal they are studying.

Taxonomic Classification is the hierarchical system biologists use to organize all living things. Each level or rank of classification has more categories and each category includes fewer organisms than those in the rank before it.

There are seven main ranks in which every organism is classified. These include Kingdom, Phylum, Class, Order, Family, Genus, and Species.

Binomial nomenclature is a system of naming all organisms within this organization system. Each organism is identified by two names: its genus and its species. Binomial nomenclature has been in use since the 1700s. All assigned names are either Greek or Latin.

To differentiate scientific names assigned under the binomial nomenclature system, we italicize or underline these names when writing in English.

Scientists classify the bigeye tuna, and distinguish it from other fish, as well as other tunas, based on distinct characteristics. These characteristics allow scientists to place the bigeye tuna into the very broad group, kingdom, and the very specific group, species. Animals of the same species are so similar that they cannot mate with animals of a different species and produce viable offspring (offspring capable of reproducing).

To accurately identify an organism, you must refer to it with both the genus and species name.

Let’s use Karenia brevis as an example. Karenia brevis is one of several species of protists that cause Harmful Algal Blooms (HABs). Karenia brevis causes Florida Red Tide. It produces chemicals. When populations of Karenia brevis are very dense, these chemicals can be harmful to vertebrates. Some rules for discussing Karenia brevis using proper binomial nomenclature:

You can say or write: “All of the plankton belonging to the genus Karenia.”

You cannot say or write: “All the plankton of the species brevis.” Instead, you must say “The K. brevis plankton species.”

The first part of a binomial name is the genus – it is a larger group of organisms.

The genus is always capitalized (Karenia brevis).

The plural form of genus is genera, not genuses.

The second part of a binomial name is the specific epitaph – it refers to the organisms belonging to one specific species.

It is never capitalized (Karenia brevis).

The plural and singular form of species is species. Specie is not a word.

The genus can be abbreviated by the first letter and a period (K. brevis)
The specific epitaph cannot be abbreviated (Karenia b.).

Most genera have more than one species. For example, there are twelve species in the genus Karenia.

If you want to refer to all species in a genus, you can replace the scientific epitaph with spp.

“Spp.” is not italicized, because it is the English abbreviation for the word species. For example, “Not all Karenia spp. cause red tides.”

To discuss any individual species in a genus, we can use the genus name and sp. For example, “We study each Karenia sp. Individually to see if it causes Red Tide.”

Reprinted from the Coastal Classroom at

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