Taxonomy, Binomial Nomenclature, and the Levels of Classification (summary of Chapter 1)

Taxonomy, binomial nomenclature, and the levels of classification are all essential for a biologist to know and understand. This, however, is not as in-depth as a biologist may tell you, but is rather a quick rundown of each of these three terms, and why they are important.

First let’s start with taxonomy. Taxonomy is simply the classification of organisms by certain rules. The first person to attempt to classify organisms was Aristotle. Aristotle classified life into two kingdoms, the inanimate plants, and the animate animals, which were further classified into three groups based on whether they moved on land, in the sea, or in the air. Aristotle also classified vertebrates and invertebrates, or animals with and without backbones, respectively, as “animals with blood” and “animals without blood”. His method of classification was used up until the seventeenth century, when scientific progress began to accelerate. Skip forward from the 300s B.C. to the mid-eighteenth century, and a man in Sweden named Carl Linnaeus proposed a new system of taxonomy based on an organism’s form. Once again the world of living organisms was divided into plants and animals, since Linnaeus did not know about bacteria and other forms of life. After evolution was popularized in the late nineteenth and early twentieth centuries, scientists came up with a new way of classifying organisms based on that theory.

Many of today’s taxonomists classify organisms using eight different levels, domain, kingdom, phylum, class, order, family, genus, and species. The domain is the highest level in terms of classification, while the species (or occasionally subspecies) is the lowest. To start there are three domains, the bacteria (Eubacteria), the archea (Archaebacteria), and the eukaryotes (Eukaryota). Also keep in mind that Eukaryotes have a nucleus to store DNA, while bacteria and archea do not. After domains, there are six kingdoms, bacteria (Eubacteria), the archea (Archaebacteria), fungi, plants (Plantae), animals (Animalia), and protists (Protista). Bacteria are the germs we think about when we think germs (along with viruses, but that is a topic for another article), and they are single-celled prokaryotes that get nutrients by absorption or by photosynthesis. Archea are also single-celled prokaryotes, but none photosynthesize and most get their nutrients from absorption. Archea generally absorb gases like oxygen and carbon dioxide, and are commonly found in underwater volcanoes. Fungi are eukaryotes that are multi cellular (composed of many cells) that absorb nutrients from dead organisms, meaning they are decomposers. Some examples of fungi are mushrooms, mold, and yeast. Plants are also multi-cellular eukaryotes that photosynthesize to gain nutrients. Obviously, plants include mosses, ferns, trees, shrubs, and flowering plants. Animals are multi cellular eukaryotes that can move (unlike fungi and plants), and they get their nutrients from other organisms. Sponges, worms, birds, fish, mammals, amphibians, etc. are all animals. Humans are also put into this kingdom since they share all basic characteristics of animals. The last category is protists, which are basically the miscellaneous eukaryotes. They include seaweed and algae. Most protists are single-celled, however some, like seaweed, are multi-cellular.

The next category down is the phylum, followed by the class, order, family, genus, ending at the individual species. Below is the classification of a polar bear.

  • Domain: Eukaryota
  • Kingdom: Animalia
  • Phylum: Chordata
  • Class: Mammalia
  • Order: Carnivora
  • Family: Ursidae
  • Genus: Ursus
  • Species: Ursus maritimus

This leads into the final term for this paper, binomial nomenclature. Binomial nomenclature is simply the term used for a scientific name. Let’s take Ursus maritimus again. There are two parts to this name, Ursus, and maritimus. The first part, as shown above in the classification, is the genus in which the species is. The second part simply identifies which member of that genus the organism is. The first part is always capitalized, while the second part is not. In addition, scientific names mean the same across different languages, so that way scientists can work together internationally.

These systems are important for biologists so that way they can classify and identify organisms and collaborate with other scientists as well. Without these systems, biology would be a mess and we wouldn’t know nearly as much as we do now.