Introduction to taxonomy

To date, biologists have named and classified over 1.5 million species on the planet, more than half of which are insects. It is estimated that there are between 5 and 30 million species left to be identified. Taxonomy is the discipline of biology that is responsible for naming and classifying organisms. Biologists employ a hierarchal system to classify life; the highest rank in this hierarchy is kingdom. Most scientists subscribe to a five kingdom system: Plantae (plants and algae), Monera (bacteria and blue-green algae), Fungi (mushrooms and such), Animalia (rotifers to elephants), and Protista (single celled organisms). The latter two groups contain the invertebrates. The lower the rung, the more similar the organisms are within it (e.g. animals in the same order are more similar to one another than animals from a different order but in the same class). This hierarchal filing system was first established by Linneus in the mid 18th century, and it is important to note that it is not a description of how nature organizes itself, but how humans organize nature so that it can be best studied.

The official ranking system looks like the following with the most general group at the top (kingdom) and the most specific at the bottom (species).

Kingdom

Phylum

Class

Order

Family

Genus

Species

There is an element of subjectivity in taxonomic systems. As a result there is often controversy concerning the taxonomic states of a group. Once an animal is placed in a certain grouping the chances are that someone believes that it belongs elsewhere. For example, there is current debate concerning whether the Crustacea are a phylum, or a class. The International Commission on Zoological Nomenclature (ICZN) was created to regulate the naming of taxa and to make the final decisions on the resolution of such controversies.