A traditional taxonomist is a biologist who classifies organisms according to their physical or cellular characteristics. These scientists also try to determine the evolutionary relationships among these organisms. When a new organism is discovered, whether it is a plant, animal, or microorganism, a taxonomist will give it a Linnaean designation. That is, he or she will put it in the appropriate categories within the taxonomic levels of kingdom, phylum, class, order, family, genus, and species. When people refer to the scientific name of an organism, such as the well-known name for dog, Canis familiaris, they are using the genus and species designations for that organism.
Taxonomic classification has been accomplished in many different ways over the years. In the early days of formal taxonomy, biotechnology was very limited and scientists had to classify organisms based only on observable physical characteristics. With the development of evolutionary theory in the mid 19th century, taxonomists began to categorize organisms into groups represented by the branches of an evolutionary tree. Species residing on branches near each other would be considered closely related in the evolutionary sense, whereas species residing on branches far away from each other would be only distantly related.
The relationships indicated by the positions of organisms on the evolutionary tree are referred to as phylogenetic relationships. Now that scientists have the ability to sequence deoxyribonucleic acid (DNA) within the cells of organisms, phylogenetic relationships can be more accurately determined. This analysis technique has resulted in more accurate evolutionary trees than those that had been developed by taxonomists going on anatomy alone. Scientists also use the techniques of embryology, serology, and immunology to further define and refine phylogenetic relationships.
To become a taxonomist, one must obtain a four year degree in a field of biology, usually microbiology, zoology, or botany. The specific field chosen would depend on the type of taxonomist the student wishes to become because taxonomists tend to specialize within certain kingdoms. That is, no one taxonomist will classify new species in all kingdoms of organisms. The student would, for instance, become a plant taxonomist or an animal taxonomist. Graduate studies in classification methodologies are often required for someone to become a practicing and respected taxonomist.
In recent years, the term taxonomy has been applied to professions beyond that of the biological systematist. One may hear about military or economic taxonomists. These are simply people who classify aspects of the military or the economy much like biological taxonomists classify organisms.