Why Do We Have Taxonomy

Firstly have you ever thought about why we name things at all? If you have you probably realised pretty quickly that names are very important for talking to, and communicating with other people. They allow you to give the other person quite a lot of information about the animal or even plant that you are talking about. However, not everybody uses the same name for the same animal. For instance the name Robin is used for different birds in different parts of the world.

Carl Linnaeus

Because common names can vary so much a scientist called Carl Linnaeus suggested in the 1750's that an international way of naming things be set up so that scientists all over the world could understand each other better. Since then his original binomial (double name) system has been improved by a number of other scientists, and now you can use the proper scientific name for an animal anywhere in the world and other scientists will know what you are talking about. The science of naming things is called taxonomy and though it can become quite complicated the basics are easy to understand. However it will help if you know that identifying, describing and naming things, i.e. assigning them to particular groups is taxonomy, while arranging those groups in a coherent order which reflects their evolution and relatedness is classification. Another word is Systematics which may be defined as the study of the diversity of organisms and the way they relate to each other, modern Systematics is called Phylogenetic Cladistics and has a whole set of special rules telling you how to do it properly. Cladistics is a good, but young science and like all tools its usefulness reflects the understanding in the mind of the person using it, i.e. not all the results that people using cladistic analyses come to are equally reliable. Although in the vertebrates, in conjunction with DNA hybridisation studies, it is much more reliable than when applied to invertebrates on morphological grounds.

How It Works

All the living things are divided into a series of sets and subsets depending on how closely related they are. For instance all living things are divided into 5 Kingdoms:

Kingdom Planta = Plants
Kingdom Fungi = Fungi
Kingdom Animalia = Animals
very small things called Protoctista
even smaller things called Bacteria

The living members of the kingdom Animalia are divided into approximately 37 smaller groups called phyla singular phylum. One of which, the Chordata is of particular interest to us. This phylum contains all the animals which have (at some stage in their lives) a notochord. This is a stiffened but flexible rod that runs along the animals back between its gut and its central nervous system. The Phylum Chordata is divided into 3 subphyla:- Urochordata (Sea Squirts and their allies; Cephalochordata (Brachiostoma, a small fish like creatures once known as Amphioxus); Vertebrata (birds, fish, frogs, mammals, snakes etc.). The subphylum Vertebrata contains 7 smaller groups called Classes, these are:

Class Agnatha = Jawless vertebrates
Class Elasmobranchiomorphi = Cartiliginous fishes (Sharks and Rays)
Class Teleostomi = Bony fishes (Salmon, Trout, Carp etc)
Class Amphibia = Frogs and Newts
Class Reptilia = Snakes and Lizards
Class Aves = Birds
Class Mammalia = Mammals (Cows, Dogs, People etc)

Now the Aves or Birds are divided into 23 even smaller groups called orders. Some of these orders are small and some are large, over half the birds known are in just one order, the Passeriformes or Passerines. After this we have Families, within the order Struthioniformes there are 4 families; within each family are a number of genera and within each genus are a number of species. You should note that most animals and plants are known only by their genus and species names, i.e. the Ostrich is Struthio camelus, note also that while the genus name is spelt with a capital letter the species name is normally spelt with a small letter, and that in printed text the pair are normally written in italics the rest usually remains unsaid. You should also note that though an animal will generally share its genus, family, order and class names etc. with other animals its combination genus/species name will be unique to it. For instance the familiar Ostrich is a member of all the following sets:

Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Struthioniformes
Family: Struthionidae
Genus: Struthio
Species: camelus

Like most classification systems the classification of birds was until recently based on morphological characters. Over the last decade however much work has been done using DNA hybridisation which give scientists a much more accurate way of viewing the affinities between bird families.