When studying any aspect of biology it is important to have a basic understanding of the classification system used to group animals.
How the species that one may meet in a veterinary practice lit into this Classilicalion system should also be Understcxxl. Classification is the way in which we ’sort’ species into orderly groups, depending on how closely they are related in terms of their evolution, structure and behaviour.
The science of classification is known as taxonomy.If organisms have certain basic features in common they are grouped together into a kingdom. For
All the species within the animal kingdom are divided into those with backbones - the vertebrates - and those that do not have backbones - the invertebrates. e.g. insects, worms, etc. The vertebrates are divided into eight classes. The classes that are of the most veterinary importance are:
Amphibia - approximately 3080 species Reptilia - approximately 6600 species Aves or birds - approximately 8 500 species Fish - approximately 30 OOO species. Mammalia - approximately 4070 species.
These classes are then further divided into orders, and so on, until a species is identified, as in Table 1.1.
Table I. I Classification of the domestic dog and car
| Taxonomic group | Dog | Cat |
| Kingdom | Animal | Animal |
| Phylum | Chordaca (Vertebrate) | Chordau (Vertebrate) |
| Class | Mammalia | Mammalia |
| (Mammal) | (Mammal) | |
| Order | Carnivora | Carnivora |
| Family | Canidae | Felidae |
| Genus | Corns | Felis |
| Species | fatτnborκ | COtUS |
| Common Name | Domestic Dog | Domestic Cat |
Most of this Section of the book concerns the mammals, because the majority of animals seen in veterinary practice will be from this class. The distinctive features of mammals are the production of milk by the mammary glands, and the possession of hair as a body covering.
Examples of mammalian orders include:⅜ Insectivores. e.g. shrews, moles
£ Rodents, e.g. mice, rats
⅛ι Lagomorphs. e.g. rabbits, hares
Carnivores, e.g, cats, dogs, bears, seals
v Ilngulatcs. e.g. cows, sheep, horses ∙> Cetaceans, e.g. whales, dolphins
Primates, e.g. monkeys, apes.
Generally speaking, all mammals have a similar basic Structund plan in terms of anatomy and physiology, but each species has been modilied to suit its specific lifestyle. In other words, mammals have become specialised for activities such as running, digging, gnawing, jumping and eating specific foods.