What are the two main forms of biological classification, and how do they differ?

Artificial classification is used to divide organisms by their characteristics, which can vary depending on the specific situation which you are considering. Features that are considered are known as analogous characteristics; those which have the same function or appearance, but potentially not the same evolutionary origin. Such features may group the wings of an insect and a bird as they are both used to fly, although they arose from different evolutionary pathways. Phylogenetic classification is used to divide organisms according to how closely they are related in an evolutionary sense. It separates organisms using, in part, homologous characteristics; features which have similar evolutionary origins even if they now fulfil different functions. One such example might be a human arm and a horse's front leg, which are used in very different ways but share a similar origin. This system separates species into groups within a hierarchy, which means that these groups are arranged within larger groups, with no overlap between them.