Classifications of Animals
Animals are multicellular, multireveloped, eukaryotic organism in the Kingdom Animalia. With few exceptions, all animals breathe air, consume oxygen, can regenerate fully, can move about on their own, can breed sexually, and reproduce. The classification of animals into classes such as carnivores (meat-eating animals) and Herbivores (plant-eating animals) is based on the mode of eating, rather than on the diet. Within the class of animals that are not in the Kingdom Animalia, there are thirty-two orders of classification, nine superorders, and several suborders. Most of the mammals and fishes belong to one of at least one order.
Within the Order Animalia, there are two broad categories of organisms: animals and e.g. humans. Humans are a diverse group of organisms, but most of us are familiar with members of the genus Hominidae, including humans, chimpanzees, cats, dogs, bunnies, pigs, horses, hippopotamuses, monkeys, gorillas, lizards, and insects.
In the Order Animalia, mammals are classified into four suborders: Prototheria, Cetacea, Metatheria, and Eutheria. These have different placements in the animal kingdom from being true mammals to becoming marsupials or archospecies. The most basal members of this order are unbranched, such as the smooth-skinned animal kingdom Triceratops and the robust-skinned Plastronifera. Other placements in this family include the placements Prototheria and Metatheria. The placements within metatheria are therefore more diverse than those within Prototheria.
In order to classify animals into classes, it is necessary to know what body features each member possesses. Body features are those physical qualities that distinguish species from one another, including color, pattern, size, shape, mobility, habits, etc. A class of animal is therefore defined by the arrangement of its organs along a comparative system of the same kind. For instance, a dog may be classified as a wild dog if it has a snout instead of a canine face; it may be classified as a wild animal if it possesses ears, teeth, and tail instead of the usual four limbs; and so on. Similarly, all living creatures can be classified into classes depending on whether their senses are developed in a sense that they are organs of the body or only organs of the brain.
Classifications of animals can also be based on whether or not the organisms reproduce asexually, i.e., sexually or asexually. Animals that reproduce asexually, while animals that reproduce asexually are those that reproduce both sexually and asexually. There are some well-known examples of animals that reproduce both sexually and asexually, such as reptiles, crustaceans, some forms of whales, some forms of fish, and so on.
A classification of animals must also include land animals and aquatic animals. Land animals include all mammals, amphibians, fishes, reptiles, non-organisms, birds, and so on. Aquatic animals belong to the class that includes all animals having soft bodies and live in water. The subclassifications of land animals include all fishes, non-aquatic mammals, amphibians, fishes, crustaceans, mollusks, shrimps, ichthyids, fishes, reptile, arboreal insects, mole-like ground-dwelling creatures, and all fossil forms.