Diversity

        With so many different habitats to live in, it is not surprising that there are so many different animals on our planet. Each animal has certain characteristics that make it possible for it to survive in its environment.

        One of the ways that some animals protect themselves from enemies is through camouflage. Other animals make poisons. Different ways to eat mean different mouthparts. Different ways to move mean different skeletons. Predators and prey have eyes in different places – one for attack and one to see danger coming. Living on land calls for different skin than living in the water. Animals living underground move differently from those that fly through the air.

Taxonomy

        How can zoologists (scientists who study animals) put all the animals on our planet into some kind of logical groups? If we ask the right questions we can put a lot of the animals into some easy to identify groups. All animals either have a backbone, or they don’t. That means we can group all the Animal Kingdom into the phylum of vertebrates (with a backbone), called Chordata, or the invertebrates (without backbones).

        Some of the ways we can put animals into even smaller groups is to look at the ways they reproduce, or look at their skeletons. We can look at the appendages (what is attached to the body, like arms, legs or fins). We can classify animals by understanding how they breathe, or by seeing if they are warm-blooded or cold-blooded. These are some of the characteristics that help us to group vertebrates into classes. The five main classes are Aves (birds), Mammalia (mammals), Reptilia (reptiles), Amphibia (amphibians), and Osteichthyes (bony fish).

        Each class can then be divided into smaller groups called orders. For instance, one order of mammals is the Primates. Primates are mammals that walk more or less upright. Each order can then be divided into even smaller groups called family and genus, and finally into individual species. A species is a group of animals that mate naturally among themselves, but not with individuals from other groups.

        Human beings belong to the Kingdom Anamalia, Phylum Chordata, Class Mammalia, Order Primates, Family Hominidae, Genus Homo, and Species Homo Sapiens.

        Warm-blooded animals keep the same body temperature no matter what the outside temperature is. The body temperature of cold-blooded animals changes when the temperature of the air or water changes. The warm-blooded classes are the mammals and birds.

Mammals

        Mammals have hair, give birth to live young, and make milk to feed their babies. There are only two animals, the platypus and the spiny anteater, that zoologists classify as mammals that do not give live birth. They belong to the order Monotremata, which means egg-laying.

Birds

        All birds have feathers and lay eggs. Not all birds can fly. The ostrich, the emu, and the kiwi run very fast, and the penguin swims with his short paddlelike wings. Whether they fly or not, all birds have a pair of wings. The female of many species of birds is camouflaged, while the male is brightly colored. A beak takes the place of a jaw with teeth.

Reptiles and Amphibians

        Reptiles, amphibians, and fish are all cold-blooded classes. Fish use gills to breathe the oxygen dissolved in water. Reptiles have lungs to breathe air. Amphibians begin their life cycle living in the water with gills, and the adult lives on land and has lungs. This life cycle that includes drastic changes from child to adult is called metamorphosis. Fish are covered with thin scales and most have fins. Reptile appendages have claws, but amphibians do not have claws. Reptiles have hard, dry, rough scaly skin or a hard shell. Amphibian skin is moist and slimy.

        Classifying animals helps us to study them and learn more about how animals are alike and how they are different.