Invertebrates are animals which do not have backbones or other bones inside their bodies. Some have soft bodies and some have hard coverings which protect their bodies. Vertebrates are animals with backbones and bones inside their bodies. The bones help to support their bodies. There are five main groups of vertebrates, the fish, the amphibians, the reptiles, the birds and the mammals. Fish, amphibians and reptiles are known as cold blooded vertebrates. The blood of a warm-blooded vertebrate remains around the same temperature both on warm and cold days. Fish live in water and have fins which help them to swim. The body of a fish is made up of the head, the trunk and the tail. The tail ends in a tail fin. There are many different kinds of fish and they are of many different shapes and colours. Some fish are long and thin while others are flat and rounded. Most fish have bodies which are broad at the trunk region and narrow towards the head and tail.