An animal class is made up of animals that are all alike in important ways. Scientists have grouped animals into classes to make it easier to study them.

There are many different animal classes and every animal in the world belongs to one of them. The six most important classes are mammals, birds, fish, reptiles, amphibians and invertebrates.

Fish - Fish were the first backboned animals to appear on earth and form the largest group of vertebrates. Fish live in water and most breathe using gills, have a body covered with scales, are cold-blooded (ectothermic), have two chambered hearts and maneuver using fins.