Vertebrates have an internal skeleton with a backbone that divides the body into three main parts - the head, trunk, and limbs. The head contains sense organs and a mouth, the trunk contains the flexible backbone, and the limbs can take the form of legs, wings, arms, or fins. Vertebrates can be covered in bare skin, fur, feathers, or scales, and most have a tail extending from the backbone. There are five main groups of vertebrates: fish, birds, amphibians, reptiles, and mammals.