Why do some animals have skeletons?

Movement. A cast of a human skull It's a simple fact, most animals move. Humans (like you) can move because your body is supported by an internal skeleton - that's right, you are just a bag of bones! Look at the bones that make up the human skeleton. read more

No, all animals do not have skeletons. Only animals considered vertebrates, such as birds, fish, amphibians, mammals and reptiles have skeletons. There is a much larger group of animals called invertebrates that do not have internal skeletons. read more

Well, many invertebrates – and all arthropods – have a protective external casing called an exoskeleton. read more