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.

Invertebrates - Intervebrates include more than 95% of all known animal species. Invertebrates as a group are defined by what all members lack – a backbone, no bones and no cartilage. Invertebrates are found in every type of habitat but are most plentiful in the oceans. There are more than 30 types of invertebrates in this diverse group which includes sponges, jellyfish, flatworms, squid, crabs, venomous spiders and butterflies. The largest group of invertebrates is the arthropods.