What is an animal called that does not have a backbone?

An animal that does not possess a backbone is called an invertebrate. Vertebrates, on the other hand, are the animals that have backbones. All the animals are divided into these two groups: vertebrates and invertebrates. Human beings and a number of other animals (such as cats, dogs, cows, etc.) are all vertebrates. Insects, crabs, snails, worms, etc., are all examples of invertebrates. Interestingly, most of the known animals are invertebrates. In comparison to (about) 58,000 known species of vertebrates, there are over 2 million known species of invertebrates. Thus, almost 97% of the known animal species are invertebrates. One of the disadvantages of not having a backbone is that invertebrates are, generally, slow moving and are smaller in size, in comparison to vertebrates. 

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