​How do we divide the animal kingdom?

​Classification is all about organising living things into groups. The members of any group all possess a shared characteristic - it is this characteristic or feature that defines the group.

​The animal kingdom is divided into two groups: vertebrates and invertebrates. Vertebrates have been around for millions of years but have evolved and changed over time. The word vertebrate means “having a backbone." Many animals have backbones. You have a backbone. So does a cow, a whale, a fish, a frog, and a bird. Vertebrates are animals that have a backbone. Most animals have a backbone that is made of bones joined together to form a skeleton. Scientists classify vertebrates into five classes: • Mammals • Fish • Birds • Reptiles • Amphibians Vertebrae All Rights Reserved 2018-Present © Heart 2 Heart Teaching LLC. Our skeleton gives us our shape and allows us to move. Mammals, fish, birds, reptiles, and amphibians have backbones so they are all vertebrates.

​Taking the animal kingdom as an example, we can see that it is split into two clear groups:

​Invertebrates - animals without a backbone.

Vertebrates - animals with a backbone.

​The animals have been divided into two groups based on the presence or absence of a backbone. The backbone is the observable feature that defines whether the animal is a vertebrate or an invertebrate.

​Sponges, corals, worms, insects, spiders and crabs are all sub-groups of the invertebrate group - they do not have a backbone.

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Fish, reptiles, birds, amphibians and mammals are different sub-groups of vertebrates - they all have internal skeletons and backbones.

​The animals that belong to these sub-groups all share the observable features of that group. Just as all the vertebrates have backbones, all birds have feathers and lay eggs, and all mammals have fur and suckle their young.

​SHORT QUIZ