The animal kingdom can be divided into two major phyla. Animals without backbones are invertebrates, such as spiders and insects. Animals with backbones are vertebrates. The vertebrates can be further divided into classes, such as mammals and birds.
| class | features | examples |
|---|---|---|
| amphibians | moist permeable skin | frog, newt, salamander |
| fish | gills, wet scales | goldfish, shark, cod |
| reptiles | dry scales | crocodile, lizard, snake |
| birds | feathers,beaks | budgerigar, sparrow, ostrich |
| mammals | fur, produce, milk | rabbit, kangaroo, human, dolphin |
Some fossil vertebrates and newly discovered species can be difficult to classify. For example, Archaeopteryx is an extinct vertebrate known only by its fossil remains. It has characteristics of birds and reptiles.
BBC © 2012 The BBC is not responsible for the content of external sites. Read more.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.