Animals

Animals are multicellular organisms that obtain energy by eating food. They live in a vast range of habitats, from deserts and Arctic tundra to the deep-sea floor. Like all living things, animals show similarities and differences that enable them to be classified into groups. Birds, for example, are the only animals that have feathers, while mammals are the only ones that have fur. Animals are also classified according to other characteristics, including their internal anatomy, patterns of development, and genetic makeup. Scientists divide the animal kingdom into approximately 30 groups, each called a phylum.