The Animal Kingdom -

The kingdom Animalia contains thousands of very different species belonging to various phyla and classes. The animal kingdom is diverse containing over 2 million different species. When you think of animals, you probably picture elephants, lions, tigers, and other large mammals. The animal kingdom is so much more. The mammals are only a small fraction of the total animal kingdom. What is an animal? With so many different animals, it is difficult to imagine they have anything in common.

There is a list of requirements to be considered an animal:

Animals are multicellular, with specialized parts

Animals are heterotrophs, so must eat to obtain energy

Animals require oxygen for their metabolism

Animals sense and respond to their environment

Animals have the capacity to reproduce sexually