Animals are multicellular eukaryotic organisms which consume organic material, breathe oxygen, are able to move, can reproduce sexually, and grow.
Animals are classified as the kingdom Animalia (or Metazoa).
- All animals can move spontaneously and independently at some point in their lives.
- All animals are heterotrophs: they must ingest other organisms or their products for sustenance.
Animals, including people, have complex interactions with each other and their environments.
There are over 7 million animal species in total, over 1.5 million animal species have been described, including 1 million insects.