It's simple to say, for example, that a giraffe, a whale, or a dog is an animal. But when it comes down to making a list of animal characteristics—identifying specific traits shared by all animals—it gets complicated.
The list that follows describes characteristics shared by all animals, from snails and zebras to mongooses and sea stars. These characteristics help us to declare that, for example, corals are animals, not plants. They help us mark out the evolution of animals and build a framework for insertion animals into subcategories that are more familiar to us such as birds, mammals, reptiles or amphibians.
