This document discusses how animals can be grouped based on their external features. It provides examples of how fish, elephants, and other animals can be identified by traits like fins, trunks, scales, legs, ears and more. Animals are grouped according to similarities in these external features, such as having scales, fins, feathers, horns, hair or other distinguishing qualities. They can also be grouped by the number of legs or characteristics of their beaks, claws, shells or wings.