MAMMALS
In the animal kingdom, the group that is considered as "highly" developed are the mammals. There are many aspects of their structure and activities that set them apart from other organisms. One of these mammals is man.
The mammals form a distinct group of animals identified today by the possession of hair. Thus the Duck-billed platypus from Australia is considered as a mammal even though its internal structure and egg laying show many similarities to reptiles and a bill like a bird.
Mammals are the most fully adapted for land. Some have adapted to water and there the largest animal - the Sperm whale, is a mammal that breathes air.
