1. mammals
Mammals: Mammals are the most developed kind of animals in the
animal kingdom. They are almost 200 million years old and had also
lived in the age of dinosaurs. Mammals give birth to young
ones, feed their young ones with mammary glands and have hair on
them, compared to feathers and scales, which other animal class
possess. The skeleton structure of mammals is very similar. They
have a very striking similarity in reproduction, physiology and
anatomy. Elephants, bear, blue whale, tiger, dogs, cats, wolf, lion
and otter, are a few examples of mammals