Cetaceans: Whales and Dolphins

About 50 million years ago some terrestrial mammals began to make the transition from a life on land to a life in the sea. In the vastness of the ocean, these animals found new sources of food and plenty of room. Over time, their bodies evolved into forms that were more suitable for swimming and diving than for walking on land. One type of animal that made a successful and complete transition from land to water in the course of its evolution is the whale. Mammals that live in the ocean are called marine mammals. This chapter discusses the whale and other marine mammals that have adapted to life in the sea.