The sperm whale is evolved from the Pakicetus, a small dog-like animal that had four legs and ate a diet of aquatic animals. Through evolution, and over millions of years, there was a overall change in appearance, the hind legs decreased in size and then disappeared, and the animal became more streamline. Primative sperm whales living about 15 million years ago (dark gray in diagram) looked like small sperm whales and were apex predators along with the Megalodon.

In this YouTube video by whale researcher Jessica Alessi learn about the unique evolution of the sperm whale that led to special characteristics that help it live and hunt in the ocean, link. 

Jessica has dedicated her life to studying cetaceans and if often found on her boat monitoring populations near her home in Agrigento, Sicily, Italy or participating in outreach and educational activities. 

If you selected all the answers on the right, you are correct! The answers on the left actually describe another class of animals: fish!