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Homologous Structures
The homologous structures I am going to compare are a killer whale and a shark’s pectoral fin. A shark’s pectoral fin is made of cartilage and has no bone or muscle. A killer whale’s pectoral fin is like a human’s hand. It has bones and muscle. A shark’s and a whale’s fin helps it swim and glide in the water but a whale’s fin can move up and down because of the joints. A shark’s fin can’t move because its just cartilage, it stabilizes the shark in the water. That is a homologous structure between a whale and a shark.



Vestigial Structure

Whales are mammals just like humans, dolphins and cats. Mammals have lungs, breathe air, and have warm blood. Their young are not born in eggs and the female produces milk to feed them. A lot of mammals also have legs and hair but not all. Whales have evolved from wild dogs in Africa millions of years ago. To this day whales still have vestigial structures like bones of their hind legs, a pelvis, fingers, and some species of whales still have hair on their heads. Over the years whales have moved back into the water from the land. Since the whales have moved into the water their muscles of the upper rear legs have become a powerful tail stock, and at the end of the tail stock, is now a pair of horizontal flukes that help the whales move through the water. The blowhole of a whale is like the nose of a human but it’s located on the top of the head. Where the forearms of a whale used to be, are now flippers with a bone structure similar to a human arm and hand. Those are some vestigial structures of a killer whale.

Evolutionary Relationships

There are many species that are closely related to a killer whale. I am going to compare a killer whale to three different species which are a dolphin, a great white shark and a porpoises. A killer whale is like a dolphin in many ways. One way is their pectoral flippers. They...