14. Homologous Structures

This is a picture of my arm and my dog's leg. This picture represents homologous structures. Homologous structures are structures that are derived from a same evolutionary origin, which agrees from the theory that animals come from the same ancestors. For instance, the flipper of a whale, the wing of the bat, the leg of a dog, and the arm of a human all share similar structures (even though the functions are different). The fact that whales, bats, dogs, and humans are all mammals, and the fact that homologous structures are present show that these mammals came from a common ancestor.