Homologous Structures

Homologous structures are structures that serve different functions but come from the same ancestor. The photos above are the arms of an alligator and the wings of a bat. These are examples of homologous structures since the alligator arm and bat wings have similar humerus, radius, ulna, and carpals in each forelimb. This supports the fact that they come from a common ancestor. Now, an alligator's arm is to swim, not to fly (unlike the bat). Therefore, these two animals have homologous structures. Human arms, bat arms, and dolphin arms are also all homologous.