This is a picture of a human hand and a dog paw. They represent homologous structures. Homologous structures are body parts that are similar internally and structurally in multiple species. However, they can look very different on the surface and have different functions. Homologous structures are evidence that the species that share them had a common ancestor. The human hand and dog paw have an extremely similar bone structure, although the bones in each of them are different in size and proportion. The limbs also have different functions - the human hand is designed for holding and picking up things, while the dog paw is designed for walking