Final answer:
Animals have homologous and vestigial structures that provide evidence for evolution and common ancestry.
Step-by-step explanation:
Animals have different structures that provide support and structure in order to carry out their functions. One type of evidence for this is the presence of homologous structures, which are structures in different animals that share the same basic form. For example, the bones in the appendages of a human, dog, bird, and whale all share the same overall construction. These homologous structures suggest a common ancestor for these animals.
Another type of evidence is the presence of vestigial structures, which are structures that no longer have a function but are still present in an organism. For example, some snakes have pelvic bones despite having no legs, which suggests that their ancestors had legs. Vestigial structures provide evidence for evolution because they suggest that an organism has changed from using the structure to not using it, or using it for a different purpose.
Overall, the presence of homologous and vestigial structures in different animals provides evidence for the evolution and common ancestry of species.