Evidence for Evolution: Anatomy Explain the difference between homologous, analogous, and vestigial structures. Provide an example of each one. Then, explain which one(s) help to support the theory of evolution.

Homologous Structures Homologous structures have the same structures but are used for different functions. Supports evolutionary relationships since the similar structures originated in a common ancestor.

Homologous Structures Example: Humans, cats, whales, and bats all have the same bones in their upper appendages, but each is used for a different function. human arm (used in grasping objects) cat leg (used in walking) whale fin (used in swimming) bat wing (used in flying)

Analogous Structures Analogous structures have different structures but are used for the same function. Does NOT support evolutionary relationships. They evolved from different origins.

Analogous Structures Example: A bird, bat, and common house fly all have wings used for flying, but a fly wing does NOT contain the same structures as a bird and bat wing.

Vestigial Structures Vestigial structures are remnant structures that performed a useful function during an earlier, ancestral stage. The root vestige means, “a remnant of.” Example: Humans still have small muscles in our skin that cause our hair to stand up when we’re cold (goose bumps). Modern humans no longer have enough body hair in order for this to help keep us warm, but we have retained the muscles.

Vestigial Structures in humans Muscles to move your ears Nictitating membrane in your eyes Body hair Pointed canine teeth Third molar (wisdom teeth) Appendix Caudal vertebrae (tailbone)