KEY CONCEPT Evidence of common ancestry among species comes from many sources.

Evidence for evolution in Darwin’s time came from several sources. Fossils provide evidence of evolution. Fossils in older layers are more primitive than those in the upper layers.

The study of geography provides evidence of evolution. island species most closely resemble nearest mainland species populations can show variation from one island to another

Embryology provides evidence of evolution. identical larvae, different adult body forms similar embryos, diverse organisms Larva Adult barnacle Adult crab

The study of anatomy provides evidence of evolution. Homologous structures are similar in structure but different in function. Homologous structures are evidence of a common ancestor. Human hand Bat wing Mole foot

The study of anatomy provides evidence of evolution. Analogous structures have a similar function. Human hand Bat wing Mole foot Fly wing Analogous structures are not evidence of a common ancestor.

Structural patterns are clues to the history of a species. Vestigial structures are remnants of organs or structures that had a function in an early ancestor. Ostrich wings are examples of vestigial structures.

Formative Assessment Describe the four sources of evidence for evolution upon which darwin based his ideas on common descent. Why are vestigial structures considered critical evidence of evolution? Describe how some of the Galapagos finches, which traditionally were seed eaters, evolved over generations to prefer insects over seeds. How can a bat’s wing be considered a homologou structure and an analogous structure? Wisdom teeth are a third set of molars that appear between ages 17 and 25. They often need to be removed. How are they an example of a vestigial structure?