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Evidence of Evolution Ch. 6 section 2 Interpreting the evidence • Scientists have found a great deal of evidence supporting evolution. • Fossils, patterns of early development, and similar body structures all provide evidence that organisms have changed over time. Fossils • Fossils show that organisms that lived in the past were very different from animals that live today. Similarities in early development • Opossum, chicken, fish, salamander • All four animals look very similar in early development. (p.183) • All four animals share a common ancestor. Similarities in body structure • Scientists look at body structures for clues in evolution. • Most vertebrates have similar body structures. • All of these animals probably inherited a similar structure from a vertebrate ancestor they shared. • Homologous Structure: similar structures that relate species have a common ancestor. Inferring species relationship • Scientists have combined the evidence from DNA, protein structures, fossils, early development, and body structure to determine the evolutionary relationships among species. Similarities in DNA • Why do some species have similar body structures and development patterns? Species inherit many of the same genes from a common ancestor. • Scientists compare N-bases in DNA. • Ex. Elephant is closely related to a tiny elephant shrew. (p. 185) Branching Tree • Diagram that shows how scientists think different groups of organisms are related. • Raccoons, lesser pandas, giant pandas, and bears may be related. How do new species form? • A new species can form when a group of individuals remains isolated from the rest of its species long enough to evolve different traits.