Evidence for Evolution

1. Fossil Record Age & Behavior patterns Show changes in climate & geography Shows evolution & adaptation Problems: Incomplete fossils & Imperfectly preserved

1. Fossil Record Shows evolution & adaptation Problems: Incomplete fossils & Imperfectly preserved

What similarities do you see among the forelimbs of these animals? If you said “yes” then you just made a type of observation that scientists use to establish evolutionary relationships among organisms.

Homologous structures – similar internal structure found in different groups of organisms

Homologous structures May or may NOT look the same on the outside May have a different function Shows common ancestor Ex. forelimbs of vertebrates

What is a similar feature of these 2 organisms?

Analogous Structures Structures w/similar function, but different internal structure Any body part that is similar in function but different in structure is an analogous structure.

Shows evolution But NOT by a common ancestor Ex: wings – bats, insects, & birds

3. Vestigial Structures Structures/organs that are no longer used May have been used by ancestor Indicate a change has occurred

Examples Ostrich wings Human appendix Cave fish eyes

4. Embryology Many different animals have the same organs when they are embryos Ex: embryos of fish, reptiles, birds & mammals all have gills. Suggests evolution from a common ancestor zebrafish chicken dog human skunk

5. Genetic Comparisons Shows evolutionary relationships using DNA sequences Ex. DNA sequence for ATP is the same for all living organisms Ex. Homologous structures require similar DNA

Which 2 species are most similar? Least similar?

Evolutionary Diagrams Phylogenic trees and Cladograms – Diagrams that shows evolutionary relationships of organisms based on similarities and differences in their physical or genetic characteristics.

Common Ancestor