1. Studies of Fossils What are Fossils? –Fossils are any trace of dead organisms.
Fossil evidence Shows history of life on Earth. Shows how different organisms have changed over time. Fossils appear in a particular order.
What can fossils tell us? Finding the age of a fossil will show us how long ago that organism existed.
Example This dinosaur fossil shows us that it existed 113 million years ago.
2. Comparison of Structures We can compare body structures of different living organisms to determine evolutionary relationships.
2A. Homologous Structures Homologous Structures: structures that share a common ancestor. The structures can be different sizes & serve different functions. Similarities and differences among the homologous structures help determine how recently species shared a common ancestor.
Example The human, cat, whale and bat all share a common mammalian ancestor.
2B. Analogous Structures Analogous Structures: Structures that serve the same function in different species, but evolved independently (NOT from a common ancestor).
Example The Wings of Birds, Bats, & Butterflies Wings serve similar function but did NOT evolve from a common organism.
2C. Vestigial Structures Vestigial Structures: Structures with NO known functions. Inherited from ancestors Structures are remnants of organism’s evolutionary past Example in humans: appendix, tailbone, wisdom teeth (Individuals still have them because they must not affect the organisms fitness)
2D. Developmental Structures Developmental structure patterns show evolutionary relationships. The more closely related show the organisms descended from a common ancestor. Example: –Human Embryos & Chicken Embryos are very similar at 4 days –Thus, must have evolved from common ancestor
3. DNA & proteins The universal genetic code provides evidence of common descent. We can also compare similarities in gene sequencing and protein production between organisms. We also know that heritable variation on which natural selection operates may be caused by mutations or the reshuffling of genes during sexual reproduction.
Example The genetic code is nearly identical in almost all organisms Humans and Chimpanzees have ~98% of the same genes and therefore have a common ancestor