1. Topic 3: Evidence for evolution

2. Fossil record The sequence that fossils appear within layers (strata) of sedimentary rocks Three types of fossils: –Mineralized bones and shells –Trace fossils –Preserved remains Aging of fossils –C-14 –U-235

3. Fossil record Earliest fossils= stromatolites 3.5 billion years old Mineralized layered mats of ancient cyanobacteria (we can thank them for early oxygen) Proterozoic rocks (~2 billion years old)

4. Fossil Record “Descent with modification”

6. Biogeography

7. Homologous Structures Similar or different function Similar structure Indicates common ancestors

8. Homologies can be used to infer evolutionary history

9. Vestigial organs Remnants or whole structures that once served a function in an ancestor but are useless now Examples: human ear muscles, hind-leg and foot bones in whales

10. Embryonic development Many organisms share traits as embryos that are not kept as adults. For example, at one stage of development in the womb, reptile, bird, and mammal fetuses have structures resembling gills and they all have tails.

11. Biochemical experiments Stanley Miller (1953): Miller-Urey experiments –Simulated the conditions of primeval earth (~4 billion years ago) –Ocean + atmosphere (water vapor, methane, ammonia) + electrical charge (lightning) amino acids and other organic compounds that are today found in living things –Proved that organic molecules can be synthesized from inorganic molecules –These experiments have been repeated independently many times, with similar results Since then, many meteorites have been analyzed and found to contain amino acids!

12. Biochemical evidence How did we get living organisms from organic compounds? –Remember the properties of cell membranes (phospholipid bilayer)? –Protobionts (lab experiments confirm) –Self-replicating RNA (lab experiments)

13. Prokaryotes and endosymbiosis Chloroplasts and mitochondria are probably remnants of those smaller prokaryotes –Evidence: both have their own DNA, replicate themselves like bacteria (binary fission)

14. Molecular evidence Universal code of life (DNA) Conserved sequences of DNA –Example: gene for cytochrome c Protein synthesis –RNA –Ribosomes –20 amino acids

15. Primate family tree

17. If we scaled time to 24 hours… Fossils present but rare Evolution and expansion of life Fossils become abundant Plants invade the land Age of reptiles Age of mammals Insects and amphibians invade the land Modern humans (Homo sapiens) appear about 2 seconds before midnight Recorded human history begins 1/4 second before midnight Origin of life (3.6–3.8 billion years ago)