Ch. 22 Descent with Modification: A Darwinian View of Life

1. Ch. 22 Descent with Modification:A Darwinian View of Life Objective: Understand how the mechanism of natural selection causes evolution.

2. 22.1 Challenging Young Earth with Unchanging Species • Bible: Earth is only a few thousand years old. • Aristotle: organisms don’t change • Scalanaturae: ladder of increasing complexity • Linnaeus: taxonomy (naming/classifying organisms) using genus and species • Cuvier: paleontologist discovered the deeper (older) the rock, the less like modern organisms fossils look. • Also found extinctions and speciations.

3. Gradualism (slow, continuous change) • Hutton: geologic features explained by graddual erosion and deposition. • Lyell: uniformitarianism – same geologic processes are operating today as in the past, at the same rate. • Darwin proposed this also happened with organisms.

4. Lamarck (INCORRECT) • Use and disuse: body parts used got bigger/stronger; not used got small/disappeared. • These body parts could be passed on to offspring (inheritance of acquired characteristics).

5. 22.2 Natural Selection Darwin’s Research • From 1831-6 Charles Darwin traveled the world on the HMS Beagle. • Earthquakes moved rocks up Andes mountains exposing sea creature fossils. • Finches were unique to islands but also were found on 2 or more. • They came from S. America and diversified according to food found on the island they were on.

6. The Origin of Species • Published in 1859 stating: • All organisms come from ancestors • Mechanism for evolution is natural selection • Populations change over generations passing beneficial heritable traits to offspring.

7. Sirenia (Manatees and relatives) Loxodonta africana (Africa) Elephas maximus (Asia) Loxodonta cyclotis (Africa) Hyracoidea (Hyraxes) Years ago Stegodon Mammut Mammuthus Deinotherium Platybelodon Millions of years ago Barytherium Moeritherium Descent with Modification • Modifications (adaptations) that helped organisms survive and have more offspring with these modifications (descent). • Evolutionary trees could be made showing where fossils fit in with living organisms.

8. Natural Selection and Adaptation How natural selection works: • Struggle for existence. • Individuals survive due to heritable phenotypic differences. • These lead to changes in characteristics of a population over generations.

9. Lateral buds Terminal bud Brussels sprouts Cabbage Flower cluster Leaves Cauliflower Kale Flower and stems Stem Broccoli Kohlrabi Wild mustard Artificial Selection • Humans change organisms by choosing traits and breeding. • Led Darwin to believe that natural selection could work the same over longer periods of time thus produces drastic changes.

10. Summary of Natural Selection • Individuals do not change. • Only works on heritable traits. • The same trait is not always favorable.

11. 22.3 Darwin’s Theory Explains Observations Guppies • Size and age differences between populations • Different predators • Killifish: preys on juveniles • Pike-cichlid: preys on mature • Result: sexual maturity in pops with killifish decreased.

12. 1 2,750,000 250,000 base pairs 2,500,000 • Drug Resistant Bacteria • Staphylococcus aureus is commonly found on people • Became resistant to: • penicillin in 1945 (2 years after it was 1st widely used) • methicillin in 1961 (2years after it was 1st widely used) • Methicillin inhibits a protein in bacteria’s cell walls • MRSA uses a different protein and is now pathogenic. • MRSAs are now resistant to many antibiotics Chromosome map of S. aureus clone USA300 500,000 Key to adaptations 2,250,000 Methicillin resistance 750,000 Ability to colonize hosts Increased disease severity 2,000,000 Increased gene exchange(within species) andtoxin production 1,000,000 1,750,000 1,250,000 1,500,000

13. Human Cat Bat Whale Evidence for Evolution • Homology: similarities resulting from common ancestry • Comparative Anatomy • Homologous: same structure different function • Vestigial: remains of structures that have no current function • Molecular: same DNA/RNA/amino acids

14. Homologies • Comparative embryology reveals anatomical homologies not visible in adult organisms • Homologies form nested patterns in evolutionary trees • Evolutionary trees can be made using different types of data, for example, anatomical and DNA sequence data Pharyngealpouches Post-analtail Chick embryo (LM) Human embryo

15. Convergent Evolution • The evolution of similar (analogous) features in distantly related groups • Analogous traits arise when groups independently adapt to similar environments in similar ways • Convergent evolution does not provide information about ancestry NORTHAMERICA Sugarglider AUSTRALIA Flyingsquirrel

16. Other even-toedungulates • The Fossil Record • The fossil record provides evidence of the extinction of species, the origin of new groups, and changes within groups over time • Fossils can document important transitions • EX: the transition from land to sea in the ancestors of cetaceans Hippopotamuses †Pakicetus †Rodhocetus Commonancestorof cetaceans †Dorudon Livingcetaceans 70 60 50 40 30 20 10 0 Pelvis Tibia Key Millions of years ago Femur Foot

17. Biogeography: closely related species are geographically close. • Earth’s continents were formerly united in a single large continent called Pangaea, but have since separated by continental drift

18. Molecular Biology • Study of molecular basis of genes and gene expression • Universality of genetic code • Conservation of amino acid sequences in proteins such as hemoglobin