Objective: Understand how the mechanism of natural selection causes evolution.

 Bible: Earth is only a few thousand years old.  Aristotle: organisms don’t change ◦ Scala naturae: 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.

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.

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).

Darwin’s Research  From 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.

 Published in 1859 stating: 1.All organisms come from ancestors 2.Mechanism for evolution is natural selection  Populations change over generations passing beneficial heritable traits to offspring.

 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. Hyracoidea (Hyraxes) Sirenia (Manatees and relatives) Years ago Millions of years ago Deinotherium Mammut Stegodon Mammuthus Platybelodon Barytherium Moeritherium Elephas maximus (Asia) Loxodonta africana (Africa) Loxodonta cyclotis (Africa)

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.

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. Terminal bud Lateral buds Brussels sprouts Cabbage Flower cluster Leaves Cauliflower Flower and stems Broccoli Wild mustard Kohlrabi Stem Kale

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

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.

 Drug Resistant Bacteria ◦ Staphylococcus aureus is commonly found on people ◦ Became resistant to:  penicillin in 1945 (2 years after it was 1 st widely used)  methicillin in 1961 (2years after it was 1 st 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 1 2,750,000 2,500,000 2,250,000 2,000,000 1,750,000 1,500,000 1,250,000 1,000, , , ,000 base pairs Chromosome map of S. aureus clone USA300 Key to adaptations Methicillin resistance Ability to colonize hosts Increased disease severity Increased gene exchange (within species) and toxin production

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 HumanCat Whale Bat

 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 Pharyngeal pouches Post-anal tail Chick embryo (LM) Human embryo

 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 Sugar glider Flying squirrel NORTH AMERICA AUSTRALIA

 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 Other even-toed ungulates Hippopotamuses † Pakicetus † Rodhocetus † Dorudon Living cetaceans Common ancestor of cetaceans Millions of years ago 70 Key PelvisTibia FemurFoot

 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

 Study of molecular basis of genes and gene expression  Universality of genetic code  Conservation of amino acid sequences in proteins such as hemoglobin