1. MECHANISMS FOR EVOLUTION Honors Biology

2. REVIEW Evidence for Evolution and Examples What is Natural Selection? How did Darwin develop theory of Natural Selection?

3. PATTERNS OF EVOLUTION Coevolution: – 2 or more species evolve in association with one another – Predators and Prey – Plants and Pollinators – Bats and Flowers

4. PATTERNS OF EVOLUTION Convergent Evolution: – Organisms that look similar but are not related – Analogous features – Similar environments – Sharks and Dolphins

5. PATTERNS OF EVOLUTION Divergent Evolution – 2 or more related populations or species become more and more dissimilar – Usually a response to new habitat – Can result in new species – Adaptive radiation – Artificial Breeding – Humans and Chimps

6. POPULATION GENETICS AND EVOLUTION What did Darwin know? – Environment is important – Competition for Resources – Natural Selection: Individuals with traits more suitable for a particular environment are more likely to survive AND reproduce What did Darwin not know? – Where does variation come from

7. POPULATION GENETICS We now know that variation comes from genetics; no variation  extinction Population genetics: study of evolution from genetic point of view

8. WHAT CAUSES VARIATION Need to think about variation in GENOTYPE – Mutation: change in DNA/chromosomes – Recombination: during meiosis – Random fusion of gametes

9. OTHER MECHANISMS FOR EVOLUTION Things that upset genetic equilibrium Using Hardy Weinberg you can predict genotypes; Only in hypothetical populations

10. MUTATION Change in DNA or chromosomes Make new alleles for a trait Many are harmful Can be neutral (code for same amino acid) Some are beneficial

11. MIGRATION/GENE FLOW Call it gene flow Populations exchange genes Increases within group variation Decreases between group variation DOESN’T HAVE TO BE MIGRATION

12. GENETIC DRIFT Occurs in small populations Allele frequencies shift as a result of RANDOM events Coin Toss Founders Effect; Bottleneck

13. NONRANDOM MATING Sexual Selection Positive assortative mating – mate with someone similar Negative assortative mating: redheads!

14. NATURAL SELECTION Darwin and neoDarwinians believe is the most important way evolution occurs Types of Selection

15. STABILIZING SELECTION Average form are selected for Lizards: – Predators caught slow small and large visible – Select for medium size

16. DIRECTIONAL SELECTION Individuals with an extreme trait are selected for Anteaters with long tongues

17. DISRUPTIVE SELECTION Individuals with either extreme are selected for Limpet shell color; light and dark on different surfaces

18. SEXUAL SELECTION Choosing mates based on traits Intersexual Selection Intrasexual Selection Bird Color

19. SPECIATION If enough changes accumulate  new species Biological concept of species: organisms can mate and produce fertile offspring; not just morphological (what they look like) Isolating mechanisms  speciation – Geographic isolation – Reproductive isolation

20. SPECIATION Rates of speciation – Gradualism: species evolve gradually over time – Punctuated equilibrium: species go through times of fast change and slow or no change