1. What is a phylogenetic tree? Agenda for Tuesday Nov 30 th 1.Mechanisms of Evolution notes

2. Genetic Equilibrium A genetic equilibrium occurs when an allele within a gene pool is not changing in frequency (i.e. evolving)

3. Disruption of Genetic Equilibrium Natural Selection Mutation Migration Genetic Drift Nonrandom Mating

4. Natural Selection

5. Types of Natural Selection Directional Selection - extreme phenotype has higher fitness than other phenotypes

6. Stabilizing Selection Stabilizing Selection - intermediate phenotypes have a higher fitness that extreme phenotypes

7. Disruptive Selection Disruptive Selection - intermediate phenotypes are of lower fitness than extreme phenotypes

8. Mutation Mutations can change one allele into a different allele Neutral mutation – affects phenotype, no impact on the survival or reproduction Beneficial mutation – affects phenotype, increase in survival or reproduction

9. Gene Flow/Migration Individuals leave a pop. or new individuals enter a pop. –emigrate = lose alleles –immigrate = gain alleles

10. Genetic Drift Unpredictable changes in allele frequency due to small population size Population bottleneck –reduction of a population –Natural disaster Founder Effect – few individuals separate from a large population and establish a new one

11. Nonrandom Mating Limited probability of mating with any other individual in the population Assortative mating – individuals select partners that are like themselves –Sexual Selection – ability to attract a mate

12. Patterns of Evolution

13. Coevolution Change of two or more species in close association with each other Predators and prey Parasites and hosts Plant eating animals and plants

14. Convergent Evolution Environment selects similar phenotypes although ancestral types were quite different Sharks and dolphins

15. Divergent Evolution Two or more related populations or species become more and more dissimilar Response in differing habitats Result in new species

16. Adaptive Radiation Many related species evolve from a single ancestral species

17. Artificial Selection Intentional breeding for specific traits –Speeds up divergent evolution

18. Rate of Speciation Gradualism Punctuated