1. Today’s Objectives: 10/21/02
TSW be able to write the Hardy-Weinberg equation and explain it.
TSW be able to list several evolutionary mechanisms.
TSW be able to list several types of speciation and discuss the rates of evolution.

2. Hardy-Weinberg Theorem
p2 + 2pq + q2 = 1
Studies genetic (allelic frequencies)

3. H-W Assumptions: Large population size. Random mating. No migration.
No mutations or mutational equilibrium.

4. Ways Evolution Can Occur

5. Genetic Drift
Neutral selection – caused allelic frequencies to change based on chance
Founder effect
Bottleneck effect
(mutation can play a part here)
Founder effect – Dunker populations of Pennsylvania who do not intermarry because of religious reasons, some blood types unknown
Bottleneck effect – cheetahs, other endangered species.

6. Gene Flow
Changes allelic frequencies because of migration of individuals.

7. Mutation
Random events.
May be beneficial, harmful or insignificant.

8. Definition Selection Pressure
Natural Selection
Definition
Selection Pressure
Whenever some phenotypes are more successful than others. Selection pressure occurs that helps the more successful phenotype to increase its frequency in a population.

9. Types of Natural Selection
Directional selection
Industrial melanism in Biston betularia
Disruptive selection
Distinct subpopulations
Stabilizing selection
Keeps phenotypes stable for long periods of time.

10. Reproductive isolation must be achieved!
Speciation
Reproductive isolation must be achieved!
Premating isolation – impenetrable barriers separating populations
Postmating isolation – cannot produce viable offspring (hybrids often sterile – ex. Ligers and mules)

11. Types of Speciation Allopatric Parapatric Sympatric
Geographic isolation – most common type
Adaptive radiation
Parapatric
In small, local subpopulations (demes)
Sympatric
Almost always in plants
In same population but do not interbreed

12. Gradualism vs. Punctuated Equilibrium
Rates of Evolution
Gradualism vs. Punctuated Equilibrium

13. Same structure is modified for multiple uses.
Mosaic Evolution
Same structure is modified for multiple uses.