1. Chapter 17 Evolution of Populations
17.2: Evolution as Genetic Change in Populations

2. A. How Natural Selection Works
Evolutionary Fitness: passing genes on to next gen
Evolutionary Adaptation: genetic trait indiv’s ability to pass on alleles
Natural Selection on Single-Gene Traits:
Changes in allele freq=changes phenotype
Causes Genetic Change
Natural Selection On Polygenic Traits
More complex
Can affect fitness of phenotypes to prod
1 of 3 types of selection
Directional
Stabilizing
Disruptive

3. Directional Selection
Indiv at 1 end has fitness than at middle or end
Range of phenotypes shift b/c more successful at surviving & reprod

4. Stabilizing Selection
Indiv near center of curve have fitness than at ends
Keeps center of curve at current position
Narrows curve overall

5. Disruptive Selection Indiv at outer ends of curve fitness than middle
Acts against indiv of intermediate type
Can use split of curve into 2

6. B. Genetic Drift A change in gene pool (allele freq) due to chance
Genetic Bottlenecks:
Reduction due to natural disasters & hunting
Reduce the size of pop

7. The Founder Effect
Few indiv colonize an isolated island, lake, or new habitat
Genetic makeup ( gene pool) diff from original colony
Change reduces genetic variation

8. C. Evolution vs. Genetic Equilibrium
                                                                                                     
Genetic Equilibrium: allele freq in pop remain same
Hardy-Weinberg Principle: allele freq in pop remain constant unless 1 or more factors cause freq to change
5 conditions that cause evolution to occur:
Nonrandom Mating
Small Pop size
Immigration or Emigration
Mutations
Natural Selection
Hardy-Weinberg Formula

9. 17.3 The Process of Speciation

10. A. Isolating Mechanisms
Species: pop or grp of pop that can interbreed & produce fertile offspring
Speciation: formation of new species
Interbreeding genetically links members
Reproductive Isolation: 2 pop no longer interbreed, split gene pool; evolve into 2 sep species
Behavioral Isolation
Geographic Isolation
Temporal Isolation

11. 1. Behavioral Isolation
2 pop develop differences in courtship rituals or other behaviors that prevent them from breeding.

12. 2. Geographic Isolation
2 pop separated by geographic barriers ex: rivers, mountains, water

13. 3. Temporal Isolation
2 or more species reproduce at diff times  can not interbreed
Ex: flowers bloom at diff times, can’t pollinate one another