Post on 21-Jan-2016
Chap 23
Evolution of Populations
Genotype
p2 AA
2pq Aa
q2 aa
Phenotype
Dominant p2 + 2pq
Recessive q2
Gene
Gene
p A
q a
p + q = 1p2 + 2pq + q2 = 1
5 Conditions of the Hardy-Weinberg Principal
• If all conditions are met then the gene frequencies stay the same (equilibrium)
1. Populations must be large
2. Random mating
3. No natural selection
4. No mutation
5. No migration
1. Why are there no plants with white flowers in Generation 3?
No individuals that carried the allele for white flowers in Generation 2 produced offspring.
2. If one RR plant and one rr plant where the only individuals that reproduced in Generation 2, would genetic drift have occurred between Generations 2 and 3? Explain.
No. The allele frequencies would still be 50% R and 50% r.
Genetic Drift:
when gene frequencies change due to random events
HW Problems
problems
animation
Bottle Neck Effect
Sample of Original Population
Founding Population A
Founding Population B
Descendants
Genetic Drifta random change in gene frequencySection 16-2
Sample of Original Population
Founding Population A
Founding Population B
Descendants
Section 16-2
Founder’s Effect
Sample of Original Population
Founding Population A
Founding Population B
Descendants
Founder’s EffectSection 16-2
Cline-Change in phenotype over a geographic range
Cline-Change in phenotype over a geographic range
Normal Distribution
Bell curve
Normal Distribution
Bell curve
Different combinations of survivors will be bring different combinations of genes together resulting in the appearance of new phenotypes
Different combinations of survivors will be bring different combinations of genes together resulting in the appearance of new phenotypes
p456
Balanced Polymorphism
Heterozygote Advantage - People with sickle cell trait have a better chance of surviving Malaria
Freq dependent Selection
One morph declines if it becomes too common
p456
Balanced Polymorphism
Heterozygote Advantage - People with sickle cell trait have a better chance of surviving Malaria
Freq dependent Selection
One morph declines if it becomes too common
Secondary Sex characteristics may not be seem adaptive - but it does make the individuals more FIT.
Darwinian fitness
Secondary Sex characteristics may not be seem adaptive - but it does make the individuals more FIT.
Darwinian fitness
Sexual Dimorphism
http://www.pbs.org/wgbh/evolution/sex/guppy/ed_pop.html