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