Quiz 11 Flashcards
What is Evolution?
The change in allelie frequency of a population over time.
What is Evolution by Natural Selection?
Change in allelie frequenceies of a population over time due to differential reproductive success within the population that is based on heritable variation.
Who contributed to Darwin’s study?
Alfred Wallace
What does evolution by natural selection require?
- Differential reproductive success
- variation: mutations (point & chromosomal) in sexual reproduction (crossing over & independent assortment)
What is fittness?
The contribution to genetic makeup of future generations (potential to reproduce).
What does fittness include?
- function of quantity of offspring
- quality of offspring (their fittness as well)
What are the 4 Modes of Natural Selection?
1) Stabalizing Selection
2) Directional Selection
3) Disruptive Selection
4) Balancing Selection
What is the most common mode of natural selection?
Stabalizing Selection
Define stabalizing selection
The natural selection acts to resist a change in allelie frequencies because the mean phenotype is the most fit. The population DOES NOT evolve.
Define directional selection
Natural selection acts to move the mean phenotype towards 1 extreme of the range because that extreme is more fit. It is caused by a change in the environment!
What is an example of directional selection?
The European Pepperd Moth:
- Preindustrial Era: Peppered were more likely to survive than dark
- Industrial Era: Dark were more likely to survive (dust and dark smog)
Define disruptive selection
Natural selection acts t create 2 or more genetically distinct forms in the population because the mean phenotype is least fit.
What is an example of disruptive selection?
Salmon:
- Females build redd and males fight for who mates.
- Mutant male (Jack salmon): drive-by fertalization of some of the eggs. are smaller
Define balancing selection
Natural selection acts to maintain genetic diversity in the population by favoring heterozygotes or rare phenotypes.
What is an example of balancing selection?
Scale Eating Cichlids: sneak up behind fish and eat their scales (lefty and righty). The rare one is always more fit than the common one.
What are the 4 Mechanisms for Evolution?
1) Mutations
2) Gene Flow
3) Genetic Drift
4) Nonrandom Mating
What is gene flow?
The movement of alleles into/out of a population
What is an example of gene flow?
Isle Royale National Park:
- frequency of skeletal abnormalities of wolfs increased since they mated with themselves. When new wolf showed up, the abnormalities decreased for a certain amount of time, but then increased again.
What is genetic drift?
The loss in genetic variation due to random events that prevent some individuals in the population from reproducing. There are 2 phenomenons
What are the 2 phenomenons of Genetic Drift?
1) Genetic Bottleneck
2) Founders Effect
Define Genetic Bottleneck
A large catastrophic event wipes out a lot of genetic variation.
What is an example of genetic bottleneck?
Northern Elephant Seals:
- 1890: 20 left
- 1970s: 30,000 - 24 genes and NO variation
Define Founders Effect
The small subset of a population immigrates and forms a new population. The new population is genetically different than the parent population.
What is an example of Founders Effect?
When the genetic flow reduces genetic differences among popultions
- Year 1:
- f of A1 = 0.90; f of A2 = 0.10
- Goes to -> f A1 and A2 = 0.50
- Year 2:
- f A1 = 0.83; f A2 = 0.17
- Goes to -> f A1=0.67; f A2=0.33
