Mechanisms of Microevolution

Question 1

Mechanisms of Microevolution: Natural Selection

Answer 1

-Acts non-randomly on phenotypes of individuals
-Changes allelic and genotypic frequencies of populations non-randomly
- Always leads to adaptation of population to current environment

Question 2

Example of Mechanisms of Microevolution: Natural Selection

Answer 2

DDT resistance in insects: There is a nonrandom selection of the phenotype for the individuals that have the chromosome with gene conferring resistance to pesticide. Because of this, the allelic frequencies changed. The population is now more resistance to DDT (adaptation of the population)
Before DDT:
DDT-R frequency = 0%
After DDT:
DDT-R frequency = 37%

Question 3

Mechanisms of Microevolution: Genetic Drift

Answer 3

-Genetic frequency of an existing gene variant in a population changes due to random events
-Often occurs in small populations
–Random events have greater impacts
–Reduces diversity and can “fix” alleles

Question 4

Genetic Drift and The Bottleneck Effect

Answer 4

-Chance event or catastrophe can reduce the genetic variability within a population
-Population is reduced in size due to natural disasters, habitat loss, or overhunting

Question 5

Genetic Drift and The Founder Effect

Answer 5

The reduction in genetic variation that results when a small subset of a large population is used to establish a new colony
-New isolated population results from a few “founders”
–Gene pool is different from source
–Small population = More drift
–Advantageous alleles may be lost
–Maladaptive or dangerous alleles increase in frequency
Ex) Retinitis pigmentosa on Tristan da Cunha

Question 6

Mechanisms of Microevolution: Gene Flow

Answer 6

Alleles move in and out of population
-Migration of adults and dispersal of gametes/seeds/larvae
-Adds diversity and reduces difference between populations
-Opposite of Bottleneck Effect
Ex) A small number of Western and Eastern deer separated from mountain range pass over to other population and mate

Question 7

Other Mechanisms of Microevolution

Answer 7

1) Mutation

2) Non-random Mating
-Sexual selection
-Assortative mating

3) Environmental Variation
-Temperature-dependent sex determination (TSD)
Ex) The sex of the American alligator is determined by the temperature at which the eggs are incubated