Selection
A population of flowers favors the AA (red) and aa (white) individuals over the Aa (pink) individuals. What type of selection is this?
Underdominance/heterozygote disadvantage
A population that is in Hardy-Weinberg equilibrium [will/will not] experience gene flow
will not
True or false? Genetic drift is the alteration of allele frequencies due to non-random events
False! Genetic drift specifically involves chance (or random) events.
True or false? Inbreeding reduces observed heterozygosity and changes allele frequencies.
False! While this mechanism reduces observed heterozygosity, it does not change allele frequencies.
In a population where the fitness for AA is 0.6, for Aa is 1.0, and for aa is 0, what would the s and t values be?
s = 0.4
t = 1.0
True or false? Gene flow tends to prevent homogenization of populations, making them more genetically diverse over time.
False! Gene flow actually promotes homogenization between populations, making them more genetically similar to one another over time.
This specific type of drift occurs when a few individuals colonize a new habitat, like the Pingelap Atoll survivors.
The founder effect
A male bird picks his mate based on how phenotypically dissimilar the female looks compared to him, while a male chihuahua choose his mate based on how similar she looks to him. The birds are an example of ____ mating, while the chihuahuas are an example of ____ mating.
disassortative; assortative
Population A: N = 1000
Population B: N = 100
Which population will experience a greater loss in heterozygosity?
Population B
If a migrant arrives in a new population, what must it also do in order for gene flow to happen?
The migrant must reproduce with others in that new population in order for their genes must be subsequently incorporated into the local gene pool.
Which of the following is false about genetic drift?
A. Drift causes a loss in heterozygosity
B. Smaller populations experience more impact from drift than larger populations
C. Larger populations experience more impact from drift than smaller populations
D. Drift results from a finite population size, implying that HWE has been violated
C (larger populations have less sampling error and do not suffer the consequences of drift as much as smaller populations do)
The probability that a randomly chosen individual carries 2 identical copies from an ancestor is known as ___?
inbreeding coefficient
A population selects against its homozygous individuals. What type of dominance is this, and would you expect stable or unstable equilibrium at p = t / s + t?
Overdominance; stable
In a case where you have a large continent and a small island, explain why migration has a larger impact on the allele frequencies of the island than the continent.
Because the migrants represent a much larger fraction of the island's small gene pool than islanders do for the continent's massive pool.
A forest fire reduces a beetle population from 10,000 to 15. The population survives, but a once-rare wing deformity becomes common, and the group loses the ability to digest a local plant. Identify this event and explain why these traits changed so rapidly.
Bottleneck; The population crashed, leaving a non-representative sample of alleles, which then allowed the deformity to increase as the surviving individuals reproduced.
In a self-fertilizing population with no other evolutionary forces, what happens to the genetic frequencies over time?
A. Allele frequencies change, but genotype frequencies stay the same.
B. Heterozygosity decreases, but allele frequencies stay the same.
C. Both allele and genotype frequencies stay the same.
D. Mutations increase to replace lost heterozygotes.
B
Inbreeding redistributes alleles into homozygotes but does not remove them from the pool
If a population showcasing underdominance, if the frequency of A is 0.6 and the unstable equilibrium point is 0.2, what will happen to the A allele?
It will increase until A reaches fixation (1.0)
Which of the following best represents gene flow and why?
A. A herd of wildebeests migrates 500 miles south for the winter to find greener pastures and then returns to their original territory to mate in the spring
B. A heavy storm carries several seeds from a mainland flower species to a barren volcanic island where no plants of that species currently exist
C. Pollen from a population of pesticide-resistant corn is carried by the wind into a neighboring farm’s non-resistant corn field, where it successfully fertilizes the plants
C (migration and reproduction with the new population)
Explain why every population follows a "unique evolutionary path" even if they start with identical allele frequencies and environments
Because drift is a random process determined by chance events; sampling error and varying population size leads to different alleles being fixed or lost by chance in each group
How does inbreeding "expose" deleterious recessive alleles to natural selection if it doesn't change allele frequencies?
It increases the frequency of homozygotes (aa), making recessive traits that are normally "hidden" in heterozygotes visible to selection.