Question 1

Show algebraically that under Hardy-Weinberg equilibrium, allele frequencies will not change from one generation to another.

Accepted Answer

The answer of Show algebraically that under Hardy-Weinberg equilibrium, allele...

Question 2

Survival is the single most important process in evolution by natural selection.

Accepted Answer

While survival is certainly an important factor in natural selection, it is not the single most important process. Natural selection also depends on reproductive success, genetic variation, and environmental factors influencing which traits are advantageous in a given population.

Question 3

Two closely related insect species are active at different times of day,with one diurnal and the other nocturnal.This is an example of spatial isolation.

Accepted Answer

This is an example of temporal isolation, as the two species are isolated by the timing of their activity, rather than by physical location or habitat.

Question 4

Some recessive mutations can be exceedingly debilitating or lethal when expressed in homozygotes.If their effects are so severe,why doesn't natural selection simply purge such alleles from the population completely?

Accepted Answer

The answer of Some recessive mutations can be exceedingly debilitating...

Question 5

The northern elephant seal,Mirounga angustirostris,suffered a significant population bottleneck in the late nineteenth century,when hunting reduced their population size to as few as 20 individuals.It has since rebounded to several tens of thousands.The related southern elephant seal,M.leonine,was not hunted as intensively.What prediction can you make about the relative levels of heterozygosity in populations of these two species?

Accepted Answer

The answer of The northern elephant seal,Mirounga angustirostris,suffered a significant...

Question 6

According to the Hardy-Weinberg principle, at equilibrium the allele frequencies are dependent on the genotypic frequencies.

Accepted Answer

The Hardy-Weinberg principle states that allele frequencies in a population remain constant from generation to generation, provided that certain conditions are met, and are not dependent on genotypic frequencies.

Question 7

With respect to a gene with two alleles,for each generation of complete inbreeding the proportion of heterozygotes is expected to be reduced by $\frac { 1 } { 2 }$ while the proportion of each homozygous class is expected to increase in frequency by $\frac { 1 } { 4 }$ .Explain why this is so.

Accepted Answer

The answer of With respect to a gene with two...

Question 8

The deciduous forest of eastern North America has experienced dramatic changes over the past two to three centuries,transitioning from a nearly continuous forested area to increasingly patchy areas of forest broken up by farming and development.Some species are more sensitive to severe habitat fragmentation than others.What are some characteristics that might make a species more susceptible to the effects of habitat and population fragmentation?

Accepted Answer

The answer of The deciduous forest of eastern North America...

Question 9

Why do we expect that postzygotic isolation will evolutionarily precede prezygotic isolation in the speciation process?

Accepted Answer

The answer of Why do we expect that postzygotic isolation...

Question 10

Red-green color blindness is an X-linked trait.In a population genetics study,1,000 people (500 men and 500 women)were tested for this trait,and 35 men were found to be color blind.Use this information to compute the frequency of the allele for color blindness and the wild-type allele in this population,and estimate the expected number of carrier females.

Accepted Answer

The answer of Red-green color blindness is an X-linked trait.In...

Question 11

In the early twentieth century,evolutionary biologists argued whether there was enough genetic variation in populations to explain the diversity of life by natural selection.With the advent of protein electrophoresis and DNA-level analysis,the problem turned on its head: the neutralist school arose from the idea that there was too much genetic variation to be maintained by natural selection.What are some of the arguments and observations neutralists cited to support the idea that much variation is neither favored nor disfavored by natural selection?

Accepted Answer

The answer of In the early twentieth century,evolutionary biologists argued...

Question 12

Populations that suffer significant reductions in number may experience two population-genetic consequences that together can hasten their decline.Which two processes are likely to act in concert in small populations,and what is their effect?

Accepted Answer

The answer of Populations that suffer significant reductions in number...

Question 13

Observed genotypic frequencies in populations rarely match

Accepted Answer

The answer of Observed genotypic frequencies in populations rarely match...

Question 14

The frequency of a recessive X-linked allele is equal to the phenotypic frequency of males exhibiting that allele.

Accepted Answer

This statement is true because males only have one X chromosome, and if they inherit the recessive allele on that X chromosome, they will exhibit the phenotype. In females, the presence of a dominant allele on the other X chromosome can mask the effects of the recessive X-linked allele. Therefore, the phenotypic frequency of males exhibiting the allele is equal to the frequency of the allele itself in the population.

Question 15

In light of the fact that the assumptions of the

Accepted Answer

The answer of In light of the fact that the...

Question 16

Two neighboring Caribbean islands harbor iguana populations.One island (island A)has a total iguana population of 800,while the other (island B)has a population less than half that size,numbering 250.On island A,the frequency of an allele p is estimated at 0.75,while this same allele is present at a frequency of 0.90 on island B.During a hurricane tracking across the islands,a group of about 100 iguanas get rafted from island A to island B.What effect does this have on the frequency of allele p on island B?

Accepted Answer

The answer of Two neighboring Caribbean islands harbor iguana populations.One...

Question 17

The genetic variation between human "races," such as Africans and Europeans,is greater than the variation within a single race.

Accepted Answer

The concept of "race" is a social construct rather than a biological fact. The genetic variation within and between populations is continuous, and there is more genetic variation within racial categories (e.g. among different African populations) than between them. Therefore, the statement that the variation between human "races" is greater than the variation within a single race is false.

Question 18

A selection coefficient of 1 means zero fitness.

Accepted Answer

A selection coefficient of 1 means that every individual with a certain genotype is eliminated from the population, indicating zero fitness.

Question 19

A gene is known to have three alleles: p,q,and r.The frequency of p is estimated at 0.70.Thus,the frequencies or q and r must be 0.15 each.

Accepted Answer

The frequencies of q and r cannot both be 0.15 if the frequency of p is 0.70. The frequencies of all three alleles must add up to 1, so if p is 0.70, the frequencies of q and r must be 0.15 and 0.15 added together, which is 0.30. Therefore, the correct frequencies would be p=0.70, q=0.15, and r=0.15.

Question 20

This chapter discussed speciation by genetic divergence following geographic isolation,which is expected to lead to reduced gene flow,a process known as allopatric speciation.A more controversial form of speciation is the genetic divergence of populations without physical isolation,a process known as sympatric speciation.Can you envision a mechanism or process that would permit two coexisting populations of the same species to begin to diverge without being isolated from one another?

Accepted Answer

The answer of This chapter discussed speciation by genetic divergence...

Quiz 21: Population Genetics