Deck 21: The Evolution of Populations

Question 1

How can genetic variation at the whole gene level (gene variability) be quantified?

A) by the average percentage of loci that are heterozygous
B) by the average percentage of loci that are homozygous
C) by nucleotide variability
D) by the differences in noncoding DNA

Answer 1

A

Question 2

How did Mendel's model of inheritance help explain Darwin's theory of natural selection?

A) by observations of individuals differences in traits
B) by proposing mechanism of how organisms transmit discrete heritable units
C) by explaining natural selection of genetic differences
D) by leading to evolutionary change

Answer 2

B

Question 3

What is the Hardy-Weinberg equation?

A) an assessment of evolution at a particular locus
B) a determination of allele frequency
C) a determination of genotype frequency
D) an assessment of heterozygosity in a population

Answer 3

A

Question 4

Which statement about variation is true?

A) All phenotypic variation is the result of genotypic variation.
B) All genetic variation produces phenotypic variation.
C) All nucleotide variability results in neutral variation.
D) All new alleles are the result of nucleotide variability.
E) All geographic variation results from the existence of clines.

Question 5

In evolution, which driving factor most consistently requires a small population as a precondition for its occurrence?

A) mutation
B) nonrandom mating
C) genetic drift
D) natural selection

Question 6

In the formula for determining a population's genotype frequencies, the pq in the term 2pq is necessary because

A) the population is diploid.
B) heterozygotes can come about in two ways.
C) the population is doubling in number.
D) heterozygotes have two alleles.

Question 7

In the formula for determining a population's genotype frequencies, the 2 in the term 2pq is necessary because

A) the population is diploid.
B) heterozygotes can come about in two ways.
C) the population is doubling in number.
D) heterozygotes have two alleles.

Question 8

The frequency of individuals born in a population with PKU is q2. There is one PKU (q2) birth per 10,000 births. The frequency of the recessive allele for PKU in this population is q = 0.01. The frequency of the dominant allele in this population is p = 1 - q = 0.99. What is the frequency of carriers (2pq) in this population?

A) 1%
B) 2%
C) 3%
D) 4%

Question 9

Over time, the movement of people on Earth has steadily increased. This has altered the course of human evolution by increasing

A) nonrandom mating.
B) geographic isolation.
C) genetic drift.
D) gene flow.

Question 10

Whenever diploid populations are in Hardy-Weinberg equilibrium at a particular locus,

A) the allele's frequency should not change from one generation to the next, but its representation in homozygous and heterozygous genotypes may change.
B) natural selection, gene flow, and genetic drift are acting equally to change an allele's frequency.
C) this means that, at this locus, two alleles are present in equal proportions.
D) the population itself is not evolving, but individuals within the population may be evolving.

Question 11

In a Hardy-Weinberg population with two alleles, A and a, that are in equilibrium, the frequency of the allele a is 0.3. What is the frequency of individuals that are homozygous for this allele?

A) 0.09
B) 0.49
C) 0.9
D) 9.0

Question 12

In peas, a gene controls flower color such that R = purple and r = white. In an isolated pea patch, there are 36 purple-flowering plants and 64 white-flowering plants. Assuming Hardy-Weinberg equilibrium, what is the value of q for this population?

A) 0.36
B) 0.64
C) 0.75
D) 0.80

Question 13

If, on average, 46% of the loci in a species' gene pool are heterozygous, then the average homozygosity of the species should be

A) 23%.
B) 46%.
C) 54%.
D) There is not enough information to say.

Question 14

Which of the following describes a mechanism for generating more genes?

A) translocation
B) duplication
C) meiosis
D) gametogenesis

Question 15

Evolution

A) must happen, due to organisms' innate desire to survive.
B) must happen whenever a population is not well adapted to its environment.
C) can happen whenever any of the conditions for Hardy-Weinberg equilibrium are not met.
D) requires the operation of natural selection.

Question 16

Which statement about the beak size of finches on the island of Daphne Major during prolonged drought is true?

A) Each bird evolved a deeper, stronger beak as the drought persisted.
B) Each bird's survival was strongly influenced by the depth and strength of its beak as the drought persisted.
C) Each bird that survived the drought produced only offspring with deeper, stronger beaks than seen in the previous generation.
D) The frequency of the strong-beak alleles increased in each bird as the drought persisted.

Question 17

Which of the following is a true statement concerning genetic variation?

A) It is created by the direct action of natural selection.
B) It arises in response to changes in the environment.
C) It must be present in a population before natural selection can act upon the population.
D) It tends to be reduced by the processes involved when diploid organisms produce gametes.
E) A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.

Question 18

Which process in sexual reproduction results in diversity at the nucleotide level?

A) chromosome shuffling
B) chromosome crossover
C) independent assortment of chromosomes
D) random distribution of chromosomes

Question 19

What is a population in biology?

A) when a group of individuals of the same species live in the same area and interbreed
B) when a group of individuals live in the same area and share resources
C) when a group of individuals of different species live in the same area
D) when closely related organisms share a low frequency of alleles

Question 20

Why don't similar genotypes always produce the same phenotype?

A) Phenotype is the product of many environmental influences.
B) Parents alter their phenotypes and pass on this phenotype to progeny.
C) Animals display different phenotypes dependent on diet, not genotype.
D) Genetic variants of ADH enzyme produce the same phenotype.

Question 21

Heterozygote advantage should be most closely linked to which of the following?

A) sexual selection
B) stabilizing selection
C) random selection
D) directional selection
E) disruptive selection

Question 22

Most Swiss starlings produce four to five eggs in each clutch. Starlings producing fewer, or more, than this have reduced fitness. Which of the following terms best describes this situation?

A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection
E) sexual selection

Question 23

What is the result of adaptive evolution?

A) formation of new genetic variants
B) sorting by natural selection
C) increase in frequency of alleles that provide reproductive advantage
D) survival of the fittest

Question 24

Blue light is a portion of the visible spectrum that penetrates deep into bodies of water. Ultraviolet (UV) light, though, can penetrate even deeper. A gene within a population of marine fish that inhabits depths from 500 m to 1,000 m has an allele for a photopigment that is sensitive to UV light, and another allele for a photopigment that is sensitive to blue light. Which of the graphs in Figure 21.1 best depicts the predicted distribution of these alleles within a population if the fish that carry these alleles prefer to locate themselves where they can see best? Figure 21.1

A) A
B) B
C) C
D) D

Question 25

The same gene that causes various coat patterns in wild and domesticated cats also causes a cross-eyed condition in these cats, the cross-eyed condition being slightly maladaptive. In a hypothetical environment, the coat pattern that is associated with crossed eyes is highly adaptive, with the result that both the coat pattern and the cross-eyed condition increase in a feline population over time. Which statement is supported by these observations?

A) Evolution is progressive and tends toward a more perfect population.
B) Phenotype is often the result of compromise.
C) Natural selection reduces the frequency of maladaptive genes in populations over the course of time.
D) Polygenic inheritance is generally maladaptive, and should become less common in future generations.

Question 26

Sexual dimorphism is most often a result of

A) pansexual selection.
B) stabilizing selection.
C) intrasexual selection.
D) intersexual selection.
E) artificial selection.

Question 27

Identify the statement that describes the imperfection of natural selection.

A) Natural selection has not had sufficient time to create the optimal design in each case, but will do so given enough time.
B) In many cases, phenotype is not merely determined by genotype, but by the environment as well.
C) Though we may not consider the fit between the current skeletal arrangements and their functions excellent, we should not doubt that natural selection ultimately produces the best design.
D) Natural selection is generally limited to modifying structures that were present in previous generations and in previous species.

Question 28

Anopheles mosquitoes, which carry the malaria parasite, cannot live above elevations of 5,900 feet. In addition, oxygen availability decreases with higher altitude. Consider a hypothetical human population that is adapted to life on the slopes of Mt. Kilimanjaro in Tanzania, a country in equatorial Africa. Mt. Kilimanjaro's base is about 2,600 feet above sea level and its peak is 19,341 feet above sea level. If the incidence of the sickle-cell allele in the population is plotted against altitude (feet above sea level), which of the following distributions is most likely, assuming little migration of people up or down the mountain?

A)
B)
C)
D)

Question 29

What is the founder effect?

A) a selection of the best-suited traits for the environment
B) a series of chance events that change allele frequency
C) when a few individuals become isolated from a larger population, and their gene pool differs from that source population
D) a sudden change in the environment that reduces the size of the population

Question 30

Adult male humans generally have deeper voices than do adult female humans, which is the direct result of higher levels of testosterone causing growth of the larynx. If the fossil records of apes and humans alike show a trend toward decreasing larynx size in adult females and increasing larynx size in adult males, then

A) sexual dimorphism was developing over time in these species.
B) intrasexual selection seems to have occurred.
C) stabilizing selection was occurring in these species concerning larynx size.
D) selection was acting more directly upon genotype than upon phenotype.

Question 31

Which one of the genetic drift effects would limit natural selection?

A) allele frequencies change at random
B) loss of genetic variation
C) cause harmful alleles to be fixed
D) alter frequencies in small population

Question 32

How can gene flow improve adaptation of population?

A) alleles mutate in different geographical areas
B) alleles increase in frequency in original population
C) beneficial alleles are transferred to a new population
D) allele frequencies decrease in new population

Question 33

Which of the following statements best summarizes evolution as it is viewed today?

A) It represents the result of selection for acquired characteristics.
B) It is synonymous with the process of gene flow.
C) It is the descent of humans from the present-day great apes.
D) It is the differential survival and reproduction of the most-fit phenotypes.

Question 34

What is true of natural selection?

A) Natural selection is a random process.
B) Natural selection creates beneficial mutations.
C) The only way to eliminate harmful mutations is through natural selection.
D) Mutations occur at random; natural selection can preserve and distribute beneficial mutations.

Question 35

Use Figure 21.2 to answer the following question. Figure 21.2
Soon after the island of Hawaii rose above the sea surface (somewhat less than 1 million years ago), the evolution of life on this new island should have been most strongly influenced by

A) genetic bottleneck.
B) sexual selection.
C) habitat differentiation.
D) founder effect.

Question 36

Which of the following is most likely to produce an African butterfly species in the wild whose members have one pattern?

A) artificial selection
B) directional selection
C) stabilizing selection
D) disruptive selection

Question 37

The restriction enzymes of bacteria protect the bacteria from successful attack by bacteriophages, whose genomes can be degraded by the restriction enzymes. The bacterial genomes are not vulnerable to these restriction enzymes because bacterial DNA is methylated. This situation selects for bacteriophages whose genomes are also methylated. As new strains of resistant bacteriophages become more prevalent, this in turn selects for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. The outcome of the conflict between bacteria and bacteriophage at any point in time results from

A) frequency-dependent selection.
B) evolutionary imbalance.
C) heterozygote advantage.
D) neutral variation.

Question 38

In seedcracker finches from Cameroon, small- and large-billed birds specialize in cracking soft and hard seeds, respectively. If long-term climatic change resulted in all seeds becoming hard, what type of selection would then operate on the finch population?

A) disruptive selection
B) directional selection
C) stabilizing selection
D) No selection would operate because the population is in Hardy-Weinberg equilibrium.

Question 39

Which of the following attributes has the least effect on the contribution an individual makes to the gene pool of the next generation?

A) more efficient at obtaining food
B) produces more offspring
C) camouflages from predators
D) spars for mating privileges

Question 40

If the original finches that had been blown over to the Galápagos Islands from South America had already been genetically different from the parental population of South American finches, even before adapting to the Galápagos, this would have been an example of

A) genetic drift.
B) the bottleneck effect.
C) the founder effect.
D) genetic drift and the founder effect.

Question 41

Please use the following information to answer the question(s) below.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
What proportion of the population is probably heterozygous (Aa) for this trait?

A) 0.05
B) 0.25
C) 0.50
D) 0.75

Question 42

Please use the following information to answer the question(s) below.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
What is the estimated frequency of allele A in the gene pool?

A) 0.25
B) 0.50
C) 0.75
D) 0.125

Question 43

Please use the following information to answer the question(s) below.
You are studying three populations of birds. Population A has 10 birds, of which 1 is brown (a recessive trait) and 9 are red. Population B has 100 birds, of which 10 are brown. Population C has 30 birds, and 3 of them are brown.
In which population would it be least likely that an accident would significantly alter the frequency of the brown allele?

A) population A
B) population B
C) population C
D) They are all the same.

Question 44

Please use the following information to answer the question(s) below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
If four of the original colonists died before they produced offspring, the ratios of genotypes could be quite different in the subsequent generations. This would be an example of

A) diploidy.
B) gene flow.
C) genetic drift.
D) disruptive selection.
E) stabilizing selection.

Question 45

Please use the following information to answer the question(s) below.
In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
With respect to the sickle-cell allele, what should be true of the β hemoglobin locus in U.S. populations of African-Americans whose ancestors were from equatorial Africa?
1) The average heterozygosity at this locus should be decreasing over time.
2) There is an increasing heterozygote advantage at this locus.
3) Diploidy is helping to preserve the sickle-cell allele at this locus.
4) Frequency-dependent selection is helping to preserve the sickle-cell allele at this locus.

A) 1 only
B) 1 and 3
C) 2 and 3
D) 1, 2, and 3
E) 1, 2, and 4

Question 46

Please use the following information to answer the question(s) below.
A large population of laboratory animals has been allowed to breed randomly for a number of generations. After several generations, 25% of the animals display a recessive trait (aa), the same percentage as at the beginning of the breeding program. The rest of the animals show the dominant phenotype, with heterozygotes indistinguishable from the homozygous dominants.
What is the most reasonable conclusion that can be drawn from the fact that the frequency of the recessive trait (aa) has not changed over time?

A) The population is undergoing genetic drift.
B) The two phenotypes are about equally adaptive under laboratory conditions.
C) The genotype AA is lethal.
D) There has been a high rate of mutation of allele A to allele a.

Question 47

Please use the following information to answer the question(s) below.
Examining the figure, which type of selection eliminates extreme frequency of individuals' phenotype?

A) directional selection
B) disruptive selection
C) stabilizing selection
D) natural selection

Question 48

Please use the following information to answer the question(s) below.
In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
Again, if this population were in equilibrium and if the sickle-cell allele is recessive, what proportion of the population should be susceptible to sickle-cell disease under typical conditions?

A) 0.04
B) 0.16
C) 0.20
D) 0.32
E) 0.80

Question 49

Please use the following information to answer the question(s) below.
In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
Considering the overall human population of the U.S. mainland at the time when the slave trade brought large numbers of people from equatorial Africa, what was primarily acting to change the frequency of the sickle-cell allele in the overall U.S. population?

A) natural selection
B) gene flow
C) genetic drift
D) founder effect
E) Two of these responses are correct.

Question 50

Please use the following information to answer the question(s) below.
HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR.
Which of the following represents the treatment option most likely to avoid the production of drug-resistant HIV (assuming no drug interactions or side effects)?

A) using a series of NAs, one at a time, and changed about once a week
B) using a single PI, but slowly increasing the dosage over the course of a week
C) using high doses of NA and a PI at the same time for a period not to exceed one day
D) using moderate doses of NA and two different PIs at the same time for several months

Question 51

Please use the following information to answer the question(s) below.
In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
The sickle-cell allele is pleiotropic (i.e., it affects more than one phenotypic trait). Specifically, this allele affects oxygen delivery to tissues and affects one's susceptibility to malaria. Under conditions of low atmospheric oxygen availability, individuals heterozygous for this allele can experience life-threatening sickle-cell "crises." Such individuals remain less susceptible to malaria. Thus, pleiotropic genes/alleles such as this can help explain why

A) new advantageous alleles do not arise on demand.
B) evolution is limited by historical constraints.
C) adaptations are often compromises.
D) chance events can affect the evolutionary history of populations.

Question 52

Please use the following information to answer the question(s) below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
Which of these is closest to the allele frequency in the founding population?

A) 0.1 a, 0.9 A
B) 0.2 a, 0.8 A
C) 0.5 a, 0.5 A
D) 0.8 a, 0.2 A
E) 0.4 a, 0.6 A

Question 53

Please use the following information to answer the question(s) below.
In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
Although selection is clearly present, if the ideal equilibrium of alleles existed, what should be the proportion of heterozygous individuals in populations that live here?

A) 0.04
B) 0.16
C) 0.20
D) 0.32
E) 0.80

Question 54

Please use the following information to answer the question(s) below.
HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR.
Every HIV particle contains two RNA molecules. If two genes from one RNA molecule become detached and then, as a unit, get attached to one end of the other RNA molecule within a single HIV particle, which of these is true?

A) There are now fewer genes within the viral particle.
B) There are now more genes within the viral particle.
C) A point substitution mutation has occurred in the retroviral genome.
D) One of the RNA molecules has experienced gene duplication as the result of translocation.

Question 55

Please use the following information to answer the question(s) below.
Examining the figure, which type of selection has two peaks of frequency of individuals?

A) directional selection
B) disruptive selection
C) stabilizing selection
D) natural selection

Question 56

Please use the following information to answer the question(s) below.
HIV's genome of RNA includes the code for reverse transcriptase (RT), an enzyme that acts early in infection to synthesize a DNA genome off of an RNA template. The HIV genome also codes for protease (PR), an enzyme that acts later in infection by cutting long viral polyproteins into smaller, functional proteins. Both RT and PR represent potential targets for antiretroviral drugs. Drugs called nucleoside analogs (NA) act against RT, whereas drugs called protease inhibitors (PI) act against PR.
In a hypothetical population's gene pool, an autosomal gene, which had previously been fixed, undergoes a mutation that introduces a new allele, one inherited according to incomplete dominance. Natural selection then causes stabilizing selection at this locus. Consequently, what should happen over the course of many generations?

A) The proportions of both types of homozygote should decrease.
B) The proportion of the population that is heterozygous at this locus should remain constant.
C) The population's average heterozygosity should decrease.
D) The two homozygotes should decrease at different rates.

Question 57

Please use the following information to answer the question(s) below.
You are studying three populations of birds. Population A has 10 birds, of which 1 is brown (a recessive trait) and 9 are red. Population B has 100 birds, of which 10 are brown. Population C has 30 birds, and 3 of them are brown.
Which population is most likely to be subject to the bottleneck effect?

A) population A
B) population B
C) population C
D) They are all equally likely.

Question 58

Please use the following information to answer the question(s) below.
In those parts of equatorial Africa where the malaria parasite is most common, the sickle-cell allele constitutes 20% of the β hemoglobin alleles in the human gene pool.
In the United States, the parasite that causes malaria is not present, but African-Americans whose ancestors were from equatorial Africa are present. What should be happening to the sickle-cell allele in the United States, and what should be happening to it in equatorial Africa?

A) stabilizing selection; disruptive selection
B) disruptive selection; stabilizing selection
C) disruptive selection; directional selection
D) directional selection; disruptive selection

Question 59

Figure 21.3
In a very large population, a quantitative trait has the distribution pattern shown in Figure 21.3. If the curve in Figure 21.3 shifts to the left or to the right, there is no gene flow, and the population size consequently increases over successive generations. Which of the following is (are) probably occurring?
1) immigration or emigration
2) directional selection
3) adaptation
4) genetic drift
5) disruptive selection

A) 1 only
B) 4 only
C) 2 and 3
D) 4 and 5
E) 1, 2, and 3

Question 60

Please use the following information to answer the question(s) below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
If one assumes that Hardy-Weinberg equilibrium applies to the population of colonists on this planet, about how many people will have attached earlobes when the planet's population reaches 10,000?

A) 100
B) 400
C) 800
D) 1,000
E) 10,000

Question 61

Natural selection changes allele frequencies because some ________ survive and reproduce more successfully than others.

A) alleles
B) loci
C) species
D) individuals

Question 62

Please use the following information to answer the question(s) below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
"Until the agricultural revolution 10,000 years ago, people used to live in small populations with little gene flow between them. That is the best situation for rapid evolution," said Sewall Wright, one of the founders of population genetics.This conclusion on gene flow conflicts with
Hardy-Weinberg equilibrium, which states that no gene flow means

A) natural selection.
B) no genetic drift.
C) no random mating.
D) no evolution.

Question 63

There are 25 individuals in population 1, all with genotype AA, and there are 40 individuals in population 2, all with genotype aa. Assume that these populations are located far from each other and that their environmental conditions are very similar. Based on the information given here, the observed genetic variation most likely resulted from

A) genetic drift.
B) gene flow.
C) nonrandom mating.
D) directional selection.

Question 64

A fruit fly population has a gene with two alleles, A1 and A2. Tests show that 70% of the gametes produced in the population contain the A1 allele. If the population is in Hardy-Weinberg equilibrium, what proportion of the flies carry both A1 and A2?

A) 0.7
B) 0.49
C) 0.42
D) 0.21

Question 65

Please use the following information to answer the question(s) below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
Mountains also have an unmatched power to drive human evolution. Starting tens of thousands of years ago, people moved to high altitudes, and there they experienced natural selection that has reworked their biology. In Tibet, for example, people have broader arteries and capillaries. In the Andes, they can dissolve more oxygen into their blood. These different traits of people who live in high altitudes illustrate

A) stabilizing evolution.
B) sexual selection.
C) adaptive evolution.
D) directional selection.

Question 66

If the nucleotide variability of a locus equals 0%, what is the gene variability and number of alleles at that locus?

A) gene variability = 0%; number of alleles = 0
B) gene variability = 0%; number of alleles = 1
C) gene variability = 0%; number of alleles = 2
D) gene variability > 0%; number of alleles = 2

Question 67

Please use the following information to answer the question(s) below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
Swine are vulnerable to infection by bird flu virus and human flu virus, which can both be present in an individual pig at the same time. When this occurs, it is possible for genes from bird flu virus and human flu virus to be combined. If the human flu virus contributes a gene for Tamiflu resistance (Tamiflu is an antiviral drug) to the new virus, and if the new virus is introduced to an environment lacking Tamiflu, then what is most likely to occur?

A) The new virus will maintain its Tamiflu-resistance gene, just in case of future exposure to Tamiflu.
B) The Tamiflu-resistance gene will undergo mutations that convert it into a gene that has a useful function in this environment.
C) If the Tamiflu-resistance gene involves a cost, it will experience directional selection leading to reduction in its frequency.
D) If the Tamiflu-resistance gene confers no benefit in the current environment and has no cost, the virus will become dormant until Tamiflu is present.

Question 68

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is

A) new mutations that occurred in the preceding generation.
B) genetic drift.
C) the reshuffling of alleles in sexual reproduction.
D) environmental effects.

Question 69

Sparrows with average-sized wings survive severe storms better than those with longer or shorter wings, illustrating

A) the bottleneck effect.
B) disruptive selection.
C) frequency-dependent selection.
D) stabilizing selection.

Question 70

Please use the following information to answer the question(s) below.
In the year 2500, five male space colonists and five female space colonists (all unrelated to each other) settle on an uninhabited Earthlike planet in the Andromeda galaxy. The colonists and their offspring randomly mate for generations. All 10 of the original colonists had free earlobes, and 2 were heterozygous for that trait. The allele for free earlobes is dominant to the allele for attached earlobes.
You are maintaining a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, you notice that the viability of the flies has decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, the best way to reverse this trend is to

A) cross your flies with flies from another lab.
B) reduce the number of flies that you transfer at each generation.
C) transfer only the largest flies.
D) change the temperature at which you rear the flies.
E) shock the flies with a brief treatment of heat or cold to make them more hardy.