Deck 23: The Evolution of Populations

Question 1

Phenotypic characters,such as height in humans and coat color in horses are

A)influenced by multiple genes.
B)determined by a single gene locus.
C)a result of different chromosomes producing distinct phenotypes.
D)due to the presence of different alleles, which express the dominant color.
E)due to the blending of several genes.

Answer 1

A

Question 2

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.

Answer 2

B

Question 3

The higher the proportion of loci that are "fixed" in a population,the lower is that population's

A)nucleotide variability only.
B)genetic polyploidy only.
C)average heterozygosity only.
D)nucleotide variability, average heterozygosity, and genetic polyploidy.
E)nucleotide variability and average heterozygosity only.

Answer 3

E

Question 4

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 5

Hardy-Weinberg equilibrium must occur in populations wherein

A)an allele remains fixed.
B)no genetic variation exists.
C)natural selection is not operating.
D)All three of the responses above are correct.
E)Only two of the responses above are correct.

Question 6

Little nucleotide variability results in phenotypic variation because

A)many of the differences are masked.
B)nucleotide variability is not expressed as often as gene variability.
C)many of the differences occur within introns.
D)many of the differences occur within exons.
E)nucleotide variability depends on the environment.

Question 7

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 8

How many of these statements regarding populations are true?
1)Mature males and females of a population can interbreed with each other.
2)Populations are sometimes geographically isolated from other populations.
3)Biological species are made up of populations.
4)Members of a population tend to be genetically more similar to each other than to members of other populations.
5)Populations have genomes,but not gene pools.

A)Only one of these statements is true.
B)Two of these statements are true.
C)Three of these statements are true.
D)Four of these statements are true.
E)All five of these statements are true.

Question 9

You are shown caterpillars of the moth Nemoria arizonaria.The caterpillars belong to the same species,but some of the caterpillars that were collected from oak flowers resemble oak flowers,while caterpillars collected from oak twigs resemble oak twigs.What is the most plausible explanation for the phenotypic variation?

A)Some of the caterpillars had a mutation that changed the genotype and phenotype.
B)The phenotypic variation appears to be influenced by the environment/diet.
C)Variation among individuals in this species is common, but over time one phenotype will outcompete the other phenotype.
D)The variation is due to heterozygote protection.
E)More data needs to be collected.

Question 10

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 genetic variation is dependent on environmental stimuli.

Question 11

Which of the following statements is a misconception about evolution of populations?

A)Natural selection acts on individuals.
B)Without genetic variation, evolution would not be possible.
C)Microevolution is a change in the genetic structure of a population over time.
D)For a population to evolve, individual members of the population must also evolve.
E)Most heritable variation involves quantitative characters.

Question 12

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 13

Most invertebrates have a cluster of ten similar Hox genes,all located on the same chromosome.Most vertebrates have four such clusters of Hox genes,located on four nonhomologous chromosomes.The process that could have potentially contributed to the cluster's presence on more than one chromosome was

A)binary fission.
B)translation.
C)gene duplication.
D)nondisjunction.
E)transcription.

Question 14

Rank the following one-base-point mutations (from most likely to least likely)with respect to their likelihood of affecting the structure of the corresponding polypeptide:
1)insertion mutation deep within an intron
2)substitution mutation at the third position of an exonic codon
3)substitution mutation at the second position of an exonic codon
4)deletion mutation within the first exon of the gene

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

Question 15

In modern terminology,diversity is understood to be a result of genetic variation.Which of the following is a recognized source of variation for evolution?

A)mistakes in translation of structural genes
B)mistakes in protein folding
C)rampant changes to the dictionary of the genetic code
D)binary fission
E)recombination by crossing over in meiosis

Question 16

Which of these variables is likely to undergo the largest change in value as the result of a mutation that introduces a brand-new allele into a population's gene pool at a locus that had formerly been fixed?

A)average heterozygosity
B)nucleotide variability
C)geographic variability
D)average number of loci

Question 17

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 18

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 19

During an individual organism's lifetime,which of these is most likely to help the organism respond properly to changes in its environment?

A)microevolution
B)change in allele or gene frequency
C)change in gene expression
D)change in average heterozygosity

Question 20

Although each of the following has a better chance of influencing gene frequencies in small populations than in large populations,which one most consistently requires a small population as a precondition for its occurrence?

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

Question 21

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.
E)genetic variation being preserved by diploidy.

Question 22

In the wild,male house finches (Carpodus mexicanus)vary considerably in the amount of red pigmentation in their head and throat feathers,with colours ranging from pale yellow to bright red.These colours come from carotenoid pigments that are found in the birds' diets; no vertebrates are known to synthesize carotenoid pigments.Thus,the brighter red the male's feathers are,the more successful he has been at acquiring the red carotenoid pigment by his food-gathering efforts (all other factors being equal).During breeding season,one should expect female house finches to prefer to mate with males with the brightest red feathers.Which of the following is true of this situation?

A)Alleles that promote more efficient acquisition of carotenoid-containing foods by males should increase over the course of generations.
B)Alleles that promote more effective deposition of carotenoid pigments in the feathers of males should increase over the course of generations.
C)There should be directional selection for bright red feathers in males.
D)Three of the statements are correct.
E)Two of the statements are correct.

Question 23

Mutation is the only evolutionary mechanism that

A)introduces new alleles into the population.
B)is more important in eukaryotes than in prokaryotes.
C)occurs frequently in all populations.
D)has no effect on genetic variation/evolution.
E)A and C

Question 24

Sexual dimorphism is most often a result of

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

Question 25

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,thereby producing a genetically distinctive virus,which can subsequently cause widespread disease.The production of new types of flu virus in the manner described above is most similar to the phenomenon of

A)bottleneck effect.
B)founder effect.
C)natural selection.
D)gene flow.
E)sexual selection.

Question 26

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.
E)Mutations occur when directed by the good of the species; natural selection edits out harmful mutations and causes populations to adapt to the beneficial mutations.

Question 27

In a Hardy-Weinberg population with two alleles,A and a,that are in equilibrium,the frequency of allele a is 0.1.What is the frequency of individuals with AA genotype?

A)0)20
B)0)32
C)0)42
D)0)81
E)Genotype frequency cannot be determined from the information provided.

Question 28

The Hardy-Weinberg equilibrium theorem

A)applies to extremely small populations that are subject to genetic drift.
B)describes two or more populations that interbreed with one another.
C)applies to populations that exhibit low rates of mutation.
D)describes a hypothetical population that is not evolving.
E)applies to populations that show differential survival and reproductive success.

Question 29

During breeding season,one should expect female house finches to prefer to mate with males with the brightest red feathers.Which of the following terms are appropriately applied to this situation?

A)sexual selection
B)mate choice
C)intersexual selection
D)Three of the responses are correct.
E)Two of the responses are correct.

Question 30

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 31

Arrange the following from most general (i.e.,most inclusive)to most specific (i.e.,least inclusive):
1 natural selection
2)microevolution
3)intrasexual selection
4)evolution
5)sexual selection

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

Question 32

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 percentage of the population that is homozygous for this allele?

A)0)09
B)0)49
C)0)9
D)9)0
E)49.0

Question 33

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.Over the course of evolutionary time,what should occur?

A)Methylated DNA should become fixed in the gene pools of bacterial species.
B)Nonmethylated DNA should become fixed in the gene pools of bacteriophages.
C)Methylated DNA should become fixed in the gene pools of bacteriophages.
D)Methylated and nonmethylated strains should be maintained among both bacteria and bacteriophages, with ratios that vary over time.
E)Both the first and second responses are correct.

Question 34

The Dunkers are a religious group that moved from Germany to Pennsylvania in the mid-1700s.They do not marry with members outside their own immediate community.Today,the Dunkers are genetically unique and differ in gene frequencies,at many loci,from all other populations including those in their original homeland.Which of the following likely explains the genetic uniqueness of this population?

A)population bottleneck and Hardy-Weinberg equilibrium
B)heterozygote advantage and stabilizing selection
C)mutation and natural selection
D)founder effect and genetic drift
E)population bottleneck and stabilizing selection

Question 35

You sample a population of butterflies and find that 56% are heterozygous at a particular locus.What should be the frequency of the recessive allele in this population?

A)0)07
B)0)08
C)0)09
D)0)70
E)Allele frequency cannot be determined from this information.

Question 36

The three main mechanisms that alter allele frequencies and change the genetic composition of populations are

A)natural selection, bottleneck effect, and founder effect.
B)natural selection, gene flow, and random mating.
C)natural selection, genetic drift, and gene flow.
D)natural selection, random mating, and gene flow.
E)natural selection, gene flow, and large population size.

Question 37

In peas,a gene controls flower colour 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 38

If the original finches that had been blown over to the Galápagos 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)bottleneck effect.
C)founder effect.
D)all three of these.
E)both the first and third of these.

Question 39

In a Hardy-Weinberg population with two alleles,A and a,that are in equilibrium,the frequency of allele a is 0.2.What is the percentage of the population that is heterozygous for this allele?

A)0)2
B)2)0
C)4)0
D)16.0
E)32.0

Question 40

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.
E)requires that populations become better suited to their environments.

Question 41

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 42

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 43

Which of the following is a fitness trade-off (compromise)?

A)In some hornbill species, the male helps seal the female in a tree with her nest until the young are ready to fledge.
B)Hummingbirds are the best pollinators of certain flowers, but bees are the best pollinators for orchids.
C)The strong, thick beak of a woodpecker helps it find insects in trees.
D)Turtle shells provide protection but are heavy and burdensome when moving.
E)Fruit bats are better pollinators of native fruit trees than birds are.

Question 44

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 45

Which of the following is most likely to produce an African butterfly species in the wild whose members have one of two strikingly different colour patterns?

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

Question 46

Use the following figure to answer the questions below.
In a very large population,a quantitative trait has the following distribution pattern:

If the curve in the above figure 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 47

Anopheles mosquitoes,which carry the malaria parasite,cannot live above elevations of 1800 metres.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 793 metres above sea level and its peak is 5895 metres 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 48

The recessive allele that causes phenylketonuria (PKU)is harmful,except when an infant's diet lacks the amino acid phenylalanine.What maintains the presence of this harmful allele in a population's gene pool?

A)heterozygote advantage
B)stabilizing selection
C)diploidy
D)balancing selection

Question 49

Use the following figure to answer the questions below.
In a very large population,a quantitative trait has the following distribution pattern:

What is true of the trait whose frequency distribution in a large population appears in the previous figure? It has probably undergone

A)directional selection.
B)stabilizing selection.
C)disruptive selection.
D)normal selection.

Question 50

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 51

Blue light is that portion of the visible spectrum that penetrates the deepest 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 1000 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 following graphs 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?

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

Question 52

If global warming permits mosquitoes to live at higher altitudes than they currently do,then in which direction should the entire plot in the correct distribution below be shifted?
A)
B)
C)
D)

A)to the right
B)to the left
C)upward
D)downward

Question 53

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 54

When imbalances occur in the sex ratio of sexual species that have two sexes (i.e.,other than a 50:50 ratio),the members of the minority sex often receive a greater proportion of care and resources from parents than do the offspring of the majority sex.This is most clearly an example of

A)sexual selection.
B)disruptive selection.
C)balancing selection.
D)stabilizing selection.
E)frequency-dependent selection.

Question 55

In Kluane National Park,red squirrels have been recorded giving birth 18 days earlier than a decade ago.Offspring born earlier become larger and more likely to survive.What mode of selection best describes these current research findings?

A)stabilizing selection
B)directional selection
C)disruptive selection
D)transitional selection
E)Selection will vary depending on temperature and amount of snow in spring.

Question 56

There are those who claim that the theory of evolution cannot be true because the apes,which are supposed to be closely related to humans,do not likewise share the same large brains,capacity for complicated speech,and tool-making capability.They reason that if these features are generally beneficial,then the apes should have evolved them as well.Which of these provides the best argument against this misconception?

A)Advantageous alleles do not arise on demand.
B)A population's evolution is limited by historical constraints.
C)Adaptations are often compromises.
D)Evolution can be influenced by environmental change.

Question 57

Which of the following statements about sexual selection is not true?

A)Mate (female)choice often leads to exaggerated traits in males.
B)Sexual selection often results in sexual dimorphism.
C)Male-male competition is an example of intrasexual selection.
D)Sexual selection has nothing to do with natural selection because sexual selection is not adaptive.
E)Evidence suggests that females choose mates based on traits that indicate "good genes."

Question 58

The same gene that causes various coat patterns in wild and domesticated cats also causes the 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.
E)In all environments, coat pattern is a more important survival factor than is eye-muscle tone.

Question 59

A proficient engineer can easily design skeletal structures that are more functional than those currently found in the forelimbs of such diverse mammals as horses,whales,and bats.The actual forelimbs of these mammals do not seem to be optimally arranged because

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 60

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 one excludes the involvement of gender in the situation,then the pattern that is apparent in the fossil record is most similar to one that should be expected from

A)pansexual selection.
B)directional selection.
C)disruptive selection.
D)stabilizing selection.
E)asexual selection.

Question 61

Use the following information to answer the questions 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 62

Use the following information to answer the questions 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 63

Use the following information to answer the questions 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 the responses are correct.

Question 64

Use this information to answer the following questions.
You are studying three populations of birds.Population A has ten birds,of which one is brown (a recessive trait)and nine are red.Population B has 100 birds,of which ten are brown.Population C has 30 birds,and three 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.
E)It is impossible to tell from the information given.

Question 65

Use the following information to answer the questions 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.
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 66

Use this information to answer the following questions.
You are studying three populations of birds.Population A has ten birds,of which one is brown (a recessive trait)and nine are red.Population B has 100 birds,of which ten are brown.Population C has 30 birds,and three 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.
E)It is impossible to tell from the information given.

Question 67

Use this information to answer the following questions
Many species once roamed across large areas of continents,and for millions of years these species were "shaped" by their environment.Today,numerous species,especially large carnivores,are found in national parks and nature reserves that are isolated by hundreds or thousands of kilometres of land now occupied by humans.The cheetah is one example of a species that has shown several dramatic decreases in numbers over time,and now occupies a small fraction of its historic range.
Captive breeding programs have the potential to save species from extinction.Which factor(s)do biologists working with captive cheetahs have to pay particular attention to and why?

A)gene flow, because it is necessary to interbreed the different populations with one another
B)gene flow, because it will lead to stabilizing selection
C)genetic drift, because small populations are very susceptible to loss of genetic variation and fixation of deleterious alleles
D)genetic drift, because it may lead to allele frequencies changing randomly and may lead to an increase in heterozygosity
E)Two of the above statements are correct.

Question 68

The following questions refer to the following paragraph.
HIV's genome of RNA includes the code for reverse transcriptase (RT),an enzyme that acts early in infection to synthesize a DNA genome from 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 analogues (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 69

The following questions refer to the following paragraph.
HIV's genome of RNA includes the code for reverse transcriptase (RT),an enzyme that acts early in infection to synthesize a DNA genome from 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 analogues (NA)act against RT,whereas drugs called protease inhibitors (PI)act against PR.
Within the body of an HIV-infected individual who is being treated with a single NA,and whose HIV particles are currently vulnerable to this NA,which of these situations can increase the relative fitness of the virus?
1)mutations resulting in RTs with decreased rates of nucleotide mismatch
2)mutations resulting in RTs with increased rates of nucleotide mismatch
3)mutations resulting in RTs that have proofreading capability

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

Question 70

Use this information below to answer the following questions.
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.
E)There has been sexual selection favouring allele a.

Question 71

The following questions refer to the following paragraph.
HIV's genome of RNA includes the code for reverse transcriptase (RT),an enzyme that acts early in infection to synthesize a DNA genome from 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 analogues (NA)act against RT,whereas drugs called protease inhibitors (PI)act against PR.
HIV has nine genes in its RNA genome.Every HIV particle contains two RNA molecules,and each molecule contains all nine genes.If,for some reason,the two RNA molecules within a single HIV particle do not have identical sequences,then which of these terms can be applied due to the existence of the nonidentical regions?

A)homozygous
B)gene variability
C)nucleotide variability
D)average heterozygosity
E)All but one of the responses are correct.

Question 72

Use the following figure to answer the questions below.
In a very large population,a quantitative trait has the following distribution pattern:

What would be the most probable cause for a population depicted in the figure above to shift both to the left and to the right?

A)when large size is important
B)when there is an extreme environmental change
C)when there are few predators
D)when there are differences in the size of food items available to members of the same species
E)when the more common alleles are lost

Question 73

The following questions refer to the following paragraph.
HIV's genome of RNA includes the code for reverse transcriptase (RT),an enzyme that acts early in infection to synthesize a DNA genome from 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 analogues (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)The retroviral equivalent of crossing over has occurred, no doubt resulting in a heightened positive effect.
E)One of the RNA molecules has experienced gene duplication as the result of translocation.

Question 74

The following questions refer to the following paragraph.
HIV's genome of RNA includes the code for reverse transcriptase (RT),an enzyme that acts early in infection to synthesize a DNA genome from 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 analogues (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 75

Use this information to answer the following questions
Many species once roamed across large areas of continents,and for millions of years these species were "shaped" by their environment.Today,numerous species,especially large carnivores,are found in national parks and nature reserves that are isolated by hundreds or thousands of kilometres of land now occupied by humans.The cheetah is one example of a species that has shown several dramatic decreases in numbers over time,and now occupies a small fraction of its historic range.
Which of the following statements would most likely apply to cheetahs currently found in Kenya and South Africa?

A)Certain alleles may be under- or over-represented in cheetah populations.
B)Cheetah populations likely passed through several bottlenecks, which may have been caused by factors such as disease, competition with other predators, overhunting, poaching, and habitat loss.
C)Over time, reduced gene flow between the isolated populations would lead to aggressive encounters if the separated populations were brought together.
D)Natural selection has much more impact on large populations than on small populations.
E)A and B

Question 76

Use this information below to answer the following questions.
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 77

Use this information below to answer the following questions.
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

Question 78

Use the following information to answer the questions 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.
If the sickle-cell allele is recessive,what proportion of the population should be susceptible to sickle-cell anemia under typical conditions?

A)0)04
B)0)16
C)0)20
D)0)32
E)0)80

Question 79

Use this information to answer the following questions.
You are studying three populations of birds.Population A has ten birds,of which one is brown (a recessive trait)and nine are red.Population B has 100 birds,of which ten are brown.Population C has 30 birds,and three of them are brown.
Which population is most likely to be subject to genetic drift?

A)population A
B)population B
C)population C
D)It would depend on the severity of a natural disaster.
E)The population with the higher number of dispersing individuals.

Question 80

Use the following information to answer the questions 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
E)directional selection; stabilizing selection