Deck 21: The Evolution of Populations

Question 1

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.

Answer 1

D

Question 2

It is estimated by a wide body of scientists that in recent decades we have begun another mass extinction event on Earth.Amphibians in particular have been in decline,sometimes due to climate change,and they therefore provide a possible early sign of dramatic biodiversity change to come.With respect to climate change and natural selection acting upon a population of one species of frog in a tropical rain forest,mutations of DNA sequences of the frog genome that are inherited by offspring

A)could either be beneficial or harmful.
B)will primarily be harmful.
C)may have no effect at all,be beneficial,or be harmful.
D)will only speed the decline and extinction of the species.

Answer 2

C

Question 3

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%.

Answer 3

C

Question 4

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

A)Phenotypes can vary depending upon environment
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 5

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 6

A mutation that is neither harmful nor beneficial is termed a

A)point mutation.
B)silent mutation.
C)deleterious mutation.
D)heterozygote advantage.

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 based upon parental gametes.
C)the population is doubling in number.
D)heterozygotes have two alleles.

Question 8

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 9

Which of the following consistently improves the degree to which organisms are well suited for life in their environment?

A)adaptation
B)natural selection
C)gene flow
D)genetic drift

Question 10

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

Question 11

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 a mechanism of how organisms could transmit discrete,heritable units to offspring
C)by explaining the natural selection of genetic differences among offspring
D)by leading to an evolutionary change

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

Which of the following is correct about 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 when diploid organisms produce gametes and reproduce.
E)A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.

Question 14

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

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

Question 15

When evolution occurred on the Galápagos Islands,the finch beaks

A)of individual birds in the population changed size and shape between the time of fledging the nest and adulthood due to the environmental stress induced by drought.
B)varied in size across the population and sometimes conferred benefits in feeding,survivorship,and reproduction that were passed down to surviving offspring.
C)had corresponding genetic codes in the DNA that were modified or mutated by individuals when attempting to survive the stressful environment of the drought.
D)changed in size and depth only during the lifetime of the fittest birds able to survive the drought.

Question 16

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 17

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 18

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 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

Recent research investigating variation in human height have found that a variety of genes at different loci,as well as early nutrition,especially that of the mother during gestation (the period of time during development of a fetus)and childhood years,influence height.Given this information,which of the following is correct?

A)Phenotypes are directly linked to genotypes and not influenced externally.
B)Phenotypes are usually the result of a combination of genes as influenced by the environment.
C)One phenotypic trait is usually related to one gene.
D)For human height,the environment is more influential than inheritance of particular alleles.

Question 21

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 22

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 23

The frequency of a disease is 30/1000.This is a disease that follows a dominant/recessive pattern of inheritance on one gene (where the only affected individuals are all homozygous recessive).What is the frequency of the disease genotype q²?

A)3%
B)13%
C)6%
D)30%

Question 24

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 25

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

Question 26

When using the Hardy-Weinberg equilibrium model,we assume that

A)the population is infinitely large.
B)the population under study has experienced gene flow.
C)the population has passed through a bottleneck.
D)natural selection is not occurring.

Question 27

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 28

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 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

Evolution of a gene

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 for that particular gene.
D)requires the operation of natural selection.

Question 31

Imagine you predict a particular frequency for a genotype,based upon detailed knowledge of that genotype frequency in population "X" of a species.Then,using the Hardy-Weinberg model,you find that the observed genotype frequency in a different population,named "Y" of the same species,is not significantly different from what you predicted/expected based on population "X."
Which of the following should you conclude?

A)The particular gene of interest is not undergoing any mechanisms of evolution.
B)Population Y must have diverged,and macroevolution has occurred.
C)Population Y is undergoing mutation,natural selection,genetic drift,and gene flow.
D)The particular gene of interest is evolving through some mechanism.

Question 32

The Hardy-Weinberg equation p² + 2pq + q² = 1 allows you to calculate

A)population declines.
B)genotype frequencies.
C)genome frequencies.
D)population abundance and mating patterns.

Question 33

If the original finches that flew 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 34

Why is the Hardy-Weinberg model useful?

A)It allows you to calculate genotype frequencies of a population and compare them to what was expected under the assumptions.
B)It is used under the assumption that natural selection is occurring,thus providing a quantitative method to detect genetic drift in a population.
C)It allows you to get an accurate count of the total population size.
D)It allows you to get a total count of all individuals in a population and compare those values to an equilibrium.

Question 35

Phenylketonuria (PKU)is a birth defect that causes an amino acid called phenylalanine to build up in the body.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 36

In a population of 200 mice,brown fur is dominant to gray fur.If 120 of the 200 mice have brown fur,what is the frequency of mice that are heterozygous?

A)46%
B)23%
C)37%
D)63%

Question 37

"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 the 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 38

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 39

In a population of 200 seagulls,dark brown feathers are dominant to having only white feathers.If 160 of the 200 seagulls have brown feathers,what is the frequency of seagulls that are homozygous dominant?

A)31%
B)55%
C)49%
D)25%

Question 40

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 41

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 42

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 43

Please use the following information to answer the questions 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 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 44

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 45

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 46

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?

A)immigration or emigration only
B)genetic drift only
C)directional selection and adaptation
D)genetic drift and disruptive selection
E)immigration or emigration,directional selection,and adaptation

Question 47

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 48

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 49

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 50

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 51

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 52

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 53

Please use the following information to answer the questions 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 54

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 55

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 56

Sexual dimorphism is most often a result of

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

Question 57

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 58

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)acclimatization.

Question 59

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 60

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 61

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 62

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 63

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 64

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 65

Please use the following information to answer the questions 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

Question 66

Please use the following information to answer the questions 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 67

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 an individual'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 68

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 69

Although selection is clearly present,if the ideal equilibrium of alleles existed,what should be the proportion of heterozygous individuals in populations who live here?

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

Question 70

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

Question 71

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 72

If you assume 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 73

Please use the following information to answer the questions 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 74

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

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

Question 75

There are 25 individuals in population 1,all with genotype AA,and there are 40 individuals in population 2,all with genotype aa.Assume 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 76

Please use the following information to answer the questions 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

Question 77

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 78

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 79

Please 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 ? hemoglobin alleles in the human gene pool.

-With respect to the sickle-cell allele,what should be true of the ? 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 80

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 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.