Deck 23: Microevolution

Question 1

The effect of which Hardy-Weinberg condition is affected by population size?

A) selection
B) genetic drift
C) gene flow
D) mutation

Answer 1

B

Question 2

Suppose 64% of the individuals in a remote mountain village can taste phenylthiocarbamide (PTC) and must, therefore, have at least one copy of the dominant PTC taster allele. If this population conforms to Hardy-Weinberg equilibrium for this gene, what percent of the population must be heterozygous for this trait?

A) 16%
B) 32%
C) 40%
D) 48%

Answer 2

D

Question 3

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

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 3

B

Question 4

Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. One allele (T1) codes for an enzyme that makes the toxin, and another allele (T2) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The researchers measured the abundance of each of the three possible genotypes and compared those numbers to the expected numbers if the population were in Hardy-Weinberg equilibrium. Those numbers are shown in the chart.

Based on these data, which answer correctly identifies whether the population is likely in Hardy-Weinberg equilibrium?

A) Yes, the population appears to be in Hardy-Weinberg equilibrium.
B) No, there are more heterozygotes than expected.
C) No, there are more homozygotes than expected.
D) More information is needed to answer this question.

Question 5

A species of moth lays eggs on oak trees in spring and summer. Spring caterpillars eat oak flowers and look like oak flowers. Summer caterpillars eat oak leaves and look like twigs. To investigate how the same population of moths can produce such variable caterpillars, a researcher collected eggs from a population of moths and allowed them to hatch and grow under the conditions shown in the table below.

If day length causes the different development of caterpillars, which treatments will most likely produce twig-like caterpillars rather than flower-like caterpillars?

A) 1, 2, 3, and 4
B) 1, 2, 5, and 6
C) 3, 4, 7, and 8
D) 5, 6, 7, and 8

Question 6

Which of the following statements about genetic variation is accurate?

A) Genetic variation is created by the direct action of natural selection.
B) Genetic variation arises in response to changes in the environment.
C) Genetic variation must be present in a population before natural selection can act upon the population.
D) Genetic variation tends to be reduced when diploid organisms produce gametes.

Question 7

A species of moth lays eggs on oak trees in spring and summer. Spring caterpillars eat oak flowers and look like oak flowers. Summer caterpillars eat oak leaves and look like twigs. To investigate how the same population of moths can produce such variable caterpillars, a researcher collected eggs from a population of moths and allowed them to hatch and grow under the conditions shown in the table below.

Comparison of which treatments would allow the researcher to assess the effect of food type on caterpillar morphology?

A) 1, 2, 3, and 4 versus 5, 6, 7, and 8
B) 1, 3, 5, and 7 versus 2, 4, 6, and 8
C) 1, 2, 4, and 5 versus 3, 6, 7, and 8
D) 1, 3, 7, and 8 versus 2, 4, 6, and 8

Question 8

Which of the following is the best definition of evolution on the smallest scale?

A) descent with modification
B) change in allele frequencies in a population over time
C) survival of the fittest
D) inheritance of acquired characters

Question 9

If individuals tend to mate within a subset of the population, there is ________.

A) no selection
B) no genetic drift
C) abundant gene flow
D) no random mating

Question 10

A species of moth lays eggs on oak trees in spring and summer. Spring caterpillars eat oak flowers and look like oak flowers. Summer caterpillars eat oak leaves and look like twigs. To investigate how the same population of moths can produce such variable caterpillars, a researcher collected eggs from a population of moths and allowed them to hatch and grow under the conditions shown in the table below.

Which of the following statements is NOT a testable hypothesis in the described experiment?

A) Food type determines the different caterpillar morphologies.
B) Day length determines the different caterpillar morphologies.
C) Temperature determines the different caterpillar morphologies.
D) The food eaten by the female parent as a caterpillar determines the different caterpillar morphologies.

Question 11

Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. One allele (T1) codes for an enzyme that makes the toxin, and another allele (T2) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The genotypes of a random sample of 200 individuals in the population were identified as shown in the table.

Based on the genotypes in the sample, which is the best estimate of the allele frequencies in the total population?

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

Question 12

Which of the following statements best explains the need for the "2" in the 2pq term in the Hardy-Weinberg equation?

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 13

Researchers studying a small milkweed population note that some plants produce a toxin and other plants do not. They identify the gene responsible for toxin production. One allele (T1) codes for an enzyme that makes the toxin, and another allele (T2) codes for a nonfunctional enzyme that cannot produce the toxin. Heterozygotes produce an intermediate amount of toxin. The allele frequency of T1 is determined to be 0.6 and the allele frequency of T2 is 0.4. What is the expected frequency of heterozygotes if the population is in Hardy-Weinberg equilibrium?

A) 0.25
B) 0.48
C) 0.5
D) 0.65

Question 14

Which one of the following conditions would most likely cause allele frequencies to change by chance?

A) large population
B) small populations
C) mutation
D) gene flow

Question 15

Cystic fibrosis is a genetic disorder in humans where the person has two homozygous recessive alleles for the gene. If the disease is left untreated, it causes severe health problems in the individual. If 9 in 10,000 newborn babies have the disease, what are the expected frequencies of the dominant (A1) and recessive (A2) alleles according to the Hardy-Weinberg equation?

A) f(A1) = 0.9997, f(A2) = 0.0003
B) f(A1) = 0.9800, f(A2) = 0.0200
C) f(A1) = 0.9700, f(A2) = 0.0300
D) f(A1) = 0.9604, f(A2) = 0.0392

Question 16

Harmful mutations occur in both diploid and haploid organisms. Which of the following statements about the abundance of harmful mutations in diploid and haploid organisms is accurate?

A) There are more harmful mutations in populations of diploids than in populations of haploids, because the mutations are protected from selection in diploid heterozygotes.
B) There are more harmful mutations in populations of diploids than in populations of haploids, because the mutations are protected from selection in diploid homozygotes.
C) There are more harmful mutations in populations of haploids than in populations of diploids, because the mutations are protected from selection in haploid heterozygotes.
D) There are more harmful mutations in populations of haploids than in populations of diploids, because the mutations are protected from selection in haploid homozygotes.

Question 17

Which of the following statements is accurate with regard to a population in Hardy-Weinberg equilibrium?

A) Allele frequencies should not change from one generation to the next.
B) Natural selection, gene flow, and genetic drift are acting equally to change allele frequencies.
C) Two alleles are present in equal proportions.
D) Individuals within the population are evolving.

Question 18

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

A) nucleotide variability
B) chromosome number
C) average heterozygosity
D) nucleotide variability and average heterozygosity

Question 19

Which of the following situations leads to microevolution?

A) An individual bird has a beak of a particular size that grows larger during a drought.
B) Mutations in muscle cells are transferred to the next generation.
C) Alleles move between populations that differ in allele frequencies.
D) All individuals within a population have the same allele at a particular locus.

Question 20

Which of the following comparisons illustrates differences in phenotypes caused by the environment?

A) coloration of monarch butterfly wings versus. viceroy butterfly wings
B) bodies of "body builders" versus "couch potatoes"
C) black versus palomino horse coat color
D) average beak depth of birds before versus after drought

Question 21

An earthquake decimates a ground-squirrel population, killing 98% of the squirrels. The surviving population has broader stripes, on average, than the initial population. If broadness of stripes is genetically determined, which of the following processes most likely caused the change?

A) directional selection
B) disruptive selection
C) a founder event
D) a bottleneck effect

Question 22

In a Hardy-Weinberg population with two alleles A1 and A2 that are in equilibrium, the frequency of the allele A2 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 23

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 (A2A2), the same percent 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 most likely heterozygous (A1A2) for this trait?

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

Question 24

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 (A2A2), 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 (A2A2) has not changed over time?

A) The two phenotypes are about equally adaptive under laboratory conditions.
B) The genotype A1A1 is lethal.
C) There has been a high rate of mutation of allele A1 to allele A2.
D) There has been sexual selection favoring allele A2.

Question 25

A population of dark-eyed junco birds became established near the California coastline, many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails.
The coastal male junco population tails were, on average, 36% white; whereas the tails of males from the mountain populations averaged 40-45% white. Which of the following factors is the most likely original cause of the difference between the populations if the trait is inherited?

A) mutations in the coastal population
B) gene flow between populations
C) a bottleneck effect in the coastal population
D) a founder effect in the coastal population

Question 26

In peas, a gene controls flower color such that R1 = purple and R2 = white. The purple allele is dominant to the white allele. 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 27

A population of dark-eyed junco birds became established near the California coastline, many miles from the junco's normal habitat in the mixed-coniferous temperate forests in the mountains. Juncos have white outer tail feathers that the males display during aggressive interactions and during courtship displays. Males with more white in their tail are more likely to win aggressive interactions, and females prefer to mate with males with more white in their tails.
Population sizes in the coastal areas have been reasonably large, and there are significant differences between the coastal and the mountain habitats. The coastal habitat is more open (making birds more visible) and has a lower junco density (decreasing intraspecific competition) than the mountain forests. Given this information, which of the following evolutionary mechanisms is the most likely cause of the difference between the coastal and mountain populations?

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

Question 28

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 allele frequencies at many loci from all other populations, including those in their original homeland. Which of the following mechanisms most 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

Question 29

In which of the following situations would genetic drift most likely cause evolution?

A) The size of the gene pool increases because a smaller group establishes a new population.
B) Chance events cause allele frequencies to fluctuate unpredictably.
C) A sudden change in the environment drastically increases the population size.
D) The population has inherited traits better suited to a different environment.

Question 30

Over time, humans have steadily increased their movements across the continents of the Earth. Which of the following results has most likely been derived from these movements?

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

Question 31

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 (A2A2), 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 A1 in the gene pool?

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

Question 32

Studies of Neanderthal DNA revealed that there are more similarities to non-African DNA than reference sequences from West Africans. Additionally, scientists found that Neanderthal DNA is as closely related to East Asians as to Europeans. These patterns indicate that interbreeding occurred before human migration further east. Which evolutionary force most likely generated these results?

A) adaptive evolution
B) gene flow
C) genetic drift
D) nonrandom mating

Question 33

The following questions are based on information from Yeh P., Rapid evolution of a sexually selected trait following population establishment in a novel habitat, Evolution 58(1):166-74 (2004). The Hawaiian Islands are the tops of undersea volcanoes in the Pacific Ocean. The oldest islands are the northwest-most islands. The islands get progressively younger to the southeast. Hawaii, the "big island," arose from the ocean less than one million years ago. Which of the following processes likely most strongly influenced the evolution of life on the big island when organisms first arrived?

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

Question 34

In 1986, a nuclear power accident in Chernobyl, USSR (now Ukraine), led to high radiation levels for miles surrounding the plant. The high levels of radiation caused elevated mutation rates in the surviving organisms, and evolutionary biologists have been studying rodent populations in the Chernobyl area ever since. Which of the following events most likely occurred in the rodent populations following the accident?

A) Mutation caused major changes in rodent physiology over time.
B) Mutation led to increased genetic variation.
C) Mutation caused genetic drift and decreased fitness.
D) Mutation caused the fixation of new alleles.

Question 35

Which of the following results is the most likely outcome of increased gene flow between two populations?

A) lower average fitness in both populations
B) higher average fitness in both populations
C) increased genetic difference between the two populations
D) decreased genetic difference between the two populations

Question 36

Which of the following processes best describes the cause of a bottleneck effect?

A) chance events that change allele frequency
B) transfer of alleles to the next generation in proportions that differ from the current generation
C) transfer of alleles in and out of a population due to movement of fertile individuals
D) drastic decrease in the size of the population

Question 37

A scientist samples a population of butterflies and finds that 56% are heterozygous at a particular locus. If the population is in Hardy-Weinberg equilibrium, what should be the frequency of the homozygous individuals in this population?

A) 0.08
B) 0.09
C) 0.44
D) 0.70

Question 38

The value of the Hardy-Weinberg equation is that it allows scientists to perform which of the following assessments?

A) to detect whether an evolutionary force is acting on a population
B) to provide proof that natural selection is acting
C) to predict the percentage of people in a population that is homozygous for the recessive allele that causes a genetic disease
D) to measure the effects of gene flow among populations

Question 39

In a Hardy-Weinberg population with two alleles A1 and A2 that are in equilibrium, the frequency of allele A2 is 0.1. What is the frequency of individuals with A1A1 genotype?

A) 0.20
B) 0.32
C) 0.42
D) 0.81

Question 40

In a Hardy-Weinberg population with two alleles A1 and A2 that are in equilibrium, the frequency of allele A2 is 0.2. What is the frequency of individuals that are heterozygous for this allele?

A) 0.02
B) 0.04
C) 0.16
D) 0.32

Question 41

The idea of relative fitness is best exemplified in which of the following statements?

A) A deer that teaches her offspring how to avoid predators has a higher relative fitness than a deer that does not teach her offspring to avoid predators.
B) A flowering plant that attracts fewer bees that transfer pollen to other plants has higher relative fitness than a plant that attracts more pollen-transferring bees.
C) A bison that does not digest grasses efficiently has a higher relative fitness than a bison that has more efficient digestion.
D) An oak seedling that always dies when infected with a certain virus has higher relative fitness than an oak seedling that always survives the infection

Question 42

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. Which of the following statements best explains why the actual forelimbs of these mammals do not seem to be optimally arranged?

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 determined by genotype and the environment.
C) Although 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 43

Imagine a small herbaceous flowering plant whose conservation status is "endangered." Which of the following possible experiments would best test if a lack of genetic variability was partially responsible for low population numbers?

A) compare flower production rates in plants from populations that occur in dry versus moist conditions
B) compare flower production rates in small versus large plants
C) compare seed production rates in plants that are hand-pollinated with pollen from nearby individuals versus individuals 10 kilometers away
D) compare seed production rates in small versus large plants

Question 44

When a species deviates from a 50:50 sex ratio (male to female), 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. Which of the following processes most likely causes this pattern?

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

Question 45

Which of the following statements about evolutionary forces is accurate?

A) Unlike the other evolutionary forces, gene flow is the only force that causes populations to become more different.
B) Unlike the other evolutionary forces, mutation is the only force that decreases genetic variability.
C) Unlike the other evolutionary forces, nonrandom mating is the only force that changes allele frequency.
D) Unlike the other evolutionary forces, natural selection is the only force that improves the match between the organism and its environment.

Question 46

Imagine a human population with an extremely low frequency of sickle cell alleles. Which of the following changes is most likely in the human population 15 generations after introducing a mosquito population that carries the malaria parasite?

A) an increase in red blood cells without nuclei
B) a decrease in the number of mosquito bites
C) an increase in the mutation rate of the hemoglobin gene
D) an increase in the sickle cell allele

Question 47

Adult male humans generally have deeper voices than do adult female humans. Which of the following processes was most likely occurring given that 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?

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

Question 48

Which of the following reasons best explains why separate populations of a given species are likely to vary genetically from one another?

A) population sizes are likely to differ
B) gene flow increases the similarity among nearby populations
C) environmental and weather conditions vary on a small scale
D) natural selection is the only evolutionary force that improves the match between a population and its environment

Question 49

Three-spined stickleback fish (Gasterosteus aculeatus) show substantial genetic variation in gill-raker length related to differences in their diets. Longer gill rakers appear to function better for capturing open-water prey, while shorter gill rakers function better for capturing shallow-water prey. Which of the following types of selection is most likely to be found in a large lake (open water in the middle and shallow water around the sides) with a high density of these fish?

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

Question 50

Pigs are vulnerable to infection by bird flu virus and human flu virus, both of which can be present in an individual pig at the same time. When both viruses infect a pig simultaneously, 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 bird flu virus, and if this new virus is introduced to an environment lacking Tamiflu, then which of the following scenarios is most likely to occur?

A) The new virus will maintain its Tamiflu-resistance gene, 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 increase in frequency.

Question 51

A researcher has maintained a small population of fruit flies in the laboratory by transferring the flies to a new culture bottle after each generation. After several generations, the viability of the flies decreased greatly. Recognizing that small population size is likely to be linked to decreased viability, which of the following approaches would be the best way to reverse this trend of decreased viability?

A) cross the flies with flies from another lab
B) reduce the number of flies that are transferred at each generation
C) transfer only the largest flies
D) change the temperature at which the flies are reared

Question 52

Two scientists measured the snout-to-vent (anus) length of Galápagos marine iguanas (lizards) and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females. (Data from M. Wikelski and L. Michael Romero. Body size, performance and fitness in Galapagos marine iguanas. Integrative and Comparative Biology 43:376-386 [2003].)
Currently, the only predators of Galápagos marine iguanas are Galápagos hawks. Although small iguanas can sprint faster than large iguanas, iguana body size is not correlated with risk of hawk predation. If predators (for example, cats) that preferentially catch and eat slower iguanas are introduced to the island, iguana body size is likely to ________ in the absence of other factors; the iguanas would then be under ________ selection.

A) increase; directional
B) increase; disruptive
C) decrease; directional
D) decrease; disruptive

Question 53

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

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

Question 54

Two researchers measured the snout-to-vent (anus) length of Galápagos marine iguanas (lizards) and observed the percent survival of different-sized animals, all of the same age. The graph shows the log snout-vent length (SVL, a measure of overall body size) plotted against the percent survival of these different size classes for males and females. (Data from M. Wikelski and L. Michael Romero. Body size, performance and fitness in Galapagos marine iguanas. Integrative and Comparative Biology 43:376-386 [2003].)
Based on the data in the figure, what type of selection for body size appears to be occurring in these marine iguanas?

A) directional selection
B) stabilizing selection
C) disruptive selection
D) You cannot determine the type of selection from the above information.

Question 55

In a very large population, a measurable trait has the distribution pattern shown in the diagram. Assume the trait is genetically determined. If there is no gene flow and the curve shifts to the left or to the right, which of the following processes is most likely occurring?

A) immigration or emigration
B) directional selection
C) disruptive selection
D) genetic drift

Question 56

Restriction enzymes in 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, they in turn select for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. Which of the following outcomes is most likely to occur over the course of evolutionary time?

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.

Question 57

A biologist doing a long-term study on a wild spider population observes increased variation in silk thickness. Which of the following processes is the most likely to be affecting the spider population?

A) directional selection
B) stabilizing selection
C) disruptive selection
D) genetic drift

Question 58

Restriction enzymes in 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, they in turn select for bacteria whose genomes are not methylated and whose restriction enzymes instead degrade methylated DNA. Which of the following factors is most likely to cause the changes?

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

Question 59

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 the sickle cell allele is present in many African-Americans whose ancestors were from equatorial Africa. Which of the following processes are most likely acting on the sickle-cell allele in the United States, and in equatorial Africa?

A) stabilizing selection in the United States; disruptive selection in equatorial Africa
B) disruptive selection in the United States; stabilizing selection in equatorial Africa
C) directional selection in the United States; disruptive selection in equatorial Africa
D) directional selection in the United States; stabilizing selection in equatorial Africa

Question 60

In some jacana (a bird) species, males take care of the eggs and young, and females compete with each other for territories that contain one to several males. Female jacanas are significantly larger than males. Which of these statements is likely NOT an accurate description of this bird species?

A) Male jacana fitness is primarily limited by the ability to take care of eggs and raise young.
B) Female jacana fitness is limited by the number of males in her territory with which she mates.
C) Variation in reproductive success should be greater in female jacanas than in males.
D) Males and females have equal variation in reproductive success.

Question 61

One population of a species has 25 individuals, all with genotype AA; a second population of this species has 40 individuals, all with genotype aa. Assume that these populations live far apart but in similar environmental conditions. Based on this information, the observed genetic variation most likely resulted from ________.

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

Question 62

No two people are genetically identical, except for identical twins. The main source of genetic variation among humans 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 63

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 64

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

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

Question 65

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