Chapter 23 Practice Test

In the context of populations, how do we define evolution?

Evolution is a change in a population’s allele frequencies over generations.

Which of the following mechanisms can alter allele frequencies?

A)Genetic drift
B) Gene flow
C) Natural selection
D) All are correct

D) All of the listed responses are correct.

Describe the average heterozygosity.

Average heterozygosity refers to the average percentage of loci that are heterozygous in a population.

The human genome consists of approximately 3 billion base pairs. If humans typically differ from one another by about 3 million base pairs, what is the nucleotide variability of Homo sapiens?

0.1%

Which example below would most likely exhibit a cline?

A) Cows are selectively bred to gain a higher milk yield.
B) Male bowerbirds decorate stations to attract females.
C) Rabbits that live in colder regions tend to have smaller ears than rabbits of the same species that live in warmer regions. D) Individuals who are heterozygotic for the sickle-cell disease allele have a greater resistance to malaria.
E) Seals have flippers that make them great swimmers, but make their movements on rocks and land very cumbersome.

Rabbits that live in colder regions tend to have smaller ears than rabbits of the same species that live in warmer regions.

Which of the following can form entirely new alleles?

A) Mutation
B) Natural selection
C) Genetic drift
D) The environment
E) Sexual recombination

mutation

Sexual recombination includes the shuffling of chromosomes in _____ and fertilization.

A) Mutation
B) Genetic drift
C) Mitosis
D) Meiosis
E) Natural selection

meiosis

Which type of mutation plays the most important role in increasing the number of genes in the gene pool?

A) Duplication
B) Rearrangement of gene loci
C) Point mutation
D) Mutations are so rare that there are no mutations that can have such an important effect.
E) Changes in nucleotide sequences.

duplication

In a large population of randomly breeding organisms, the frequency of a recessive allele is initially 0.3. There is no migration and no selection. Humans enter this ecosystem and selectively hunt individual showing the dominant trait. When the gene frequency is reexamined at the end of the year, _____.

A) The frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will remain the same, and the frequency of the recessives will go up.
B) the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go up
C) The frequency of the homozygous dominants will go up, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go down
D) The frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will go up, and the frequency of the homozygous recessives will remain the same
E) The frequency of the homozygous dominants will go up, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go up

the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go up

In the Hardy-Weinberg equation, p2 represents _____.

A) The expected frequency of homozygous dominant individuals in the population
B) The frequency of homozygous recessive individuals in the population
C) The frequency of dominant alleles in the population
D) The frequency of heterozygous dominant individuals in the population
E) The total alleles in the gene pool

the expected frequency of homozygous dominant individuals in the population

In a large population of bonobos, the frequency of the recessive allele is initially 0.1. There is no migration and no selection. What is the frequency of the dominant allele? Assume that there are two alleles of this gene.
A) 50%
B) 20%
C) 99%
D) 10%
E) 90%

90%

In a population in Hardy-Weinberg equilibrium, 1% of the individuals in a population show the recessive trait of a certain characteristic. In this situation, what is the value of p?
A) 99%
B) 0.9
C) 0.18
D) The answer cannot be determined from the information given.
E) 0.81

0.9

In the equation for Hardy-Weinberg equilibrium, 1 represents _____.

A) The frequency of homozygous recessive individuals in the population
B) The frequency of homozygous dominant individuals in the population
C) The frequency of heterozygous individuals in the populations
D) All the possible phenotypes in the population
E) The sum of the frequencies of the genotypes for a particular gene locus

the sum of the frequencies of the genotypes for a particular gene locus

Approximately 1 out of every 2,500 Caucasians in the United States is born with the recessive disease cystic fibrosis. According to the Hardy-Weinberg equilibrium equation, approximately what percentage of people are carriers?
A) about .08%
B) about 2%
C) about 96%
D) about 10%
E) about 4%

about 4%

In a certain group of African people, 4% are born with sickle-cell disease (homozygous recessive). If this group is in Hardy-Weinberg equilibrium, what percentage of the group has the selective advantage of being more resistant to malaria (heterozygous) than those individuals who are homozygous for normal hemoglobin or for sickle-cell disease?
A) 2%
B) 16%
C) 4%
D) 8%
E) 32%

32%

Assume a population in Hardy-Weinberg equilibrium for a character trait with these genotypic frequencies: AA = 0.25, Aa = 0.50, and aa = 0.25. If you remove all the homozygous dominants and allow the remaining population to reproduce (again under Hardy-Weinberg conditions), what will be the frequency of homozygous dominants in the next generation?
A) 0.22
B) 0.44
C) 0
D) 0.11
E) 0.50

0.11

Which of the following sets of conditions is required for Hardy-Weinberg equilibrium?

A) Random mating, no natural selection, and a large population.
B) Random mating, a small population, and no mutations
C) No mutations, no natural selection, with sexual selection
D) A large population, no mutations, with natural selection
E) A large population, random mutations, and no migration of alleles in or out of the population

random mating, no natural selection, and a large population

_____ and _____ generate variation, whereas _____ results in an adaptation to the environment.

A) Sexual recombination … natural selection … overproduction
B) Mutation … sexual recombination … natural selection
C) Overproduction of offspring … mutation … sexual recombination
D) Natural selection … mutation … sexual recombination
E) Genetic drift … natural selection … mutation

Mutation … sexual recombination … natural selection

A population of 15 birds inhabits a fairly new island. Ten of the birds are dark brown and five of them are light brown. By chance, two of the dark brown birds and three of the light brown birds die before producing any offspring. All of the birds in the next generation are dark brown. This change in phenotypic frequency can be attributed to _____.

A) Natural selection
B) Sexual selection
C) Genetic drift
D) A cline
E) Gene flow

genetic drift

An earthquake hits a small island. All but a small group of closely related lizards are eliminated, and the survivors spread out over the island. This is an instance of _____.

A)Natural selection
B) Founder effect
C) Mutation
D) Bottleneck effect
E) Gene flow

bottleneck effect

Which of the following scenarios would most likely result in the microevolution of a population of humans?

A) The incidence of skin cancer in adults over age 40 rises significantly.
B) All of the listed responses are correct.
C) Hundreds of thousands of people are killed in a natural disaster.
D) A colony of humans on the moon is isolated from Earth.
E) Only random mating takes place among all the people that reproduce in North America.

A colony of humans on the moon is isolated from Earth.

Which of the following is the best example of gene flow?

A) Wind blows pollen from one population of plants to another and cross-fertilization occurs.
B) Genes are shuffled by the crossing over of chromosomes during meiosis.
C) A fire drastically reduces the size of a white-tailed deer population. The remaining individuals spread out throughout the remaining forest.
D) A small population of humans colonizes a newly formed island.
E) An earthquake results in the formation of a canyon, splitting a population of toads apart.

Wind blows pollen from one population of plants to another and cross-fertilization occurs.

Which of the following most accurately measures an organism’s fitness?

A) Its ability to withstand environmental extremes
B) Its mutation rate
C) How many fertile offspring it produces
D) How strong the organism is when pitted against others of its species
E) How much food it is able to make or obtain

how many fertile offspring it produces

Antibiotic resistance in bacteria is an example of which of the following?

A) Stabilizing selection
B) Hardy-Weinberg equilibrium
C) Macroevolution
D) Directional selection
E) Disruptive selection

directional selection

For several years, scientists have warned doctors of the danger of overprescribing antibiotics such as penicillin. Scientists are concerned because _____.

A) The drugs will be metabolized more quickly by our bodies, decreasing their effectiveness
B) Strains of microorganisms that are resistant to these drugs will be selected for
C) The organisms that produce many of the antibiotics are overexploited and could become extinct
D) Humans will become tolerant to the effects of drugs
E) None of the listed responses is correct.

strains of microorganisms that are resistant to these drugs will be selected for

A population of squirrels is preyed on by small hawks. The smaller squirrels can escape into burrows. The larger squirrels can fight off the hawks. After several generations, the squirrels in the area tend to be very small or very large. What process is responsible for this outcome?

A) Stabilizing selection
B) Disruptive selection
C) Directional selection
D) Balancing selection
E) Hardy-Weinberg equilibrium

disruptive selection

Stabilizing selection _____.

A) Usually results in two distinct phenotypes
B) Occurs only in plants
C) Prevents mutations from occurring
D) Occurs when some individuals migrate to an area with different environmental conditions
E) Favors intermediate variants in a population

favors intermediate variants in a population

Birds with average-size wings survived a severe storm more successfully than other birds in the same population with longer or shorter wings. If severe storms occur regularly, then over time, one should expect these storms to bring about _____.

A) Stabilizing selection
B) Directional selection
C) The bottleneck effect
D) Gene flow
E) Disruptive selection

stabilizing selection

Tay-Sachs disease, which is lethal, results from having the homozygous recessive condition of the responsible gene. Which of the following statements is true?

A) Homozygous dominant individuals will be more likely to reproduce than heterozygous individuals.
B) Because homozygous recessive individuals die, the recessive allele will eventually be lost from the population.
C) Only homozygous dominant individuals will be able to survive and reproduce.
D) Heterozygous individuals will survive and may pass the recessive allele on to their offspring.
E) In the heterozygous condition, the dominant allele will overcome the recessive allele and only the dominant allele will be passed on to offspring.

Heterozygous individuals will survive and may pass the recessive allele on to their offspring.

Which type of selection maintains stable frequencies of two or more phenotypic forms in a population?

A) Balancing selection
B) Neutral variation
C) Stabilizing selection
D) Directional selection
E) Heterozygote advantage

balancing selection

Which of the following would seem to be an example of neutral variation?

A) Polymorphism of the Gálapagos finches
B) Human fingerprints
C) Founder effect
D) Moth coloration
E) Homozygosity of the cheetah population

human fingerprints

What is the importance of neutral variation in evolution?

A) DNA forensics relies on neutral variation among humans.
B) Neutral variation increases genetic variation, allowing a population to carry more alleles that may help it respond to environmental change.
C) Many mutations are silent and do not affect the amino acid that is coded for.
D) Neutral variation is usually removed from the population by natural selection because it does not confer an advantage in the current environment.
E) Relative frequencies of neutral variations are controlled by natural selection.

Neutral variation increases genetic variation, allowing a population to carry more alleles that may help it respond to environmental change.

Selection that acts over evolutionary time to preserve traits that increase an individual’s ability to mate is known as _____.

A) Disruptive selection
B) Balancing selection
C) Stabilizing selection
D) Sexual selection
E) Directional selection

sexual selection

Which statement below is true about sexual selection?

A) Sexual selection can result in sexual dimorphism—marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction.
B)Intrasexual selection leads to the death of most unfit males in combat.
C) Showy secondary sexual characteristics cannot be explained because they break all of the rules of natural selection.
D) There is no evidence that intrasexual selection takes place between females.
E) In most vertebrates, females court the males.

Sexual selection can result in sexual dimorphism—marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction.

How does natural selection fashion organisms?

A) Chance and the environment interact with natural selection, so that the best available traits are selected for.
B) Sexual selection acts to make organisms better adapted to their environments.
C) Brand new body plans arise often, giving natural selection many new possibilities to work with.
D) The best traits for the current environment arise in the population and are selected for.
E) Neutral traits are often selected for because they will eventually produce alleles that confer an advantage.

Chance and the environment interact with natural selection, so that the best available traits are selected for.

A number of mosquito populations today are resistant to insecticides that were once quite effective. Biologists think that insecticide resistance evolved in mosquitoes because _____.

A) Individual mosquitoes built up an immunity to an insecticide after being exposed to it
B) A new allele developed in response to the insecticide that provided future generations the benefit of resistance
C) Mosquitoes needed to develop insecticide resistance to survive after the insecticide was used
D) A few mosquitoes were probably resistant to the insecticide before it was ever used, and these individuals were more likely to survive and reproduce
E) Mosquitoes attempted to adapt to their environment

a few mosquitoes were probably resistant to the insecticide before it was ever used, and these individuals were more likely to survive and reproduce