Chapter 23: The Evolution of Populations

In the Hardy-Weinberg equation, 2pq represents __________. -the expected frequency of the recessive allele -the expected frequency of the homozygous recessive genotype -the expected frequency of the heterozygous genotype -the expected frequency of the homozygous dominant genotype -the expected frequency of the dominant allele

the expected frequency of the heterozygous genotype

In a population that is in Hardy-Weinberg equilibrium, 64% of the individuals express the recessive phenotype for a particular gene locus. What is the expected frequency of the dominant allele in this population? -0.64 -0.2 -0.04 -1 -0.8

0.2

In a population that is in Hardy-Weinberg equilibrium, 64% of the individuals express the recessive phenotype for a particular gene locus. What is the expected frequency of the recessive allele in this population? -0.64 -0.8 -0.2 -1 -0.36

0.8

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? -32% -4% -2% -16% -8%

32%

Which of the following statements correctly describe(s) characteristics of genetic drift? -It can lead to a loss of genetic variation in a population. -All of the listed responses are correct. -It is significant in small populations. -It can cause allele frequencies to change at random. -It can cause harmful alleles to become fixed in a population.

All of the listed responses are correct

Natural selection leads to adaptation, but there are many organisms on Earth that exhibit characteristics that are less than ideal for their environment. Which of the following statements correctly explain(s) this? -Selection can act only on existing variations. -Evolution is limited by historical constraints. -Adaptations are often compromises. -Chance, natural selection, and the environment interact. -All of the listed responses are correct.

All of the listed responses are correct.

Which of the following statements correctly describes a population in Hardy-Weinberg equilibrium? -Allele and genotype frequencies in the population change from generation to generation. -Allele and genotype frequencies in the population will remain constant from generation to generation. -All of the listed responses are correct. -The population is evolving. -The population exhibits no genetic variation.

Allele and genotype frequencies in the population will remain constant from generation to generation.

Which type of selection maintains stable frequencies of two or more phenotypic forms in a population? -Heterozygote advantage -Stabilizing selection -Balancing selection -Neutral variation -Directional selection

Balancing selection

Antibiotic resistance in bacteria is an example of which of the following? -Disruptive selection -Hardy-Weinberg equilibrium -Stabilizing selection -Directional selection -Macroevolution

Directional Selection

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 -Hardy-Weinberg equilibrium -Disruptive selection -Directional selection -Stabilizing selection -Balancing selection

Disruptive selection

Which type of mutation plays the most important role in increasing the number of genes in the gene pool? -Mutations are so rare that there are no mutations that can have such an important effect. -Duplication -Changes in nucleotide sequence -Point mutation -Rearrangement of gene loci

Duplication

In the context of populations, how do we define evolution? -Evolution is always caused by natural selection. -Evolution is the tendency for some individuals in a population to leave more offspring than others. -Evolution is the explanation for how organic molecules formed from inorganic molecules. -Evolution is the way in which sexual reproduction can rapidly spread advantageous traits throughout a population. -Evolution is a change in a population's allele frequencies over generations.

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

Which of the following statements explains why male peacocks with brightly colored feathers are more prevalent than those with plain colors? -Showy males are larger and kill off the plain-colored males. -Female mate choice is random, and the showier males happen to be chosen by the females as mates. -Male peacocks with showy feathers have no selective advantage over plain-colored males. -Female peacocks choose the plain-colored males as mates, causing this trait to be more prevalent in the population. -Female peacocks choose the showiest males as mates, causing this trait to be more prevalent in the population.

Female peacocks choose the showiest males as mates, causing this trait to be more prevalent in the population.

Which of the following would seem to be an example of neutral variation? -Moth coloration -Founder effect -Homozygosity of the cheetah population -Human fingerprints -Polymorphism of the Galápagos finches

Human Fingerprints

Which of the following can form entirely new alleles? -Mutation -Sexual recombination -Natural selection -Genetic drift -The environment

Mutation

Point mutations in noncoding regions of DNA result in __________. -phenotypic variation -neutral variation -molecular variability -None of the listed responses is correct. -population variation -gene variability

Neutral variation

Which of the following sets of conditions is required for Hardy-Weinberg equilibrium? -A large population, no mutations, with natural selection -Random mating, no natural selection, and a large population -No mutations, no natural selection, with sexual selection -A large population, random mutations, and no migration of alleles in or out of the population -Random mating, a small population, and no mutations

Random mating, no natural selection, and a large population

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

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

At what level does gene variability quantify genetic variation? -Species -Population -Whole-gene -Individual -Molecular

Whole-gene

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

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

The gene pool of a population consists of __________. -only the gene loci that are heterozygous -all of the genes in the females of a population -only the gene loci that are homozygous -all of the genes in a single organism -only the gene loci that exhibit variation within the population -all copies of every type of allele at every locus in all members of the population

all copies of every type of allele at every locus in all members of the population

Stabilizing selection __________. -favors intermediate variants in a population -prevents mutations from occurring -occurs when some individuals migrate to an area with different environmental conditions -occurs only in plants -usually results in two distinct phenotypes

favors intermediate variants in a population

Sexual recombination includes the shuffling of chromosomes in __________ and fertilization. -mutation -genetic drift -natural selection -meiosis -mitosis

meiosis

All of the following conditions are required for Hardy-Weinberg equilibrium except __________. -random mating -no gene flow -natural selection -a large population -no mutation

natural selection

A hurricane hits a small island, killing all but a few members of a bird population. This is an example of __________. -the founder effect -gene flow -the bottleneck effect -natural selection -random mating

the bottleneck effect

In the Hardy-Weinberg equation, q2 represents __________. -the expected frequency of the homozygous dominant genotype -the expected frequency of the dominant allele -the expected frequency of the homozygous recessive genotype -the expected frequency of the recessive allele -the expected frequency of the heterozygous genotype

the expected frequency of the homozygous recessive genotype

A storm separates a small number of birds in a migrating population. These birds end up at a destination different from where they usually migrate and establish a new population in this new area. This is an example of __________. -natural selection -mutation -the founder effect -the bottleneck effect -gene flow

the founder effect

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 individuals showing the dominant trait. When the gene frequency is reexamined at the end of the year, __________. -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 -the frequency of the homozygous dominants will go down, the frequency of the heterozygous genotype will remain the same, 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 up, and the frequency of the homozygous recessives will remain the same -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

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

The sickle-cell allele, which is recessive, causes anemia but confers resistance to malaria in individuals who possess it. However, homozygous recessive individuals often die from anemia but not from malaria, and homozygous dominant individuals do not have anemia but could die from malaria. Heterozygous individuals have the highest relative fitness. This is an example of __________. -the homozygous recessive advantage -gene flow -the heterozygote advantage -genetic drift -the homozygous dominant advantage

the heterozygote advantage

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is __________. -environmental effects -the reshuffling of alleles in sexual reproduction -geographic variation within the population -genetic drift due to the small size of the population -new mutations that occurred in the preceding generation

the reshuffling of alleles in sexual reproduction