CH 23

Which type of selection maintains stable frequencies of two or more phenotypic forms in a population? A)Balancing selection B)Neutral variation C)Directional selection D)Heterozygote advantage E)Stabilizing selection

A)Balancing selection

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

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

Which of the following can form entirely new alleles? A)Mutation B)The environment C)Sexual recombination D)Genetic drift E)Natural selection

A)Mutation

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

A)Random mating, no natural selection, and a large population

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)Showy secondary sexual characteristics cannot be explained because they break all of the rules of natural selection. C)There is no evidence that intrasexual selection takes place between females. D)Intrasexual selection leads to the death of most unfit males in combat. E)In most vertebrates, females court the males.

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

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)An earthquake results in the formation of a canyon, splitting a population of toads apart. C)A fire drastically reduces the size of a white-tailed deer population. The remaining individuals spread out throughout the remaining forest. D)Genes are shuffled by the crossing over of chromosomes during meiosis. E)A small population of humans colonizes a newly formed island.

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

In the Hardy-Weinberg equation, 2pq represents __________. A)the expected frequency of the heterozygous genotype B)the expected frequency of the homozygous dominant genotype C)the expected frequency of the recessive allele D)the expected frequency of the homozygous recessive genotype E)the expected frequency of the dominant allele

A)the expected frequency of the heterozygous genotype

In the Hardy-Weinberg equation, q2 represents __________. A)the expected frequency of the homozygous recessive genotype B)the expected frequency of the homozygous dominant genotype C)the expected frequency of the dominant allele D)the expected frequency of the heterozygous genotype E)the expected frequency of the recessive allele

A)the expected frequency of the homozygous recessive genotype

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 __________. A)the heterozygote advantage B)genetic drift C)the homozygous recessive advantage D)the homozygous dominant advantage E) Gene flow

A)the heterozygote advantage

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

A)the reshuffling of alleles in sexual reproduction

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? A)Evolution is limited by historical constraints. B)Adaptations are often compromises. C)Selection can act only on existing variations. D)Chance, natural selection, and the environment interact. E)All of the listed responses are correct.

All of the listed responses are correct.

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? A)0.04 B)0.2 C)0.8 D)1 E)0.64

B)0.2

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)8% B)32% C)2% D)4% E)16%

B)32%

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

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

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

B)Duplication

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

B)natural selection

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

C)All of the listed responses are correct.

Which of the following would seem to be an example of neutral variation? A)Moth coloration B)Polymorphism of the Galápagos finches C)Human fingerprints D)Homozygosity of the cheetah population E)Founder effect

C)Human fingerprints

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

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

Antibiotic resistance in bacteria is an example of which of the following? A)Macroevolution B)Hardy-Weinberg equilibrium C)Stabilizing selection D)Directional selection E)Disruptive selection

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

E)Disruptive selection

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

E)Duplication

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

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

At what level does gene variability quantify genetic variation? A)Species B)Individual C)Population D)Molecular E)Whole-gene

E)Whole-gene

Point mutations in noncoding regions of DNA result in __________. A)population variation B)None of the listed responses is correct. C)molecular variability D)gene variability E)neutral variation F)phenotypic variation

E)neutral variation

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 __________. A)natural selection B)gene flow C)the bottleneck effect D)mutation E)the founder effect

E)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, __________. A)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 B)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 C)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 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 down, the frequency of the heterozygous genotype will go down, and the frequency of the homozygous recessives will go up

E)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

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

b)the bottleneck effect

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? A)1 b)0.36 c)0.8 d)0.64 e)0.2

c)0.8

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

favors intermediate variants in a population

Sexual recombination includes the shuffling of chromosomes in __________ and fertilization. A)genetic drift B)mutation C)meiosis D)natural selection E)mitosis

meiosis

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

natural selection