Ch. 23 The Evolution of Populations Dynamic Study Module

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?

0.2

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?

0.8

In a certain group of people, 4% are born with sickle-cell disease (homozygous recessive). If this group is in Hardy-Weinberg equilibrium, what percentage of the group is heterozygous for the sickle hemoglobin allele?

32%

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

A) 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? A) all of the listed responses are correct B) evolution is limited by historical constraints C) selection can act only on existing variations D) adaptations are often compromises E) chance, natural selection, and the environment interact

A) All of the listed responses are correct.

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 mate choice is random, and the showier males happen to be chosen by the females as mates. C) Showy males are larger and kill off the plain-colored males. D) Male peacocks with showy feathers have no selective advantage over plain-colored males. E) Female peacocks choose the plain-colored males as mates, causing this trait to be more prevalent in the population.

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

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

A) natural selection

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 dominant allele D) the expected frequency of the homozygous recessive genotype E) the expected frequency of the recessive allele

A) the expected frequency of the heterozygous genotype

Which statement below is true about sexual selection? A) Showy secondary sexual characteristics cannot be explained because they break all of the rules of natural selection. B) Sexual selection can result in sexual dimorphism—marked differences between the sexes in secondary sexual characteristics that are not associated directly with reproduction. 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.

B) 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) a small population of humans colonizes a newly formed island B) wind blows pollen from one population of plants to another and cross-fertilization occurs 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) an earthquake results in the formation of a canyon, splitting a population of toads apart

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

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 change from generation to generation C) allele and genotype frequencies in the population will remain constant from generation to generation D) the population is evolving E) the population exhibits no genetic variation

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

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

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

Which type of mutation plays the most important role in increasing the number of genes in the gene pool? A) mutations are so rare that there are no mutations that can have such an important effect B) rearrangement of gene loci C) changes in nucleotide sequence D) duplication E) point mutation

D) duplication

Which of the following would seem to be an example of neutral variation? A) moth coloration B) homozygosity of the cheetah population C) polymorphism of the Galapagos finches D) human fingerprints E) founder effect

D) human fingerprints

Which of the following can form entirely new alleles? A) sexual recombination B) the environment C) natural selection D) mutation E) genetic drift

D) mutation

Which type of selection maintains stable frequencies of two or more phenotypic forms in a population? A) stabilizing selection B) heterozygote advantage C) directional selection D) neutral variation E) balancing selection

E) balancing selection

Antibiotic resistance in bacteria is an example of which of the following? A) disruptive selection B) stabilizing selection C) hardy-Weinberg equilibrium D) macroevolution E) directional selection

E) directional selection

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

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

Stabilizing selection _____________.

Favors intermediate variants in a population

A hurricane hits a small island, killing all but a few members of a bird population. This is an example of __________.

The bottleneck effect

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 __________.

The founder effect

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 heterozygote advantage

At what level does gene variability quantify genetic variation?

Whole-gene

The gene pool of a population consists of __________.

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

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?

disruptive selection

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

meiosis

Point mutations in non coding regions of DNA result in ___________.

neutral variation

In the Hardy-Weinberg equation, q2 represents ______.

the expected frequency of the homozygous recessive genotype

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

No two people are genetically identical, except for identical twins. The main source of genetic variation among human individuals is

the reshuffling of alleles in sexual reproduction