BSC 114 Chp 23

Which of the following statements correctly describes a population in Hardy-Weinberg equilibrium?

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?

Balancing selection

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

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?

Disruptive selection

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

Duplication

Which statement below is true about sexual selection?

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

Which statement correctly describes the role of chance in evolution?

The ultimate source of new alleles is mutation, random changes in the nucleotide sequences of an organism's DNA.

Long necks make it easier for giraffes to reach leaves high on trees, while also making them better fighters in "neck wrestling" contests. In both cases, which kind of selection appears to have made giraffes the long-necked creatures they are today? a.) Directional selection b.) Stabilizing selection c.) Disruptive selection

a.) Directional selection; drives the average of the population in one direction, in this case, toward longer necks.

Black-bellied seedcrackers have either small beaks (better for eating soft seeds) or large beaks (better for hard seeds). There are no seeds of intermediate hardness; therefore, which kind of selection acts on beak size in seedcrackers? a.) Disruptive selection b.) Stabilizing selection c.) Directional selection

a.) Disruptive selection; causes both extreme phenotypes (large and small beaks) to be favored over the intermediate phenotypes.

Which of the following would seem to be an example of neutral variation? a.) Human fingerprints b.) Homozygosity of the cheetah population c.) Polymorphism of the Galápagos finches d.) Founder effect e.) Moth coloration

a.) Human fingerprints

Women often have complications during labor while giving birth to very large babies, whereas very small babies tend to be underdeveloped. Which kind of selection is most likely at work regarding the birth weight of babies? a.) Stabilizing selection b.) Disruptive selection c.) Directional selection

a.) Stabilizing selection; causes no change in the average of the population; extreme phenotypes (in this case, large and small babies) become less common.

If a person has two normal copies of the hemoglobin allele, which statements are true? Select all that apply. a.) The person is homozygous at the hemoglobin locus. b.) The person is heterozygous at the hemoglobin locus. c.) The person is susceptible to malaria. d.) The person is protected against malaria.

a.) The person is homozygous at the hemoglobin locus. c.) The person is susceptible to malaria.

At what level does gene variability quantify genetic variation? a.) Whole-gene b.) Molecular c.) Population

a.) 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

Which type of selection tends to increase genetic variation? a.) Directional selection b.) Disruptive selection c.) Stabilizing selection

b.) Disruptive selection; eliminates phenotypes near the average and favors the extreme phenotypes, resulting in increased genetic variation in a population.

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.) 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.

In the Hardy-Weinberg equation, q2 represents __________. a.) the expected frequency of the recessive allele b.) the expected frequency of the homozygous recessive genotype

b.) the expected frequency of the homozygous recessive genotype

Small Aristelliger lizards have difficulty defending territories, but large lizards are more likely to be preyed upon by owls. Which kind of selection acts on the adult body size of these lizards? a.) Disruptive selection b.) Directional selection c.) Stabilizing selection

c.) Stabilizing selection

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 homozygous dominant advantage b.) the homozygous recessive advantage c.) the heterozygote advantage d.) genetic drift e.) gene flow

c.) the heterozygote advantage

Which of the following can form entirely new alleles? a.) Natural selection b.) Genetic drift c.) Sexual recombination d.) Mutation e.) The environment

d.) Mutation

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.) Selection can act only on existing variations. b.) Evolution is limited by historical constraints. c.) Adaptations are often compromises. d.) Chance, natural selection, and the environment interact. e.) All of the listed responses are correct.

e.) All of the listed responses are correct.

Which of the following statements correctly describe(s) characteristics of genetic drift? a.) It is significant in small populations. 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.) All of the listed responses are correct.

e.) All of the listed responses are correct.

What situation most likely explains the occasional high frequency of certain inherited disorders among human populations established by a small population?

founder effect; is genetic drift attributable to colonization by a limited number of individuals from a parent population.

Drag each statement into the appropriate bin depending on whether it applies to natural selection, genetic drift, or gene flow. -can introduce new alleles into a population's gene pool -a result of the movement of fertile individuals or their gametes

gene flow

Allele frequencies in a gene pool may shift randomly and by chance. What is this random shift called?

genetic drift

Drag each statement into the appropriate bin depending on whether it applies to natural selection, genetic drift, or gene flow. -causes allele frequencies to fluctuate randomly -can result from the bottleneck effect -can result from the founder effect

genetic drift

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

meiosis

Drag each statement into the appropriate bin depending on whether it applies to natural selection, genetic drift, or gene flow. -consistently causes a population to become better adapted to its environment -a result of differential success in reproduction -cannot cause a harmful allele to become more common

natural selection

Point mutations in noncoding regions of DNA result in __________ variation.

neutral variation

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

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

The evolutionary effects of genetic drift are greatest when __________.

the population size is small