Question 1

​A random change in allele frequency over time that is brought about by chance alone is known as ____.
A) ​genetic drift
B) ​gene flow
C) ​natural selection
D) ​disruptive selection
E) ​balanced polymorphism

Accepted Answer

Genetic drift is a mechanism of evolution that refers to random fluctuations in the frequencies of alleles within a population over time. These changes are not due to natural selection but occur by chance alone, especially in small populations.

Question 2

​In a population of rabbits, those able to outrun predators will survive to reproduce, eventually leading to a population of faster rabbits. This is an example of ____ selection.
A) ​directional
B) ​stabilizing
C) ​disruptive
D) ​mutational
E) ​restricted

Accepted Answer

This is an example of directional selection because it favors individuals at one extreme end of the trait spectrum (in this case, speed), leading to a shift in the population's average trait over time towards faster individuals.

Question 3

​What is one result of the bottleneck effect?
A) ​balanced alleles
B) ​heterozygosity
C) ​decreased genetic diversity
D) ​disruptive selection
E) ​random mating

Accepted Answer

The bottleneck effect leads to decreased genetic diversity because a significant portion of the population is suddenly removed, leaving a smaller pool of genes. This reduction in population size means that the remaining individuals have less genetic variation among them.

Question 4

In a tropical forest, some leaves are dark green, and some are light green. In a population of caterpillars, homozygous dominant dark green caterpillars thrive eating the dark green foliage, while homozygous recessive light green caterpillars thrive eating light green foliage. However, heterozygous caterpillars of an intermediate color green are easily seen by birds and eaten, thus their numbers are far less than the dominants or recessives. This is an example of ____ selection.
A) directional
B) stabilizing
C) disruptive
D) frequent
E) mutational

Accepted Answer

Disruptive selection is illustrated here, where extreme traits (dark green and light green caterpillars) are favored over the intermediate trait, leading to a decrease in the population of heterozygous, intermediate-colored caterpillars.

Question 5

​Which population is more likely to be affected by genetic drift?
A) ​12 squirrels in a forest
B) ​49 herons in a colony
C) ​215 fleas on a dog
D) ​1350 mice in a house
E) ​3000 zebra in a herd

Accepted Answer

Genetic drift has a more significant effect on smaller populations because random events can more drastically alter the frequency of alleles within the population. With only 12 squirrels, this population is the smallest and therefore most susceptible to genetic drift compared to the larger populations listed.

Question 6

​The movement of alleles among populations is called _____.
A) ​bottleneck
B) ​mutation
C) ​founder effect
D) ​gene flow
E) ​genetic drift

Accepted Answer

Gene flow refers to the transfer of alleles or genes from one population to another, which can occur through various means such as migration of individuals or the dispersal of seeds and pollen in plants. This process can lead to changes in the genetic composition of a population by introducing new genetic material.

Question 7

​In Cameroon, seedcrackers have either small bills (adapted for feeding on soft sedge seeds) or large bills (adapted for feeding on hard sedge seeds). During competition for scarce resources, these birds primarily feed on the seeds for which they are best adapted. This is an example of ____ selection.
A) ​stabilizing
B) ​disruptive
C) ​frequent
D) ​directional
E) ​mutational

Accepted Answer

Disruptive selection is illustrated here, where two extreme phenotypes (small bills and large bills) are favored over any intermediate phenotype, leading to a split in the population into two distinct groups adapted to different ecological niches.

Question 8

The Old Order Amish in Lancaster County is descended from one man and woman and has an unusually high frequency of a recessive allele that causes Ellis-van Creveld syndrome. This is an example of ____.
A) a bottleneck
B) mutation
C) a founder effect
D) gene flow
E) genetic drift

Accepted Answer

The Old Order Amish in Lancaster County's high frequency of a recessive allele causing Ellis-van Creveld syndrome is an example of a founder effect, where a small group of individuals establishes a population with a genetic makeup that differs from the original population, leading to the prevalence of certain genetic traits.

Question 9

The following graphs show the frequency of the b+ allele over 20 generations in two populations of heterozygous flour beetles (data for a population of 10 individuals is shown in graph A; data for a population of 100 individuals is shown in graph B). Why does the frequency of the b+ allele increase in both populations? 
A) b+ is a lethal allele.
B) b+ is a balanced polymorphism.
C) b+ is a fixed allele.
D) b+ allele is adaptive.
E) b+ is a neutral mutation.

Accepted Answer

The answer of The following graphs show the frequency of...

Question 10

​A small Dutch population settled in South Africa in the 17th century and became known as Afrikaners. By chance, a few Dutch settlers carried the gene for Huntington's disease. Today, Huntington's disease occurs at a relatively high frequency in this population. This is an example of ____.
A) ​the bottleneck effect
B) ​the founder effect
C) ​gene flow
D) ​artificial selection
E) ​natural selection

Accepted Answer

The founder effect occurs when a new colony is started by a few members of the original population. This small population size means that the new colony may have reduced genetic variation from the original population and a non-random sample of the genes in the original population. In the case of the Dutch settlers in South Africa, the relatively high frequency of Huntington's disease among their descendants is a classic example of the founder effect, as the disease's prevalence is attributed to the genes of the initial settlers.

Question 11

In the universal ABO blood grouping system, there are four phenotypes-A, B, AB, and O-which are determined by three different alleles. The presence of three alleles in the ABO blood grouping system is an example of ____.
A) a polymorphism
B) genetic drift
C) the bottleneck effect
D) a dimorphism
E) the founder effect

Accepted Answer

The presence of three alleles in the ABO blood grouping system is an example of a polymorphism, which refers to the occurrence of two or more distinct forms (in this case, alleles) in the population's genetic makeup.

Question 12

​Many male birds will expend a great deal of energy building nests. Females will mate with the males who build the best nests. This is best described as an example of ____.
A) ​natural selection
B) ​sexual selection
C) ​runaway selection
D) ​an invasive species
E) ​disruptive selection

Accepted Answer

Sexual selection is a mode of natural selection where members of one biological sex choose mates of the other sex to mate with, and compete with members of the same sex for access to members of the opposite sex. In this scenario, female birds choose mates based on the quality of the nests built by male birds, which is a classic example of sexual selection.

Question 13

​Heterozygotes for the sickle cell trait have an adaptive advantage in areas where malaria is prevalent. This is an example of ____.
A) ​a fixed allele
B) ​genetic drift
C) ​a balanced polymorphism
D) ​sexual selection
E) ​disruptive selection

Accepted Answer

This is an example of a balanced polymorphism, where two or more alleles persist in a population because the heterozygous condition confers a survival advantage, in this case, resistance to malaria.

Question 14

​Puppies born too large experience difficulties during birthing and tend to have respiratory and other problems. Puppies born too small often can't compete with their siblings for their mother's milk. Thus, puppies of intermediate size have a survival advantage. This is an example of ____ selection.
A) ​directional
B) ​stabilizing
C) ​disruptive
D) ​frequency
E) ​allelic

Accepted Answer

This is an example of stabilizing selection, where individuals with intermediate traits (in this case, size) have a survival advantage over those with extreme traits (either too large or too small). Stabilizing selection tends to reduce variation in a population by favoring the average individuals.

Question 15

​____ selection occurs when individuals choose mates with a particular desirable trait.
A) ​Stabilizing
B) ​Sexual
C) ​Artificial
D) ​Asexual
E) ​Disruptive

Accepted Answer

Sexual selection is a mode of natural selection where members of one biological sex choose mates of the other sex to mate with, and compete with members of the same sex for access to members of the opposite sex. This process often leads to individuals with certain advantageous traits being more likely to reproduce and pass those traits on to the next generation.

Question 16

​The observation that female lions prefer male lions with darker manes is an example of ____.
A) ​directional selection
B) ​disruptive selection
C) ​dominance
D) ​a sexual handicap
E) ​sexual selection

Accepted Answer

Female lions preferring male lions with darker manes is an example of sexual selection, where certain traits increase an individual's chances of mating.

Question 17

​Overhunting of species, such as tigers, reduces their numbers and their genetic diversity. This is an example of _____.
A) ​a bottleneck
B) ​a mutation
C) ​a founder effect
D) ​gene flow
E) ​genetic drift

Accepted Answer

A bottleneck effect occurs when a population's size is significantly reduced for at least one generation, leading to a loss of genetic diversity. Overhunting reduces the population size, causing a bottleneck.

Question 18

The increased variability in the frequency of the b+ allele in the smaller flour beetle population in the given graph is an example of ____.
A) genetic drift
B) gene flow
C) the founder effect
D) a fixed allele
E) a dimorphic trait

Accepted Answer

Genetic drift refers to random changes in allele frequencies, which are more pronounced in smaller populations, leading to increased variability.

Question 19

​Exposure of wild rat populations to warfarin led to the evolution of warfarin-resistant rats. These rats had a mutated version of the VKORC1 gene, indicating that ____ had occurred in these resistant rat populations.
A) ​extinction
B) ​stabilizing selection
C) ​microevolution
D) ​macroevolution
E) ​artificial selection

Accepted Answer

Microevolution refers to small evolutionary changes within a species or population, often involving changes in allele frequencies over time. The development of warfarin resistance in rats due to a mutation in the VKORC1 gene is an example of microevolution, as it represents a genetic adaptation to an environmental pressure within a population.

Question 20

Peahens prefer to mate with peacocks that have the brightest and largest tail displays. The peacock's tail is a disadvantage to the males, because it is large and cumbersome and hinders them from escaping from predators. Given these facts, why isn't the peacock's tail selected against by natural selection?
A) Peacocks lack the mutations to allow selection to work.
B) Only a few peacocks have large tail displays.
C) In spite of the disadvantage, peacocks with larger tails leave more offspring.
D) It is selected against, but because a peahen gives birth to so many males, the population is not greatly affected.
E) Peacocks do not reproduce sexually.

Accepted Answer

Peacocks with larger and brighter tails are preferred by peahens for mating, which means they have more opportunities to reproduce. Despite the survival disadvantage posed by the large tail, the reproductive advantage ensures that the genes for larger tails are passed on to more offspring, thus not being selected against by natural selection.

Quiz 13: Processes of Evolution

​A random change in allele frequency over time that is brought about by chance alone is known as ____.

​In a population of rabbits, those able to outrun predators will survive to reproduce, eventually leading to a population of faster rabbits. This is an example of ____ selection.

​What is one result of the bottleneck effect?

​Which population is more likely to be affected by genetic drift?

​The movement of alleles among populations is called _____.

The Old Order Amish in Lancaster County is descended from one man and woman and has an unusually high frequency of a recessive allele that causes Ellis-van Creveld syndrome. This is an example of ____.

​A small Dutch population settled in South Africa in the 17th century and became known as Afrikaners. By chance, a few Dutch settlers carried the gene for Huntington's disease. Today, Huntington's disease occurs at a relatively high frequency in this population. This is an example of ____.

In the universal ABO blood grouping system, there are four phenotypes-A, B, AB, and O-which are determined by three different alleles. The presence of three alleles in the ABO blood grouping system is an example of ____.

​Many male birds will expend a great deal of energy building nests. Females will mate with the males who build the best nests. This is best described as an example of ____.

​Heterozygotes for the sickle cell trait have an adaptive advantage in areas where malaria is prevalent. This is an example of ____.

​____ selection occurs when individuals choose mates with a particular desirable trait.

​The observation that female lions prefer male lions with darker manes is an example of ____.

​Overhunting of species, such as tigers, reduces their numbers and their genetic diversity. This is an example of _____.

The increased variability in the frequency of the b+ allele in the smaller flour beetle population in the given graph is an example of ____.

​Exposure of wild rat populations to warfarin led to the evolution of warfarin-resistant rats. These rats had a mutated version of the VKORC1 gene, indicating that ____ had occurred in these resistant rat populations.

A random change in allele frequency over time that is brought about by chance alone is known as ____.

In a population of rabbits, those able to outrun predators will survive to reproduce, eventually leading to a population of faster rabbits. This is an example of ____ selection.

What is one result of the bottleneck effect?

Which population is more likely to be affected by genetic drift?

The movement of alleles among populations is called _____.

A small Dutch population settled in South Africa in the 17th century and became known as Afrikaners. By chance, a few Dutch settlers carried the gene for Huntington's disease. Today, Huntington's disease occurs at a relatively high frequency in this population. This is an example of ____.

Many male birds will expend a great deal of energy building nests. Females will mate with the males who build the best nests. This is best described as an example of ____.

Heterozygotes for the sickle cell trait have an adaptive advantage in areas where malaria is prevalent. This is an example of ____.

____ selection occurs when individuals choose mates with a particular desirable trait.

The observation that female lions prefer male lions with darker manes is an example of ____.

Overhunting of species, such as tigers, reduces their numbers and their genetic diversity. This is an example of _____.

Exposure of wild rat populations to warfarin led to the evolution of warfarin-resistant rats. These rats had a mutated version of the VKORC1 gene, indicating that ____ had occurred in these resistant rat populations.