Question 1

Being a carrier for sickle cell anemia results in
A) the Red Queen effect.
B) genetic drift.
C) a balanced polymorphism.
D) sexual selection.
E) disruptive selection.

Accepted Answer

Being a carrier for sickle cell anemia results in a balanced polymorphism. This is because carriers have a selective advantage in areas where malaria is common, as they are less likely to contract the disease. Therefore, the sickle cell trait is maintained at a frequency higher than what would be expected under genetic drift or disruptive selection. The Red Queen effect and sexual selection are not applicable in this scenario.

Question 2

Which population's allele frequency is considered to be fixed?
A) 30 chimpanzees: 100% are AA
B) 76 garter snakes: 50% are AA and 50% are aa
C) 1100 fruit flies: 100% are aa
D) more than one of these
E) none of these

Accepted Answer

A population's allele frequency is considered fixed when all individuals have the same allele. Both A and C have 100% of individuals with the same allele, indicating fixation.

Question 3

____ is a random change in allele frequency over time that is brought about by chance.
A) Genetic drift
B) Gene flow
C) Natural selection
D) Disruptive selection
E) Balanced polymorphism

Accepted Answer

Genetic drift is a random change in allele frequency that occurs due to chance events, such as a sudden reduction in population size, that can lead to the loss of alleles that are not necessarily harmful. Gene flow refers to the movement of alleles between populations, while natural selection is a non-random process that favors certain traits or alleles that enhance an organism's survival and reproduction. Disruptive selection and balanced polymorphism are types of natural selection.

Question 4

When individuals choose mates are a particular trait they desire it is called
A) stabilizing selection.
B) sexual selection.
C) artificial selection.
D) Red Queen selection.
E) disruptive selection.

Accepted Answer

Sexual selection is the process whereby individuals choose mates based on particular traits they desire. This can lead to the evolution of elaborate physical or behavioral traits in one sex that are used to attract members of the opposite sex. Stabilizing selection occurs when selection favors average values of a trait, disruptive selection occurs when selection favors extreme values of a trait, artificial selection is carried out by humans to selectively breed plants or animals for desired traits, and Red Queen selection refers to the constant evolutionary arms race between hosts and pathogens.

Question 5

Females choosing males with elongated eyestalks over those with short eyestalks is an example of
A) directional selection.
B) disruptive selection.
C) dominance.
D) a sexual handicap.
E) sexual selection.

Accepted Answer

The preference of females for males with elongated eyestalks is a classic example of sexual selection. This preference is not due to any inherent survival advantage but arises purely due to sexual attractiveness.

Question 6

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

Smaller populations are more likely to be affected by genetic drift because there is less genetic variation and less opportunity for rare alleles to become established in a small gene pool. A population of 12 squirrels is the smallest population size listed, making it the most likely to be affected by genetic drift.

Question 7

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 green foliage; homozygous recessive light green caterpillars thrive eating light green foliage; heterozygous caterpillars of an intermediate color green are easily seen by birds and eaten,thus there frequency is 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

This scenario describes disruptive selection, where extreme traits (dark green and light green caterpillars) are favored over intermediate traits (heterozygous caterpillars), leading to a decrease in the frequency of the intermediate phenotype.

Question 8

The old order Amish in Lancaster County is an example of a population that underwent
A) a bottle neck.
B) mutation.
C) a founder effect.
D) gene flow.
E) genetic drift.

Accepted Answer

The Amish population in Lancaster County is an example of a founder effect, which occurs when a small group of individuals leave their larger population and establish a new, isolated population. As a result, the genetic diversity of the new population is limited to the genetic variation present in the original group of founders. The Amish population in Lancaster County is descended from a small group of individuals who immigrated to the area in the early 18th century, and this population has remained relatively isolated ever since. This has resulted in a higher incidence of certain genetic disorders that are rare in the general population.

Question 9

The favoring of the heterozygote within the population is an example of a
A) balanced polymorphism.
B) genetic drift.
C) the Red Queen effect.
D) sexual selection.
E) disruptive selection.

Accepted Answer

The favoring of the heterozygote within the population is an example of balanced polymorphism, where both the homozygous dominant and homozygous recessive alleles have a disadvantage, whereas the heterozygous advantage contributes to the maintenance of genetic diversity within the population.

Question 10

Staphlococcus aureus is a bacterium that causes wound infections.Many strains of S.aureus now exist that have evolved resistance to the potent antibiotic,methicillin.This is an example of ____ selection.
A) directional
B) stabilizing
C) disruptive
D) frequent
E) more than one of these types of

Accepted Answer

This is an example of directional selection because the environment (use of methicillin) is favoring the survival and reproduction of individuals with traits that allow them to resist the antibiotic, leading to an increase in the frequency of antibiotic-resistant strains over time.

Question 11

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) the Red Queen effect.
E) disruptive selection.

Accepted Answer

The fact that females choose males with the best nests is an example of sexual selection, which is a type of natural selection that depends on an individual's ability to attract a mate. In this case, the male's ability to build a good nest is seen as an attractive trait by the female, and therefore gives him a greater chance of mating and passing on his genetic material.

Question 12

Individuals who are heterozygous for sickle-cell anemia have a greater resistance to
A) malaria.
B) diphtheria.
C) cholera.
D) typhoid fever.
E) all of these.

Accepted Answer

Heterozygous individuals for sickle-cell anemia have a genetic advantage against malaria because the alteration of their red blood cells makes it more difficult for the malaria parasite to survive within them. However, they do not have any greater resistance to diphtheria, cholera, or typhoid fever.

Question 13

In the universal ABO blood grouping system,there are four phenotypes: A,B,AB,and O.Various populations have different frequencies of these four phenotypes but,in most populations O is most common and AB least common.The ABO blood grouping system exemplifies
A) polymorphism.
B) genetic drift.
C) the bottleneck effect.
D) the Red Queen effect.
E) the founder effect.

Accepted Answer

The ABO blood grouping system demonstrates polymorphism, which refers to the coexistence of multiple distinct phenotypes within a population, with each phenotype being maintained at levels greater than would be expected by mutation alone.

Question 14

The movement of alleles among populations is called
A) a bottle neck.
B) mutation.
C) a founder effect.
D) gene flow.
E) genetic drift.

Accepted Answer

Gene flow is the movement of alleles from one population to another, which can occur through migration, mating or transfer of gametes. This process can affect the genetic diversity of both populations and can also bring new alleles that can be advantageous or disadvantageous.

Question 15

By the year 1900,the American bison had been hunted to near extinction.From those that survived the slaughter,breeding programs have increased the population of American bison to close to 500,000 today.This is an example of
A) artificial selection.
B) the founder effect.
C) the bottleneck effect.
D) the Red Queen effect.
E) gene flow.

Accepted Answer

The increase in population of American bison from near extinction to close to 500,000 today is an example of the bottleneck effect. The severe reduction in the population of American bison due to hunting is indicative of a bottleneck event. The surviving individuals had reduced genetic diversity, creating a new population with a reduced gene pool. The breeding programs then increased the population and allowed for the reintroduction of genetic diversity.

Question 16

____ is a drastic reduction in population size brought about by severe pressure.
A) A bottle neck
B) Mutation
C) A founder effect
D) Gene flow
E) Genetic drift

Accepted Answer

A bottleneck is a drastic reduction in population size brought about by severe pressure, like natural disasters or human-induced factors.

Question 17

Puppies born too large experience difficulties in 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 born not too large or too small have a survival advantage.This is an example of ___ selection.
A) directional
B) stabilizing
C) disruptive
D) frequency
E) more than one of these types of

Accepted Answer

Stabilizing selection favors the intermediate trait value, in this case, puppies born not too large or too small have a better chance of survival compared to those born too large or too small.

Question 18

A small population of Dutch 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) the Red Queen effect.
E) natural selection.

Accepted Answer

This is an example of the founder effect, where a small group of individuals colonize a new area, carrying only a subset of the total genetic variation. In this case, the few Dutch settlers carried the gene for Huntington's disease, and this small, founding population became the source of a larger population of Afrikaners. As a result, Huntington's disease occurs at a relatively high frequency in this population.

Question 19

The HbS allele that causes sickle-cell anemia in the recessive condition is most common in areas that experience a high frequency of
A) polio.
B) typhus.
C) diphtheria.
D) malaria.
E) cystic fibrosis.

Accepted Answer

The HbS allele provides some protection against malaria when in the heterozygous condition. Therefore, in areas where malaria is prevalent, the frequency of the HbS allele is higher due to natural selection.

Question 20

Peahens prefer to mate with peacocks that have the brightest and largest tail displays.The peacock's tail is,in and of itself,a disadvantage to the males.It is large and cumbersome and the males are more easily caught by predators because of it.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) it is working- peacocks are slowly going extinct
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) this is one of those mysteries of biology

Accepted Answer

Despite the disadvantage of a cumbersome tail, peacocks with larger and brighter tail displays are preferred by peahens for mating. This leads to these peacocks leaving more offspring, resulting in the maintenance and even enhancement of the trait over time. This is an example of sexual selection, where the selection pressure may not necessarily be on survival, but on attracting mates.

Quiz 12: Processes of Evolution

Being a carrier for sickle cell anemia results in

Which population's allele frequency is considered to be fixed?

____ is a random change in allele frequency over time that is brought about by chance.

When individuals choose mates are a particular trait they desire it is called

Females choosing males with elongated eyestalks over those with short eyestalks is an example of

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

The old order Amish in Lancaster County is an example of a population that underwent

The favoring of the heterozygote within the population is an example of a

Staphlococcus aureus is a bacterium that causes wound infections.Many strains of S.aureus now exist that have evolved resistance to the potent antibiotic,methicillin.This is an example of ____ selection.

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

Individuals who are heterozygous for sickle-cell anemia have a greater resistance to

In the universal ABO blood grouping system,there are four phenotypes: A,B,AB,and O.Various populations have different frequencies of these four phenotypes but,in most populations O is most common and AB least common.The ABO blood grouping system exemplifies

The movement of alleles among populations is called

By the year 1900,the American bison had been hunted to near extinction.From those that survived the slaughter,breeding programs have increased the population of American bison to close to 500,000 today.This is an example of

____ is a drastic reduction in population size brought about by severe pressure.

A small population of Dutch 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

The HbS allele that causes sickle-cell anemia in the recessive condition is most common in areas that experience a high frequency of