Question 1

Refer to the following populations of a plant species and then answer the questions that follow.
1. 20 plants capable of asexual reproduction only.
2. 50 plants with unisexual flowers. Some plants bear male and some female flowers.
3. 1,000 plants with bisexual, self-fertilizing flowers.
4. 500 plants with bisexual, self-sterile flowers that make seeds only when cross-pollinated.
-The physical appearance of which population is most likely to be affected by the founder effect?
A) 1
B) 2
C) 3
D) 4

Accepted Answer

The founder effect is more pronounced in smaller populations where genetic diversity is limited. Population 1, with only 20 plants capable of asexual reproduction, is the smallest and would show the most significant impact of the founder effect due to its limited genetic variability and small size.

Question 2

Refer to the following populations of a plant species and then answer the questions that follow.
1. 20 plants capable of asexual reproduction only.
2. 50 plants with unisexual flowers. Some plants bear male and some female flowers.
3. 1,000 plants with bisexual, self-fertilizing flowers.
4. 500 plants with bisexual, self-sterile flowers that make seeds only when cross-pollinated.
-Which population would be most likely to survive in the event of a drastic environmental change?
A) 1
B) 2
C) 3
D) 4

Accepted Answer

Population 4, with 500 plants having bisexual, self-sterile flowers that require cross-pollination, would likely have the highest genetic diversity due to the necessity of cross-pollination. This genetic diversity increases the population's ability to adapt to environmental changes, making it more likely to survive drastic environmental changes.

Question 3

Refer to the following populations of a plant species and then answer the questions that follow.
1. 20 plants capable of asexual reproduction only.
2. 50 plants with unisexual flowers. Some plants bear male and some female flowers.
3. 1,000 plants with bisexual, self-fertilizing flowers.
4. 500 plants with bisexual, self-sterile flowers that make seeds only when cross-pollinated.
-Which population would probably show the most variation?
A) 1
B) 2
C) 3
D) 4

Accepted Answer

Population 4, with 500 plants having bisexual, self-sterile flowers that require cross-pollination, would likely show the most genetic variation. Cross-pollination mixes genetic material from different individuals, promoting diversity.

Question 4

Which of the following males in a given population would be considered the most fit in an evolutionary sense? One that produced:
A) 1,000 offspring, of which 100 survived but 99 did not reproduce.
B) 100 offspring, of which 10 survived but 9 did not reproduce.
C) 1,000 offspring all of which died before reaching reproductive age.
D) two offspring, both of which survived and produced offspring of their own.

Accepted Answer

In an evolutionary context, fitness is measured by an individual's ability to pass on its genes to the next generation. Therefore, the male whose offspring not only survive but also reproduce themselves (option D) is considered the most fit, as this ensures the continuation of his genetic lineage.

Question 5

In central Africa, the frequency (percentage) of the sickle-cell gene, compared to the normal gene, has remained stable over the years because the sickle-cell gene protects against malaria. In the United States, malaria was eradicated shortly before World War II by eliminating the mosquito that spreads the disease. What has likely happened to the frequency of the sickle-cell gene in African Americans living in the United States since the elimination of malaria?
A) The sickle-cell gene has disappeared from the African American population.
B) The normal gene has disappeared from the African American population.
C) The frequency of the sickle-cell gene has increased.
D) The frequency of the sickle-cell gene has decreased.

Accepted Answer

The sickle-cell gene confers a survival advantage in areas where malaria is prevalent, as carriers are less likely to suffer from severe forms of malaria. In the United States, where malaria has been eradicated, this advantage is no longer present, leading to a decrease in the selective pressure for the sickle-cell gene. Consequently, its frequency in the African American population is likely to have decreased over time.

Question 6

You are studying leaf size in a natural population of plants. The second season is particularly dry, and the following year the average leaf size in the population is smaller than the year before. But the amount of overall variation is the same, and the population size hasn't changed. Also, you've done experiments that show that small leaves are better adapted to dry conditions than are large leaves. Which of the following has occurred?
A) stabilizing selection
B) directional selection
C) genetic drift
D) disruptive selection

Accepted Answer

Directional selection has occurred because the average trait (leaf size) in the population shifted towards smaller leaves, which are better adapted to the new, drier conditions. This indicates that individuals with smaller leaves had a selective advantage, leading to a change in the average trait of the population without affecting the variation or population size.

Question 7

The previously described state of the sickle-cell gene in African Americans since malaria was eliminated in the United States is an example of:
A) genetic drift.
B) disruptive selection.
C) the founder effect.
D) directional selection.

Accepted Answer

The decrease in the frequency of the sickle-cell gene in African Americans after the elimination of malaria in the United States is an example of directional selection. This is because the selective pressure that favored the sickle-cell trait (protection against malaria) was removed, leading to a decrease in the gene's prevalence. Directional selection occurs when an environmental change favors a specific allele or genetic trait, leading to a shift in the population's genetic variance over time.

Question 8

The construction of housing developments on the beaches of southern California has resulted in the loss of areas with sufficient weeds to support certain butterflies. This can result in:
A) natural selection.
B) migration.
C) population bottlenecks.
D) increased mutation.

Accepted Answer

Population bottlenecks occur when a population is reduced to a small number of individuals, which can lead to a loss of genetic diversity. In this case, the loss of areas with sufficient weeds to support certain butterflies has resulted in a population bottleneck for those butterflies.

Question 9

Which of the following traits probably arose through sexual selection?
A) speed in cheetahs
B) camouflage in walking stick insects
C) brighter plumage in male birds than in female birds of the same species
D) migration in whales

Accepted Answer

Brighter plumage in male birds than in female birds of the same species is a trait that likely arose through sexual selection. This is because such traits are often used to attract mates and signal fitness, rather than for survival purposes like camouflage or speed.

Question 10

The common genetic defects of certain dog breeds are due to:
A) disruptive selection.
B) inbreeding.
C) mutation.
D) random mating.

Accepted Answer

Inbreeding is a common practice in dog breeding to maintain or enhance specific breed characteristics. However, it also increases the likelihood of genetic defects being passed on and expressed in offspring, as it reduces genetic diversity and increases the probability of recessive genetic disorders being inherited.

Question 11

The evolutionary advantage of incest taboos in humans is that they protect against:
A) wasted energy.
B) the cost of inbreeding.
C) familial discord.
D) police charges.

Accepted Answer

Incest taboos help prevent the genetic problems associated with inbreeding, such as increased risk of congenital defects and decreased biological fitness.

Question 12

How efficient is sexual reproduction alone in gauging the frequency of an allele?
A) very efficient
B) barely efficient
C) not efficient at all

Accepted Answer

Sexual reproduction alone is not efficient at all in gauging the frequency of an allele because it only provides information about the alleles that are present in the offspring, not the entire population.

Question 13

Suppose we find a population with 60 AA individuals, 20 Aa individuals, and 20 aa individuals, what is the allele frequency of A?
A) 0.20
B) 0.40
C) 0.60
D) 0.70

Accepted Answer

The allele frequency of A can be calculated by taking the total number of A alleles and dividing it by the total number of alleles. Here, there are 60 AA individuals (2 A alleles each), 20 Aa individuals (1 A allele each), and 20 aa individuals (0 A alleles). So, the total number of A alleles is (60*2) + (20*1) = 120 + 20 = 140. The total number of alleles is 2*(60+20+20) = 200. Therefore, the frequency of A is 140/200 = 0.70.

Question 14

Suppose we find a population with 60 AA individuals, 20 Aa individuals, and 20 aa individuals, what is the genotype frequency of Aa?
A) 0.20
B) 0.40
C) 0.60
D) 0.70

Accepted Answer

The genotype frequency of Aa is calculated by dividing the number of Aa individuals by the total population. Here, there are 20 Aa individuals out of a total of 100 individuals (60 AA + 20 Aa + 20 aa = 100). Therefore, the genotype frequency of Aa is 20/100 = 0.20.

Question 15

Nonrandom mating (for example, assortative mating) directly affects gene frequencies in populations.

Accepted Answer

Nonrandom mating, such as assortative mating, affects the distribution of genotypes within a population but does not directly change allele frequencies. It can lead to changes in genotype frequencies and can increase the proportion of homozygous individuals, but the overall allele frequencies in the population remain unchanged unless accompanied by other evolutionary forces.

Question 16

The process by which a species of bird with an intermediate beak size becomes two separate species with large and small beaks respectively is called disruptive selection.

Accepted Answer

Disruptive selection occurs when extreme values for a trait are favored over intermediate values, leading to the evolution of two distinct forms within a population, such as birds with large and small beaks, from an original population with intermediate beak sizes.

Question 17

Match the following description with the term.
-A small number of individuals from one area establish a new isolated population in another area. The gene frequencies of the new population differ from those of the original population.
A) founder effect
B) gene flow
C) genetic drift
D) stabilizing selection
E) sexual selection

Accepted Answer

The founder effect occurs when a small number of individuals from a population move to a new location and establish a new population, leading to genetic differences between the new population and the original due to the limited genetic variation of the founders.

Question 18

Match the following description with the term.
-Females tend to mate with brightly colored males.
A) founder effect
B) gene flow
C) genetic drift
D) stabilizing selection
E) sexual selection

Accepted Answer

This behavior is an example of sexual selection, a form of natural selection where individuals with certain inherited characteristics are more likely than other individuals to obtain mates. In this case, the preference for brightly colored males by females influences which traits are passed on to future generations.

Question 19

Assume that protein synthesis always reads along a chromosome three bases at a time to code for each successive amino acid in a protein. There are two kinds of point mutations, a base substitution and a base deletion. How are these two types of mutations likely to affect the protein coded for by a mutated gene?

Accepted Answer

The answer of Assume that protein synthesis always reads along...

Question 20

Why do most human societies have laws or customs against marrying close relatives?

Accepted Answer

The answer of Why do most human societies have laws...

Quiz 17: Microevolution

Which of the following males in a given population would be considered the most fit in an evolutionary sense? One that produced:

The previously described state of the sickle-cell gene in African Americans since malaria was eliminated in the United States is an example of:

The construction of housing developments on the beaches of southern California has resulted in the loss of areas with sufficient weeds to support certain butterflies. This can result in:

Which of the following traits probably arose through sexual selection?

The common genetic defects of certain dog breeds are due to:

The evolutionary advantage of incest taboos in humans is that they protect against:

How efficient is sexual reproduction alone in gauging the frequency of an allele?

Suppose we find a population with 60 AA individuals, 20 Aa individuals, and 20 aa individuals, what is the allele frequency of A?

Suppose we find a population with 60 AA individuals, 20 Aa individuals, and 20 aa individuals, what is the genotype frequency of Aa?

Nonrandom mating (for example, assortative mating) directly affects gene frequencies in populations.

The process by which a species of bird with an intermediate beak size becomes two separate species with large and small beaks respectively is called disruptive selection.

Match the following description with the term. -A small number of individuals from one area establish a new isolated population in another area. The gene frequencies of the new population differ from those of the original population.

Match the following description with the term. -Females tend to mate with brightly colored males.

Why do most human societies have laws or customs against marrying close relatives?