Question 1

Natural selection selects for or against certain

Accepted Answer

Natural selection acts on phenotypes, which are the observable traits of an organism, because these traits affect an organism's ability to survive and reproduce in its environment.

Question 2

If the tallest and shortest individuals of a population of humans do not survive and reproduce as well as the individuals of "average" height, which type of selection would most likely result?

Accepted Answer

Stabilizing selection occurs when individuals with average traits have higher fitness than those with extreme traits, leading to a reduction in variation around the average.

Question 3

When a species lives in a constant environment for a long time, the "average type" of individual may have the best chance of surviving and producing the most offspring. What type of selection is occurring?

Accepted Answer

Stabilizing selection occurs when the average phenotype is favored in a stable environment, reducing variation and maintaining the status quo.

Question 4

A flock of birds with various beak sizes migrates to a new island where their traditional food is not available. However, there are plants that produce a variety of large nuts, which can be eaten by birds with the largest beaks, and plants that produce a variety of small, soft seeds, which can be eaten by birds with the smallest beaks. Over time, this population divides into two species with large and small beaks. This is an example of

Accepted Answer

This scenario is an example of disruptive selection because it favors extreme values (large or small beaks) at the expense of intermediate values. This results in the population splitting into two distinct groups, each adapted to a different food source.

Question 5

In some butterfly populations, there are equal frequencies of alleles that code for black and yellow coloration. This is an example of

Accepted Answer

Balanced polymorphism occurs when two or more alleles persist in a population due to selective advantages, maintaining genetic diversity, as seen with equal frequencies of black and yellow coloration alleles in butterflies.

Question 6

A population of hummingbirds with a variety of beak sizes finds a new food source in a plant that has a long trumpet flower with nectar at the bottom of the trumpet. Over time, these hummingbirds develop longer beaks. This is an example of

Accepted Answer

This is an example of directional selection because the trait being selected for (longer beaks) is being favored over other variations of the trait, resulting in a shift in the population towards longer beaks.

Question 7

The type of selection most likely to act on a well- adapted population in a relatively constant environment is

Accepted Answer

Stabilizing selection is most likely to act on a well-adapted population in a constant environment, as it favors the average individuals and reduces variation.

Question 8

In a certain species of salmon, some adult males are extremely large whereas other adult males are very small, compared to the females. There are no intermediate- sized adult males in the population. This is probably the result of

Accepted Answer

Disruptive selection occurs when extreme values for a trait are favored over intermediate values, leading to two distinct phenotypes, such as the large and small males in this salmon population.

Question 9

Suppose a new mutation that improves metabolic efficiency is lost from a small population of mammals living in a region of seasonal food scarcity after a hurricane eliminates half the mammal population. This is an example of

Accepted Answer

The loss of a beneficial mutation from a small population due to a random event (hurricane) is an example of genetic drift, which refers to random changes in gene frequencies in a small population. The other options do not fit the scenario described. Directional selection refers to a trend towards one extreme phenotype due to selective pressure, while stabilizing selection favors an intermediate phenotype and disruptive selection favors two or more distinct phenotypes. Sexual selection involves non-random mating based on traits that increase mating success.

Question 10

If two or more phenotypes in a population are both favored by selection, what is happening?

Accepted Answer

Balanced polymorphism occurs when two or more phenotypes are maintained in a population because they are both favored by natural selection.

Question 11

In one butterfly species, the colors of individuals range from white to black, with many shades of gray in between. If the butterflies in a mountain population become more and more similar in color over several generations (e.g., if most butterflies are the same shade of gray), what kind of evolutionary force is likely acting on the population?

Accepted Answer

Stabilizing selection is likely acting on the population because it favors the intermediate shades of gray, reducing variation and making the population more similar in color.

Question 12

As predator and prey species acquire new adaptations to help them survive the constant "arms race" between them, what evolutionary phenomenon is occurring?

Accepted Answer

Coevolution is the evolutionary phenomenon where two or more species reciprocally affect each other's evolution, such as predators and prey developing adaptations in response to each other.

Question 13

Members of one gender influence allele frequencies in a population by choosing mates according to some conspicuous feature in the other gender in the process called

Accepted Answer

Sexual selection is the process where members of one gender choose mates based on specific traits, influencing allele frequencies in the population.

Question 14

The change in one population driven by a change in an associated population is called

Accepted Answer

Coevolution refers to the process where changes in one species lead to changes in another species that is closely associated with it, often due to mutual influence or interaction.

Question 15

Evolution by natural selection is

Accepted Answer

Evolution by natural selection is a process that occurs due to differences in fitness among individuals, leading to changes in allele frequencies over time. It is an ongoing natural process observed in various environments, not limited to laboratories or the past.

Question 16

Female finches, which do not sing, often choose to mate with males that sing a specific, elaborate song. This is an example of

Accepted Answer

Sexual selection is the process by which certain traits are selected for or against based on their effect on mating success. In this case, female finches are choosing to mate with males that sing a specific, elaborate song, which is an example of sexual selection.

Question 17

The elaborate courtship displays common among animals are the result of

Accepted Answer

Elaborate courtship displays are typically a result of sexual selection, where individuals with certain traits are more likely to attract mates and reproduce, passing those traits on to future generations.

Question 18

A new predator is introduced to an area that can feed on any millipedes shorter than 200 millimeters. No millipedes that live in that area are longer than 15 millimeters. What will happen?

Accepted Answer

All millipedes are shorter than 200 millimeters, making them all potential prey for the new predator.

Question 19

The male peacock's beautiful tail is really a trade- off between

Accepted Answer

The male peacock's tail is an example of sexual selection, where traits are favored because they increase an individual's chances of mating, even if they pose a survival disadvantage, which is a trade-off with natural selection.

Question 20

Which trait is the best example of an adaptation?

Accepted Answer

A heat-resistant enzyme in a bacterium living in a hot spring is an adaptation because it enhances the organism's ability to survive and reproduce in its specific environment.

Quiz 16: How Populations Evolve