Question 1

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 relatively constant environment because it favors the average individuals in the population, thus maintaining the status quo and reducing variation.

Question 2

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, where extreme values for a trait are favored over intermediate values. In this case, birds with very large or very small beaks are favored because they can exploit the available food sources, leading to the population splitting into two distinct groups.

Question 3

Natural selection selects for or against certain

Accepted Answer

The answer of Natural selection selects for or against certain
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Question 4

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

Since all millipedes in the area are shorter than 200 millimeters, and the predator can feed on any millipedes shorter than 200 millimeters, all millipedes will be potential prey for the new predator.

Question 5

The elaborate courtship displays common among animals are the result of

Accepted Answer

Sexual selection is the evolutionary process by which certain traits increase an individual's chances of attracting mates and reproducing. Elaborate courtship displays are often developed through sexual selection because they help individuals attract mates by demonstrating their fitness or suitability as partners.

Question 6

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 favors individuals at both extremes of a trait, in this case, size among adult males, leading to the presence of both very large and very small males, with no intermediates.

Question 7

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

Accepted Answer

Stabilizing selection is the type of selection where individuals with traits that are at the average, or intermediate, range of the trait distribution in a population have a higher fitness compared to individuals with extreme traits. In this scenario, since both the tallest and shortest individuals have lower survival and reproductive success compared to those of average height, it leads to a selection against the extremes, favoring the average traits, which is characteristic of stabilizing selection.

Question 8

When a species lives in a constant environment for a long time, the ʺaverage typeʺ 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 environment is constant and unchanging, favoring the average individuals within a population. This type of selection tends to reduce variation around the average phenotype and maintains the status quo for the traits in the population.

Question 9

Which trait is the best example of an adaptation?

Accepted Answer

A mutation resulting in 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.

Question 10

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

This is an example of sexual selection, where females choose mates based on specific traits, in this case, the ability and complexity of the male's song, which is seen as an indicator of the male's quality or fitness.

Question 11

The male peacockʹs beautiful tail is really a trade-off between

Accepted Answer

The male peacock's elaborate tail is a result of sexual selection, where traits that are attractive to mates are favored, even if they might be a disadvantage in terms of survival (natural selection). This creates a trade-off between attracting mates and avoiding predators or other natural challenges.

Question 12

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 at high frequencies, often due to selective advantages or a balance between different selective pressures, as seen in the example of equal frequencies of alleles for black and yellow coloration in some butterfly populations.

Question 13

Evolution by natural selection is

Accepted Answer

Natural selection is an ongoing process in nature, driven by differences in reproductive success (fitness) among individuals due to variations in their traits. This process is not confined to the past, does not occur at a uniform rate across all organisms, has been observed in nature (not just in laboratories), and is not considered a rare event.

Question 14

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 average individuals in a population and reduces variation by selecting against extreme phenotypes, leading to a more uniform population in terms of the trait under selection, in this case, color.

Question 15

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

Accepted Answer

Coevolution is the term used to describe the process where the change in one population drives a change in an associated population, often due to close ecological interactions such as between predators and their prey, or between pollinators and the plants they pollinate.

Question 16

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 a mode of natural selection where members of one biological sex choose mates of the other sex to mate with (intersexual selection), and compete with members of the same sex for access to members of the opposite sex (intrasexual selection). This can lead to changes in allele frequencies in a population, as certain traits become more desirable and thus more common over generations.

Question 17

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 population evolves towards one extreme phenotype, in this case, longer beaks, which are favored for accessing nectar in long trumpet flowers.

Question 18

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

This is an example of genetic drift, which refers to random changes in allele frequencies in a population, especially in small populations. The loss of the beneficial mutation due to a hurricane (a random event) reducing the population size illustrates genetic drift, not a selection process.

Question 19

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 in a population are favored by selection, maintaining genetic diversity within the population.

Question 20

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

Accepted Answer

Coevolution occurs when two or more species reciprocally affect each other's evolution through the natural selection pressures they impose on one another, such as in the predator-prey dynamic.

Quiz 16: How Populations Evolve