Question 1

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 15 millimeters, they will all be potential prey for the new predator that can feed on any millipedes shorter than 200 millimeters. There is no indication that the millipedes will necessarily mutate or evolve in response to the predator. Disruptive or directional selection may occur, but there is not enough information to determine if this will happen.

Question 2

Evolution by natural selection is:

Accepted Answer

Evolution by natural selection occurs as a result of differences in fitness, where certain traits are advantageous and are more likely to be passed on to future generations. This process is ongoing and occurs in all organisms, but the rate and direction of evolution can vary depending on environmental factors and other influences. It has also been observed and studied by scientists.

Question 3

Imagine that a population of hummingbirds with an intermediate beak size develops longer beaks over time. This is an example of:

Accepted Answer

Directional selection favors individuals with traits that are at one extreme of the range and against those with average or intermediate traits. In this case, hummingbirds with longer beaks are being favored over those with intermediate beak sizes.

Question 4

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 the best example of an adaptation because it provides a selective advantage to the bacterium in its environment.

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

This scenario describes balanced polymorphism, where both black and yellow alleles are maintained at relatively equal frequencies in the population. This suggests that both colors provide a selective advantage, leading to the balanced polymorphism.

Question 6

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

Accepted Answer

This is an example of sexual selection, where traits are selected for based on their ability to attract mates. In this case, female finches are selecting for males with a specific trait (the ability to sing an elaborate song) that they find attractive.

Question 7

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 phenomenon where two or more species influence each other's evolution through natural selection. In the case of predator-prey relationships, as predators evolve new adaptations to aid in hunting, prey species may develop new adaptations to evade predation. Over time, these changes in one species place selective pressure on the other, leading to further adaptations in response.

Question 8

Imagine that a species of bird with an intermediate beak size becomes two separate species with large and small beaks. This is an example of:

Accepted Answer

Disruptive selection occurs when individuals with intermediate traits are selected against, leading to the formation of two distinct groups with different traits. In this case, the individuals with intermediate beak sizes were selected against, leading to the formation of two separate species with large and small beaks.

Question 9

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 due to:

Accepted Answer

Disruptive selection favors extreme phenotypes over intermediates, and in this case, it has resulted in the development of extremely large and extremely small adult males with no intermediates.

Question 10

The change in one population due to a change in another population is called:

Accepted Answer

Coevolution is the term used to describe the reciprocal evolutionary change in two or more interacting species. It is a process in which the characteristics of one species influence the evolution of the other, and vice versa. Therefore, the change in one population due to a change in another population is called coevolution.

Question 11

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

Accepted Answer

When two or more phenotypes in a population are both favored by selection, it leads to balanced polymorphism, where different alleles or phenotypes are maintained in a population at relatively stable frequencies. This can occur through various mechanisms such as heterozygote advantage or frequency-dependent selection.

Question 12

Natural selection selects for or against certain:

Accepted Answer

Natural selection selects for or against certain phenotypes. It is not directly selecting for or against genotypes, gene pools, populations, or alleles, but rather the expression of those traits in the form of phenotypes.

Question 13

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

Accepted Answer

The male peacock's elaborate and colorful tail is a result of sexual selection, a type of natural selection driven by competition among members of one sex (in this case, males) for access to mates. While the tail may be a disadvantage in terms of survival (being cumbersome and attracting predators), it is advantageous in attracting females and thus passing on the male's genes. Therefore, it is a trade-off between sexual selection and natural selection.

Question 14

The process by which allele frequencies are altered in a population to improve the odds of attracting a mate is called:

Accepted Answer

Sexual selection is the process by which certain traits in a population become more prevalent over time due to their attractiveness to potential mates. This can lead to non-random mating patterns and an increase in the frequency of certain alleles in a population. Random evolution (A) and random mutation (D) do not necessarily involve changes that improve the odds of attracting a mate. Genetic drift (C) refers to random fluctuations in allele frequency that occur due to chance events, and is not specifically tied to mate attraction. Fitness (E) refers to an individual's ability to survive and reproduce, which is related to sexual selection but is not the specific process by which allele frequencies are altered.

Question 15

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 (for example, 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 acting on the population, as it is favoring individuals that are more similar to the average color phenotype, and reducing the variation of color in the population.

Question 16

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

Accepted Answer

Stabilizing selection favors individuals with average traits and selects against extreme traits, which helps to maintain a well-adapted population in a constant environment.

Question 17

The elaborate courtship displays common among animals are the result of:

Accepted Answer

Elaborate courtship displays are a result of sexual selection, which occurs when individuals of one gender (usually males) compete for the attention and/or mating opportunities of the other gender (usually females). The displays allow the males to showcase their genetic fitness, increasing their chances of being chosen as a mate. This can result in the evolution of elaborate and often costly courtship displays.

Question 18

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 would most likely result in this scenario, as it favors individuals with traits close to the average of the population, while selecting against extreme variations. The elimination of the very tall and very short individuals would narrow the range of variation in height, leading to a more stable average height in the population.

Question 19

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 favors the "average type" of individual and selects against extreme variations. This type of selection occurs in a constant environment where the traits that are best suited to the environment are already established.

Question 20

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 scenario describes genetic drift, which is a random fluctuation in allele frequencies due to chance events, such as a natural disaster reducing a population size. The loss of the beneficial mutation is not due to selection pressure, but rather the chance event of the hurricane reducing the population size and potentially eliminating the individuals with the advantageous mutation.

Quiz 15: How Populations Evolve