Question 1

How was the mechanism of sympatric speciation among hemp nettles in nature verified experimentally?

Accepted Answer

The mechanism of sympatric speciation among hemp nettles was verified experimentally by producing experimental hybrids that formed fertile offspring with the naturally occurring hybrid. This approach demonstrated that the hybrids could integrate genetically with the populations they originated from, supporting the concept of sympatric speciation through hybridization and subsequent fertility.

Question 2

The continued geographic isolation of Kaibab squirrels from Abert squirrels has allowed the animals to evolve into two distinct subspecies. This is an example of:

Accepted Answer

The geographic isolation of Kaibab squirrels from Abert squirrels leading to their evolution into two distinct subspecies is an example of allopatric speciation. This process occurs when populations of the same species become isolated from each other due to geographic barriers, leading to reproductive isolation and eventually, the evolution of new species.

Question 3

Which mechanism prevents fish sperm from fertilizing frog eggs?

Accepted Answer

Prezygotic barriers prevent different species from mating or ensure that if they do mate, fertilization does not occur. In the case of fish sperm and frog eggs, prezygotic barriers such as differences in reproductive organs, mating behaviors, or timing of reproduction prevent cross-species fertilization.

Question 4

In the example of the flicker hybrid zone, why does it appear that the flicker hybrids are in a stable hybrid zone?

Accepted Answer

The flicker hybrid zone appears stable because the two kinds of flickers have not shown reinforcement (strengthening of reproductive barriers) or fused into one distinct group, and the hybrid zone has remained stable without expansion, indicating a balance between the hybrid and parent populations.

Question 5

Charles Darwin called choosing a mate based on its color or some other characteristic:

Accepted Answer

Darwin referred to the process where individuals select mates based on their physical characteristics, such as color, as "sexual selection." This concept explains how certain traits become more prevalent in a population because they are attractive to the opposite sex.

Question 6

Allopolyploidy is a significant factor in the evolution of which type of organism?

Accepted Answer

Allopolyploidy is a significant factor in the evolution of flowering plants. It involves the combination of chromosomes from different species through hybridization and subsequent chromosome doubling, leading to new species with genetic contributions from both parent species. This process has played a crucial role in the diversification and evolution of flowering plants.

Question 7

Figure 20-1

The most common outcome of the process in the accompanying figure is no viable gametes. This happens because of:

Accepted Answer

The answer of Figure 20-1

The most common outcome of the...

Question 8

Hybrid zones are typically ____, presumably because the hybrid organisms are not well adapted for either parental environment.

Accepted Answer

Hybrid zones are typically narrow because the hybrid organisms often have reduced fitness compared to their parent species, limiting their ability to spread and compete in either parental environment.

Question 9

Polyploidy is much more common among which type of organism?

Accepted Answer

Polyploidy, the condition of having more than two complete sets of chromosomes, is much more common in plants than in other organisms. This genetic characteristic can lead to greater variability and adaptability in plant species.

Question 10

Which evolutionary process occurs when the hybrids in a hybrid zone are as fit as either of the parental populations?

Accepted Answer

The answer of Which evolutionary process occurs when the hybrids...

Question 11

What are the two major forces contributing to allopatric speciation?

Accepted Answer

Allopatric speciation occurs when populations are geographically separated, leading to genetic drift and natural selection acting on the isolated populations, causing them to diverge over time.

Question 12

Which mechanism would prevent interbreeding between two species of fish living in the same habitat?

Accepted Answer

Reproductive isolating mechanisms are biological features of animals, plants, or species that prevent species from interbreeding and producing fertile offspring. These mechanisms can be prezygotic (before fertilization) or postzygotic (after fertilization) and are crucial for maintaining species boundaries, especially for species living in the same habitat (sympatric species).

Question 13

Allopatric speciation is often exemplified in which type of geographical area or biome?

Accepted Answer

Islands are classic examples of allopatric speciation because they provide geographical isolation, which is a key factor in this type of speciation.

Question 14

Which best describes a population that forms a new species within the same geographical region as the original species?

Accepted Answer

Sympatric speciation occurs when a new species evolves from a single ancestral species while inhabiting the same geographic region. This contrasts with allopatric speciation, where a population is geographically separated, leading to the formation of new species.

Question 15

What type of organism possesses multiple sets of chromosomes from different species?

Accepted Answer

An allopolyploid is an organism that has multiple sets of chromosomes derived from different species, typically through hybridization and chromosome doubling.

Question 16

Gradualism is rarely observed in the fossil record because:

Accepted Answer

The fossil record is incomplete, which makes it difficult to observe gradual changes in species over time. Many organisms do not fossilize well, and even when they do, the conditions necessary for fossilization are rare. This leads to gaps in the record that can make evolutionary transitions appear more abrupt than they might have been.

Question 17

The Hawthorne and apple maggot flies appear to have become reproductively isolated from each other largely because they:

Accepted Answer

The Hawthorne and apple maggot flies have become reproductively isolated primarily because they have adapted to two different hosts (Hawthorne trees and apple trees, respectively). This adaptation to different host plants affects where they live, feed, and lay eggs, leading to reproductive isolation over time.

Question 18

Which statement about allopolyploidy is FALSE?

Accepted Answer

Allopolyploidy does contribute to species diversity, but it is not the sole or primary reason for the remarkable species diversity observed on Earth today. Other factors such as mutation, natural selection, and genetic drift also play significant roles.

Question 19

If a small population of mice colonizes a new area away from the range of the original species, the colony that is geographically isolated may eventually evolve into a new species. These events can be used to describe:

Accepted Answer

Allopatric speciation occurs when a population is geographically isolated from the rest of its species and evolves into a new species due to the lack of gene flow and the different selective pressures in the new environment.

Question 20

Which model would predict that populations diverge from one another through the slow accumulation of adaptive changes within each population?

Accepted Answer

Gradualism is the model that predicts populations will diverge from one another through the slow and steady accumulation of adaptive changes. This concept contrasts with punctuated equilibrium, which suggests that evolution occurs in sharp, sudden bursts separated by long periods of stability.

Quiz 20: Speciation and Macroevolution