Question 1

For two populations to accumulate enough genetic differences to cause speciation,the factors that promote these differences

Accepted Answer

In order for speciation to occur, the genetic differences between populations must be significant enough to prevent interbreeding or produce sterile offspring. Ongoing gene flow can limit the accumulation of these differences, so the factors that promote genetic differences (such as natural selection, mutation, and genetic drift) must have a greater impact than the amount of gene flow occurring between populations.

Question 2

How does geographic isolation lead to speciation?

Accepted Answer

Geographic isolation physically separates populations, which can lead to different mutations and environmental pressures acting on each population. Over time, these differences can accumulate and cause genetic divergence. This can eventually lead to speciation, where the two populations can no longer interbreed and are considered separate species.

Question 3

Which of the following is an example of a postzygotic barrier?

Accepted Answer

A postzygotic barrier occurs after fertilization has taken place. Option A describes a prezygotic barrier. Options C and D both describe behavioral barriers, which are also prezygotic barriers. Option B is an example of a postzygotic barrier because it involves the failure of the zygote to develop properly. This can occur if the parents have different numbers of chromosomes or if their chromosomes are not compatible.

Question 4

The two squirrel species shown in the figure below arose from the same ancestor.The Kaibab squirrel lives on the north rim of the Grand Canyon and the Abert's squirrel lives on the south rim.Which is the MOST likely explanation for their speciation?

Accepted Answer

The most likely explanation is that the population of the ancestral squirrel was split by the formation of the Grand Canyon, which led to reproductive isolation and subsequent evolution of different characteristics on each rim, resulting in the two distinct squirrel species.

Question 5

Which of the following would NOT be expected after a population undergoes geographic isolation?

Accepted Answer

The occurrence of geographic isolation leads to a reduction in gene flow between the separated populations, which over time can lead to differences in allele frequencies and potentially result in speciation. An increase in gene flow would require the populations to come back into contact, which would negate the effects of the geographic isolation. Therefore, option (B) is the correct answer as it is the opposite of what is expected after a population undergoes geographic isolation.

Question 6

Before the cultivation of the apple tree,apple maggot flies laid their eggs exclusively on the fruit of Hawthorne trees.As apple orchards became more prominent,apple maggot flies began to lay their eggs on both the fruit of the Hawthorne tree and the fruit of cultivated apple trees.Now,apple maggot flies that live on apple trees mate and lay their eggs at different times of the year than apple maggot flies that live on Hawthorne trees.Is this an example of reproductive isolation?

Accepted Answer

This scenario describes a behavioral prezygotic barrier, as the apple maggot flies that live on apple trees and those that live on Hawthorne trees mate and lay their eggs at different times of the year, which prevents their gametes from encountering each other. This can lead to reproductive isolation, as the two populations are no longer interbreeding and producing viable offspring, ultimately leading to speciation. Option A is incorrect as postzygotic barriers refer to barriers that occur after fertilization and prevent the resulting hybrid offspring from developing properly. Option B is incorrect as the question does not mention anything about the DNA sequence of the two populations. Option C is incorrect as the scenario does not describe a complete speciation event but rather the initial stages of reproductive isolation.

Question 7

Which of the following is an example of a prezygotic barrier that can isolate two species living in the same geographic area?

Accepted Answer

The inability of the gametes of one species of orchid to fuse with the gametes of another species in the same rainforest is an example of a prezygotic barrier. This means that even if they are living in the same geographic area, they are still reproductively isolated from each other. Option A is incorrect because it states that the two populations of birds freely interbreed, which means that there is no prezygotic barrier between them. Option B is incorrect because having the same mating behavior does not necessarily establish a prezygotic barrier between species. Option D is incorrect because the successful breeding of the hybrid with either species suggests that there is no prezygotic barrier between the two parental species.

Question 8

Sympatric speciation

Accepted Answer

Sympatric speciation occurs when a new species emerges from a population in the absence of a geographical barrier. It can occur through various mechanisms such as polyploidy, behavioral differences, or ecological niche differentiation. It is not limited to plants and does not require polyploidy.

Question 9

Although populations of North American apple maggot flies are not geographically isolated,they appear to be in the process of diverging into two new species.Which of the following could be causing speciation between two populations in the lack of geographic isolation?

Accepted Answer

Feeding on two different types of food could create divergent selective pressures on the two populations, leading to genetic and phenotypic differences that could eventually result in speciation. The other choices do not provide a sufficient explanation for speciation in the absence of geographic isolation.

Question 10

Two species live in the same area but breed in different parts of their habitat.These species are

Accepted Answer

Species that live in the same area but breed in different parts of their habitat are considered ecologically isolated because their breeding locations or ecological niches do not overlap, preventing them from interbreeding.

Question 11

A rain forest is a highly complex habitat with organisms living at various levels in the trees,on the ground,and underground.Is it possible to consider two populations of insects living in the same tree to be geographically isolated?

Accepted Answer

Different levels and microhabitats within a single tree can act as barriers to interaction between insect populations, effectively isolating them geographically despite their proximity.

Question 12

A large population of animals is split in two by a physical barrier.Over time,the genetic makeup of the two resulting populations becomes more and more different until each population becomes a separate species.This is an example of

Accepted Answer

Allopatric speciation occurs when a physical barrier separates a population into two geographically isolated groups. Over time, genetic differences accumulate in each group, leading to the evolution of separate species.

Question 13

Geographic isolation limits the ________ between separated populations of a species.

Accepted Answer

Geographic isolation limits the movement of individuals between populations, which reduces gene flow between populations. This can lead to genetic differences and potentially even the development of new species over time. Therefore, gene flow is limited, but genetic differences and adaptation may still occur through other means such as mutation, genetic drift, and natural selection. Directional selection may also occur, but it is not necessarily limited by geographic isolation.

Question 14

In general,geographical isolation occurs when

Accepted Answer

Geographical isolation occurs when populations are separated by a distance that is great enough to limit gene flow. This can occur due to physical barriers such as mountains, rivers, or oceans. The lack of gene flow can lead to genetic divergence and, over time, the formation of new species. Option A refers to migration, which can cause gene flow and is therefore not a form of isolation. Option B refers to how much gene flow is reduced, but not what causes the reduction. Option C refers to mutations overcoming genetic drift, which is not related to geographical isolation.

Question 15

Two birds that are similar in morphology and live in the same forest exhibit different courtship behaviors.Which of the following describes the relationship of these birds?

Accepted Answer

The different courtship behaviors exhibited by the two birds suggest that they are likely different species. Even though they may have similar morphologies due to convergent evolution, their different behaviors would prevent them from successfully mating with each other.

Question 16

Genetic adaptations in two closely related species living within the same territory indicates that

Accepted Answer

The genetic adaptations in two closely related species living within the same territory suggest that sympatric speciation has occurred. This is because in sympatric speciation, new species arise from the same geographic area, without the need for geographic isolation. The fact that the two species have adapted differently to their shared environment indicates that they have undergone divergent evolution, leading to the formation of two distinct species.

Question 17

Two populations of ________ are NOT an example of speciation.

Accepted Answer

Speciation refers to the process by which populations evolve to become distinct species. The key factor in speciation is the inability of populations to interbreed and produce fertile offspring. In choice C, even though the lizards are morphologically distinct, the lack of differences in their DNA sequences suggests they can still interbreed and produce fertile offspring, meaning they have not undergone speciation.

Question 18

For which of the following would a mountain range MOST likely represent a geographic barrier that would block gene flow?

Accepted Answer

Mountain ranges can significantly impede the movement of terrestrial animals that are less capable of traversing steep or high obstacles, such as mice. Birds and butterflies can often fly over such barriers, and deer, depending on the species, might be able to navigate around or over smaller mountain ranges, making mice the most likely to be geographically isolated by mountains.

Question 19

Two populations that live ________ do NOT provide an example of geographic isolation.

Accepted Answer

Geographic isolation refers to populations being separated by physical barriers that prevent them from interbreeding. A small lake does not typically present a significant physical barrier to movement and gene flow for many species, unlike mountains, valleys, or rivers, which can significantly hinder the movement of organisms and thus lead to geographic isolation.

Question 20

Some freshwater snail eggs are accidentally introduced into a new habitat that is geographically isolated from the original population.Which of the following must occur before these snails are described as two separate species?

Accepted Answer

Genetic divergence must occur before the snails can be described as two separate species. This means that over time, the snails in the two populations must accumulate enough genetic differences that prevent or reduce interbreeding if the populations were to come into contact. Without genetic divergence, the snails would still be considered one species regardless of their physical location.

Quiz 13: Adaptation and Species