Question 1

It has been observed that organisms on islands are different from, but closely related to, similar forms found on the nearest continent. This is taken as evidence that ________.

Accepted Answer

The observation that organisms on islands are closely related to similar forms found on the nearest mainland suggests that the island forms are descended from mainland forms that colonized the island. This is known as the theory of island biogeography.

Question 2

Which of the following evidence most strongly supports the common origin of all life on Earth? All organisms ________.

Accepted Answer

The fact that all organisms use essentially the same genetic code, with minor variations, strongly supports the idea of a common origin of life on Earth. This indicates that all organisms share a common ancestor that passed down the same genetic code. The other options (A, C, and D) are shared characteristics of all living organisms, but do not necessarily imply a common origin.

Question 3

Which of the following observations helped Darwin shape his concept of descent with modification?

Accepted Answer

Darwin's concept of descent with modification is supported by the observation that species in a given area are more similar to each other than to species in other areas, regardless of climate. This suggests that geographic proximity and shared ancestry, rather than similar environmental conditions, are more important in determining the characteristics of species. The similarity between South American temperate plants and the tropical plants of South America, rather than to the temperate plants of Europe (D), illustrates this principle by showing that plants in the same geographic region (South America) are more similar to each other despite different climates, supporting the idea of descent with modification from common ancestors.

Question 4

The following questions refer to the evolutionary tree in the figure below.
The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.
 
-Which of the five species, labeled V-Z, is the common ancestor of the fewest number of species?

Accepted Answer

Species V is the common ancestor of only one distinct species, while the other labeled common ancestors (W, X, Y, and Z) are each ancestral to multiple distinct species.

Question 5

The questions below refer to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right) and the vertical axis represents morphological change.
 
-Which of these is the extant (that is, living) species most closely related to species X?

Accepted Answer

Species V is the only extant species, and it is most closely related to species X.

Question 6

The following questions refer to the evolutionary tree in the figure below.
The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.
 
-About thirteen different species of finches inhabit the Galápagos Islands today, all descendants of a common ancestor from the South American mainland that arrived a few million years ago. Genetically, there are four distinct lineages, but the thirteen species are currently classified among three genera. The first lineage to diverge from the ancestral lineage was the warbler finch (genus Certhidea). Next to diverge was the vegetarian finch (genus Camarhynchus), followed by five tree finch species (also in genus Camarhynchus) and six ground finch species (genus Geospiza). If the six ground finch species have evolved most recently, then which of these is the most logical prediction?

Accepted Answer

The six ground finch species, having evolved most recently, are likely to have more similar genomes to each other compared to the older diverged tree finch species.

Question 7

Pseudogenes are ________.

Accepted Answer

Pseudogenes are nonfunctional vestigial genes that are similar to functional genes but have accumulated mutations that render them nonfunctional. They are often remnants of genes that were functional in ancestors but have become nonfunctional in a particular species.

Question 8

The following questions refer to the evolutionary tree in the figure below.
The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.
 
-How many distinct species, both living and extinct, are depicted in this tree?

Accepted Answer

The answer of The following questions refer to the evolutionary...

Question 9

The questions below refer to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right) and the vertical axis represents morphological change.
 
-Logically, which of these should cast the most doubt on the relationships depicted by an evolutionary tree?

Accepted Answer

DNA sequences are considered more reliable and conserved than morphological traits, therefore if the relationships between the DNA sequences do not match the relationships depicted by the morphological traits, it can cast doubt on the accuracy of the evolutionary tree.

Question 10

What must be true of any organ described as vestigial?

Accepted Answer

The term "vestigial" refers to a structure or organ that has lost most or all of its original function over the course of evolutionary history, but remains in the organism due to its presence in ancestors. Homology refers to structures that have a common evolutionary origin, and vestigial structures are homologous to structures in ancestors, but have lost their original function. Analogy refers to structures that have a similar function, but do not have a common evolutionary origin. Therefore, vestigial structures need to be homologous to some feature in an ancestor, making choice B the correct answer.

Question 11

DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees. The most likely explanation for this result is that

Accepted Answer

The similarity in DNA sequences between many human genes and corresponding genes in chimpanzees suggests that humans and chimpanzees share a relatively recent common ancestor. This is the most widely accepted explanation among scientists. The other choices are not supported by the available evidence and are not consistent with the theory of evolution.

Question 12

Within six months of effectively using methicillin to treat S. aureus infections in a community, all new S.aureus infections were caused by MRSA. How can this best be explained?

Accepted Answer

This phenomenon is most likely due to the presence of some drug-resistant bacteria at the start of the treatment, and natural selection increasing their frequency. The use of methicillin would have killed off the susceptible strains, allowing the resistant strains to thrive and eventually become the dominant type. This rapid evolution and selection of resistant strains is a well-known consequence of antibiotic use.

Question 13

Given what we know about evolutionary biology, we expect to find the largest number of endemic species in which of the following geological features, which have existed for at least a few million years?

Accepted Answer

Isolated oceanic islands tend to have high levels of endemism because the species on them are often isolated from other populations and are subject to unique selective pressures, leading to speciation. This process is known as adaptive radiation. Additionally, island isolation prevents many species from colonizing the island, further promoting endemism.

Question 14

Members of two different species possess a similar-looking structure that they use in a similar way to perform about the same function. Which of the following would suggest that the relationship more likely represents homology instead of convergent evolution?

Accepted Answer

Sharing many proteins suggests that the two species may have a common ancestor and inherited the similar structure from a shared ancestor (homology) rather than evolving the structure independently due to similar environmental pressures (convergent evolution).

Question 15

The greatest number of endemic species is expected in environments that are ________.

Accepted Answer

The answer of The greatest number of endemic species is...

Question 16

The following questions refer to the evolutionary tree in the figure below.
The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.
 
-Evolutionary trees such as this are properly understood by scientists to be ________.

Accepted Answer

Evolutionary trees are hypotheses that are subject to modification as new evidence is discovered.

Question 17

The upper forelimbs of humans and bats have fairly similar skeletal structures, whereas the corresponding bones in whales have very different shapes and proportions. However, genetic data suggest that all three kinds of organisms diverged from a common ancestor at about the same time. Which of the following is the most likely explanation for these data?

Accepted Answer

The fact that the forelimbs of whales have very different shapes and proportions compared to humans and bats suggests that natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy. This could be due to the need for different types of movement or adaptations for hunting in water. The genetic data indicating a common ancestor suggests that these changes occurred after the divergence of these three organisms. Therefore, option B is the best choice. Option A is incorrect because forelimb evolution could have been adaptive in whales as well, just in a different way. Option C is not relevant to the given information. Option D is incorrect because whales are properly classified as mammals.

Question 18

Which of the following is not an observation or inference on which natural selection is based?

Accepted Answer

The statement "Poorly adapted individuals never produce offspring" is not an observation or inference on which natural selection is based. Instead, natural selection is based on the observation and inference that there is heritable variation among individuals, species produce more offspring than the environment can support, and only a fraction of an individual's offspring may survive.

Question 19

The following questions refer to the evolutionary tree in the figure below.
The horizontal axis of the cladogram depicted below is a timeline that extends from 100,000 years ago to the present; the vertical axis represents nothing in particular. The labeled branch points on the tree (V-Z) represent various common ancestors. Let's say that only since 50,000 years ago has there been enough variation between the lineages depicted here to separate them into distinct species, and only the tips of the lineages on this tree represent distinct species.
 
-Which of the five common ancestors, labeled V-Z, is the common ancestor of the greatest number of species, both living and extinct?

Accepted Answer

Common ancestor Y is the common ancestor of the greatest number of species, both living and extinct. Y is the only branch point that has descendants that are still alive today (humans). The other branch points represent extinct lineages.

Question 20

The questions below refer to the following evolutionary tree, in which the horizontal axis represents time (present time is on the far right) and the vertical axis represents morphological change.
 
-Which species is most closely related to species W?

Accepted Answer

Species V is the most closely related to species W because they share a more recent common ancestor than any other species in the tree.

Quiz 22: Descent with Modification: A Darwinian View of Life