Question 1

What must be true of any organ described as vestigial?

Accepted Answer

A vestigial organ is an organ that has lost most or all of its original function through evolution. For an organ to be vestigial, it must be homologous to some feature in an ancestor, meaning it has a similar structure to an organ or feature that was present in a common ancestor. Analogy refers to features that have a similar function in different species but have different origins. Therefore, while vestigial organs may be analogous to other organs in other species, this is not a requirement for an organ to be considered vestigial.

Question 2

About 13 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

If the six ground finch species have evolved most recently, their genomes should be more similar to each other than are the genomes of the five tree finch species. This is because they have had less time to accumulate genetic differences between them.

Question 3

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

The sharing of many proteins is evidence of common ancestry and suggests that the similarities in structure and function are due to homology rather than convergent evolution. The distance between the species (A) or their adaptation to their environment (D) are not relevant to the question of homology vs. convergent evolution. The similarity in size of the structures (C) could be evidence of either homology or convergent evolution, depending on other factors.

Question 4

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 labelled 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 horizontal axis of the cladogram depicted...

Question 5

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

Some drug-resistant bacteria were present at the start of treatment, and natural selection increased their frequency.

Question 6

Pseudogenes are ________.

Accepted Answer

Pseudogenes are nonfunctional vestigial genes that have lost their ability to code for proteins. They are often the result of mutations in functional genes that render them nonfunctional.

Question 7

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 whales have very different forelimb anatomy despite sharing a common ancestor with humans and bats suggests that natural selection in an aquatic environment resulted in significant changes to whale forelimb anatomy. This is supported by the theory of evolutionary adaptation, which posits that organisms evolve certain traits in order to better adapt to their environment.

Question 8

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 labelled 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, labelled V-Z, is the common ancestor of the fewest number of species?

Accepted Answer

V is the common ancestor of only one species, W.

Question 9

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 continent suggests that the island forms are descended from mainland forms, as they share a common ancestor. This is because it is unlikely that two unrelated species would evolve to be so similar in appearance and genetics in the same region.

Question 10

Logically, which of these should cast the most doubt on the relationships depicted by an evolutionary tree?

Accepted Answer

Relationships between DNA sequences are considered to be a more accurate reflection of evolutionary relationships than skeletal structures. If the relationships between DNA sequences do not match those depicted by the skeletal patterns on the tree, it suggests that the evolutionary relationships depicted may be inaccurate. Therefore, this should cast the most doubt on the relationships depicted by the evolutionary tree.

Question 11

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 ocean islands in the tropics are known to have a high number of endemic species because they are geographically isolated and have unique environmental conditions. This isolation allows for unique genetic diversification due to lack of gene flow with mainland species. Additionally, the tropical climate and complex topography create microhabitats that are suitable for a wide range of species to evolve and adapt to.

Question 12

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 entirely accurate, as some poorly adapted individuals may still produce offspring, but they may produce fewer or have lower survival rates compared to well-adapted individuals. The other statements are observations and inferences on which natural selection is based.

Question 13

Evolutionary trees such as this are properly understood by scientists to be ________.

Accepted Answer

Evolutionary trees are based on hypotheses that are supported by evidence, but they are not considered absolute facts. As new evidence is discovered, the hypothesis may be revised or even overturned.

Question 14

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 15

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

Accepted Answer

Darwin observed that Australian temperate plants were more similar to Australian tropical plants than to the temperate plants of Europe. This observation provided evidence for the idea that species descended from common ancestors and then diverged in different directions based on their environments. The similarity between Australian plants also suggested that the common ancestor of these species likely existed in Australia rather than Europe.

Question 16

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 labelled 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, labelled 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, as its lineage has evolved into three distinct species (X, Y1, and Y2). The other common ancestors have only given rise to two distinct species or less.

Question 17

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

Accepted Answer

The use of essentially the same genetic code in all organisms is strong evidence for their common origin as it suggests that this code was likely present in the last universal common ancestor (LUCA) from which all life on Earth descended. While all organisms do require energy, reproduce, and show heritable variation, these traits are not exclusive to a common origin and can also be present in unrelated organisms.

Question 18

Which species is most closely related to species W?

Accepted Answer

The answer of Which species is most closely related to...

Question 19

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 fact that DNA sequences in many human genes are very similar to the sequences of corresponding genes in chimpanzees suggests that humans and chimpanzees share a relatively recent common ancestor. This is supported by additional evidence from fossil records and comparative anatomy.

Question 20

Which of these is the extant (that is, living) species most closely related to species X?

Accepted Answer

The answer of Which of these is the extant (that...

Quiz 22: Descent With Modification: a Darwinian View of Life