Question 1

What is true of pseudogenes?
A)They are composed of RNA, rather than DNA.
B)They are the same things as introns.
C)They are unrelated genes that code for the same gene product.
D)They are vestigial genes.

Accepted Answer

Pseudogenes are non-functional copies of genes that have accumulated mutations and are no longer transcribed or translated. Therefore, they are considered vestigial genes.

Question 2

Of the following anatomical structures, which is homologous to the bones in the wing of a bird?
A)cartilage in the dorsal fin of a shark
B)bones in the hind limb of a kangaroo
C)chitinous struts in the wing of a butterfly
D)bony rays in the tail fin of a flying fish
E)bones in the flipper of a whale

Accepted Answer

The bones in the flipper of a whale are homologous to the bones in the wing of a bird, as they both serve a similar function in flight and swimming, respectively. The other structures listed are not homologous as they serve different functions and are composed of different materials.

Question 3

Members of two different species possess a similar-looking structure that they use in a similar fashion to perform the same function. Which information would best help distinguish between an explanation based on homology versus one based on convergent evolution?
A)The two species live at great distance from each other.
B)The two species share many proteins in common, and the nucleotide sequences that code for these proteins are almost identical.
C)The sizes of the structures in adult members of both species are similar in size.
D)Both species are well adapted to their particular environments.

Accepted Answer

The fact that the two species share many proteins in common and have almost identical nucleotide sequences coding for these proteins suggests that the similar structure is likely due to homology rather than convergent evolution, which would not result in such close genetic similarity.

Question 4

Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?
A)Natural selection cannot account for losses, only for innovations.
B)Natural selection accounts for these losses by the principle of use and disuse.
C)Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits.
D)The ancestors of these organisms experienced harmful mutations that forced them to find new habitats that these species had not previously used.

Accepted Answer

Natural selection accounts for these losses by the principle of use and disuse. Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. For example, in dark caves, eyes are of no use and can be costly to maintain, so organisms that lost their eyes may have had a selective advantage. Similarly, if a digestive system is no longer necessary for obtaining nutrients from a host, as in the case of tapeworms, it may be more beneficial to lose this structure entirely. In the case of whales, hind limbs were no longer necessary for their aquatic lifestyle, and may have even presented risks of entanglement or drag, so they were gradually lost over time through natural selection.

Question 5

If two modern organisms are distantly related in an evolutionary sense, then one should expect that
A)they live in very different habitats.
B)they should share fewer homologous structures than two more closely related organisms.
C)their chromosomes should be very similar.
D)they shared a common ancestor relatively recently.
E)they should be members of the same genus.

Accepted Answer

The further two organisms are in evolutionary terms, the fewer homologous structures they should share. Homologous structures are those that are inherited from a common ancestor and suggest a close evolutionary relationship. Therefore, organisms that are distantly related are expected to have fewer homologous structures than those that are closely related.

Question 6

A high degree of endemism is most likely in environments that are
A)easily reached and heterogeneous.
B)isolated and heterogeneous.
C)isolated and homogeneous.
D)isolated and extremely cold.
E)easily reached and homogeneous.

Accepted Answer

Endemism refers to the occurrence of unique species in a specific geographic location. Environments that are isolated and heterogeneous, meaning there are barriers preventing migration and the environment is varied, are more likely to have high levels of endemism. This is because species have had limited opportunities to disperse from that location and adapt to the particular environmental conditions. Thus, option B is the best choice.

Question 7

DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run?
A)Larger doses of DDT should have been applied.
B)All habitats should have received applications of DDT at about the same time.
C)The frequency of DDT application should have been higher.
D)None of the individual insects should have possessed genomes that made them resistant to DDT.
E)DDT application should have been continual.

Accepted Answer

DDT resistance in insects arises from changes in their genetic makeup, specifically mutations in the genes involved in DDT metabolism. Therefore, for the eradication effort to be successful, it would have required that no insects possessed genomes that conferred resistance to DDT.

Question 8

If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more antibiotic-resistance genes, then what should happen in environments from which antibiotics are missing?
A)These genes should continue to be maintained in case the antibiotics ever appear.
B)These bacteria should be outcompeted and replaced by bacteria that have lost these genes.
C)The bacteria should try to make the cost worthwhile by locating, and migrating to, microenvironments where traces of antibiotics are present.
D)The bacteria should start making and secreting their own antibiotics.

Accepted Answer

In the absence of antibiotics, there is no advantage to maintaining antibiotic-resistance genes, and these genes come with a fitness cost. Therefore, bacteria that have lost these genes would be at an advantage and outcompete the antibiotic-resistant bacteria.

Question 9

Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are
A)homologous.
B)examples of convergent evolution.
C)adaptations to a common environment.
D)Three of the responses above are correct.
E)Two of the responses above are correct.

Accepted Answer

The dorsal fins and tails of ichthyosaurs and fish are examples of convergent evolution (B) and adaptations to a common environment (C), making them not homologous but rather analogous structures that evolved independently in response to similar environmental challenges.

Question 10

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
A)island forms and mainland forms descended from common ancestors.
B)common environments are inhabited by the same organisms.
C)the islands were originally part of the continent.
D)the island forms and mainland forms are converging.
E)island forms and mainland forms have identical gene pools.

Accepted Answer

The observation suggests that island forms and mainland forms share common ancestry, as they are closely related but have evolved differently due to geographic isolation on the islands. This is known as the theory of island biogeography, which proposes that isolated islands provide a natural laboratory to study evolution and biogeography.

Question 11

Which of the following pieces of evidence most strongly supports the common origin of all life on Earth?
A)All organisms require energy.
B)All organisms use essentially the same genetic code.
C)All organisms reproduce.
D)All organisms show heritable variation.
E)All organisms have undergone evolution.

Accepted Answer

The fact that all organisms use essentially the same genetic code, which is based on the specific sequence of nucleotide bases in DNA, strongly supports the idea that all life on Earth evolved from a common ancestor. This suggests that the genetic machinery of all organisms has been refined and optimized over billions of years of evolution, with only minor variations in the specific genetic code used by each organism.

Question 12

Both ancestral birds and ancestral mammals shared a common ancestor that was terrestrial. Today, penguins (which are birds)and seals (which are mammals)have forelimbs adapted for swimming. What term best describes the relationship of the bones in the forelimbs of penguins and seals, and what term best describes the flippers of penguins and seals?
A)homologous; homologous
B)analogous; homologous
C)homologous; analogous
D)analogous; analogous

Accepted Answer

The forelimbs of penguins and seals share a common ancestry and have similar bone structure, making them homologous. However, their function in swimming evolved independently, making their flippers analogous.

Question 13

In a hypothetical environment, fish called pike-cichlids are visual predators of algae-eating fish (in other words, they locate their prey by sight). If a population of algae-eaters experiences predation pressure from pike-cichlids, which of the following is least likely to be observed in the algae-eater population over the course of many generations?
A)selection for drab colouration of the algae-eaters
B)selection for nocturnal algae-eaters (active only at night)
C)selection for larger female algae-eaters, bearing broods composed of more, and larger, young
D)selection for algae-eaters that become sexually mature at smaller overall body sizes
E)selection for algae-eaters that are faster swimmers

Accepted Answer

It is unlikely that selection for larger female algae-eaters would occur in this scenario. Predation pressure typically selects for smaller body size and earlier maturation to increase survivorship and reproduction.

Question 14

What must be true of any organ that is described as vestigial?
A)It must be analogous to some feature in an ancestor.
B)It must be homologous to some feature in an ancestor.
C)It must be both homologous and analogous to some feature in an ancestor.
D)It need be neither homologous nor analogous to some feature in an ancestor.

Accepted Answer

A vestigial organ is one that no longer serves its original function or has reduced in size and function over time. This means that it must have had a function or greater size in an ancestor. Homologous structures are those that have the same developmental origin in a common ancestor, which means that vestigial organs must be homologous to some feature in an ancestor. Therefore, the correct answer is B. Option A (analogous to some feature in an ancestor) is incorrect because analogous structures have a similar function but are not necessarily derived from a common ancestor, and vestigial organs are specifically homologous. Option C (both homologous and analogous to some feature in an ancestor) is incorrect because vestigial organs may have lost their original function and no longer have similar functions to current structures in other organisms. Option D (neither homologous nor analogous to some feature in an ancestor) is incorrect because vestigial organs must have a historical connection to ancestral structures.

Question 15

Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, these bones having developed from very similar embryonic tissues. How do biologists interpret these similarities?
A)by identifying the bones as being homologous structures
B)by the principle of convergent evolution
C)by proposing that humans, bats, and dolphins share a common ancestor
D)Three of the statements above are correct.
E)Two of the statements above are correct.

Accepted Answer

The similarities in bone structures among humans, bats, and dolphins are interpreted as evidence of homologous structures (A) and a shared common ancestor (C), indicating evolutionary relationships. Convergent evolution (B) explains similar traits in unrelated species due to similar environmental pressures, not shared ancestry, so it does not apply in this context.

Question 16

Logically, which of these should cast the most doubt on the relationships depicted by an evolutionary tree?
A)None of the organisms depicted by the tree ate the same foods.
B)Some of the organisms depicted by the tree had lived in different habitats.
C)The skeletal remains of the organisms depicted by the tree were incomplete (in other words, some bones were missing).
D)Transitional fossils had not been found.
E)Relationships between DNA sequences among the species did not match relationships between skeletal patterns.

Accepted Answer

DNA sequence comparison is considered the most reliable method for constructing evolutionary trees. If the relationships between DNA sequences among the species did not match relationships between skeletal patterns, it casts the most doubt on the accuracy of the evolutionary tree. The other options may affect the accuracy of the tree but to a lesser extent.

Question 17

If one wanted to find the largest number of endemic species, one should visit which of the following geological features (assuming each has existed for several millions of years)?
A)an isolated ocean island in the tropics
B)an extensive mountain range
C)a midcontinental grassland with extreme climatic conditions
D)a shallow estuary on a warm-water coast

Accepted Answer

An isolated ocean island in the tropics is the best choice for finding the largest number of endemic species because it is a geographically isolated area, which provides unique ecological niches for species to evolve and adapt to. Due to its isolation, it is less likely for species to migrate to and from the island, thus leading to the evolution of distinct endemic species. Additionally, the tropics offer a high degree of biodiversity, which would only add to the number of endemic species found on the island.

Question 18

The rise of methicillin-resistant Staphylococcus aureus (MRSA)can be considered to be an example of artificial selection because
A)humans purposefully raise MRSA in large fermenters in an attempt to make the bacteria ever-more resistant.
B)S. aureus is cultivated by humans to replenish the soil with nutrients.
C)humans synthesize methicillin and create environments in which bacteria frequently come into contact with methicillin.
D)humans are becoming resistant to bacteria by taking methicillin.

Accepted Answer

Artificial selection is the process where humans, through selective breeding or manipulation of the environment, encourage or discourage certain traits in a population of organisms. In the case of MRSA, humans create environments where the bacteria frequently come into contact with methicillin, an antibiotic. This creates selective pressure and leads to the evolution of MRSA strains that are resistant to methicillin. Humans do not purposefully raise MRSA in large fermenters or cultivate it to replenish soil with nutrients, and are not becoming resistant to bacteria by taking methicillin.

Question 19

Currently, two extant elephant species (X and Y)are placed in the genus Loxodonta, and a third species (Z)is placed in the genus Elephas. Thus, which statement should be true?
A)Species X and Y are not related to species Z.
B)Species X and Y share a greater number of homologies with each other than either does with species Z.
C)Species X and Y share a common ancestor that is still extant (in other words, not yet extinct).
D)Species X and Y are the result of artificial selection from an ancestral species Z.
E)Species X, Y, and Z share a common ancestor, but nothing more can be claimed than this.

Accepted Answer

Because species X and Y are placed in the same genus, they are more closely related to each other than either is to species Z, which is in a different genus. Therefore, option B is the correct answer. Option A is incorrect because even though species Z is in a different genus, they are related through a common ancestry. Option C is also incorrect because the common ancestor of X and Y is extinct, not extant. Option D is incorrect because it suggests artificial selection, which is not relevant to this scenario, and Option E is incorrect because we know that species X and Y share more than just a common ancestor - they also share a genus.

Question 20

Which of the following statements most detracts from the claim that the human appendix is a completely vestigial organ?
A)The appendix can be surgically removed with no immediate ill effects.
B)The appendix might have been larger in fossil hominids.
C)The appendix has a substantial amount of defensive lymphatic tissue.
D)Individuals with a larger-than-average appendix leave fewer offspring than those with a below-average-sized appendix.
E)In a million years, the human species might completely lack an appendix.

Accepted Answer

This statement suggests that the appendix may have some current function in immune defense, which detracts from the claim that it is completely vestigial.

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

What is true of pseudogenes?

Of the following anatomical structures, which is homologous to the bones in the wing of a bird?

Members of two different species possess a similar-looking structure that they use in a similar fashion to perform the same function. Which information would best help distinguish between an explanation based on homology versus one based on convergent evolution?

Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?

If two modern organisms are distantly related in an evolutionary sense, then one should expect that

A high degree of endemism is most likely in environments that are

DDT was once considered a "silver bullet" that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run?

If the bacterium Staphylococcus aureus experiences a cost for maintaining one or more antibiotic-resistance genes, then what should happen in environments from which antibiotics are missing?

Ichthyosaurs were aquatic dinosaurs. Fossils show us that they had dorsal fins and tails, as do fish, even though their closest relatives were terrestrial reptiles that had neither dorsal fins nor aquatic tails. The dorsal fins and tails of ichthyosaurs and fish are

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

Which of the following pieces of evidence most strongly supports the common origin of all life on Earth?

What must be true of any organ that is described as vestigial?

Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, these bones having developed from very similar embryonic tissues. How do biologists interpret these similarities?

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

If one wanted to find the largest number of endemic species, one should visit which of the following geological features (assuming each has existed for several millions of years) ?

The rise of methicillin-resistant Staphylococcus aureus (MRSA) can be considered to be an example of artificial selection because

Currently, two extant elephant species (X and Y) are placed in the genus Loxodonta, and a third species (Z) is placed in the genus Elephas. Thus, which statement should be true?

Which of the following statements most detracts from the claim that the human appendix is a completely vestigial organ?