Question 1

The following questions refer to Figure 19.1, which shows an outcrop of sedimentary rock whose strata are labeled A-D.
  Figure 19.1
-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. Assuming this classification reflects evolutionary relatedness, which of the following is the most accurate phylogenetic tree?
A)

B)

C)

D)

E)

Accepted Answer

Option D shows the correct phylogenetic tree where species X and Y are more closely related to each other than either is to species Z, reflecting their current classification in the same genus.

Question 2

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 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.
D) Both species are well adapted to their particular environments.

Accepted Answer

The shared proteins and nearly identical nucleotide sequences suggest a common ancestry and homology, rather than convergent evolution.

Question 4

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 has lost most or all of its ancestral function in a given species. The term "homologous" refers to organs that are similar in structure and origin between species. Therefore, a vestigial organ must have some similarity to an organ in an ancestor, meaning it is homologous. Analogous features are ones that have similar functions in different organisms but have different origins, so it is not necessary for a vestigial organ to be analogous to an ancestral feature.

Question 5

Two plant species live in the same biome but on different continents. Although the two species are not at all closely related, they may appear quite similar as a result of
A) parallel evolution.
B) convergent evolution.
C) allopatric speciation.
D) introgression.
E) gene flow.

Accepted Answer

Convergent evolution is the process by which different organisms independently evolve similar phenotypic traits, often due to similar environmental pressures. Therefore, the two plant species might appear similar as a result of convergent evolution.

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 species in a particular geographic region and nowhere else in the world. Isolated and heterogeneous environments, such as islands, mountains or isolated pockets of habitat, have limited exchange with other areas and thus promote the development of unique species over time. Homogeneous environments with higher connectivity, on the other hand, allow for greater gene flow and dispersal of species, which reduces the likelihood of endemism. Therefore, isolated and heterogeneous environments are the best choice for a high degree of endemism.

Question 7

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 have a similar structure and share a common evolutionary origin, indicating homology. However, the forelimbs of penguins and seals have evolved to serve a similar function (swimming), even though they look different, indicating analogy. Therefore, the forelimbs are best described as homologous for their bone structure, and analogous for their function as flippers for swimming.

Question 8

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 serve a defensive function, which contradicts the idea that it is completely vestigial.

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

The following questions refer to Figure 19.1, which shows an outcrop of sedimentary rock whose strata are labeled A-D.
  Figure 19.1
-If x indicates the fossils of two closely related species, neither of which is extinct, then their remains may be found in how many of these strata?
A) one stratum
B) two strata
C) three strata
D) four strata

Accepted Answer

The fossils of two closely related species would most likely be found in two strata, as they would have existed during a specific period of time and then become extinct or evolved. These strata would be adjacent to each other and separated by a layer without the fossils. In this case, the most likely strata for the fossils would be C and D, as they are adjacent and of the same age. Therefore, the answer is B.

Question 11

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

Under particular circumstances that persisted for long periods, each of these structures presented greater costs than benefits. The loss of eyes in cave-dwelling organisms, the loss of digestive systems in tapeworms, and the loss of hind limbs in whales all occurred due to natural selection favoring individuals that did not possess these structures. In the particular environments where these organisms lived, these structures were not necessary or even detrimental to survival and reproduction, so individuals without them were more likely to pass on their genes to the next generation. This process of natural selection gradually resulted in the loss of these structures over time.

Question 12

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 13

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 that island organisms are closely related to, but different from, forms on the nearest continent indicates that they share a common ancestry. This is because these organisms must have evolved from a common ancestor and then diverged due to isolation and other selective pressures on the island. The fact that they are closely related suggests that the divergence is a relatively recent event.

Question 14

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, the cost of maintaining antibiotic-resistance genes becomes a burden on the bacterium. Bacteria that have lost these genes will have a fitness advantage over the resistant counterparts and outcompete them, leading to a reduction or loss of these genes in the population over time.

Question 15

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 strongly suggests a common origin of life, as the same basic molecular machinery is used across all living organisms, from single-celled bacteria to complex multicellular organisms. This suggests that all life on Earth shares a common ancestor that developed this basic genetic code, which has been retained and adapted throughout the history of life on Earth.

Question 16

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 genes that have lost their function due to mutations or deletions in their DNA sequence. They are considered vestigial, meaning they are remnants of functional genes that were present in a previous ancestor but are no longer functional in the current organism.

Question 17

The following questions refer to Figure 19.1, which shows an outcrop of sedimentary rock whose strata are labeled A-D.
  Figure 19.1
-If x indicates the location of fossils of two closely related species, then fossils of their most-recent common ancestor are most likely to occur in which stratum?
A) A
B) B
C) C
D) D

Accepted Answer

The principle of superposition states that in an undisturbed sequence of sedimentary rocks, the oldest rocks are at the bottom and the youngest rocks are at the top. Therefore, the stratum that is closest to x and older than the fossils of the two closely related species would be the most likely location for the fossils of their most-recent common ancestor. In this case, that would be stratum C.

Question 18

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, both of which are adapted for swimming and/or flying. The other options are not homologous to the bones in a bird's wing.

Question 19

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

Isolated ocean islands in the tropics are known for having high levels of endemism, meaning species found only in that particular location. This is due to the islands' isolation, unique ecological conditions, and lack of competition and predators that would limit the development of new species. Mountain ranges may also have high levels of endemism, but not as consistently as isolated ocean islands. Midcontinental grasslands and shallow estuaries are less likely to have high levels of endemism.

Question 20

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

Homologous structures are anatomical features that are similar in different species because they have evolved from a common ancestor. The more distantly related two organisms are, the fewer homologous structures they share. Therefore, if two modern organisms are distantly related in an evolutionary sense, one should expect that they share fewer homologous structures than two more closely related organisms.

Quiz 19: Descent With Modification

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?

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?

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

Two plant species live in the same biome but on different continents. Although the two species are not at all closely related, they may appear quite similar as a result of

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

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

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

The following questions refer to Figure 19.1, which shows an outcrop of sedimentary rock whose strata are labeled A-D. Figure 19.1 -If x indicates the fossils of two closely related species, neither of which is extinct, then their remains may be found in how many of these strata?

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?

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

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

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?

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

What is true of pseudogenes?

The following questions refer to Figure 19.1, which shows an outcrop of sedimentary rock whose strata are labeled A-D. Figure 19.1 -If x indicates the location of fossils of two closely related species, then fossils of their most-recent common ancestor are most likely to occur in which stratum?

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

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) ?

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