Chapter 25 Practice problems

A

Which gas was least abundant in Earth’s early atmosphere, prior to 2 billion years ago? A) O2 B) CO2 C) CH4 D) H2O E) NH3

A

In their laboratory simulations of the early Earth, Miller and Urey observed the abiotic synthesis of A) amino acids. B) complex organic polymers. C) DNA. D) liposomes. E) genetic systems.

D

Which of the factors below weaken the hypothesis of abiotic synthesis of organic monomers in early Earth’s atmosphere? 1. the relatively short time between intense meteor bombardment and appearance of the first life forms 2. the lack of experimental evidence that organic monomers can form by abiotic synthesis 3. uncertainty about which gases comprised early Earth’s atmosphere A) 1 B) 2 C) 3 D) 1 and 3 E) 2 and 3

D

Which of the following has not yet been synthesized in laboratory experiments studying the origin of life? A) liposomes B) liposomes with selectively permeable membranes C) oligopeptides and other oligomers D) protobionts that use DNA to program protein synthesis E) amino acids

B

In what way were conditions on the early Earth of more than 3 billion years ago different from those on today’s Earth? A) Only early Earth had water vapor in its atmosphere. B) Only early Earth was intensely bombarded by large space debris. C) Only early Earth had an oxidizing atmosphere. D) Less ultraviolet radiation penetrated Earth’s early atmosphere. E) Earth’s early atmosphere had significant quantities of ozone.

B) The proportion of the amino acids was similar to those produced in the Miller-Urey experiment.

What is true of the amino acids that might have been delivered to Earth within carbonaceous chondrites? A) They had the same proportion of L and D isomers as Earth does today. B) The proportion of the amino acids was similar to those produced in the Miller-Urey experiment. C) There were fewer kinds of amino acids on the chondrites than are found in living organisms today. D) They were delivered in the form of polypeptides.

C

Which of the following is the correct sequence of these events in the origin of life? I. formation of protobionts II. synthesis of organic monomers III. synthesis of organic polymers IV. formation of DNA-based genetic systems A) I, II, III, IV B) I, III, II, IV C) II, III, I, IV D) IV, III, I, II E) III, II, I, IV

B

Which is a defining characteristic that all protobionts had in common? A) the ability to synthesize enzymes B) a surrounding membrane or membrane-like structure C) RNA genes D) a nucleus E) the ability to replicate RNA

D

Although absolute distinctions between the "most evolved" protobiont and the first living cell are unclear, biologists generally agree that one major difference is that the typical protobiont could not A) possess a selectively permeable membrane boundary. B) perform osmosis. C) grow in size. D) perform controlled, precise reproduction. E) absorb compounds from the external environment.

C

The first genes on Earth were probably A) DNA produced by reverse transcriptase from abiotically produced RNA. B) DNA molecules whose information was transcribed to RNA and later translated in polypeptides. C) auto-catalytic RNA molecules. D) RNA produced by autocatalytic, proteinaceous enzymes. E) oligopeptides located within protobionts.

A

) RNA molecules can both carry genetic information and be catalytic. This supports the proposal that A) RNA was the first hereditary information. B) protobionts had an RNA membrane. C) RNA could make energy. D) free nucleotides would not have been necessary ingredients in the synthesis of new RNA molecules. E) RNA is a polymer of amino acids.

A

What probably accounts for the switch to DNA-based genetic systems during the evolution of life on Earth? A) DNA is chemically more stable and replicates with fewer errors (mutations) than RNA. B) Only DNA can replicate during cell division. C) RNA is too involved with translation of proteins and cannot provide multiple functions. D) DNA forms the rod-shaped chromosomes necessary for cell division. E) Replication of RNA occurs too slowly.

B

The synthesis of new DNA requires the prior existence of oligonucleotides to serve as primers. On Earth, these primers are small RNA molecules. This latter observation is evidence in support of the hypothesized existence of A) a snowball Earth. B) earlier genetic systems than those based on DNA. C) the abiotic synthesis of organic monomers. D) the delivery of organic matter to Earth by meteors and comets. E) the endosymbiotic origin of mitochondria and chloroplasts.

C

Several scientific laboratories across the globe are involved in research concerning the origin of life on Earth. Which of these questions is currently the most problematic and would have the greatest impact on our understanding if we were able to answer it? A) How can amino acids, simple sugars, and nucleotides be synthesized abiotically? B) How can RNA molecules catalyze reactions? C) How did RNA sequences come to carry the code for amino acid sequences? D) How could polymers involving lipids and/or proteins form membranes in aqueous environments? E) How can RNA molecules act as templates for the synthesis of complementary RNA molecules?

D

If natural selection in a particular environment favored genetic systems that permitted the production of daughter "cells" that were genetically dissimilar from the mother "cells," then one should expect selection for I. polynucleotide polymerase with low mismatch error rates. II. polynucleotide polymerases without proofreading capability. III. batteries of efficient polynucleotide repair enzymes. IV. polynucleotide polymerases with proofreading capability. V. polynucleotide polymerases with high mismatch error rates. A) I only B) I and IV C) I, III, and IV D) II and V E) II, III and V

C

If relatively small carbonaceous chondrites from space were a significant source of Earth’s original amino acids, then which two of these would have been most important in permitting their organic materials to survive impact with Earth? I. Carbonaceous chondrites must contain no D-amino acids. II. Earth’s early atmosphere must have had little free oxygen. III. The chondrites must have arrived on Earth before 4.2 billion years ago. IV. Earth’s early atmosphere must have been dense enough to dramatically slow the chondrites before they impacted. V. The chondrites must have impacted land, rather than a large body of water. A) I & II B) II & III C) II & IV D) II & V E) III & IV

E

If the half-life of carbon-14 is about 5,730 years, then a fossil that has one-sixteenth the normal proportion of carbon-14 to carbon-12 should be about how many years old? A) 1,400 B) 2,800 C) 11,200 D) 16,800 E) 22,400

E

Which measurement would help determine absolute dates by radiometric means? A) the accumulation of the daughter isotope B) the loss of parent isotopes C) the loss of daughter isotopes D) all three of these E) only A and B

D

How many half-lives should have elapsed if 6.25% of the parent isotope remains in a fossil at the time of analysis? A) one B) two C) three D) four E) five

D

Approximately how far back in time does the fossil record extend? A) 6,000 years B) 3,500,000 years C) 6,000,000 years D) 3,500,000,000 years E) 5,000,000,000,000 years

D

Assuming that the rate of sea-floor spreading was constant during the 1-million-year period depicted above, Earth’s magnetic field has undergone reversal at an average rate of once every A) 10,000 years. B) 25,000 years. C) 100,000 years. D) 250,000 years. E) 1,000,000 years.

E

Earth’s current magnetic field is the same as it had been when which sea-floor areas solidified? I. area B II. area C III. area D IV. area E A) I only B) II only C) I and II D) I and III E) II and IV

C

Assuming that the rate of sea-floor spreading was constant during the 1-million-year period depicted above, what should be the approximate age of marine fossils found in undisturbed sedimentary rock immediately overlying the igneous rock at the arrow labeled "II"? A) 10,000 years B) 250,000 years C) 500,000 years D) 1,000,000 years

D

Argon-40, the daughter isotope of potassium-40, is a gas. Elemental potassium has an atomic mass of about 39. If the submersible robot (which is equipped with a drill that is long enough to get to the igneous rock) ascends from depth too quickly, gases trapped within igneous rock may rapidly expand, fracture the rock, and escape from the sample before it can be dated aboard the floating research vessel. Rock samples can also absorb argon gas. Which of these techniques has the highest chance of providing inaccurate dates of igneous rocks distant from the rift valley, and what type of inaccuracy would it cause? A) if the date of the rock is determined by comparing the ratio of potassium-40 to potassium-39, underestimation of age B) if the submersible robot is retrieved from the sea floor at a very slow speed, overestimation of age C) if the submersible robot is equipped with a decompression chamber for the samples, underestimation of age D) if the submersible robot keeps the sample in a chamber of pure argon at high pressure, overestimation of age

C

What is true of the fossil record of mammalian origins? A) It is a good example of punctuated equilibrium. B) It shows that mammals and birds evolved from the same kind of dinosaur. C) It includes transitional forms with progressively specialized teeth. D) It indicates that mammals and dinosaurs did not overlap in geologic time. E) It includes a series that shows the gradual change of scales into fur.

D

If a fossil is encased in a stratum of sedimentary rock without any strata of igneous rock (e.g., lava, volcanic ash) nearby, then it should be A) easy to determine the absolute age of the fossil, because the radioisotopes in the sediments will not have been "reset" by the heat of the igneous rocks. B) easy to determine the absolute age of the fossil, because the igneous rocks will not have physically obstructed the deposition of sediment of a single age next to the fossil. C) difficult to determine the absolute age of the fossil, because the "marker fossils" common to igneous rock will be absent. D) difficult to determine the absolute age of the fossil, because radiometric dating of sedimentary rock is less accurate than that of igneous rock.

E

Let’s say that a hypothetical submersible robot was used to collect samples of sedimentary rock from the sea floor along the section illustrated. The robot moved back and forth along the transect, collecting first from site A, then site III, then site B, then site II, and lastly site D. Assuming that sedimentation has occurred at a constant rate along the transect over the past million years, rearrange the sites mentioned above on the basis of the thickness of the sediments overlying the igneous rock, from thickest to thinnest. A) A, B, II, D, III B) I, II, III C) III, II, D, B, A D) III, A, II, B, D E) III, D, II, B, A

D

An early consequence of the release of oxygen gas by plant and bacterial photosynthesis was to A) make life on land difficult for aerobic organisms. B) change the atmosphere from oxidizing to reducing. C) make it easier to maintain reduced molecules. D) cause iron in ocean water and terrestrial rocks to rust (oxidize). E) prevent the formation of an ozone layer.

B

Arrange these events from earliest to most recent. 1. emission of lava in what is now Siberia at time of Permian extinctions 2. emission of lava that solidified at the same time as iron-bearing terrestrial rocks began to rust 3. emission of lava that solidified at the same time as rusted iron precipitated from seawater 4. emission of lava in what is now India at time of Cretaceous extinctions A) 3, 1, 2, 4 B) 3, 2, 1, 4 C) 3, 1, 4, 2 D) 1, 3, 2, 4 E) 1, 2, 3, 4

Answer: A

Which free-living cells were the earliest contributors to the formation of Earth’s oxidizing atmosphere? A) cyanobacteria B) chloroplasts C) mitochondria D) seaweeds E) endosymbionts

E) The oldest fossilized cells resemble prokaryotes.

Which of the following statements provides the strongest evidence that prokaryotes evolved before eukaryotes? A) the primitive structure of plants B) meteorites that have struck Earth C) abiotic laboratory experiments that produced liposomes D) Liposomes closely resemble prokaryotic cells. E) The oldest fossilized cells resemble prokaryotes.

C

What is thought to be the correct sequence of these events, from earliest to most recent, in the evolution of life on Earth? 1. origin of mitochondria 2. origin of multicellular eukaryotes 3. origin of chloroplasts 4. origin of cyanobacteria 5. origin of fungal-plant symbioses A) 4, 3, 2, 1, 5 B) 4, 1, 2, 3, 5 C) 4, 1, 3, 2, 5 D) 4, 3, 1, 5, 2 E) 3, 4, 1, 2, 5

C

If it were possible to conduct sophisticated microscopic and chemical analyses of microfossils found in 3.2-billion-year-old stromatolites, then within such microfossils, one should be surprised to observe evidence of: I. double-stranded DNA II. a nuclear envelope III. a nucleoid IV. a nucleolus V. nucleic acids A) II only B) III only C) II and IV D) II, III, and IV E) all five of these

C

Recent evidence indicates that the first major diversification of multicellular eukaryotes may have coincided in time with the A) origin of prokaryotes. B) switch to an oxidizing atmosphere. C) melting that ended the "snowball Earth" period. D) origin of multicellular organisms. E) massive eruptions of deep-sea vents.

A

Which of these observations fails to support the endosymbiotic theory for the origin of eukaryotic cells? A) the existence of structural and molecular differences between the plasma membranes of prokaryotes and the internal membranes of mitochondria and chloroplasts B) the existence of size differences between the cytosolic ribosomes of eukaryotes and the ribosomes within mitochondria and chloroplasts C) the existence of size differences between some prokaryotic cells and mitochondria D) the existence of rRNA sequence differences between the cytosolic ribosomes of eukaryotes and the ribosomes within mitochondria and chloroplasts

C

Which event is nearest in time to the end of the period known as snowball Earth? A) oxygenation of Earth’s seas and atmosphere B) evolution of mitochondria C) Cambrian explosion D) evolution of true multicellularity E) Permian extinction

A

The snowball Earth hypothesis provides a possible explanation for the A) diversification of animals during the late Proterozoic. B) oxygenation of Earth’s seas and atmosphere. C) colonization of land by plants and fungi. D) origin of O2-releasing photosynthesis. E) existence of prokaryotes around hydrothermal vents on the ocean floor.

A

If two continental land masses converge and are united, then the collision should cause A) a net loss of intertidal zone and coastal habitat. B) the extinction of any species adapted to intertidal and coastal habitats. C) an overall decrease in the surface area located in the continental interior. D) a decrease in climatic extremes in the interior of the new super-continent. E) the maintenance of the previously existing ocean currents and wind patterns.

C

A major evolutionary episode that corresponds in time most closely with the formation of Pangaea was the A) origin of humans. B) Cambrian explosion. C) Permian extinctions. D) Pleistocene ice ages. E) Cretaceous extinctions.

C

On the basis of their morphologies, how might Linnaeus have classified the Hawaiian silverswords? A) He would have placed them all in the same species. B) He would have classified them the same way that modern botanists do. C) He would have placed them in more species than modern botanists do. D) He would have used evolutionary relatedness as the primary criterion for their classification. E) Both B and D are correct.

B

Anatomically, what was true of Lystrosaurus? A) Its jaw would have been hinged the same way as the jaws of the early reptiles were hinged. B) It was a tetrapod. C) It had thin, moist skin without scales. D) Its dentition (tooth pattern) was typical of modern mammals. E) It would have had no temporal fenestra in its skull.

D

Which of Lystrosaurus’ features help explain why these organisms fossilized so abundantly? I. the presence of hard parts, such as tusks II. its herbivorous diet III. its persistence across at least two geological eras IV. its widespread geographic distribution V. its mixture of reptilian and mammalian features A) I and III B) III and V C) III and V D) I, III, and IV E) II, III, IV, and V

C

Which of these is the most likely explanation for the modern-day distribution of dicynodont fossils? A) There had been two previous super-continents that existed at different times long before the Permian period. B) The dicynodonts were evenly distributed throughout all of Pangaea. C) The dicynodonts were distributed more abundantly throughout Gondwanaland than throughout any other land mass. D) The dicynodonts were able to swim long distances, up to thousands of kilometers. E) The dicynodonts could survive for periods of months aboard "rafts" of vegetation, which carried them far and wide, but not to the northern hemisphere.

E

The observation that tusks were limited to males in several species, and were apparently not used in food-gathering, is evidence that the tusks probably A) were used by males during the sex act. B) served as heat-dissipation structures. C) are homologous to claws. D) were insignificant to the survival and/or reproduction of dicynodonts. E) were maintained as the result of sexual selection.

Answer: C

Which of these is the most likely explanation for the existence of dicynodont fossils on modern-day Antarctica? A) They arrived there aboard "rafts" of vegetation, and quickly adapted to the bitterly cold climate. B) Earth’s polar regions were once so warm (especially immediately after the "snowball Earth period") that reptiles and mammal-like reptiles flourished there. C) The landmass that is now the Antarctic continent was formerly located at a more-northerly position, and was also united to other landmasses. D) Dicynodonts originated on the island continent of Antarctica and went extinct as the continent migrated to its current position at the South Pole.

Answer: A

Dicynodonts survived the Permian extinction and, therefore, existed during both the A) Paleozoic and Mesozoic eras. B) Proterozoic and Archaean eons. C) Proterozoic and Phanerozoic eons. D) Mesozoic and Cenozoic eras. E) Carboniferous and Permian periods.

Answer: B

There are at least a dozen known species in the extinct genus Lystrosaurus. If each species was suited to a quite different environment, then this relatively large number of species is likely due to A) sexual selection. B) adaptive radiation. C) heterochrony. D) polyploidy. E) species selection.

Answer: D

The dicynodonts survived the mass extinction that was most closely correlated in time, if not in cause, with A) snowball Earth. B) a large (10 km) meteor striking the Earth. C) an intense period of sun-spot formation, with subsequent increase in solar radiation. D) the formation of Pangaea and lava flows that covered large portions of Pangaea. E) the pleistocene Ice Age.

Answer: E

The dicynodonts that survived the Permian extinction would initially have had to endure (or escape from) the physical effects of __________, and subsequently, the biological effects of __________. A) warm temperatures, decreased metabolism B) arid conditions, disease C) meteorite shock waves, lack of food D) increased sea level, lack of freshwater E) volcanic ash in the atmosphere, increased predation

B

If an increase in dicynodont species diversity (i.e., number of species) occurred soon after the Permian extinction, and if it occurred for the same general reason usually given for the increase in mammalian diversity following the Cretaceous extinction, then it should be attributed to A) an innovation among the dicynodonts that allowed them to fill brand new niches. B) the availability of previously occupied niches. C) the extinction of the dinosaurs (except the birds). D) the evolution of humans.

B

An organism has a relatively large number of Hox genes in its genome. Which of the following is not true of this organism? A) It evolved from evolutionary ancestors that had fewer Hox genes. B) It must have multiple paired appendages along the length of its body. C) It has the genetic potential to have a relatively complex anatomy. D) At least some of its Hox genes owe their existence to gene duplication events. E) Its Hox genes cooperated to produce the positional patterns of this organism as it developed.

B

Bagworm moth caterpillars feed on evergreens and carry a silken case or bag around with them in which they eventually pupate. Adult female bagworm moths are larval in appearance; they lack the wings and other structures of the adult male and instead retain the appearance of a caterpillar even though they are sexually mature and can lay eggs within the bag. This is a good example of A) allometric growth. B) paedomorphosis. C) sympatric speciation. D) adaptive radiation. E) changes in homeotic genes.

E

As rat pups mature, the growth of their snouts and tails outpaces growth of the rest of their bodies, producing the appearance of sexually mature males. It is found that sexually mature female rats prefer to mate with mutant, sexually mature males that possess snouts and tails with juvenile proportions. Which of the following terms is (are) appropriately applied to this situation? A) sexual selection B) paedomorphosis C) allometric growth D) B and C only E) A, B, and C

Answer: D

A hypothetical mutation in a squirrel population produces organisms with eight legs rather than four. Further, these mutant squirrels survive, successfully invade new habitats, and eventually give rise to a new species. The initial event, giving rise to extra legs, would be a good example of A) punctuated equilibrium. B) species selection. C) habitat selection. D) changes in homeotic genes. E) allometry.

Answer: D

The loss of ventral spines by modern freshwater sticklebacks is due to natural selection operating on the phenotypic affects of Pitx1 gene A) duplication (gain in number). B) elimination (loss). C) mutation (change). D) silencing (loss of expression). E) up-regulation (increase in expression).

Answer: B

If these fly species lost the ability to fly independently of each other as a result of separate mutation events in each lineage, then the flightless condition in these species could be an example of A) adaptive radiation. B) species selection. C) sexual selection. D) allometric growth. E) habitat differentiation.

Answer: E

In each fly species, the entire body segment that gave rise to the original flight wings is missing. The mutation(s) that led to the flightless condition could have A) duplicated all of the Hox genes in these flies’ genomes. B) altered the nucleotide sequence within a Hox gene. C) altered the expression of a Hox gene. D) either A or B E) either B or C

Answer: E

If the foods preferred by each species are found on different parts of the island, and if the flies mate and lay eggs on their food sources, regardless of the location of the food sources, then the speciation events involving these fly species may have been driven, at least in part, by which of the following? A) autopolyploidy B) allopolyploidy C) species selection D) genetic drift E) habitat differentiation

D

If the males’ halteres have species-specific size, shape, color, and use in courtship displays, and if the species’ ranges overlap, then the speciation events may have been driven, at least in part, by which of the following? A) autopolyploidy B) allopolyploidy C) species selection D) sexual selection E) habitat differentiation

Answer: E

Fly species W, found in a certain part of the island, produces fertile offspring with species Y. Species W does not produce fertile offspring with species X or Z. If no other species can hybridize, then species W and Y A) have genomes that are still similar enough for successful meiosis to occur in hybrid flies. B) have more genetic similarity with each other than either did with the other two species. C) may fuse into a single species if their hybrids remain fertile over the course of many generations. D) A and B only E) A, B, and C

Answer: B

Which of these fly organs, as they exist in current fly populations, best fits the description of an exaptation? A) wings B) balancing organs C) mouthparts D) thoraxes E) walking appendages

B) Evolution is limited by historical constraints.

The existence of the phenomenon of exaptation is most closely associated with which of the following reasons that natural selection cannot fashion perfect organisms? A) Natural selection and sexual selection can work at cross-purposes to each other. B) Evolution is limited by historical constraints. C) Adaptations are often compromises. D) Chance events affect the evolutionary history of populations in environments that can change unpredictably.

B) ancestral versions of this protein assemblage were either less functional, or had different functions, than modern prokaryotic flagella.

If the complex protein assemblage of the prokaryotic flagellum arose by the same general processes as those of the complex eyes of mollusks (such as squids and octopi), then A) natural selection cannot account for the rise of the prokaryotic flagellum. B) ancestral versions of this protein assemblage were either less functional, or had different functions, than modern prokaryotic flagella. C) scientists should accept the conclusion that neither eyes nor flagella could have arisen by evolution. D) we can conclude that both of these structures must have arisen through the direct action of an "intelligent designer." E) Both A and C are true.

C) exaptation

If the prokaryotic flagellum developed from assemblages of proteins that originally were not involved with cell motility but with some other function instead, then the modern prokaryotic flagellum is a(n) A) vestigial organ. B) adoption. C) exaptation. D) homogeneous organ. E) allometric organ.

D) He would have proposed that less complicated, but still functional, versions (maybe even with a different function) had existed in ancestral prokaryotes.

In certain motile prokaryotes, dozens of different proteins comprise the motor that powers the prokaryotic flagellum. The motor has a complicated structure, and its various proteins interact to carry out its function. Based on Darwin’s explanation for the existence of human eyes, how would he probably have explained the existence of such motors? A) Because he could not have explained their existence, he would have used supernatural agents as a temporary explanation until the gap in scientific knowledge had been filled. B) Because he could not have explained their existence, he would have concluded that the human brain has not (and probably cannot) evolve the capability to solve such complex problems. C) He would have proposed that these motors were the products of aliens, and had been delivered to Earth by extraterrestrial visitors. D) He would have proposed that less complicated, but still functional, versions (maybe even with a different function) had existed in ancestral prokaryotes.

D) natural selection can produce new structures by cobbling together parts of other structures

It has been found that certain proteins of the complex motor that drives bacterial flagella are modified versions of proteins that had previously belonged to plasma membrane pumps. This is evidence in support of the claim that A) some structures are so complex that natural selection cannot, and will not, explain their origins. B) the power of natural selection allows it to act in an almost predictive fashion, producing organs that will be needed in future environments. C) the motors of bacterial flagella were originally synthesized abiotically. D) natural selection can produce new structures by cobbling together parts of other structures. E) bacteria that possess flagella must have lost the ability to pump certain chemicals across their plasma membranes.

C) exaptations.

An explanation for the evolution of insect wings suggests that wings began as lateral extensions of the body that were used as heat dissipaters for thermoregulation. When they had become sufficiently large, these extensions became useful for gliding through the air, and selection later refined them as flight-producing wings. If this hypothesis is correct, insect wings could best be described as A) adaptations. B) mutations. C) exaptations. D) isolating mechanisms. E) examples of natural selection’s predictive ability.

B) They are homologous organs.

If one organ is an exaptation of another organ, then what must be true of these two organs? A) They are both vestigial organs. B) They are homologous organs. C) They are undergoing convergent evolution. D) They are found together in the same hybrid species. E) They have the same function.

C) species selection.

Many species of snakes lay eggs, but in the forests of northern Minnesota where growing seasons are short, only live-bearing snake species are present. This trend toward species that perform live birth is an example of A) natural selection. B) sexual selection. C) species selection. D) goal direction in evolution. E) directed selection.

A) species selection

In the 5—7 million years that the hominid lineage has been diverging from its common ancestor with the great apes, dozens of hominid species have arisen, often with several species coexisting in time and space. As recently as 30,000 years ago, Homo sapiens coexisted with Homo neanderthalensis. Both species had large brains and advanced intellects. The fact that these traits were common to both species is most easily explained by which of the following? A) species selection B) uniformitarianism C) sexual selection D) A and B only E) A, B, and C

D) in particular environments, similar adaptations can be beneficial in more than one species.

The existence of evolutionary trends, such as increasing body sizes among horse species, is evidence that A) a larger volume-to-surface area ratio is beneficial to all mammals. B) an unseen guiding force is at work. C) evolution always tends toward increased complexity or increased size. D) in particular environments, similar adaptations can be beneficial in more than one species. E) evolution generally progresses toward some predetermined goal.

B) their feathers originally served as insulation, and only later became flight surfaces.

Fossil evidence indicates that several kinds of flightless dinosaurs possessed feathers. If some of these feather-bearing dinosaurs incubated clutches of eggs in carefully constructed nests, this might be evidence supporting the claim that A) dinosaurs were as fully endothermal (warm-blooded) as modern birds and mammals. B) their feathers originally served as insulation, and only later became flight surfaces. C) the earliest reptiles could fly, and the feathers of flightless dinosaurs were vestigial flight surfaces. D) the feathers were plucked from the bodies of other adults to provide nest-building materials. E) all fossils with feathers are actually some kind of bird.

C) The Pax-6 gene was an innovation of an ancestral animal of the early Cambrian. Animals with eyes or eyespots are descendants of this ancestor.

The appearance of Pax-6 in all animals with eyes can be explained in multiple ways. Based on the information above, which explanation is most likely? A) Pax-6 in all of these animals is not homologous; it arose independently in many different animal phyla due to intense selective pressure favoring vision. B) The Pax-6 gene is really not "one" gene. It is many different genes that, over evolutionary time and due to convergence, have come to have a similar nucleotide sequence and function. C) The Pax-6 gene was an innovation of an ancestral animal of the early Cambrian. Animals with eyes or eyespots are descendants of this ancestor. D) The perfectly designed Pax-6 gene appeared instantaneously in all animals created to have eyes or eyespots.

D) differences in the control of Pax-6 expression among these organisms.

Fruit fly eyes are of the compound type, structurally very different from the camera-type eyes of mammals. Even the camera-type eyes of mollusks, such as octopi, are structurally quite different from those of mammals. Yet, fruit flies, octopi, and mammals possess very similar versions of Pax-6. The fact that the same gene helps produce very different types of eyes is most likely due to A) the few differences in nucleotide sequence among the Pax-6 genes of these organisms. B) variations in the number of Pax-6 genes among these organisms. C) the independent evolution of this gene at many different times during animal evolution. D) differences in the control of Pax-6 expression among these organisms.

B) During vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual receptor pigments.

Pax-6 usually causes the production of a type of light-receptor pigments. In vertebrate eyes, though, a different gene (the rh gene family) is responsible for the light-receptor pigments of the retina. The rh gene, like Pax-6, is ancient. In the marine ragworm, for example, the rh gene causes production of c-opsin, which helps regulate the worm’s biological clock. Which of these most likely accounts for vertebrate vision? A) The Pax-6 gene mutated to become the rh gene among early mammals. B) During vertebrate evolution, the rh gene for biological clock opsin was co-opted as a gene for visual receptor pigments. C) In animals more ancient than ragworms, the rh gene(s) coded for visual receptor pigments; in lineages more recent than ragworms, rh has flip-flopped several times between producing biological clock opsins and visual receptor pigments. D) Pax-6 was lost from the mammalian genome, and replaced by the rh gene much later.

C) resemble structures formed by bacterial communities that are found today in some warm, shallow, salty bays.

Fossilized stromatolites A) all date from 2.7 billion years ago. B) formed around deep-sea vents. C) resemble structures formed by bacterial communities that are found today in some warm, shallow, salty bays. D) provide evidence that plants moved onto land in the company of fungi around 500 million years ago. E) contain the first undisputed fossils of eukaryotes and date from 2.1 billion years ago.

A) the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules

The oxygen revolution changed Earth’s environment dramatically. Which of the following adaptations took advantage of the presence of free oxygen in the oceans and atmosphere? A) the evolution of cellular respiration, which used oxygen to help harvest energy from organic molecules B) the persistence of some animal groups in anaerobic habitats C) the evolution of photosynthetic pigments that protected early algae from the corrosive effects of oxygen D) the evolution of chloroplasts after early protists incorporated photosynthetic cyanobacteria E) the evolution of multicellular eukaryotic colonies from communities of prokaryotes

E) India was a separate continent until 55 million years ago.

Select the factor most likely to have caused the animals and plants of India to differ greatly from species in nearby Southeast Asia. A) The species have become separated by convergent evolution. B) The climates of the two regions are similar. C) India is in the process of separating from the rest of Asia. D) Life in India was wiped out by ancient volcanic eruptions. E) India was a separate continent until 55 million years ago.

B) genetic drift

Adaptive radiations can be a direct consequence of four of the following five factors. Select the exception. A) vacant ecological niches B) genetic drift C) colonization of an isolated region that contains suitable habitat and few competitor species D) evolutionary innovation E) an adaptive radiation in a group of organisms (such as plants) that another group uses as food

C) a change in a developmental gene or in its regulation that altered the spatial organization of body parts.

A genetic change that caused a certain Hox gene to be expressed along the tip of a vertebrate limb bud instead of farther back helped to make possible the evolution of the tetrapod limb. This type of change is illustrative of A) the influence of environment on development. B) paedomorphosis. C) a change in a developmental gene or in its regulation that altered the spatial organization of body parts. D) heterochrony. E) gene duplication.

D) formation of protobionts that use DNA to direct the polymerization of amino acids

Which of the following steps has not yet been accomplished by scientists studying the origin of life? A) synthesis of small RNA polymers by ribozymes B) abiotic synthesis of polypeptides C) formation of molecular aggregates with selectively permeable membranes D) formation of protobionts that use DNA to direct the polymerization of amino acids E) abiotic synthesis of organic molecules

C) exaptation.

A swim bladder is a gas-filled sac that helps fish maintain buoyancy. The evolution of the swim bladder from lungs of an ancestral fish is an example of A) an evolutionary trend. B) paedomorphosis. C) exaptation. D) adaptive radiation. E) changes in the Hox gene expression.