Mel Bio 25

A sediment core is removed from the floor of an inland sea. The sea has been in existence, off and on, throughout the entire time that terrestrial life has existed. Researchers wish to locate and study the terrestrial organisms fossilized in this core. The core is illustrated as a vertical column, with the top of the column representing the most recent strata and the bottom representing the time when land was first colonized by life. In order to assign absolute dates to fossils in this sediment core, it would be most helpful if A. volcanic ash layers were regularly interspersed between the sedimentary strata. B. the sediments had not been affected by underwater currents during their deposition. C. metamorphic rock strata alternated with sedimentary rock strata. D. we knew the order in which the fossils occurred in the core. E. fossils throughout the column had equal ratios of a parental radioisotope to its daughter isotope.

A

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

A

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

A

Larval flies (maggots) express the Ubx gene in all of their segments, and thereby lack appendages. If this same gene continued to be expressed throughout subsequent developmental stages, except in the head region, and if the result was a fit, sexually mature organism that still strongly resembled a maggot, this would be an example of A. paedomorphosis. B. exaptation. C. adaptive radiation. D. homochrony.

A

Many species of snakes lay eggs. However, 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 in a particular environment is an example of A. species selection. B. sexual selection. C. natural selection. D. directed selection. E. goal direction in evolution.

A

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 did RNA sequences come to carry the code for amino acid sequences? B. How could polymers involving lipids and/or proteins form membranes in aqueous environments? C. How can RNA molecules act as templates for the synthesis of complementary RNA molecules? D. How can RNA molecules catalyze reactions? E. How can amino acids, simple sugars, and nucleotides be synthesized abiotically?

A

The following question refers to the description below. All animals with eyes or eyespots that have been studied so far share a gene in common. When mutated, the gene Pax-6 causes lack of eyes in fruit flies, tiny eyes in mice, and missing irises (and other eye parts) in humans. The sequence of Pax-6 in humans and mice is identical. There are so few sequence differences with fruit fly Pax-6 that the human/mouse version can cause eye formation in eyeless fruit flies, even though vertebrates and invertebrates last shared a common ancestor more than 500 million years ago. Fruit fly eyes are of the compound type, which is structurally very different from the camera-type eyes of mammals. Even the camera-type eyes of molluscs, 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. differences in the control of Pax-6 expression among these organisms. B. the few differences in nucleotide sequence among the Pax-6 genes of these organisms. C. the independent evolution of this gene at many different times during animal evolution. D. variations in the number of Pax-6 genes among these organisms.

A

The major evolutionary episode corresponding most closely in time with the formation of Pangaea was the A. Permian extinctions. B. Cretaceous extinctions. C. Cambrian explosion. D. Pleistocene ice ages.

A

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. earlier genetic systems than those based on DNA. B. the abiotic synthesis of organic monomers. C. the endosymbiotic origin of mitochondria and chloroplasts. D. a snowball Earth. E. the delivery of organic matter to Earth by meteors and comets

A

Which of the following is the correct sequence of 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. II, III, I, IV B. I, II, III, IV C. II, III, IV, I D.I, III, II, IV

A

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. adaptive radiation. B. exaptation. C. paedomorphosis. D. an evolutionary trend. E. changes in Hox gene expression.

B

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

B

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

B

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

B

The evolution of mammals from early tetrapods A. involves changes in the temporal fenestra of the skull. B. is an example of macroevolution. C. involves specialization in teeth. D. is well documented by a series of transitional fossils. E. All of the above statements are true.

B

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

B

The existence of the phenomenon of exaptation is most closely associated with which of the following observations 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.Chance events affect the evolutionary history of populations in environments that can change unpredictably. D. Adaptations are often compromises.

B

The following question is based on the observation that several dozen different proteins comprise the prokaryotic flagellum and its attachment to the prokaryotic cell, producing a highly complex structure. If the complex protein assemblage of the prokaryotic flagellum arose by the same general processes as those of the complex eyes of molluscs (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. we can conclude that both of these structures must have arisen through the direct action of an "intelligent designer." D. scientists should accept the conclusion that neither eyes nor flagella could have arisen by evolution.

B

What is true of the amino acids that might have been delivered to Earth within carbonaceous chondrites? A.They were delivered in the form of polypeptides. B. There were more kinds of amino acids on the chondrites than are found in living organisms today. C. Their abundance would have been dramatically reduced upon passage through early Earth's oxidizing atmosphere. D. They had the same proportion of L and D isomers as Earth does today.

B

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

B

Which factor most likely caused animals and plants in India to differ greatly from species in nearby southeast Asia? A. India is in the process of separating from the rest of Asia. B. India was a separate continent until 45 million years ago. C. Life in India was wiped out by ancient volcanic eruptions. D. The climates of the two regions are similar. E.The species became separated by convergent evolution.

B

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

B

Which statement about natural selection on early Earth is correct? A. Natural selection could only act on populations of living organisms that had DNA as their genetic material. B. Natural selection could act on a population of proto-cells on early Earth, selecting for those that were stable and had self-replicating, catalytic RNA that allowed them to grow and divide to produce similar daughter proto-cells. C. Natural selection acted on populations of proto-cells on early Earth in order to make them more like modern living cells that have DNA as their genetic material.

B

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

C

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

C

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

C

What was the "oxygen revolution," which took place 2.3 billion years ago? A. The "oxygen revolution" was the rapid increase in atmospheric oxygen that took place 2.3 billion years ago, with the origin of plants. B. The "oxygen revolution" was the rapid increase in atmospheric oxygen that took place 2.3 billion years ago, immediately preceding the origin of animals. C. The "oxygen revolution" was the rapid increase in atmospheric oxygen that took place 2.3 billion years ago, dooming many prokaryotic groups.

C

Hox genes are thought to play an important role in the development of different morphologies because _____. A. they paved the way for the development of multicellular organisms B. they affect the timing of reproductive development in the organism C. they affect the timing of development in the embryo D. they provide positional information in the embryo E. they affect the order of genes on certain chromosomes

D

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

D

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

D

Which of these observations gives the most support to the endosymbiotic theory for the origin of eukaryotic cells? A. the observation that some eukaryotic cells lack mitochondria B. the size disparity between most prokaryotic cells and most eukaryotic cells C. the existence of structural and molecular differences between the plasma membranes of prokaryotes and the internal membranes of mitochondria and chloroplasts D. the similarity in size between the cytosolic ribosomes of prokaryotes and the ribosomes within mitochondria and chloroplasts

D

Why do some scientists believe that RNA, rather than DNA, was the first genetic material? A. RNA can replicate more accurately than DNA. B. All the proto-cells on early Earth contained RNA. C. RNA could have evolved into DNA. D. RNA has both information storage and catalytic properties. E. RNA contains uracil in place of thymine

D

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 make possible the evolution of the tetrapod limb. This type of change is illustrative of A. gene duplication. B. the influence of environment on development. C. heterochrony. D. paedomorphosis. E. a change in a developmental gene or in its regulation that altered the spatial organization of body parts.

E

Upon being formed, oceanic islands, such as the Hawaiian Islands, should feature what characteristic, leading to which phenomenon? A. overcrowding, leading to rafting to nearby lands B. adaptive radiation, leading to founder effect C.major evolutionary innovations, leading to rafting to nearby continents D.mass extinctions, leading to bottleneck effect E. a variety of empty ecological niches, leading to adaptive radiation

E

Which measurement(s) would help determine absolute dates by radiometric means? A. the accumulation of the daughter isotope B. the loss of daughter isotopes C. the loss of parent isotopes D. Three of the responses above are correct. E. Two of the responses above are correct.

E

Which of the following characteristics should have been possessed by the first animals to colonize land? 1. were probably herbivores (ate photosynthesizers) 2. had four appendages 3. had the ability to resist dehydration 4. had lobe-finned fishes as ancestors 5. were invertebrates A. 3 and 5 B.1, 2, 3, and 4 C. 2, 3, and 4 D. 3 only E/ 1, 3, and 5

E

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

E