A scientist is developing a mathematical model of cells of different shapes. To construct the model, the scientist has specified that the width of each cell at its widest point must be

30μm and the height of each cell must be 90 μm. Table 1 shows the three-dimensional shapes that the scientist is considering for the model cells. Which of the proposed shapes for the model cells will allow the most efficient exchange of materials with the surrounding environment?

A Right circular cylinder

B Triangular prism

C Rectangular prism

D Square-based pyramid

A

A student formulated a hypothesis that water-soluble pollutants damage living organisms by increasing the permeability of cellular membranes. To test the hypothesis, the student investigated the effect of isopropanol and acetone on beet root cells. The vacuoles of beet root cells contain large amounts of betacyanin, a water-soluble pigment that is released into the extracellular environment as a result of increased membrane permeability.

The student prepared identical samples of beet root tissue and incubated each sample for 15 minutes in the specific solution for that group. At the end of the incubation period, the student measured the absorbance of 460 nm light for each sample. A greater concentration of betacyanin in the solution surrounding the beet root cells results in a greater absorbance of 460 nm light. The results of the experiment are shown in the table above.

The student analyzed the data from the investigation and concluded that the estimate of the mean of one treatment group was unreliable. Which of the following identifies the treatment group most likely to have provided an unreliable estimate of the mean, and correctly explains why the estimate appears unreliable?

A Treatment group II; it has a lower than expected mean absorbance and the largest standard error of the mean.

B Treatment group III; it has a higher than expected mean absorbance and the largest standard error of the mean.

C Treatment group IV; it has a higher than expected mean absorbance and the smallest standard error of the mean.

D Treatment group V; it has a lower than expected mean absorbance and the smallest standard error of the mean.

A

A student peeled the skins from grapes, exposing cells with membranes that are only permeable to water and small diffusible solutes. The student measured the mass of the peeled grapes. The student then placed each peeled grape into one of five solutions. After 24 hours, the student removed the peeled grapes from the solutions, measured their final mass, and calculated the percent change in mass (Table 1).

Based on the data in Table 1, which of the following best evaluates the student’s hypothesis?

A The hypothesis is supported because the mass of the grape decreased in the grape juice.

B The hypothesis is supported because the grape juice has a greater solute potential than the grape has.

C The hypothesis is not supported because the grape was isotonic to the grape juice.

D The hypothesis is not supported because the mass of the grape increased in the grape juice.

D

The following questions refer to an experiment that is set up to determine the relative volume of O2 consumed by germinating and nongerminating (dry) pea seeds at two different temperatures. The change in volume is detected by using a respirometer over a given period of time. The data are given below.

The rate of oxygen consumption in germinating pea seeds at 26ºC is

A 0.05 mL / min

B 0.25 mL / min

C 0.50 mL / min

D 0.75 mL / min

E 1.00 mL / min

A

Which of the following statements about the rate of CO2 fixation in the two types of plants is supported by the data shown in the figures?

A At 21% O2, plant type 2has a lower rate of CO2 fixation than plant type 1 does in both types of soil.

B At 1% O2, plant type 2 has a higher rate of CO2 fixation than plant type 1 does in the dry soil but not in the control soil.

C Plant types 1 and 2 have a statistically different rate of CO2 fixation in both soil types at both oxygen levels.

D The rate of CO2 fixation is the same in both types of plants in the control soil at both oxygen levels.

A

Certain reef-building corals contain photosynthetic, symbiotic algae that have the ability to make dimethylsulphoniopropionate (DMSP), a chemical involved in the marine sulfur cycle. DMSP is released into the surrounding water, where it is converted to the gas dimethyl sulfide (DMS) by microorganisms and enters the atmosphere. Once in the atmosphere, it triggers the formation of sulfate aerosols, which induce cloud formation and block sunlight from heating up the water.

The symbiotic algae produce DMSP when they are stressed by a high water temperature. If water temperature is too high, corals will expel the symbiotic algae that produce DMSP. Researchers measured the amount of DMSP produced by juvenile and adult coral and their symbionts under normal and thermally stressed conditions. The data are shown in the graphs in Figure 1.

A The symbiont density at 32°C on day 5 was less than the density on day 0 of the experiment.

B The symbiont density at 27°C on day 0 was less than the density on day 5 of the experiment.

C The symbiont density at 32°C was different from the density at 27°C on days 5 and 10 of the experiment.

D The symbiont density at 27°C was higher than the density at 32°C for the entire length of the experiment.

C

Melanocytes are skin cells that can become cancerous and develop into a cancer known as melanoma. Some cancerous melanocytes have developed resistance to the drugs currently used to treat melanoma. As a result, researchers are investigating the effects of a new compound (drug X) on four different melanoma cell lines. Researchers analyzed cell survival in two cell lines (Figure 1) and oxygen consumption in the presence of drug X in all four cell lines (Figure 2). Figure 3 shows the proposed mechanism by which drug X affects cells.

A In the absence of drug X, melanoma lines 1 and 4 consume similar amounts of oxygen.

B In the presence of drug X, melanoma line 2 consumes statistically more oxygen per cell than does melanoma line 3.

C Melanoma line 3 consumes statistically less oxygen per cell in the presence of drug X than it does in the presence of the solvent alone.

D Melanoma line 2 in the presence of drug X consumes statistically less oxygen than does melanoma line 4 in the absence of drug X.

C

If 2n = 48 for a particular cell, then the chromosome number in each cell after meiosis would be

A 96

B 48

C 24

D 12

E 6

C

A researcher hypothesizes that, in mice, two autosomal dominant traits, trait Q and trait R, are determined by separate genes found on the same chromosome. The researcher crosses mice that are heterozygous for both traits and counts the number of offspring with each combination of phenotypes. The total number of offspring produced was 64. The researcher plans to do a chi-square analysis of the data and calculates the expected number of mice with each combination of phenotypes. Which of the following is the expected number of offspring that will display both trait Q and trait R?

A 4

B 12

C 36

D 48

C

The data above represent the results of three different crosses involving the inheritance of a gene that determines whether a certain organism is blue or white. Which of the following best explains the mechanism of inheritance of the gene?

A The allele for white is an autosomal dominant allele because a 1:1 phenotype ratio of blue to white among both sexes is observed in cross 3.

B The allele for blue is an autosomal dominant allele because an approximate 3:1 phenotype ratio of blue to white is observed in cross 1.

C The allele for white is an X-linked dominant allele because no white females are produced in cross 1.

D The allele for blue is an X-linked dominant allele because there are no blue male offspring in cross 2.

D

In a species of cactus, the number of spines on a plant is genetically determined. The graph above shows frequency distributions for populations of the cactus species growing in the presence or absence of two herbivores: peccaries (a New World pig) and wasp larvae. Which of the following best accounts for the different frequency distributions in the graph?

A Peccaries eat cacti with the greatest number of spines, and wasp larvae show no preference with respect to spine number.

B Peccaries eat cacti with a smaller number of spines, and wasp larvae eat cacti with a greater number of spines.

C Wasps have increasing difficulty depositing eggs on cacti with more spines, and peccaries show no preference with respect to spine number.

D Both peccaries and wasp larvae will eat the most abundant types of cacti, which are the plants with the greatest number of spines.

A

The table shows the changes in allele frequencies of a specific gene in two populations of randomly mating small mammals after 30 years. The populations inhabit adjacent equatorial islands that have similar topography and climate. Which of the following is the most reliable conclusion that can be drawn from analysis of the data above?

A Genetic drift has occurred in population 1.

B Population 2 is in Hardy-Weinberg equilibrium.

C Selection for allele r is occurring in both populations.

D The reduced frequency of allele R in population 1 will eventually lead to the extinction of population 1.

A

A survey reveals that 25 percent of a population of 1,000 individuals have attached earlobes (are homozygous recessivefor the trait). For the following questions, assume that the population fits the parameters of the Hardy-Weinberg law.

What is the frequency of the recessive allele?

A √0.75

B 0.75

C √0.50

D √0.25

E0.25

D

A researcher analyzed four different samples of macromolecules, where all macromolecules in each sample are of the same type. The researcher measured the percent of carbon, oxygen, hydrogen, nitrogen, phosphorus, and sulfur atoms in each sample. The results are shown in Table 1.

Which of the following claims is best supported by the data in Table 1 ?

A Sample A contains nucleic acids.

B Sample B contains protein.

C Sample C contains nucleic acids.

D Sample D contains protein.

B

Investigators studied the interactions between two different proteins, proteinI and protein II. Each protein has two structural domains (Figure 1) that represent different functional parts of the protein. Different combinations of the protein domains were tested for their ability to bind to a known DNA sequence, interact with each other, and activate transcription. The results are shown in Table 1.

Which of the following claims is best supported by the data from test 5 in Table 1 ?

A Domain L is required for transcription activation.

B Domain F is not required for protein-protein interaction.

C Protein-protein interaction is necessary for DNA binding.

D Protein-protein interaction is sufficient for transcription activation.

B

A researcher measured the temperature at which two different samples of double-stranded DNA denature (separate into single strands). Sample 1 denatured at a significantly lower temperature than sample 2 did. Based on the data, the researcher claims that the DNA in sample 2 is composed of a higher percentage of guanine and cytosine than the DNA in sample 1 is.

Which of the following best supports the researcher’s claim?

A The bonds between guanine and cytosine are covalent bonds, which require more energy to disrupt than those between adenine and thymine.

B Guanine-cytosine pairs denature at a higher temperature because they have more hydrogen bonds between them than adenine-thymine pairs do.

C Adenine-thymine pairs require less energy to separate because adenine and thymine are both single-ring bases.

D Guanine-cytosine pairs require more energy to separate because one is a purine and one is a pyrimidine.

B

A mutation in the upland cotton plant causes the development of chloroplasts with a single outer membrane and no internal membranes. Which of the following would most likely be observed in chloroplasts of cotton plants with this mutation?

A They would be unable to remove waste products, because internal transport proteins would not be present.

B They would be unable to generate the ATP and NADPH needed to make sugars, because these processes occur on membranes within the chloroplast.

C They would be unable to take up carbon dioxide, because CO2 is transported into the chloroplast in membrane-bound vesicles.

DThey would be unable to move within the cell, because only organelles with double membranes are mobile.

B

A student peeled the skins from grapes, exposing cells with membranes that are only permeable to water and small diffusible solutes. The student measured the mass of the peeled grapes. The student then placed each peeled grape into one of five solutions. After 24 hours, the student removed the peeled grapes from the solutions, measured their final mass, and calculated the percent change in mass (Table 1).

In a second experiment (Table 2), the student placed a peeled grape into a solution containing both small diffusible solutes and solutes to which the membrane is impermeable (nondiffusible solutes).

Mercurial sulfhydryl is an inhibitor of aquaporins. Which of the following is the most likely effect of adding mercurial sulfhydryl to the distilled water solution?

A The grape cells will burst because of excess water entering by active transport.

B The grape cells will gain more water because of the activation of the transport protein.

C The grape cells will shrink because active transport has been inhibited.

D The grape cells will gain water more slowly because of a lack of facilitated diffusion.

D

Stickleback fish are found in both marine and freshwater habitats. The marine fish have no scales but have hardened, armorlike plates along their sides. The plates are thought to protect sticklebacks from certain predators.

In the late 1980s, sticklebacks from a marine population colonized Loberg Lake, a freshwater lake in Alaska. Starting in 1990, researchers sampled fish from the lake every four years and recorded the armor-plate phenotypes of the male sticklebacks in each sample. The armor-plate phenotypes were categorized as either complete (plates extending from head to tail), partial (plates extending from head to abdomen), or low (a few plates near the head only). The results are shown in the table below.

Intact cells of two unknown cell types were placed into solutions with different concentrations of NaCl. Type I cells swelled and burst in the solution with the lowest concentration of NaCl. Type II cells swelled but did not burst in the solution with the lowest concentration of NaCl.

Which of the following descriptions of cell type I and cell type II are most consistent with the data?

A

Cell Type I - Animal cell surrounded by a plasma membrane only

Cell Type II - Plant cell surrounded by a plasma membrane and a cell wall

B

Cell Type I - Plant cell surrounded by a plasma membrane only

Cell Type II - Bacterial cell surrounded by a cell wall only

C

Cell Type I - Plant cell surrounded by a plasma membrane only

Cell Type II - Animal cell surrounded by a plasma membrane and a cell wall

D

Cell Type I - Animal cell surrounded by a cell wall only

Cell Type II - Bacterial cell surrounded by a plasma membrane only

A

Membrane-bound organelles have been an important component in the evolution of complex, multicellular organisms. Which of the following best summarizes an advantage of eukaryotic cells having internal membranes?

A Eukaryotic cells are able to reproduce faster because of the presence of organelles.

B Some organelles, such as mitochondria and chloroplasts, are similar to prokaryotic cells in structure.

C Organelles isolate specific reactions, increasing metabolic efficiency.

D Compartmentalization leads to a higher mutation rate in DNA, which leads to more new species.

C

Which of the following is the strongest evidence supporting the endosymbiont hypothesis?

A Mitochondria have their own DNA and divide independently of the cell.

B Mitochondria can carry out hydrolytic reactions on organic molecules.

C Mitochondria have a highly folded membrane.

D Mitochondria are found in both plants and animals.

A

An increase in the concentration of protons in the cytosol will most likely have which of the following effects on glycolysis?

A Glycolytic enzymes will denature as a result of the increased H+concentration.

B Reaction rate will increase as a result of the increased H+concentration.

C H+ will replace phosphorous and inhibit ATP formation from ADP.

D The water potential will increase, resulting in a decrease in the rate of glycolysis.

A

Dichlorophenolindophenol (DCPIP) is a chemical dye. When DCPIP is chemically reduced, it changes color from blue to clear. DCPIP can be used as an electron acceptor in experiments that measure the rate of electron transport through the electron transport chain. A student performed an experiment to study the effects of a chemical, DCMU, on photosynthesis.

The student prepared four tubes with a liquid buffer and chloroplasts that had been extracted from spinach leaves. The student then added DCPIP to three of the tubes and added DCMU to one of them. Additionally, tube 3 was wrapped in tin foil. The contents of each tube are shown in the table. The student then incubated each tube for 60 minutes and measured the absorbance (A600) of each solution at five-minute intervals. The absorbance readings of each solution are shown in Figure

Which of the following claims is best supported by the experimental results?

A Light is required for the electron transport chain to transfer electrons.

B Water, not carbon dioxide, is the source of electrons used in the light-dependent reaction of photosynthesis.

C Carbon dioxide is the source of carbon used by green plants to build carbohydrates.

D DCPIP provides a significant source of electrons to the electron transport chain of the light reaction in the absence of light.

A

Newborn babies and hibernating animals contain a large amount of brown adipose (fat) tissue (BAT). Certain proteins in the BAT cells increase the permeability of the inner mitochondrial membrane to protons, disrupting the proton gradient.

Which of the following best predicts the effect of disrupting the proton gradient in BAT?

A The pH of the matrix will increase, allowing the production of more ATP per gram of substrate.

B The pH of the intermembrane space will decrease, allowing a steeper proton gradient to form.

C Electron transport and oxidative phosphorylation will be decoupled, generating more heat but less ATP.

D The number of protons available to pass through ATP synthase will increase, resulting in more

ATP.

C

After a search of nucleotide sequence databases, researchers identified an IRE in the 5¢ untranslated region of a gene encoding aconitase, an enzyme involved in the Krebs cycle. Which of the following pieces of experimental evidence best supports the claim that the synthesis of aconitase is controlled by a mechanism similar to ferritin regulation?

A IRP binds to aconitase mRNA in the presence of iron.

B The relative amount of aconitase protein increases in the presence of high levels of iron.

C Oxygen consumption by cells increases in the presence of high levels of iron.

D The levels of reduced electron carriers, NADH and FADH2, increase in the presence of high levels of iron.

B

Based on the information provided, which of the following best justifies the claim that osteocalcin is a hormone?

A The phosphorylation of the insulin receptor causes a response in osteoblast bone cells.

B The osteoblasts in the bone secrete osteocalcin, which causes cells in the pancreas to change their activity.

C The change in expression of Esp changes the insulin receptor activity of the osteoblast.

D The activation of the osteocalcin by a bone cell is pH dependent.

B

The Esp gene encodes a protein that alters the structure of the insulin receptor on osteoblasts and interferes with the binding of insulin to the receptor. A researcher created a group of osteoblasts with an Esp mutation that prevented the production of a functional Esp product (mutant). The researcher then exposed the mutant strain and a normal strain that expresses Esp to glucose and compared the levels of insulin in the blood near the osteoblasts (Figure 2).

Which of the following claims is most consistent with the data shown in Figure 2 ?

A Esp expression is necessary to prevent the overproduction of insulin.

B Esp protein does not regulate blood-sugar levels in normal mice.

C Normal mice require a higher blood concentration of insulin than mutant mice do.

D Mutant mice have a cyclical pattern of insulin secretion.

A

Based on the information presented, which of the following genetic changes in an individual without diabetes is most likely to result in a disrupted cellular response to insulin signaling similar to that of an individual with type 2 diabetes?

A A deletion in the gene encoding the insulin receptor that removes only the cytoplasmic domain of the protein

B Duplication of the gene encoding a PI-3 kinase that results in synthesis of a muscle-specific variant of the enzyme in skin cells as well as in muscle cells

C A mutation in the gene encoding IRS-1 that causes the protein to be active in muscle cells even in the absence of insulin signaling

D Insertion of a small segment of DNA into the promoter of the Glut4 gene that results in increased synthesis of GLUT4 proteins in muscle cells

A

Which of the following is a valid interpretation of the experimental results that explains how individuals with type 2 diabetes differ from individuals without diabetes?

A The relatively low levels of glucose uptake in individuals with type 2 diabetes indicate that mobilization of GLUT4 to the cell surface is reduced in muscle cells of those individuals.

B The relatively low levels of glucose uptake in individuals with type 2 diabetes indicate that no functional GLUT4 protein is produced in the muscle cells of those individuals.

C The absence of activated insulin receptors in individuals with type 2 diabetes indicates that no insulin is secreted by the pancreatic cells of those individuals.

D The absence of activated IRS-1 in individuals with type 2 diabetes indicates that no functional insulin receptor protein is produced in the muscle cells of those individuals.

A

Which of the following observations provides the best evidence that acetyl-CoA negatively regulates pyruvate dehydrogenase activity?

A The rate of the pyruvate dehydrogenase–catalyzed reaction is slower in the presence of a higher concentration of acetyl-CoA.

B The gene that encodes pyruvate dehydrogenase is transcribed when excess acetyl-CoA is detected.

C The accumulation of acetyl-CoA stops after 70 seconds, regardless of the reaction mixture.

D Acetyl-CoA is continuously broken down in the Krebs cycle.

A

The drug 5-fluorouracil inhibits thymine production in eukaryotic cells. Which of the following cell cycle stages will be most directly affected by it?

A The first growth phase (G1)

B Synthesis of DNA phase (S)

C Preparation for mitosis (G2)

D Cytokinesis

B

Which of the following best explains the most likely method by which this antitumor drug works?

A Trabectedin increases the production of cyclin proteins that signal the cancer cells to enter prophase.

B Trabectedin interferes with the plasma membrane, causing it to break down and expose the DNA to damage.

C Trabectedin interferes with the duplication of DNA during interphase and thus prevents cancer cells from passing the G2 checkpoint.

D Trabectedin interferes with the regulations of cyclin proteins, causing their levels to increase and creating errors in DNA.

C

Humans have a diploid number (2n) of 46. Which of the following statements best predicts the consequence if meiosis did not occur during gametogenesis?

A The gametes would get larger from one generation to the next.

B The chromosome number would double with each generation.

C The chromosome number would be halved with each generation.

D The chromosome number would triple with each generation.

B

Which of the following best supports the claim that organisms of different domains share a common ancestor?

A Photosynthesis occurs in chloroplasts, and the citric acid cycle occurs in mitochondria.

B Glycolysis occurs in both prokaryotic cells and eukaryotic cells.

C Introns are present in eukaryotic DNA but not in prokaryotic DNA.

D Errors in DNA synthesis provide some of the genetic variation in a population.

B

A series of crosses is performed with fruit flies (Drosophila melanogaster) to examine inheritance of the genes vestigial (vg) and cinnabar (cn). The recessive vg allele causes small, malformed wings called vestigial wings. The recessive cn allele causes bright-red eyes called cinnabar eyes.

In the first cross, a female with wild-type wings and eyes is mated with a male with vestigial wings and cinnabar eyes. All the F1 individuals have wild-type wings and eyes. In the second cross, female F1 flies are mated with males with vestigial wings and cinnabar eyes. The phenotypes of 500 F2 individuals are shown in the table

Which of the following is the most likely explanation of the results?

A The two genes are located on two different chromosomes.

B The two genes are sex-linked.

C The two genes are located on mitochondrial DNA.

D The two genes are linked on an autosome.

D

Butterflies of the genus Colias live in the Rocky Mountains, where they experience a wide range of temperatures. Different variants of a particular glycolytic enzyme in the flight muscles are optimally active at different temperatures. Within the same population, some individual butterflies fly most effectively at 29°C , while others fly most effectively at 40°C. Still others can be equally active at both temperatures. Which of the following claims is most consistent with the observed butterfly behavior?

A Butterflies that express two variants of the enzyme are active over a greater range of temperature.

B Butterflies that are active over a wide range of temperatures produce greater amounts of the enzyme.

C Temperature has little effect on the activity of butterflies.

D Butterflies that are active at warmer temperatures produce more offspring.

A

These cells are the result of nondisjunction during which of the following phases?

A Interphase (G1 or G2)

B Interphase (S)

C Mitosis

D Meiosis I

E Meiosis II

D

A scientist adds a chemical to a culture of dividing cells in order to disrupt DNA replication. The replicated DNA produced by the cells is double-stranded, but sections of it lack covalent bonds between adjacent nucleotides (Figure 1).

DNA produced after a chemical is introduced.

Which of the following claims is best supported by the data?

A The chemical prevents the formation of RNA primers.

B The chemical inhibits DNA ligase.

C The chemical blocks DNA polymerase.

D The chemical disrupts hydrogen bonding.

B

Which of the following messenger RNA sequences could code for both of the two amino acid sequences above, simply by a shift in the reading frame?

A . . . AGCAGCAGCAGC . . .

B . . . AGUAGUAGUAGU . . .

C . . . CAACAACAACAA . . .

D . . .GCUGCUGCUGCU . . .

E . . . GCAAGCGCAAGC . . .

A

The following the DNA sequence is a small part of the coding (nontemplate) strand from the open reading frame of β-hemoglobin gene. Given the codon chart listed below, what would be the effect of a mutation that deletes the G at the beginning of the DNA sequence?

5'- GTT TGT CTG TGG TAC CAC GTG GAC TGA - 3'

A The mutation precedes the gene, so no changes would occur.

B Lysine (lys) would replace glutamine (gln), but there would be no other changes.

C The first amino acid would be missing, but there would be no other change to the protein.

D The reading frame of the sequence would shift, causing a change in the amino acid sequence after that point.

D

Arctic foxes typically have a white coat in the winter. In summer, when there is no snow on the ground, the foxes typically have a darker coat.

Which of the following is most likely responsible for the seasonal change in coat color?

A

The decrease in the amount of daylight in winter causes a change in gene expression, which results in the foxes growing a lighter-appearing coat.

B

The diet of the foxes in summer lacks a particular nutrient, which causes the foxes to lose their white coat and grow a darker-colored coat.

C

Competition for mates in the spring causes each fox to increase its camouflage with the environment by producing a darker-appearing coat.

D

The lower temperatures in winter denature the pigment molecules in the arctic fox coat, causing the coat to become lighter in color.

A

Lactase is the enzyme needed to digest lactose, the sugar found in milk. Most mammals produce lactase when they are young but stop once nursing ends. In humans however, many people continue to produce lactase into adulthood and are referred to as lactase-persistent.

Which of the following mutations is most likely to cause lactase persistence in humans?

A A nucleotide substitution in the coding region of the lactase gene that interferes with the interaction between lactase and lactose

B A mutation that turns off the expression of transcription factors that activate the expression of lactase

C A mutation that increases the binding of transcription factors to the promoter of the lactase gene

D The insertion of a single nucleotide into the lactase gene that results in the formation of a stop codon

C

Which of the following is the most likely effect of a mutation in the gene coding for a DNA repair enzyme?

A The cell containing the mutation will divide more frequently because the cell cycle checkpoints will not function properly.

B Mutations will accumulate more quickly because the cell will not be able to fix errors in replication.

C The mutated gene will not be transcribed because RNA polymerase cannot transcribe mutated DNA.

D The cell will immediately undergo apoptosis so that mutated DNA is not replicated in future rounds of cell division.

B

Researchers studying the bacterium Escherichia coli split a population of the bacteria into two samples. Sample 1 was transformed with a plasmid containing a gene that makes the bacteria resistant to the antibiotic kanamycin. Sample 2 was transformed with a plasmid lacking the antibiotic resistance gene. A portion of each sample was then added to growth plates containing just nutrients or growth plates containing nutrients and kanamycin.

After being allowed to grow for 24 hours at 37∘C, the number of colonies on each growth plate was counted (Table 1).

TABLE 1. BACTERIAL GROWTH FOLLOWING TRANSFORMATION WITH OR WITHOUT THE KANAMYCIN RESISTANCE GENE

Which of the following claims is best supported by the data in Table 1 ?

A The transformation procedure killed all the bacteria that were added to plate 3.

B More bacteria on plates 1 and 2 were successfully transformed than on any other plate.

C None of the bacteria on plate 2 were successfully transformed with the kanamycin resistance gene.

D Only the bacteria that were successfully transformed with the kanamycin resistance gene grew on plate 4.

D

While there is only one species of Galápagos Island tortoise, there are several subspecies. Larger islands with more wet highlands have lush vegetation near the ground. Tortoises there tend to have high-domed shells and shorter necks, which restrict upward head movement. They also have shorter limbs. They are the heaviest and largest of the subspecies.

Smaller, drier islands are inhabited by tortoises with longer necks and limbs and with shells that are elevated above the neck, which allow them to browse taller vegetation.

Based on the information given, which of the following is a plausible explanation for the ancestry of the tortoise subspecies?

A The subspecies share a recent common ancestor whose neck length, shell shape, and leg length were intermediate between the two subspecies.

B The tortoises with shorter legs and necks were most easily preyed on as young animals by the rats that were introduced, so they survived only on a few islands.

C Random mutations coupled with the inheritance of acquired characteristics resulted in distinct subspecies.

D Individuals with different adaptations in shell shape and leg length best exploited the food resources and left more surviving offspring on each island.

D

Pesticides are chemicals that are often sprayed on crops to kill plant-eating insects, preventing damage to the crops. While pesticides are effective initially, many researchers claim that any single pesticide will see reduced effectiveness in as little as ten to fifteen years.

Which of the following best supports the claim by scientists that the pesticides will eventually lose their effectiveness?

A Insects will evolve to avoid any plant sprayed with pesticides to increase their chances of survival.

B Insects that are naturally resistant to the pesticide will survive and reproduce more than the insects that are sensitive to the pesticide.

C The insects will build up a tolerance to the pesticides, and eventually the pesticide will not affect them.

D The pesticides will increase the mutation rate in the insects, resulting in higher genetic diversity and higher survival rate.

B

Poaching is the illegal hunting or capturing of wild animals. Both male and female African elephants have tusks that are a significant source of ivory used for ornaments and jewelry.

Assuming that the size of the tusks is heritable, which of the following is the most likely long-term effect of poachers targeting African elephants with large tusks?

A An increase in average tusk size because of the need to provide more ivory for the poaching hunters

B A decrease in average tusk size because elephants with large tusks are less likely to survive to reproduce

C An increase in average tusk size to provide the elephants with a defensive mechanism against poachers

D A decrease in average tusk size to reduce the energy investment in the tusks

B

Undersea landslides can disrupt marine habitats by burying organisms that live on the ocean floor. The graph above shows the size of a population of a certain organism that lives on the ocean floor. The population was affected by a recent landslide at the time indicated on the graph. Which of the following best predicts how the population will be affected by the landslide?

A The surviving organisms will evolve into a new species.

B The reduced population will likely have allelic frequencies that are different from the initial population.

C The population will adapt to deeper waters to avoid future landslides.

D The reduced population will have a greater number of different genes than the initial population.

B

For following group of questions first study the description of the situation and then choose the one best answer to each question following it and fill in the corresponding oval on the answer sheet.

A survey reveals that 25 percent of a population of 1,000 individuals have attached earlobes (are homozygous recessivefor the trait). For the following questions, assume that the population fits the parameters of the Hardy-Weinberg law.

Unlike most natural populations, this population is best characterized in which of the following ways?

A There is genetic equilibrium.

B There is gene flow.

C There is genetic drift.

D Mutations occur.

E Mating is nonrandom.

A

The amino acid sequence of cytochrome c is exactly the same in humans and chimpanzees. There is a difference of 13 amino acids between the cytochrome c of humans and dogs, and a difference of 20 amino acids between the cytochrome c of humans and rattlesnakes.

Which of the following statements is best supported by these data?

A Rattlesnakes apparently gave rise evolutionarily to the dog, chimpanzee, and human.

B Cytochrome c apparently has an entirely different function in rattlesnakes than in mammals, which explains the difference in the number of amino acids.

C Cytochrome c is not found universally in animals.

D Cytochrome c from a rattlesnake could function in a dog, but not in a chimpanzee.

E The human is apparently more closely related to the chimpanzee than to the dog or rattlesnake.

E

MRSA is the acronym for methicillin-resistant Staphylococcus aureus. Many of the strains of the common bacterium are also resistant to other antibiotics in use today. The resistance is linked to a collection of genes carried on plasmids that are passed from one bacterium to another by conjugation. Suppose a newly discovered, chemically different antibiotic is used in place of methicillin. Which of the following would be the most likely effect on Staphylococcus aureus antibiotic resistance?

A The gene for methicillin resistance, no longer needed, would disappear entirely from Staphylococcus aureus populations within a few generations.

B Transmission of the methicillin-resistance plasmid by conjugation would increase among the Staphylococcus aureus population as the genes would confer resistance to the new antibiotic.

C Transmission of the methicillin-resistance plasmid would gradually decrease but the plasmid would not entirely disappear from the Staphylococcus aureus population.

D Transmission of the methicillin-resistance plasmid by conjugation would increase among the Staphylococcus aureus population due to destruction of bacteria without the plasmid through use of the new antibiotic.

C

The figure shows a phylogenetic tree of various members of the order Proboscidea, which includes modern elephants. Which of the following claims is best supported by the information in the figure ?

A The Asian and African elephants are the most closely related species shown on the tree.

B The mammoth diverged from its most recent common ancestor with African elephants before the mastodon diverged from its most recent common ancestor with Stegodons.

C The mastodon and the Stegodon diverged from their common ancestor 2 million years ago.

D The common ancestor of the African elephant and the mastodon is the Palaeomastodon.

D

On a large volcanic island, researchers are studying a population of annual herbaceous plants. Which of the following observations best supports the prediction that speciation will occur within the existing plant population?

A Individuals of the species sometimes reproduce asexually by producing runners.

B Lava has separated the population into two areas: an upland forest and a lowland marsh.

C Multiple groups of birds depend on the fruit produced by the plants as a source of food.

D The plants produce more seeds during warm summers than they do during cool summers.

B

Modern bananas originated from a cross between a tetraploid banana species and a diploid banana species. The product of this cross was the triploid Cavendish banana strain, a sterile hybrid that is only grown asexually. Recently, the Panama fungus has been observed more frequently parasitizing the Cavendish banana, and scientists claim that this type of banana is on the brink of extinction.

Which of the following provides the best explanation of the scientists’ claim regarding the threat to the Cavendish banana?

A The triploid genome of the Cavendish banana makes it susceptible to the negative impact of recessive alleles.

B Having three of each chromosome interferes with normal function of the cells and increases the likelihood of contracting a disease.

C The lack of genetic diversity of the Cavendish banana decreases the chance that a variation exists in the population that is immune to the fungus.

D Asexual reproduction increases the mutation rate during replication, resulting in a greater chance that the offspring have a dysfunctional immune system.

C

By discharging electric sparks into a laboratory chamber atmosphere that consisted of water vapor, hydrogen gas, methane, and ammonia, Stanley Miller obtained data that showed that a number of organic molecules, including many amino acids, could be synthesized. Miller was attempting to model early Earth conditions as understood in the 1950s. The results of Miller’s experiments best support which of the following hypotheses?

A The molecules essential to life today did not exist at the time Earth was first formed.

B The molecules essential to life today could not have been carried to the primordial Earth by a comet or meteorite.

C The molecules essential to life today could have formed under early Earth conditions.

D The molecules essential to life today were initially self-replicating proteins that were synthesized approximately four billion years ago.

C

The pesticide DDT was widely used in the 1940s as a method of insect control. In the late 1950s the first DDT-resistant mosquitoes were discovered, and eventually DDT-resistant mosquitoes were found globally. When DDT is used now, the development of DDT resistance in mosquito populations occurs in months rather than years.

Which of the following best explains the observations concerning DDT resistance in mosquitoes?

A Competition for limited resources causes mosquitoes to migrate to geographical areas that have richer supplies of DDT.

B The proportion of DDT-resistant mosquitoes in a population remains constant due to the metabolic costs of DDT utilization

C Natural selection favors DDT-resistant mosquitoes that are already present in a population when DDT exposure occurs.

D DDT is a chemical signal that delays normal reproductive cycles in many mosquito populations.

C

Developers have approved a project that will permanently reduce the primary producers’ biomass by 50 percent and remove all rabbits and deer.

Which of the following is the most likely result at the completion of the project?

A The biomass of coyotes will be 6 kg, and the biomass of hawks will be 0.5 kg.

B The biomass of coyotes will be dramatically reduced.

C The coyotes will switch prey preferences and outcompete the hawks.

D There will be 50 percent fewer voles and 90 percent fewer hawks.

B

In an investigation of interspecies competition, researchers grew the unicellular protozoan Paramecium aurelia in a 5 mL culture and Paramecium caudatum in a separate 5 mL culture. P. aurelia and P. caudatum were grown together in a third 5 mL culture. Each day a small sample of each culture was removed so the total number of individuals could be estimated, and the remainder of the population was transferred to fresh growth medium. The experimental results are represented in the graphs below.

Which of the following conclusions is best supported by the results of the experiment?

A

Neither population grows as large when cultured together as each does when cultured separately.

B

1. caudatum prefers different food when cultured with P. aurelia than when cultured separately.

C

Competition for mates increases when the species are cultured together compared with when they are cultured separately.

D

Individuals of the species P. caudatum are smaller when cultured together with P. aurelia than when cultured separately.

A

Which of the following communities is likely to be most stable?

A One where a keystone predator has been removed

B One with uniformly spaced vegetation

C One with high species diversity

D One that lacks decomposers

C

Mosquitoes are frequently a target of insect control strategies because of their ability to spread disease. One strategy is to introduce guppies, a type of freshwater fish, into areas where mosquitoes are a problem. Guppies can consume large numbers of mosquito larvae, which cuts down on the number of mosquitoes living to adulthood.

Researchers assessing the effectiveness of the guppy solution are concerned that the introduction of guppies might cause more problems than it is fixing. Guppies are hardy, tolerant of a wide range of environmental conditions, and fast-reproducing.

Which of the following predicts the most likely ecological problem that would occur if guppies are introduced into new areas to control the mosquito population?

A

The guppies might have no natural predators, which will result in a dramatic increase in the guppy population and an increase in competition for other native species.

B

The guppy population will likely evolve to consume another food source instead of the mosquito larvae.

C

The larvae will evolve a mechanism that will enable them to avoid predation from the guppies.

D

Predators in the area will consume the guppies, requiring the addition of more guppies on a regular basis.

A