AP Biology - Final Trials

13. The diagram below shows energy changes in a specific chemical reaction with and without the addition of an enzyme to the reaction. Which of the following questions can best be answered by the diagram? (A) Does the addition of an enzyme reduce the activation energy required for a reaction? (B) Does the addition of an enzyme result in the formation of covalent bonds? (C) Does the addition of an enzyme produce a greater amount of products? (D) Does the addition of an enzyme change the pathway for the reaction?

(A) Does the addition of an enzyme reduce the activation energy required for a reaction?

44. Based on the data, which of the following behaviors in elk could account for the differences between the percent of aspens browsed by herbivores and the height of aspen trees in riparian and upland environments? (A) Elk tend to avoid riparian areas where the steep, wooded riverbanks make it difficult to escape predators. (B) Elk tend to prefer riparian areas where there is easy access to water. (C) Elk tend to avoid upland areas where trees are too tall to be easily eaten. (D) Elk tend to prefer upland areas where there are richer sources of mineral nutrients, such as potassium and iodine.

(A) Elk tend to avoid riparian areas where the steep, wooded riverbanks make it difficult to escape predators.

36. The table below describes the action of two genes involved in the regulation of nervous system development in the nematode C. elegans. Gene A Gene B Observation Pattern 1 Inactive Inactive No neurons develop. Pattern 2 Inactive Active No neurons develop. Pattern 3 Active Inactive Greater-than-normal number of neurons develop. Pattern 4 Active Active Normal number of neurons develop. Which of the following claims is best supported by the data? (A) Gene A promotes neuron development; gene B promotes programmed cell death in neuronal precursors. (B) Gene A promotes programmed cell death in neuronal precursors; gene B promotes neuron development. (C) Gene B must be active before gene A can function. (D) Gene B must be inactive before gene A can function.

(A) Gene A promotes neuron development; gene B promotes programmed cell death in neuronal precursors.

29. Based on the data in Table I, which of the following best explains why there are no individuals with constricted pods in the F1 generation? (A) Inflated pod shape is dominant to constricted pod shape. (B) The inflated-pod offspring in the F1 generation are homozygous. (C) Constricted pod shape typically arises from a new mutation in the F1 generation. (D) The constricted-pod offspring are carriers for the inflated pod shape allele.

(A) Inflated pod shape is dominant to constricted pod shape.

20. The phylogenetic trees in Figures 2 and 3 depict two different phylogenies of the same populations of sticklebacks. Which of the following questions will best help determine which tree represents the most accurate phylogeny? (A) Is the EDA gene as representative of the differences between the populations as the 25 random genes that were examined for Figure 3 ? (B) Are the low-plated populations found only in freshwater and the high-plated populations found only in saltwater environments? (C) Is the common ancestor of the organisms represented in Figure 2 different from the common ancestor of the organisms represented in Figure 3 ? (D) Is the expression level of the EDA gene analyzed in Figure 2 significantly greater than the expression levels of the 25 genes analyzed in Figure 3 ?

(A) Is the EDA gene as representative of the differences between the populations as the 25 random genes that were examined for Figure 3 ?

21. Which of the following occurs in all species of living organisms and may lead to an increase in genetic variation? (A) Mutations in the genome (B) Crossing-over in meiosis (C) Random assortment of chromosomes (D) Alternative splicing of mRNA

(A) Mutations in the genome

10. To refine their model of deep-sea biological communities, the researchers investigated areas of the seafloor that are distant from any active hydrothermal vents. Which of the following is the best interpretation of the observation that some octopus species are only found near active hydrothermal vents? (A) Octopuses depend indirectly on inorganic compounds in the seawater surrounding hydrothermal vents. (B) Organisms capable of moving across the seafloor are more difficult to observe than are organisms that are rooted in place. (C) Genetic bottleneck events in isolated areas of the deep ocean adversely affect some octopus populations but not others. (D) Biomass in a typical marine food web is expected to be greater in higher trophic levels than in lower trophic levels.

(A) Octopuses depend indirectly on inorganic compounds in the seawater surrounding hydrothermal vents.

5. Water in a pond contaminated with the weed killer atrazine is suspected of inhibiting metamorphosis in northern leopard frogs. A team of scientists collected fertilized northern leopard frog eggs from a different pond that is not contaminated. Which of the following is the best experimental design to determine whether atrazine is responsible for inhibiting metamorphosis in northern leopard frogs? (A) Place half of the fertilized eggs in a pool of water with the same concentration of atrazine as the contaminated pond and place the other half of the fertilized eggs in a pool of water that has no atrazine. Monitor the development of the embryos through metamorphosis into adulthood. (B) Place all of the fertilized eggs in a pool of pond water with the same concentration of atrazine as the contaminated pond and compare the number of frogs that reach metamorphosis to those that reach adulthood in the contaminated pond. (C) Allow all fertilized eggs to develop into adults. Expose one-third of the frogs to one-half of the concentration of atrazine in the contaminated pond and expose another one-third of the frogs to the same concentration of atrazine as the contaminated pond. Leave the last one-third of the frogs in water with no atrazine and note any adverse changes in the physical condition of the atrazine-treated frogs in three months. (D) Divide the fertilized eggs into three groups and expose each group to a different concentration of atrazine. Release the eggs back into the contaminated pond and check for metamorphosis after three months.

(A) Place half of the fertilized eggs in a pool of water with the same concentration of atrazine as the contaminated pond and place the other half of the fertilized eggs in a pool of water that has no atrazine. Monitor the development of the embryos through metamorphosis into adulthood.

32. In Table II, the F1 offspring of the cross between broad-leaved, white-flowered plants with narrowleaved, purple-flowered plants have a phenotype that differs from that of either parent. However, many testcross offspring have the same phenotype as one of the two plants in the parental cross, but relatively few testcross offspring have the same phenotype as the F1 offspring. Which of the following best explains the observation? (A) Recombination between the leaf-shape and flower-color genes resulted in chromosomes carrying a dominant allele of both genes. (B) Recombination between the broad and narrow alleles of the leaf-shape gene resulted in chromosomes carrying three different alleles at the same genetic locus. (C) Independent assortment of homologous chromosomes resulted in the combinations of alleles present in the parental generation. (D) The computer model cannot capture the possible assortments of gametes when multiple genes are considered.

(A) Recombination between the leaf-shape and flower-color genes resulted in chromosomes carrying a dominant allele of both genes.

38. The bacterium Vibrio cholerae is harmless unless a lysogenic bacteriophage provides the gene coding for the cholera toxin, which converts the bacterium to the virulent form that causes cholera. Which of the following best explains how the gene encoding cholera toxin becomes part of the bacterial genome? (A) The bacteriophage inserts the toxin gene into the host cell DNA, and the gene is expressed with the rest of the host cell's genes. (B) The bacteriophage makes copies of the toxin gene and expresses the copies inside the bacteriophage. (C) The bacteriophage converts its toxin gene into mRNA, which is then translated by the host cell. (D) The bacteriophage transforms itself into a self-replicating protein that can survive inside the host cell.

(A) The bacteriophage inserts the toxin gene into the host cell DNA, and the gene is expressed with the rest of the host cell's genes.

28. Two nutrient solutions are maintained at the same pH. Actively respiring mitochondria are isolated and placed into each of the two solutions. Oxygen gas is bubbled into one solution. The other solution is depleted of available oxygen. Which of the following best explains why ATP production is greater in the tube with oxygen than in the tube without oxygen? (A) The rate of proton pumping across the inner mitochondrial membrane is lower in the sample without oxygen. (B) Electron transport is reduced in the absence of a plasma membrane. (C) In the absence of oxygen, oxidative phosphorylation produces more ATP than does fermentation. (D) In the presence of oxygen, glycolysis produces more ATP than in the absence of oxygen.

(A) The rate of proton pumping across the inner mitochondrial membrane is lower in the sample without oxygen.

8. Researchers are investigating the evolutionary relationships among organisms found near deepsea hydrothermal vents and similar organisms found closer to the ocean surface. Which of the following scientific questions is most relevant to the investigation? (A) What are the nucleotide sequences of ribosomal RNA genes that are found in the genomes of the different species? (B) What large-scale geological events have occurred recently in the Mid-Atlantic Ocean? (C) Does water temperature at different ocean depths affect the relative levels of dissolved oxygen? (D) Do species found near deep-sea hydrothermal vents all have the same haploid number of chromosomes?

(A) What are the nucleotide sequences of ribosomal RNA genes that are found in the genomes of the different species?

1. The lionfish is a venomous fish found primarily in the Red Sea and the Indian Ocean. In the 1990s, lionfish were accidentally released into the Atlantic Ocean, where they found abundant resources and favorable environmental conditions. Which of the following scenarios is most likely to result in the lionfish having a major impact on the communities into which they were introduced? (A) With no natural predators, the lionfish population will become very large. (B) Some native species of invertebrates will develop a resistance to lionfish venom. (C) Random mating will allow the lionfish population to reach Hardy-Weinberg equilibrium. (D) A virus that specifically infects lionfish will become more prevalent.

(A) With no natural predators, the lionfish population will become very large.

24. In the following human pedigree, squares represent males, circles represent females, and shaded symbols indicate individuals affected with a disorder. One of the affected males from the third generation has a child with a female who is a carrier. For the pedigree shown above, which of the following best expresses the probability that the couple's first son will be affected with the disorder? (A) 25% (B) 50% (C) 75% (D) 100%

(B) 50%

4. Ethylene is an organic compound produced by ripening fruits. In a controlled experiment, researchers found that ethylene gas stimulated the ripening process in newly harvested fruits. Which of the following describes the most likely connection between natural ethylene production and fruit ripening? (A) As a result of metabolic inactivity, newly harvested fruits are unable to absorb ethylene gas from the atmosphere. (B) Ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits. (C) Because of normal phenotypic variation, only some of the fruits in a given generation are expected to produce ethylene gas. (D) The rate of ethylene gas production by ripening fruits is an indicator of the relative age of an ecosystem

(B) Ethylene gas is a chemical signal through which ripening fruits trigger the ripening process in other fruits.

18. Prior to 1960, Lake Washington was highly polluted and underwater visibility was limited to one or two meters. In the late 1960s, a large cleanup effort reduced pollution, resulting in visibility that increased to six to seven meters by 1976. Which of the following best explains how the change in underwater visibility affected armor plating in Lake Washington sticklebacks between 1957 and 1976 ? (A) Higher visibility allowed sticklebacks to increase their food consumption to make armor production easier. (B) Higher visibility made the sticklebacks more susceptible to large-toothed predators in the lakes, giving complete armor a selective advantage. (C) Clearer water allowed sunlight to penetrate to deeper depths, so the sticklebacks had to increase the amount of armor to protect themselves from the resulting increase in water temperature. (D) Clearer water contained fewer of the molecular building blocks needed for armor production, so sticklebacks showed a reduction in the amount of armor.

(B) Higher visibility made the sticklebacks more susceptible to large-toothed predators in the lakes, giving complete armor a selective advantage.

26. The Trp operon is a coordinately regulated group of genes (trpA-trpE) that are required for tryptophan biosynthesis in E. coli. Based on the figure above, which of the following correctly describes the regulation of the Trp operon? (A) In the absence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon. (B) In the presence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon. (C) In the absence of tryptophan, the trpR gene is inactive, preventing the production of the repressor that blocks expression of the operon. (D) In the presence of tryptophan, the trpR gene is inactive, preventing the production of the repressor that blocks expression of the operon.

(B) In the presence of tryptophan, the repressor is active and binds to the Trp operator, preventing RNA polymerase from transcribing the operon.

25. Chytridiomycosis is a potentially lethal fungal infection that adversely affects some frog populations. The incidence and severity of the fungal infection can vary over time. Which of the following statements best describes the changes in the frog population that are depicted in the model above? (A) The fungus that infected the frog population was initially virulent but it later became harmless. Based on the trend over the past few years of the study, the fungus has become extinct. (B) Infected individuals gradually died out, and genetically resistant individuals became more common. The frog population recovered because of the increased frequency of resistant individuals. (C) The patterns of the curves on the graph indicate a sudden increase in the severity of the fungal infection. A large proportion of the frog population died because the individuals could not evolve fast enough. (D) The size of the frog population decreased sharply upon initial contact with the fungus. The fungus eventually became symbiotic with individual frogs, and the frog population began to recover.

(B) Infected individuals gradually died out, and genetically resistant individuals became more common.

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

22. A researcher examining a root tip observes a plant cell with condensed sister chromatids, kinetochores with attached microtubules, and individual chromosomes that are aligned at the equatorial plate of the cell. Which of the following best describes what the next process will be in the cell? (A) Homologous chromosomes (each with two sister chromatids) will move toward opposite poles of the cell. (B) Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell. (C) The nuclear envelope will break down, and the spindle will begin to form. (D) The chromatin will decondense, and the daughter cell will enter interphase.

(B) Paired chromatids will separate, and the new daughter chromosomes will move toward opposite poles of the cell.

42. Based on the data, which of the following is the best explanation for the changes in the elk population size between 2000 and 2005 ? (A) The heights of aspen trees increased during that time period. (B) Predation by wolves was higher than before 1995. (C) The numbers of aspen trees increased during that time period. (D) Wolf populations increased more rapidly in the upland areas.

(B) Predation by wolves was higher than before 1995.

14. The salinity of a small inland lake has recently started to increase. Researchers are planning to study the lake over several decades to investigate how freshwater organisms survive significant changes in their natural habitat. Which of the following physiological mechanisms will the researchers most likely observe among the surviving organisms in the lake? (A) Prokaryotic organisms will use various mechanisms to counteract swelling of cells as a result of increased water uptake. (B) Single-celled organisms will use various mechanisms to counteract the increased flow of water from cells to the environment. (C) Eukaryotic organisms will use various mechanisms to counteract the diffusion of positively charged ions across the cell membrane. (D) Multicellular organisms will use various mechanisms to counteract the loss of cell adhesion as a result of calcium deficiencies.

(B) Single-celled organisms will use various mechanisms to counteract the increased

7. Based on an analysis of the food web, an observation that deep-sea bacteria consume molecular hydrogen (H2) is most relevant to resolving which of the following apparent contradictions? (A) Water gushing from deep-sea hydrothermal vents can be as hot as 400∞C, which is a lethal temperature for most organisms. (B) Some deep-sea organisms appear to be primary consumers, but no plants live near the hydrothermal vents. (C) Zoarcid fish are thought to be aggressive predators, but they are frequently described as being lazy swimmers. (D) Some tissues of tubeworms contain hemoglobin, which is an oxygen-carrying molecule, but there is little free oxygen at this depth.

(B) Some deep-sea organisms appear to be primary consumers, but no plants live near the hydrothermal vents.

35. Researchers conducted a controlled experiment to investigate the effect of diet on the health of beef cattle. The initial hypothesis was that an abrupt change in diet will benefit beef cattle by reducing the sizes of bacterial populations living in the digestive systems of the cattle. In the experiment, the researchers determined the relative abundance of two bacterial species found in the rumen of cattle. The rumen is a part of the stomach that acts as a fermentation chamber in cattle and other ruminants. Shown in the table are the results from before and after an abrupt change in the cattle's diet. Based on the results, which of the following best explains why the initial hypothesis should be revised? (A) The diets were too similar, since cellulose and starch are both carbohydrates obtained from eating plants. (B) The abundance of one of the bacterial species increased in response to the change in diet. (C) The change in the diversity of microorganisms had no observable effect on cattle physiology. (D) The ability of rumen fluid to resist changes in pH counteracted the changes in microorganism diversity.

(B) The abundance of one of the bacterial species increased in response to the change in diet.

17. A completely-plated stickleback from a marine population was mated to a low-plated stickleback from a freshwater population. The resulting F1 hybrids all displayed a completely plated phenotype. When the F1 hybrids were allowed to interbreed, the resulting F2 generation included completely plated offspring and low-plated offspring in an approximate 3:1 ratio. Which of the following conclusions is best supported by the results of the breeding experiments? (A) Phenotypic variation in the F2 generation suggests that armor morphology is controlled by many alleles of a single gene. (B) The completely-plated phenotype is controlled by a dominant allele of a single gene. (C) Armor loss is an acquired characteristic that is affected by one or more environmental factors. (D) Patterns of armor plating in stickleback populations are regulated by sex-specific signals.

(B) The completely-plated phenotype is controlled by a dominant allele of a single gene.

51. In animals, the hox genes encode a family of transcription factors that are important for proper development of embryonic segments and are widely conserved in organisms. The figure below shows the embryonic segments in which one such gene, Hoxc6, is expressed in the embryo of a mouse, a chick, and a goose. Embryonic segments are counted from the anterior end. During the formation of vertebrae, the most anterior embryonic segment that expresses Hoxc6 marks the end of the cervical (neck) vertebrae and the beginning of the thoracic (rib) vertebrae. All mammals have seven cervical vertebrae. Which of the following statements is most likely to be true? (A) The chick and the goose have the same number of thoracic vertebrae. c (C) Hoxc6 is expressed in the same embryonic segments in birds and mammals. (D) Hoxc6 is expressed in the same vertebra at the anterior end of all bird embryos.

(B) The most anterior expression of Hoxc6 is the eighth vertebra in mammals.

31. Which of the following provides the best justification for an assumption that might have been used in the computer simulation (Table II) ? (A) The broad allele is recessive to the narrow allele because broad leaves appear in every generation. (B) The purple allele is dominant to the white allele because all the offspring from the cross of purple-flowered and whiteflowered plants had purple flowers. (C) The narrow allele is codominant with the purple allele because the purple-flower trait and the narrow-leaf trait segregate together. (D) The white allele is dominant to both the broad and narrow alleles because plants with either type of leaf shape can have white flowers.

(B) The purple allele is dominant to the white allele because all the offspring from the cross of purple-flowered and whiteflowered plants had purple flowers.

23. The figure below illustrates a eukaryotic cell. Which of the following best describes how the three structures indicated by the arrows work together? (A) To synthesize lipids and modify toxic substances in order to render them harmless (B) To synthesize and isolate proteins for secretion or for use in the cell (C) To catabolize nutrients and produce ATP for intracellular energy storage (D) To synthesize all ribosomal proteins

(B) To synthesize and isolate proteins for secretion or for use in the cell

3. A colony of termites was exposed to an atmosphere of 100 percent oxygen for three days. The insects were not immediately harmed by the treatment, but the protozoa that lived in the termites' guts were eliminated. The treated termites continued to behave normally and to eat wood, but they began to starve after a short time. When the treated termites were instead fed wood contaminated with the feces of untreated termites, the treated termites regained the ability to digest wood and no longer starved. The best analysis of the results of the experiment is that (A) infection with protozoa causes the termites to switch to fermentation (B) cooperative interactions between the termites and the protozoa allow termites to extract energy from wood to survive (C) the termite immune system eliminates protozoa from the gut (D) termites digest protozoa as their main source of energy

(B) cooperative interactions between the termites and the protozoa allow termites to extract energy from wood to survive

48. The graph above shows changes in glucagon and insulin secretions at different concentrations of blood glucose. Which of the following feedback mechanisms is best supported by the data? (A) A falling glucagon level causes a rise in the insulin level, which maintains equal amounts of both hormones in the blood. (B) A high glucagon level causes a rise in the insulin level, which maintains high levels of both hormones in the blood. (C) A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released. (D) A low glucose level causes the release of insulin, which stimulates the release of more glucose from tissues, which in turn increases the amount of insulin being released.

(C) A low glucose level causes the release of glucagon, which stimulates the release of more glucose from tissues, which in turn lowers the amount of glucagon being released.

16. Which of the following best explains the differences in the armor of the Lake Washington stickleback population summarized in Figure 1 ? (A) Analysis of somatic cells using chromosomal staining and light microscopy indicates that stickleback fish have a diploid number of 42. (B) Stickleback males from natural freshwater populations are typically more aggressive when competing for mates than are stickleback males from laboratory-bred populations. (C) Fish exhibiting the low-plated phenotype were selected against in the Lake Washington stickleback population over the last 50 years. (D) Migration of individuals from other freshwater environments to Lake Washington led to gene flow between populations that were once geographically isolated.

(C) Fish exhibiting the low-plated phenotype were selected against in the Lake Washington stickleback population over the last 50 years.

50. Gregor Mendel's pioneering genetic experiments with pea plants occurred before the discovery of the structure and function of chromosomes. Which of the following observations about inheritance in pea plants could be explained only after the discovery that genes may be linked on a chromosome? (A) Pea color and pea shape display independent inheritance patterns. (B) Offspring of a given cross show all possible combinations of traits in equal proportions. (C) Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other. (D) Recessive phenotypes can skip a generation, showing up only in the parental and F2 generations.

(C) Most offspring of a given cross have a combination of traits that is identical to that of either one parent or the other.

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

2. Cell communication is critical for the function of both unicellular and multicellular eukaryotes. Which of the following is likely true of cell signaling? (A) Cell signaling uses the highest molecular weight molecules found in living cells. (B) Cell signaling has largely been replaced by other cell functions in higher mammals. (C) Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes. (D) Cell signaling functions mainly during early developmental stages.

(C) Similar cell signaling pathways in diverse eukaryotes are evidence of conserved evolutionary processes.

6. Which of the following best explains how biological communities near deep-sea hydrothermal vents can exist in a habitat lacking sunlight? (A) Environmental conditions on some distant planets resemble those experienced by organisms living near hydrothermal vents. (B) Heterotrophs metabolize carbon-containing compounds produced by the photosynthetic organisms that live on the seafloor. (C) Some organisms rely on energy captured from inorganic compounds to drive basic biological processes. (D) Some organisms that can tolerate high temperatures are single celled, whereas others are multicellular.

(C) Some organisms rely on energy captured from inorganic compounds to drive basic biological processes.

53. A biologist is studying territoriality in three related species of birds found in the same section of a forest. For each observed pair of nesting adults, the biologist measured the distance to the next closest nesting pair of the same species (nearest-neighbor distance). An analysis of the results is shown in the table below. Which of the following would be most appropriate for identifying the species with the most even distribution of nests? (A) Area of the forest in which the nearest-neighbor measurements were made (B) Total number of nearest-neighbor observations collected during the study period (C) Standard deviation of the nearest-neighbor distances for each species (D) Proportion of nearest-neighbor distances that were less than the median

(C) Standard deviation of the nearest-neighbor distances for each species

30. In Table I, the ratio of phenotypes in the offspring from the testcross with F1 plants that had purple flowers and inflated pods suggests that the genes for flower color and pod shape are located (A) close together on the same autosome (B) on the X chromosome (C) on different chromosomes (D) on a mitochondrial chromosome

(C) on different chromosomes

43. Which of the following predictions about the community is most likely true? (A) A decrease in the elk population will cause wolves to feed on aspen trees. (B) An increase in the wolf population will lead to a decrease in aspen growth. (C) An increase in the growth of aspens will lead to a decrease in the wolf population. (D) A decrease in the wolf population will lead to a decrease in the mean aspen height.

(D) A decrease in the wolf population will lead to a decrease in the mean aspen height.

39. A species of snail lives in the intertidal zone along the coast of New England. The dark-colored variety of the species is more common in northern New England, the light-colored variety is more common two hundred miles away in southern New England, and both varieties are commonly found together in central New England. Which of the following best explains the observed distribution pattern of the snails? (A) The founder effect suggests that dark-colored snails migrated from the southern regions to the north and established the populations found there. (B) Genetic drift at the shell-color locus caused the northern population to become homozygous for the dark-color allele. (C) The mutation rate is higher in the south, as the longer days expose the snails to more ultraviolet radiation than in the north. (D) Dark-colored snails absorb more solar energy and so survive more readily in the colder northern waters.

(D) Dark-colored snails absorb more solar energy and so survive more readily in the colder northern waters.

52. The process depicted in the image above is best summarized by which of the following descriptions? (A) During the synthesis phase of the cell cycle, DNA molecules replicate to generate identical daughter cells. (B) Centromeres align specific gene sequences of homologous chromosomes during mitotic divisions. (C) The spindle apparatus attaches at chiasma during metaphase of mitosis. (D) During meiosis, crossing over leads to recombination of alleles between homologous chromosomes.

(D) During meiosis, crossing over leads to recombination of alleles between homologous chromosomes.

49. Which of the following best describes an advantage that eukaryote organisms have over prokaryote organisms? (A) Prokaryotes lack a cell membrane and therefore are unable to control what enters or exits the cell. (B) Eukaryotes have a nuclear envelope separating their DNA from the rest of the cell, which increases the likelihood of advantageous mutations. (C) Eukaryotes have mitochondria and chloroplasts that contain their own genome, which allows the cells to reproduce more rapidly. (D) Eukaryotes have organelles that allow for compartmentalization of cellular processes, which increases the efficiency of those processes.

(D) Eukaryotes have organelles that allow for compartmentalization of cellular processes, which increases the efficiency of those processes.

34. Methicillin-resistant Staphylococcus aureus (MRSA) can be a serious threat to human health. There is evidence that S. aureus infections are common in hospitals and that MRSA have become resistant to other antibiotics besides methicillin. This suggests that the rapid evolution of resistance in the bacteria poses a serious public-health challenge. Which of the following best explains the ability of MRSA to evade existing drug therapies? (A) MRSA have very long generation times and very large population sizes. (B) MRSA develop new alleles by intentionally introducing specific mutations that will give them a selective advantage over other bacteria. (C) MRSA metabolize many drugs in their lysosomes and therefore evolve resistance at a high rate. (D) MRSA exchange genetic material with other antibiotic-resistant bacteria, which can spread resistance in the S. aureus population.

(D) MRSA exchange genetic material with other antibiotic-resistant bacteria, which can spread resistance in the S. aureus population.

19. Evolution of a new trait typically takes many generations. Yet a dramatic shift in the extent of armor plating in the Lake Washington stickleback population occurred in the 50 years following the cleanup of the lake. Which of the following best describes the mechanism of the rapid evolution of the armor phenotype in the Lake Washington sticklebacks? (A) Pollutants in Lake Washington forced the sticklebacks to increase their mutation rate. (B) The rapid change in the Lake Washington ecosystem required individual sticklebacks to evolve complete armor quickly. (C) The increase in visibility in Lake Washington allowed sticklebacks to visually select mates with low armor. (D) New selective pressures favored individuals with the plated phenotype, causing the plated allele frequency in the population to quickly increase.

(D) New selective pressures favored individuals with the plated phenotype, causing the plated allele frequency in the population to quickly increase.

9. On the basis of the food web, which of the following members of a deep-sea biological community is most likely to also have a symbiotic relationship with chemosynthetic organisms? (A) Octopuses (B) Blind crabs (C) Zoarcid fish (D) Shrimp

(D) Shrimp

12. Individuals with an inherited autosomal recessive disorder called primary ciliary dyskinesia (PCD) often have severe respiratory problems due to defective cilia. Males with PCD are often sterile because they produce sperm with defective flagella. Which of the following most likely explains the effect of the recessive allele? (A) The mitochondria are defective and do not produce sufficient protein to synthesize microtubules in the cilia and flagella. (B) The plasma membrane of the alveoli is not permeable to carbon dioxide during respiration because it is too hydrophobic. (C) The Golgi bodies secrete an enzyme that destroys the proteins in the flagella and cilia. (D) The cells do not produce functional motor proteins in flagella and cilia.

(D) The cells do not produce functional motor proteins in flagella and cilia.

47. 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. 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) The two genes are linked on an autosome.

15. Assume there are 50,000 joules (J) of energy available in trophic level II in the figure. According to the conventional model of energy flow in ecosystems, which of the following statements correctly describes the flow of energy in the system? (A) Trophic level I generates a maximum of 50,000 J of energy. (B) Trophic level I has approximately 5,000 J of available energy. (C) Trophic level III has approximately 50 J of available energy. (D) Trophic level IV has approximately 500 J of available energy.

(D) Trophic level IV has approximately 500 J of available energy.

41. Precise regulation of specific hormone levels is required for optimal sperm production in mammals, as summarized in the figure above. Anabolic-androgenic steroids (AAS) are synthetic variants of testosterone that are sometimes abused by persons who desire to enhance their athletic performance or alter their physique. Assuming that AAS function in the same way as naturally occurring testosterone, it is most likely that long-term abuse of AAS would (A) stimulate FSH secretion (B) stimulate testosterone production (C) stimulate LH secretion (D) reduce sperm production

(D) reduce sperm production

121. Researchers observe a large population of birds on a remote island. Birds in the population are found to have either red crest feathers or white crest feathers on their heads. Genetic analysis indicates that the allele for red crest feathers is dominant over the allele for white crest feathers. In a survey of the population, the researchers determine the frequencies of the crest-feather phenotypes. The results of the survey are shown in the table below. Assuming that the bird population is in HardyWeinberg equilibrium, what proportion of future populations is expected to be heterozygous for the allele controlling crest feather color? Give your answer as a value between 0 and 1, rounded to two decimal places.

0.47

124. As part of a study to observe the activity of photosynthetic organisms in a temperate-zone lake, measurements of light penetration were made at different water depths. The results are presented in the graph below. Note that higher light penetration values indicate a greater amount of light reaching the water at that depth. According to the data above, what is the deepest water level at which light penetration is expected to be at least 200 µEin m-2 s-1 ? Give your answer to the nearest tenth of a meter.

1.4

122. A typical human lymphocyte has a radius of about 10 µm, while a typical bacterium (e.g., S. pneumoniae) has a radius of about 1 µm. Assuming that both cell types are perfectly spherical, how many times larger is the surface area of a typical human lymphocyte compared to the surface area of a typical bacterium?

100

125. An experiment on plant defenses was conducted on three identical groups of lima bean plants. The first group was treated with a solution containing a chemical similar to an organic compound that is released by herbivore-damaged plants (solvent plus chemical). The second group was treated with only the solvent used in the first treatment. The third group was left untreated. One week after the treatment phase, the numbers of carnivorous ants (predators of herbivores) found residing on the plants in each group were determined. The results of the experiment are provided below. Based on the information in the graph, how many times more ants are found on plants exposed to the solvent plus chemical compared to plants exposed to the solvent only? Give your answer to the nearest tenth.

2.4

123. One method for predicting the average temperature (in ºC) at which a short DNA molecule binds with its complement is to calculate a melting temperature (Tm) using the following formula. Tm = 4 (G + C) + 2 (A + T) Using the formula, what is the predicted Tm for the short single-stranded DNA molecule shown above?

60

45. Which of the following models best predicts the effect on the ecosystem if a deadly communicable disease is introduced into the wolf population?

A) - wolf + elk

40. Which of the following representations best shows a portion of an axon at rest (before or after an action potential)?

A) Small circle K+

37. Which of the following diagrams best represents hormone-activated gene expression?

A) Steroid Hormone as ligand

33. When a stimulus is applied to a receptor in the skin, an action potential is propagated along a neuron to the brain, where another signal is sent back to the muscle for a response. Which of the following best describes what occurs when the action potential reaches a chemical synapse at the end of an axon? (A) The action potential jumps from one axon to the next connecting axon. (B) The action potential travels through the synapse to the next connecting dendrite. (C) The action potential jumps the synapse to the next connecting dendrite. (D) The action potential causes a release of neurotransmitters that travel across the synapse.

D(D) The action potential causes a release of neurotransmitters that travel across the synapse.

46. Information is transmitted through the nervous system when one neuron signals another neuron. The structure of neurons enables transmission to proceed quickly and efficiently. Which of the following diagrams correctly identifies both the structure of neurons and the direction of information flow between neurons?

D) dendrite -> axon -> dendrite -> axon