AP Biology Final

Cycloheximide (CHX) is a eukaryote protein synthesis inhibitor. It is used in biomedical research to inhibit protein synthesis in eukaryotic cells studied in vitro. Its effects are rapidly reversed by simply removing it from the culture medium. In a translation experiment using a fungus culture, radiolabeled amino acids were added to the culture, allowing the researchers to measure the growth of a single polypeptide chain by measuring counts per minute (CPM). As the chain grew, the CPM increased. After a certain amount of time, CHX was added to the mixture, and the experiment continued. After an additional amount of time, the CHX was removed from the culture medium. Which of the following graphs best predicts the data collected during the experiment?

(graph CPM x Time)increase=>Inhibitor added=>constant=>inhibitor removed=>decrease

In addition to the ABO blood groups, humans have an MN blood type system in which the M and N alleles are codominant to one another. A group of scientists found that in one population the frequency of the M allele was 0.82, and the frequency of the N allele was 0.18.Assuming that the population is in Hardy‑Weinberg equilibrium, which of the following is the expected frequency of individuals with the genotype MN?

0.295

Based on the data in the figure, a student claimed that since 2007, the carrying capacity of wolves in Yellowstone National Park has been 100 wolves, and the maximum annual per capita growth rate of gray wolves is 0.6 wolves per wolf per year. Which of the following is closest to the calculated wolf population size in 2017 based on the student's claim?

103

The students plan to use a significance level of p=0.01. Based on Table 5-4, which of the following is the most appropriate critical value for the students to use in their chi-square goodness-of-fit test?

11.34

In the mid-1920s, gray wolves, Canis lupus, were eliminated from Yellowstone National Park in the northwestern United States. Over the course of 1995 and 1996, 31 wolves from Canada were relocated to the park. Researchers have tracked the growth of the wolf population from 21 in 1995 to 108 at the end of the study in 2016 (Figure 1).Figure 1. Yellowstone National Park annual wolf population from 1995 to 2016The wolves prey on large herbivores, primarily elk. The carcasses of wolf kills are a valuable food source for coyotes, Canis latrans. When coyotes are feeding on carcasses, they may be chased off the carcass and/or killed by wolves. Coyotes also hunt small mammals for food. Researchers were studying the effect of wolves' presence on the behavior of coyotes. Researchers observed coyotes in a specific area of Yellowstone National Park and recorded the proportion of the coyotes' time spent on five different activities when wolves were present in the study area and when wolves were absent (Figure 2).Figure 2. Coyote behavior in the presence and absence of wolves. Error bars represent a confidence interval of 95% (±2 standard errors of the mean).Based on information in Figure 1, which of the following is closest to the annual growth rate of the wolf population in Yellowstone National Park from 1996 to 2004 ?

17 wolves per year

Based on Table 5-5, the mean map distance between gene R and gene L is closest to which of the following?

28 map units

Based on Table 5-8, the mean number of fruit flies per student that are homozygous recessive for both genes is closest to which of the following?

29.0

How many degrees of freedom should be used when looking up the critical value for a chi-square analysis of the ratios of phenotypes observed among the F2 offspring versus the expected phenotypic ratio assuming independent assortment based on Table 5-1?

3

Based on Figure 5-8, If the woman and a man with normal clotting function have children, what is the probability of their children exhibiting hemophilia A?

50 percent for sons, 0 percent for daughters

Owls (primary predators of rock pocket mice) are nocturnal visual predators that are able to distinguish effectively between dark and light colors in low-light conditions. Which of the following best explains the relationship between coat color and predation rate in the rock pocket mouse population on the lava flow rocks with respect to the different coat color phenotypes?

A dark coat color provides camouflage to mice on the lava flow rocks; therefore, mice with dark coats have a lower predation rate in that habitat.

A scientist wishes to provide experimental evidence to support the model shown in Figure 1 by demonstrating the ability to synthesize an RNA molecule. Which of the following is an alternative hypothesis that can be tested to support the RNA World Hypothesis?

A mixture of ribonucleotides such as adenine and uracil will spontaneously form single-stranded chains of RNA.

(melanin synthesis pt. 5) Which of the following best explains a process occurring between point 1 and point 2 in Figure 3 ?

A poly‑A tail is added to RNA.

Based on Table 5-9, which of the following is most likely the immediate cause of the first appearance of Huntington's disease in a person?

An allele with more than 39 CAG repeats was inherited by the affected person.

For this condition, which of the following modes of inheritance is most consistent with the observations based on Figure 5-5?

Autosomal dominant

Which of the following is closest to the calculated chi-square (χ2) value for the data presented in Table 5-2?

B) 72.01

Students in a class were divided into five groups to analyze community structure. Each group of students assessed the species of plants in four environments and determined the Simpson's Diversity Index for each environment. The Simpson's Diversity Index takes into account the number of species present as well as the abundance of each species. The index values are shown in Figure 1.Figure 1. Simpson's Diversity Index for four environments. Based on the data in Figure 1, which of the following statements is most accurate about the species diversity of the four different environments that the students analyzed?

Based on the data, there is no statistically significant difference between the species diversity of plants in the light, moist environment and in the dark, moist environment

Which of the following best explains the trend shown in Figure 1? (Kentucky Derby)

By 1940, most genetic variation for speed had been lost from the gene pool.

Relationships of selected organisms based on catalase structure. Which of the following student claims is best supported by the data provided?

Cattle and sheep are separated by only one node, and they are separated from the other organisms by more than one node.

Figure 1. Models of a prokaryote, first eukaryotic common ancestor, and last eukaryotic common ancestor. Based on the information provided in the figure, which of the following best describes how membrane-bound organelles provided unique evolutionary advantages to the last eukaryotic common ancestor?

Cells with mitochondria were able to utilize metabolic energy more efficiently.

Of the following, which is the best next step for the researchers to best determine the long-term effectiveness of these insecticides with regards to the development of resistance?

Continue treating the three insect populations with the same insecticides and determine whether their efficiencies decline significantly after several generations.

Human activities can drive changes in ecosystems that affect the risk of extinction. An experiment is designed to help prevent the further decline and extinction of the Henslow's sparrow in which controlled burns will be set in the each of the ten Midwest counties in order to prevent the regrowth of the forest. Which of the following represents an alternate hypothesis tested by this experiment with regard to the population sizes of Henslow's sparrows?

Controlled fires in counties 4 and 5 will lead to an increase in the sparrow population.

Based on the phylogenetic relationships shown in Figure 1, which of the following best explains the similarities exhibited by whales, bony fishes, and cartilaginous fishes?

Convergent evolution, because these organisms do not share a recent common ancestor.

Which of the following best describes the processes occurring between the mouse populations and their environments?

Dark color is selected for in mice from the West, Mid, and East populations.

Which of the following best describes the change in coyote behavior in the presence of wolves?

Decrease, No Effect, No effect, Increase, Increase

Cystic fibrosis (CF) is a progressive genetic disease that causes persistent lung infections and affects the ability to breathe. CF is inherited in an autosomal recessive manner, caused by the presence of mutations in both copies of the gene for the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Partial nucleotide sequences and the corresponding amino acid sequences for an unaffected individual and an affected individual are modeled in Figure 1.Figure 1. CFTR protein sequences in unaffected and affected individuals. Based on the information in Figure 1, which type of mutation explains the nature of the change in DNA that resulted in cystic fibrosis in the affected individual?

Deletion, because a thymine is missing, which changes the reading frame

Based on Figure 5-3, which of the following questions could best be addressed?

Does synapsis of homologous chromosomes in the parent cell contribute to an increase in genetic diversity in the daughter cells?

Some researchers claim that the decrease in plant species richness of this woodlot is unrelated to human activities over the last forty years. Which of the following would be an appropriate alternative hypothesis?

During the last few decades, tall buildings have been built around the woodlot, and species 3, 4, and 5 are shade‑intolerant plants

Scientists conducted a transformation experiment using E. coli bacteria and the pTru plasmid. Samples of the pTru plasmid (lane A) and the chromosomal DNA from two different E. coli strains that the scientists attempted to transform (lane B and lane C) were compared using gel electrophoresis. The results are shown in Figure 1.Figure 1. Results of E. coli transformation with pTru plasmid. Which of the following statements best explains the experimental results observed in Figure 1 ?

E. coli in lane C have been successfully transformed and contain additional genetic information.

Labeled nucleotides were supplied to a cell culture before the cells began DNA replication. A simplified representation of the process for a short segment of DNA is shown in Figure 1. Labeled DNA bases are indicated with an asterisk (*).Figure 1. A simplified representation of the DNA replication process. Which of the following best helps explain how the process represented in Figure 1 produces DNA molecules that are hybrids of the original and the newly synthesized strands?

Each newly synthesized strand remains associated with its template strand to form two copies of the original DNA molecule.

A simplified model of a DNA replication fork is represented in Figure 1. The protein labeled Enzyme 1 carries out a specific role in the DNA replication process. Figure 1. A simplified model of a DNA replication fork. Which of the following statements best explains the role of Enzyme 1 in the DNA replication process?

Enzyme 1 is a topoisomerase that relieves tension in the overwound DNA in front of a replication fork.

A population geneticist is conducting an investigation on a population of mice. The geneticist determines the genotypes for a particular trait of all of the mice in the population during generation 1 and then removes all of the mice with the genotype aa. The remaining members of the population are allowed to randomly mate with one another to produce generation 2 and future generations. A model of the investigation is shown in Figure 1. Each of the fifteen genotypes shown in generation 1 and generation 2 represents 100 mice. Figure 1. Model of effect of selective mouse removal on a population. Which of the following best illustrates the change in the frequencies of the A and a alleles from generation 1 to generation 2 and to future generations, assuming Hardy-Weinberg equilibrium is present after generation 1 ?

Future generations will have the same frequencies of the AA and aa alleles as generation 2. Individuals with the aa genotype could be produced.

Geologic events such as mountain building can directly affect biodiversity. The Sino‑Himalayan fern, Lepisorus clathratus is widely distributed on the Qinghai‑Tibetan plateau. If geologic events lead to a series of new mountain ranges that divide the plateau into several discrete valleys, which of the following best describes how the L. clathratus population would be affected?

Geographic isolation will create separate gene pools, leading to speciation over time.

Which of the following best predicts the effect of the chromosomal segregation error shown in Figure 5-7?

Half of the resulting gametes will have the correct number of chromosomes, and the other half will have an incorrect number of chromosomes.

Which of the following best explains a distinction between metaphase I and metaphase II?

Homologous pairs of chromosomes are aligned during metaphase II, but individual chromosomes are aligned during metaphase IIII.

Which of the following best predicts why humans and mice have identical telomeric repeat sequences?

Humans and mice share a recent common ancestor that had the 5′-TTAGGG-3′′ repeat sequence in its telomeres.

Nucleotide base pairing in DNA is universal across organisms. Each pair (T−A; C−G) consists of a purine and a pyrimidine. Which of the following best explains how the base pairs form?

Hydrogen bonds join a double-ringed structure to a single-ringed structure in each pair.

Figure 1 depicts a simplified model of a replication bubble. Figure 1. DNA replication bubble. Which of the following best explains how this model illustrates DNA replication of both strands as a replication fork moves?

I is synthesized continuously in the 5′ to 3′ direction, and III is synthesized in segments in the 5' to 3′ direction

Based on the data in Figure 1, which of the following would most affect the allelic frequencies of the populations on Isabela and Butuan?

Immigration of individuals from Metro Manila into the two populations

Which statement below best states an alternative hypothesis Fox could have used to frame his research?

In the presence of available energy and the absence of a significant quantity of atmospheric O2 simple proteins will form spontaneously from a mixture of amino acids.

Soluble reactive phosphate (SRP) is a term used to describe the amount of phosphate available for uptake by living things. A study of river plants species and water phosphate levels was completed in Great Britain. Recently, in a section of one of the rivers studied, a population of fennel-leaved pondweed was replaced by spiked water-milfoil, even though these two plants are associated with different environmental conditions as indicated in the table below. A group of researchers suggest that the concentration of available phosphate in this particular section of the British river does not have a significant impact on which plant species grow. Alternatively, another group of researchers hypothesize that levels of available phosphate do affect which plant species grow at this location. Which of the following observations would best support this alternative hypothesis?

Increased fertilizer use near this section of the river has led to increased runoff of phosphates into the river

A group of researchers noticed that using a particular drug to treat cancer in mice would reduce the size of the tumor, but some of the tumor cells appeared to be resistant to the drug since some of these cells would increase in number over time. The researchers wish to increase the reliability of their experimental observations before investigating new claims that chemotherapy-resistant tumors are an example of continuing evolution. Of the following, which is the best next step the researchers might take to increase the reliability of their evidence?

Increasing the number of trials and the number of mice in each treatment group

Which of the following best predicts why the recombinant bacteria will fail to produce the eukaryotic protein?

Introns must be removed from eukaryotic DNA before the gene is inserted into the plasmid.

A compound that prevents the separation of the homologous chromosomes in anaphase I is being studied. Which of the following questions can be best answered during this study based on Figure 5-3?

Is there a pattern to the movement of homologous chromosomes in the presence of this compound?

The tadpoles of Mexican spadefoot toads are known to exhibit phenotypic plasticity depending on food availability. Tadpole mouthparts can vary significantly, prompting researchers to categorize them as either omnivore-morph or carnivore-morph. Carnivore-morph tadpoles are larger and have mouthparts that are better suited for predation. Remarkably, carnivore-morph tadpoles can change into omnivore-morph tadpoles when the food supply changes. Which of the following best describes an advantage of the phenotypic plasticity displayed by the tadpoles?

It gives the tadpoles increased versatility with respect to diet.

(melanin synthesis pt. 2) Which of the following claims best explains why keratinocytes do not produce melanin?

Keratinocytes do not express the MITF gene.

Zebra mussels, Dreissena polymorpha, were introduced into the Great Lakes on shipping vessels, first appearing in Lake St. Clair in the 1980s. Since that time, they have rapidly expanded in range, as shown in Figure 1.Figure 1. Map showing the current range of zebra mussels in the United States. Which of the following best supports the alternate hypothesis that zebra mussels display characteristics of an invasive species?

Lacking natural predators and able to outcompete native species of mussels and other freshwater species for food, zebra mussels have experienced exponential population growth and rapid expansion into new habitats.

There are two species of elephant seals: northern elephant seals, Mirounga angustirostris, found off the western coast of North America from Baja California to the Gulf of Alaska, and southern elephant seals, M. leonine, found in the southern oceans. Hunting in the nineteenth century has been blamed for a drastic reduction in the northern elephant seal population. Even though the population has rebounded following restrictions on seal hunting, genetic variation is greatly reduced in the northern species compared to that in the southern species.Which of the following conditions of Hardy-Weinberg equilibrium was most likely not met in the northern elephant seal population following overhunting?

Large population size

When a mustard plant seedling is transferred to an environment with higher levels of carbon dioxide, the new leaves have a lower stomata-to-surface-area ratio than do the seedling's original leaves. Which of the following best explains how the leaves from the same plant can have different stomatal densities when exposed to an elevated carbon dioxide level?

Leaf growth is promoted through increased photosynthesis, but the genetically regulated rate of stomatal production is not altered, leading to a decrease in stomatal density.

Which of the following best explains how the sweet pea plants in the parental generation produce F1 offspring with 14 chromosomes based on Figure 5-1 and Table 5-1?

Meiosis I and II lead to the formation of cells with 7 chromosomes. During meiosis I, homologous chromosomes separate. During meiosis II, sister chromatids separate. Two cells combine during fertilization to produce offspring with 14 chromosomes.

Mollusk fossils were excavated and collected from a coastal cliff. Scientists studying the fossils observed patterns of changing shell shape in the mollusks. The scientists identified a period of stability or stasis, followed by rapid change, and then stasis again with regard to shell shape. Which of the following statements best predicts the result of a comparison between the fossils found before and after the period of rapid change?

Most of the species found in the first static period will be absent in the second static period.

Students created a model showing one possible mechanism for speciation in which a geographic barrier separated one large population into two smaller populations, A and B. Over time, populations A and B developed into two distinct species. The model is shown in Figure 1.

Natural selection acted on variation that was present in both populations A and B, and the lack of gene flow eventually led to the formation of two new species.

Figure 1 shows a food web that describes the relationships within a community containing nine species. Each circle represents a separate species. The size of the circle represents the population size of the species relative to other species in the same trophic level. Figure 1. Trophic relationships among organisms in a community. Based on the information in Figure 1, which of the following best predicts a short-term effect of removing secondary consumer X from the community?

No Consumer X and a significantly larger white striped circle (for the primary consumer), with two much smaller circles under it

Some scientists propose that due to human activity and climate change, a sixth mass extinction has already begun. Select the best alternate hypothesis to support this claim.

Observed modern extinction rates will resemble the rates found early in previous extinctions.

In a study of energy flow, the following data were collected: Each human requires 55 grams of protein per day. An acre of soybeans produces 200,000 grams of protein per year. A cow grazing on one acre of land produces 19,000 grams of protein per year. Based on these data, an acre of land would support:10 humans per year on a diet of soy, or0.9 human per year on a diet of beef. Which of the following statements best explains these relationships in terms of energy transfer?

Only 10% of the energy on each level of the trophic pyramid is available for use by the next level. The rest is lost as heat or used for growth and repair

Which of the following sets of data provides evidence that best supports common ancestry for organisms in all three domains?

Organisms in Bacteria, Archaea, and Eukarya each have adenine, thymine, guanine, and cytosine bases forming their DNA.

Glycolysis is a metabolic pathway that converts glucose into pyruvate and is observed in each of the three domains. The hexokinase family of enzymes is required during glycolysis to phosphorylate six-carbon sugars. Researchers designed a general hexokinase inhibitor that is effective in the neurons of rats. Which of the following best predicts the effect of adding this inhibitor to a culture of plant cells?

Plant cells will be unable to perform glycolysis due to the inhibitor and will die.

Because cheetahs, Acinonyx jubatus, experienced a bottleneck event about ten thousand years ago, living cheetahs exhibit very little genetic variation compared to other living species of large cats. Which of the following principles best justifies a claim that cheetahs, compared to other large cats, have a relatively low resilience to environmental perturbations?

Populations with little genetic diversity are less likely to contain individuals that can withstand different selective pressures.

Which of the following best explains how the pattern of DNA arrangement in chromosomes could be used, in most cases, to determine if an organism was a prokaryote or a eukaryote?

Prokaryotic DNA: singular circular chromosome Eukaryotic DNA: multiple linear chromosomes

All cells must transcribe rRNA in order to construct a functioning ribosome. Scientists have isolated and identified rRNA genes that contribute to ribosomal structure for both prokaryotes and eukaryotes. Figure 1 compares the transcription and processing of prokaryotic and eukaryotic rRNA. Figure 1. Comparison of rRNA processing in prokaryotes and eukaryotes. Which of the following statements provides the best explanation of the processes illustrated in Figure 1 ?

Sections of the pre-rRNA are removed, and the mature rRNA molecules are available to combine with proteins to form the ribosomal subunits.

For sexually reproducing diploid parent cells, which of the following statements best explains the production of haploid cells that occurs in meiosis but not in mitosis?

Separation of chromatids occurs once, and there are two rounds of cell division in meiosis.

Huntington's disease, an autosomal dominant disorder, is caused by a mutation in the HTT gene. The HTT gene contains multiple repeats of the nucleotide sequence CAG. A person with fewer than 35 CAG repeats in the HTT gene is unlikely to show the neurological symptoms of Huntington's disease. A person with 40 or more CAG repeats almost always becomes symptomatic. Due to errors in meiosis, an individual without symptoms of Huntington's disease can produce gametes with a larger number of CAG repeats than there are in their somatic cells. A woman develops Huntington's disease. Her father had the disorder. Her mother did not, and there is no history of the disorder in the mother's family. Which of the following best explains how the woman inherited Huntington's disease?

She inherited an allele with more than 40 CAG repeats in the HTT gene from her father.

(melanin synthesis pt. 4) Based on the information provided in Figure 1 and Figure 2, which of the following best predicts the effects of a mutation in the promoter of the TYR gene that prevents it from being transcribed?

Skin pigmentation will not be able to change, resulting in a negative selection pressure.

In a particular region, a species of lizard lives in the lowlands. Even though there are numerous mountains in the region, the climate on the mountains is too cold for the lizards to survive. Scientists are concerned that the lowlands will become much warmer by the end of the twenty-first century and will become unsuitable for this lowland lizard species. Which of the following best predicts the impact on the lizard species if there is a gradual increase in the average temperatures found in both the lowlands and mountains in this region?

Some lizards will migrate to new habitats in the mountains and become isolated, leading to allopatric speciation.

Figure 1 represents a portion of a process that occurs during protein synthesis. Figure 1. Model of selected features of DNA transcription. Which claim is most consistent with the information provided by the diagram and current scientific understanding of gene regulation and expression?

Some sequences of DNA can interact with regulatory proteins that control transcription.

An evolutionary biologist hypothesizes that two morphologically similar plant species are not closely related. To test the hypothesis, the biologist collects DNA samples from each of the two plant species and then uses restriction enzymes to cut the DNA samples into fragments, which are then subjected to gel electrophoresis. The results are shown in Figure 1.Figure 1. DNA analysis of two species. Given the results shown in Figure 1, which of the following correctly describes a relationship between the two species?

Species B has more short fragments of DNA than species A does.

Specimen 1 Specimen 2 Specimen 3 Specimen 4Amino acid differences* 5 21 18 11 Percent of original carbon-14 remaining 38 73 25 11 Composition Sandstone Sandstone Limestone Shale DNA analysis 35% Guanine 28% Guanine 12% Guanine 29% Guanine *amino acid differences of a conserved protein compared with a fifth fossil specimen. Which of the specimens indicated in the table is the oldest?

Specimen 4

A group of researchers claim that chance events play an important role in the evolution of populations. To test their claim, they monitored 12 populations of E. coli for 10,000 generations under the same environmental conditions. They found that although all 12 populations were exposed to the same environmental pressures, each population had differentiated from one another genetically after 10,000 generations. Which of the following statements includes a reasonable refinement that researchers could use in repeating the experiment?

Start each population with genetically identical bacterial cells from a single culture to make sure that the initial genetic variation in all of the populations was exactly the same.

The degrees of relatedness in several native populations of prairie chickens in Marion and Jasper Counties in Illinois were determined. The degree of relatedness is inversely proportional to genetic diversity; that is, populations with a high degree of relatedness have less genetic diversity. Table 1 shows the collected data. Populations J1 through J5 are located in Jasper County. Populations M1 through M5 are located in Marion County. Numbers above 0.125 indicate a high degree of relatedness. Table 1. RELATEDNESS OF PRAIRIE CHICKEN POPULATIONS Population Degree of Relatedness J1 0.215J2 0.215J3 0.339J4 0.280J5 0.362M1 0.305M2 0.365M3 0.199M4 0.432M5 0.405 Scientists claim that some of the populations in Marion County are at an increased risk of decline or extinction. Based on the data in table 1, which of the following best provides evidence to support this claim?

The M4 and M5 populations have the lowest genetic diversity of all populations.

Based on the data in Table 1, which of the following best describes the relationship between the MC1R gene and coat color in the Carrizozo, New Mexico, rock pocket mouse population?

The MC1RD allele is not responsible for dark coat color in the Carrizozo population, so the dark coat color is likely a result of convergent evolution.

Based on the data in Figure 5-4, which of the following is the best prediction of the mode of inheritance of red eyes in Japanese koi?

The allele for red eyes is inherited in an autosomal dominant pattern.

The island was surveyed again in 2015, and scientists determined that the giant kangaroo rats originally in population A are now to be considered as a new species. Which of the following best explains the mechanism that caused this speciation event in the giant kangaroo rats of population A?

The animals in population A were reproductively isolated from those in populations B, C, and D.

Using a significance level of p=0.05, which of the following statements best completes a chi-square goodness-of-fit test for a model of independent assortment based on Table 5-3?

The calculated chi-square value is 3.91, and the critical value is 7.82. The null hypothesis cannot be rejected.

Eukaryotes transcribe RNA from DNA that contains introns and exons. Alternative splicing is one posttranscriptional modification that can create distinct mature mRNA molecules that lead to the production of different proteins from the same gene. Figure 1 shows a gene and the RNA produced after transcription and after alternative splicing. Figure 1. Model of posttranscriptional alternate splicing of mRNAA cell needs to metabolize the substrate illustrated in Figure 1 for a vital cellular function. Which of the following best explains the long-term effect on the cell of splicing that yields only enzyme C mRNA?

The cell will die because it is unable to metabolize the substrate without enzyme AA, which is structurally specific for the substrate shown.

The researchers calculated a chi-square value of 29.25. If there are three degrees of freedom and the significance level is p=0.05, which of the following statements best completes the chi-square test based on Table 5-6?

The critical value is 7.82, and the null hypothesis can be rejected because the calculated chi-square value is greater than the critical value.

A biologist was investigating the effects of herbivory on the amount of nicotine produced by the leaves of tobacco plants (Nicotiana rustica). Six groups of plants were grown from seed in the same greenhouse with identical environmental conditions. Three groups were then each exposed for a different interval of time to tobacco hornworms (Maduca sexta), which feed on the foliage of tobacco plants. The amount of nicotine present in the leaves was measured at the beginning and end of each time interval. As a control, the other three groups were not exposed to hornworms. The results of the experiment are summarized in Table 1.Which of the following correctly identifies the dependent variable and the independent variable for the experiment?

The dependent variable is the percent change in the amount of nicotine, and the independent variable is the time interval the plants were exposed to the hornworms.

Himalayan rabbits are a breed of rabbits with highly variable fur color. If genetically similar rabbits are raised in environments that have different temperature conditions, the rabbits can have different color patterns. Which of the following statements best explains how the fur color can be different in Himalayan rabbits raised under different temperature conditions?

The environment determines how the genotype is expressed.

In a certain small mammal, fur color is controlled by a pair of alleles, with B being dominant over b. The genotypes BB and Bb result in dark-colored fur, the genotype bb results in light-colored fur. A population of the species has the following allele frequencies: B=0.85 and b=0.15. If a fire caused the surface of the ground in the habitat of the species to become darker in color, which of the following claims about the impact on the allele frequencies in this population is most reasonable?

The frequency of the B allele will increase because light-colored individuals will be more visible to predators.

The researchers built an enclosure to prevent migration into and out of the O'Neill rock pocket mouse population for a period of two years. Which of the following best predicts the effect of the enclosure on the O'Neill population?

The frequency of the MC1RD allele will decline due to natural selection.

A scientist is studying the impact of mutagens on genetic variation in mice. In an experiment, the scientist creates two groups of twenty highly inbred mice. Because the mice are highly inbred, they are essentially identical to one another. One group is given food with an added substance that is known to be a mutagen. The second group is fed the same food without the mutagen. After several generations, both groups of mice are given a new type of food that is harder to digest than the previous food. After rearing five additional generations of the mice on this new food, the two groups are assessed for how efficiently this new food is digested. Which of the following is the most reasonable prediction about the results of the experiment?

The group of mice fed the mutagen will show a greater ability to digest the food, because the higher genetic variation within the group makes it more likely that some individuals will have a combination of genes better adapted to the new food.

A famous study from the nineteenth century involves the peppered moth, Biston betularia, commonly found in Great Britain and Ireland. At that time, the moths, normally white with black speckles, known as the peppered variety, became less common than the solid black variety. The population was predominantly black throughout the nineteenth century. By the end of the twentieth century, the peppered version of the moth was again more common than the black version. Which of the following best explains the phenotypic pattern in the moths over time?

The increased air pollution of the nineteenth century due to the use of coal led to a darkening of surfaces from soot. The darker backgrounds conferred a selective advantage to the black variety, as described by natural selection. A shift to less polluting fuel in the twentieth led to cleaner air and a lightening of the moth's normal habitat.

Lynch syndrome is an inherited condition associated with an increased risk for colon cancer, as well as certain other cancers. Mutations in one of several genes involved in DNA repair during DNA replication have been associated with Lynch syndrome. DNA sequencing was performed for an individual. The results indicated that the individual carries one of the dominant alleles that has been associated with Lynch syndrome. Which of the following best explains how the results should be interpreted?

The individual has an increased risk of developing colon cancer.

Which of the follow indicates the mean number per cross of F2 plants producing medium-red grain and correctly explains the distribution of the phenotypes based on Table 5-7?

The mean number of medium-red phenotypes per cross is 20.8. The distribution of phenotypes suggests that multiple genes are involved in grain color determination.

(melanin synthesis pt. 6) Which of the following best predicts the phenotype of an individual who is homozygous for this TYR mutation?

The mutation will change all subsequent amino acids in the TYRTYR protein, leading to nonfunctional TYRTYR protein. Individuals with this mutation will lack melanin in their hair, skin, and eyes and will not tan in response to UVUV radiation.

Climate change can affect oceanic ecosystems and their food webs. In the East China Sea (ECS), three major climactic events were considered: the Pacific Decadal Oscillation (PDO), the East Asia winter monsoon (EAWM), and the El Niño Southern Oscillation. Figure 1 shows the relationships among these climactic events, surface sea temperature (SST), amount of phytoplankton, and copepod abundance. Copepods are important primary consumers in this ecosystem, and many species of fish depend on copepods as a food source. Solid arrows on the diagram indicate a statistically significant effect. The thicker the arrow, the greater the effect. Dashed arrows indicate statistically insignificant relationships. Figure 1. Structural equation model deciphering interactions among climate, phytoplankton, and copepods in the southern East China Sea. Solid arrows indicate significant effects, with the thickness of the arrow reflecting the relative effect. Dashed arrows indicate inconsequential effects. What do the data in Figure 1 suggest about a null hypothesis that the East China Sea ecosystem is unaffected by climatic events?

The null hypothesis is rejected since there are significant effects of EAWM and PDO on surface sea temperature and copepod abundance.

Some plant species flower in response to increasing daily temperatures in the spring. Many of these species rely on pollinators that migrate based on changes in day length and the position of the Sun. The current global warming trend is placing new selective pressures on the species involved in these relationships. Which of the following best explains the impact of these new selective pressures on the organisms involved?

The plant species will flower earlier in the spring in response to rising temperatures before the arrival of the pollinators, so seeds will not be produced.

Bison in Yellowstone National Park have a food-limited carrying capacity that determines how their population grows. If the population grows too large, some bison will either starve or migrate to search for more food. The park is able to support a maximum population of 4,500 bison. Park conservation officials must watch the population and prevent the bison from overpopulating, since they would migrate to nearby farms, causing agricultural damage and creating hazards to drivers. The bison begin to migrate when the population reaches 4,000 because of competition for food. If the current population size of bison is 3,652 and the maximum growth rate of the population is 0.28, calculate the population size after one year and determine whether the park will need to take measures to control the population.

The population will be 3,845 after a year. The bison will not pose a problem until the following year, and no conservation action will need to take place:

The researchers determined that the East lava flow population is not in Hardy-Weinberg equilibrium. Which of the following best explains why the population is not in Hardy-Weinberg equilibrium?

The presence of MC1Rd alleles in the East lava flow population is an indication of gene flow from mice populations living on light granite rocks.

Meerkats live together in groups to help raise and protect their offspring. Meerkat pups are most vulnerable when they are away from their burrow foraging for food. Adult meerkats exhibit sentinel behavior, standing upright and making alarm calls to warn other members in the group that predators are nearby. In a study of meerkat behaviors, scientists observed meerkat foraging groups and recorded the presence or absence of pups along with the frequency of adult sentinel behavior. The scientists determined that sentinel behavior increased when pups were present in the foraging group. Which of the following correctly identifies the dependent and independent variables in the described study?

The presence of pups is the independent variable, and the frequency of sentinel behavior is the dependent variable.

Identify the independent variable for the experimental results shown in Figure 2.

The presence of wolves

A study recorded changes in the distribution of some commercial marine species off the East Coast of the United States over a period of several decades. The results of the study are summarized in Figure 1.Figure 1. Latitude that is the center of commercial harvesting of specified marine species. Some researchers link changes in the distribution of these species to warming of the oceans due to climate change. Which of the following pieces of data best supports this alternative hypothesis?

The prey of these species require colder waters to survive, and owing to warming in the oceans, they are moving farther north, to higher latitudes, where the water is colder

Figure 1 shows the population fluctuations of phytoplankton and zooplankton in the eastern Pacific Ocean over the course of six years. The major dip in phytoplankton was attributed to a lack of nutrients for phytoplankton. Of the following, which explains why the zooplankton also dipped during the same year and then seemed to cycle over the next three years?

The reduction in the phytoplankton population meant that the zooplankton's energy source was drastically reduced, leading to the decrease in the zooplankton population size. After the dip, the phytoplankton provided a steady energy source, and the zooplankton population fluctuated around its carrying capacity

Following the reintroduction of wolves to Yellowstone National Park, researchers measured the mean height of young aspen trees in upland and streamside areas. Which of the following is the most likely cause of the change in mean aspen height from 1998 to 2010?

The reintroduction of wolves led to a decrease in the population of elk, allowing aspen trees to grow taller

Sea otters living along the Pacific coast were hunted to near extinction in the nineteenth century. After being protected from hunting in the early 1900s, a remnant population of otters near Adak Island, Alaska, recovered rapidly. Otters did not return to the environmentally similar nearby island, Alaid Island. Sea otters eat sea urchins, which eat kelp, a brown alga. Researchers surveyed both islands in 1988, to measure sea urchin biomass and kelp density. The data are presented in Table 1.In 1991, researchers at Adak Island observed the first attack by a killer whale on a sea otter in historical times. The researchers hypothesized that the population sizes of the larger marine mammals that the killer whales normally prey on declined, so the killer whales were starting to prey on different prey, including the smaller sea otters. Which of the following best predicts the effects of an increase in killer whale predation on sea otters on the Adak Island ecosystem?

The sea urchin population will increase and the kelp population will decrease, leading to reduced total biomass and diversity in the Adak Island ecosystem

Bt corn varieties are genetically modified to produce a toxin that specifically kills corn borers, a type of insect that eats and damages corn crops. Insects that are not closely related to corn borers are not affected by the toxin. Figure 1 shows the increasing production of Bt corn varieties and the change in the use of broad-spectrum pesticides that were the primary means of killing corn borers before the invention of Bt corn. Figure 1. Relative use of pesticides on corn fields and percent of Bt corn in crops. How do the data in Figure 1 support the alternative hypothesis that increased use of Bt corn reduces the impact of corn farming on the natural environment?

The toxin in Bt corn kills only the corn pests, leaving other insects unharmed:

A scientist maintains a large population of the fruit fly Drosophila affinis in the laboratory. After 20 generations of allowing this population of about 1000 flies to mate randomly, 10 females and 10 males were isolated from the rest of the population. Both the larger population and the isolated population were maintained under identical conditions and allowed to mate randomly for another 20 generations. After the 20 generations, DNA sequencing was used to determine the genetic composition of each population. Which of the following predicts the expected outcome of the experiment?

The two populations will show significant genetic differences because the founder effect will result in significant losses in diversity in the smaller population.

Iridium is an element that is rare on Earth but commonly found in meteorites. A scientist believes that the first organic molecules may have come to Earth on meteorites 3.6 billion years ago. Which of these would be an appropriate null hypothesis to test related to whether meteorites hit the Earth 3.6 billion years ago?

There is no difference in iridium levels in sediments that were deposited on Earth 3.6 billion years old, compared to recent sediments.

Retroviruses such as HIV and hepatitis B virus use RNA as their genetic material rather than DNA. In addition, they contain molecules of reverse transcriptase, an enzyme that uses an RNA template to synthesize complementary DNA.Which of the following best predicts what will happen when a normal cell is exposed to a retrovirus? (C) The reverse transcriptase will produce DNA from the viral RNA, which can be incorporated into the host's genome and then transcribed and translated. Exposure to ultraviolet (UV) radiation is the leading cause of skin cancer in humans. Figure 1 shows a model of how UV exposure damages DNA. Figure 1. Model of damage to DNA caused by UV exposure. Which of the following statements best explains what is shown in Figure 1 ?

UV photons cause dimers to form, leading to misshapen DNA, which results in replication and transcription errors.

The marine iguana, Amblyrhynchus cristatus, is endemic to the Galápagos Islands and is especially vulnerable to El Niño events. These iguanas feed on red and green algae. During an El Niño climate event, surface waters and their currents in the central and eastern Pacific Ocean become significantly warmer than usual. Also during El Niño years, land masses experience increased rainfall. A researcher suggests that El Niño conditions cause a significant decrease in the size of the Galápagos marine iguana population. Which of the following would best support this alternative hypothesis?

Warm surface water contains fewer nutrients needed by red and green algae than cooler surface waters does

Which of the following questions would be most useful to researchers trying to determine the role of meiosis in the F2 phenotypic frequencies based on Figure 5-1 and Table 5-1?

What is the recombination frequency between the genes for petal shape and pollen shape?

(melanin synthesis pt. 3) Which of the following pieces of evidence would best support the researchers' claim above?

When researchers applied a drug that activates adenylyl cyclase to the mutant mice's ears, the level of melanin increased.

Small single-stranded RNA molecules called microRNAs (miRNAs) are capable of base pairing with specific binding sites in the 3′ untranslated region of many mRNA transcripts. Transcription of gene Q yields an mRNA transcript that contains such an miRNA binding site, which can associate with miRNA‑delta, a specific miRNA molecule. Which of the following best supports the claim that binding of miRNA‑delta to the miRNA binding site inhibits translation of gene Q mRNA?

When the miRNA binding site sequence is altered, translation of Q mRNA occurs in the presence of miRNA-delta.

The trp operon in E. coli is an example of a repressible operon that consists of genes coding for enzymes used to synthesize tryptophan. When tryptophan levels are high, the operon is turned off and these genes are not transcribed. However, it is also known that tryptophan does not bind directly to the operator DNA sequence. A regulatory gene called trpR has also been discovered although it is not part of the trp operon. The proposed model of how tryptophan acts as a corepressor is shown in Figure 1.Figure 1. Model of proposed regulation of the trp operon by corepressors trp repressor and tryptophan. Which of the following evidence best supports a claim that tryptophan functions as a corepressor?

When trpR is mutated, the trp operon is transcribed regardless of tryptophan levels.

Which of the following would most likely represent the types of individuals found in one of the species resulting from shape becoming a prezygotic isolating mechanism in the initial population represented in Figure 1 ?

White Circle Gray Circle Black Circle

Baker's yeast, Saccharomycetes cerevisiae, is the species of yeast that is commonly used in baking, brewing, and making wine. It is a single-celled organism; each cell is capable of undergoing asexual reproduction by mitosis and sexual reproduction by meiosis, forming spores that combine with other spores. To find out if energy and nutritional resource availability determines which form of reproduction is used, researchers grew twenty yeast colonies on an agar medium plate providing ideal nutrient environments. Each colony was composed of a population of yeast that originated from a single yeast cell that had reproduced asexually to form a population of millions of yeast clones. That plate was used to produce replicate plates of yeast colonies. Each replicate plate was a mirror image of the original cultures, so each colony could be subjected to each treatment group. The replicate plates contained different media as follows. Robust media: Contains all nutrients required by yeast in excess amounts. Complete media: Contains all nutrients at a level promoting exponential growth at rmax. Minimal media: Nutrients available at a low level, allowing growth, but stressing the yeast colonies. Deficient media: Nutrient content less than what is needed to sustain growth, extreme stress on yeast colonies. Eight replica plates were made, two plates of each media, and all plates were incubated at 30°C for 24 hours. Yeast from each colony were observed through a microscope and their means of reproduction determined. Table 1 summarizes these results. Which of the following best explains the data in Table 1 ?

Yeast respond to nutritional stress with sexual reproduction, producing new genetic combinations, or dormancy

Researchers were studying the effects of microbes on the growth of the yellow bedstraw plant, Galium verum. They grew yellow bedstraw plants under four treatments: in the presence of soil bacteria only, arbuscular mycorrhizal (AM) fungi only, both bacteria and AM fungi, or neither. After 6 months, they measured the biomass of the plants (Figure 1).Figure 1. The Effect of Soil Microbes on the Biomass of Galium verum. Which of the following best describes a statistically significant relationship indicated in Figure 1 ?

Yellow bedstraw plants grow significantly more in the presence of both soil bacteria and AM fungi (treatment 4) than in the presence of soil bacteria alone (treatment 2)

(melanin synthesis pt 1)In mammals, the dark color of skin, hair, and eyes is due to a pigment called melanin. Melanin is produced by specialized skin cells called melanocytes. The melanin is then transferred to other skin cells called keratinocytes. Melanocytes synthesize melanin in a multistep metabolic pathway (Figure 1). The amount of melanin produced is dependent on the amount of the enzymes TYR, TRP2, and TRP1 present inside melanocytes. Figure 1. Melanin synthesis pathway. The peptide hormone α-melanocyte stimulating hormone (α-MSH) activates a signal transduction pathway leading to the activation of MITF. MITF is a transcription factor that increases the expression of the TYR, TRP2, and TRP1 genes (Figure 2).Figure 2. Activation of melanin synthesis genes in melanocytes. Some mammals increase melanin production in response to ultraviolet (UV) radiation. The UV radiation causes damage to DNA in keratinocytes, which activates the p53 protein. p53 increases the expression of the POMC gene. The POMC protein is then cleaved to produce α-MSH. The keratinocytes secrete α-MSH, which signals nearby melanocytes. The increased melanin absorbs UV radiation, reducing further DNA damage. Figure 3. Production of α-MSH in keratinocytes in response to UV radiation. Which of the following claims about the TYR, TRP2, and TRP1 mammalian genes is most likely to be accurate?

the TYR, TRP2, and TRP1 genes may be located on different chromosomes but are activated by the same transcription factor.