Learn Extracted exam questions AP Biology 2016 Free Response
2016 Free Response
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Leucine aminopeptidases (LAPs) are found in all living organisms and have been associated with the response of the marine mussel, Mytilus edulis, to changes in salinity. LAPs are enzymes that remove N-terminal amino acids from proteins and release the free amino acids into the cytosol. To investigate the evolution of LAPs in wild populations of M. edulis, researchers sampled adult mussels from several different locations along a part of the northeast coast of the United States, as shown in Figure 1. The researchers then determined the percent of individuals possessing a particular lap allele, $lap^{94}$, in mussels from each sample site (table 1).
[Blank graphing grid provided below part (a): a rectangular grid of small squares, no axis labels or scale printed, for the student to construct their own bar graph.]
On the axes provided, construct an appropriately labeled bar graph to illustrate the observed frequencies of the $lap^{94}$ allele in the study populations.
Based on the data, describe the most likely effect of salinity on the frequency of the $lap^{94}$ allele in the marine mussel populations in Long Island Sound. Predict the likely $lap^{94}$ allele frequency at a sampling site between site 1 and site 2 in Long Island Sound.
Describe the most likely effect of $LAP^{94}$ activity on the osmolarity of the cytosol. Describe the function of $LAP^{94}$ in maintaining water balance in the mussels living in the Atlantic Ocean.
Marine mussel larvae are evenly dispersed throughout the study area by water movement. As larvae mature, they attach to the rocks in the water. Explain the differences in $lap^{94}$ allele frequency among adult mussel populations at the sample sites despite the dispersal of larvae throughout the entire study area. Predict the likely effect on distribution of mussels in Long Island Sound if the $lap^{94}$ allele was found in all of the mussels in the population. Justify your prediction.
[Figure 1. Bacterial population growth in the presence of two nutrients (nutrient I and nutrient II). Graph with left y-axis "Bacterial Population Density (cells/mL)" on a log scale from $10^1$ to $10^9$, right y-axis "Relative Concentration of Nutrient" (unlabeled scale), and x-axis "Time (hours)" from 0 to 9 (gridlines at 3, 6, 9). A solid curve labeled "Bacterial Population Density" starts near $10^1$ at $t=0$, rises steeply to about $10^4$ by $t \approx 3$–4, plateaus around $10^{4.5}$–$10^5$ from about $t=4$ to $t=6$, then rises again to about $10^8$ by $t=9$. A dotted curve labeled "Nutrient I" starts high (around $10^{3.7}$ on the relative-concentration scale) at $t=0$ and declines steadily to near zero by about $t=5$. A dashed curve labeled "Nutrient II" starts at a high, roughly constant relative concentration (around $10^4$ on the same scale) from $t=0$ to about $t=6$–7, then declines steeply to near zero by $t=9$.]
Bacteria can be cultured in media with a carefully controlled nutrient composition. The graph above shows the growth of a bacterial population in a medium with limiting amounts of two nutrients, I and II.
Estimate the maximum population density in $\dfrac{\text{cells}}{\text{mL}}$ for the culture. Using the data, describe what prevents further growth of the bacterial population in the culture.
Using the data, calculate the growth rate in $\dfrac{\text{cells}}{\text{mL}\times\text{hour}}$ of the bacterial population between hours 2 and 4.
Identify the preferred nutrient source of the bacteria in the culture over the course of the experiment. Use the graph to justify your response. Propose ONE advantage of the nutrient preference for an individual bacterium.
Describe how nutrient I most likely regulates the genes for metabolism of nutrient I and the genes for metabolism of nutrient II. Provide TWO reasons that the population does not grow between hours 5 and 6.
[Figure 1. Percent dry weight of different plant structures during the growing season for an annual plant. Line/area graph with y-axis "Percent Dry Weight" from 0 to 100 and x-axis "Time (weeks)" labeled May, June, July, August, with germination marked by an arrow at the start of May. Seven stacked bands (bottom to top at the start, May): Roots (largest band, filling most of the graph, shrinking from 100% at germination down to about 20–30% by June and staying around 20–30% through August), Stems (a thin band above roots), Leaves (a hatched band that grows from a small sliver at germination to become the dominant band by June–July, remaining large (roughly 40–60%) through July–August), Vegetative buds (a thin black band appearing briefly around late May–June, peaking near 45–50% total height around early June then narrowing and disappearing by July), Flowers (a dark gray band appearing from July onward, growing to roughly 15–25% of the total by August), Receptacles (a thin white band appearing in August above flowers), and Seeds (a stippled/dotted band appearing at the very top from late July through August, reaching the 100% line). The bands together always sum to 100% at every time point.]
The graph above illustrates the percent dry weight of different parts of a particular annual plant (plants that live less than one year) from early May to late August. The percent dry weight can be used to estimate the amount of energy a plant uses to produce its leaves, vegetative buds, stems, roots, and reproductive parts (seeds, receptacles, and flowers).
Identify the direct source of the energy used for plant growth during the first week of May, and identify the part of the plant that grew the most during the same period.
Based on the data on the graph, estimate the percent of the total energy that the plant has allocated to the growth of leaves on the first day of July.
Compared with perennials (plants that live more than two years), annual plants often allocate a much greater percentage of their total energy to growth of their reproductive parts in any given year. Propose ONE evolutionary advantage of the energy allocation strategy in annual plants compared with that in perennial plants.
[Figure showing gene expression in a eukaryotic cell (nucleus enclosed within the cell membrane). A DNA strand is shown with alternating black and white segments labeled "introns" (white segments) and "exons" (black segments) at the top, inside the nucleus. An arrow points down from the DNA to a shorter bar labeled "Primary transcripts," which still has alternating black/white (intron/exon) segments. A second arrow points from the primary transcript down through the nuclear envelope to a solid black bar labeled "Mature mRNA" (now containing only the exon segments, introns removed) in the cytoplasm. A third arrow points from the mature mRNA down to a shorter gray bar labeled "Protein."]
The figure represents the process of expression of gene $X$ in a eukaryotic cell.
The primary transcript in the figure is 15 kilobases (kb) long, but the mature mRNA is 7 kb in length. Describe the modification that most likely resulted in the 8 kb difference in length of the mature mRNA molecule. Identify in your response the location in the cell where the change occurs.
Predict the length of the mature gene $X$ mRNA if the full-length gene is introduced and expressed in prokaryotic cells. Justify your prediction.
[Graph showing plant mass over time for two plant species grown attached to each other, then separated. Y-axis "Plant Mass" (unlabeled scale), x-axis "Time" (unlabeled scale). A vertical dashed line marks "Plants Separated" partway along the x-axis. Before separation, a solid line labeled "Species 1 Plant" rises from the origin more steeply, reaching a higher plant mass value at the separation line; a dashed line labeled "Species 2 Plant" rises less steeply from the origin, reaching a lower plant mass value at the separation line. After the separation line, both lines are drawn only up to that point (undefined beyond), since the task is to predict their continuation.]
The graph above shows the mass of plants from two different species over time. The plants grew while attached to each other. The plants were separated at the time indicated by the vertical line in the graph.
Using template 1, graph the predicted shape of the plant-mass lines after separation of the two plants if the plants were in an obligate mutualistic relationship. On template 2, graph the predicted shape of the plant-mass lines if the species 2 plant was a parasite of the species 1 plant. Justify each of your predictions.
[Template 1: Obligate Mutualism - blank axes with "Plant Mass" (y-axis, unlabeled scale) vs. "Time" (x-axis, unlabeled scale), a vertical dashed line marking the separation point, and the same pre-separation solid (Species 1) and dashed (Species 2) lines drawn up to the separation point, left blank afterward for the student to complete.]
[Template 2: Parasitism - identical blank axes and pre-separation lines as Template 1, left blank after the separation point for the student to complete.]
[Figure 1. Detectability of eDNA fragments of varying lengths. Bar graph with y-axis "Days that eDNA is Detectable after Shedding" from 0 to 5, x-axis "Amplified eDNA Fragment Length" with two categories: "Short" (bar height approximately 4.2 days) and "Long" (bar height approximately 2.7 days).]
[Figure 2. Map of the waterways that connect a nearby river system to Lake Michigan. A map showing a river system on the left connecting to Lake Michigan on the right, with numerous open circles (labeled "No silver carp eDNA detected") scattered mostly within Lake Michigan and a few in the connecting rivers, and five filled/solid circles (labeled "Silver carp eDNA detected") clustered along the connecting river/waterway near where it meets the lake, with one filled circle located just inside the lake boundary near the river mouth. Legend: filled circle = Silver carp eDNA detected; open circle = No silver carp eDNA detected; solid line = Rivers connected to Lake Michigan.]
Living and dead organisms continuously shed DNA fragments, known as eDNA, into the environment. To detect eDNA fragments in the environment, the polymerase chain reaction (PCR) can be used to amplify specific eDNA fragments. eDNA fragments of different lengths persist in the environment for varying amounts of time before becoming undetectable (Figure 1).
To investigate whether silver carp, an invasive fish, have moved from a nearby river system into Lake Michigan, researchers tested water samples for the presence of eDNA specific to silver carp (Figure 2).
Justify the use of eDNA sampling as an appropriate technique for detecting the presence of silver carp in an environment where many different species of fish are found. Propose ONE advantage of identifying long eDNA fragments as opposed to short fragments for detecting silver carp.
The researchers tested a large number of water samples from Lake Michigan and found eDNA specific to silver carp in a single sample in the lake, as indicated in Figure 2. The researchers concluded that the single positive sample was a false positive and that no silver carp had entered Lake Michigan. Provide reasoning other than human error to support the researchers' claim.
[Figure showing a diploid cell undergoing meiosis (2n = 4). Inside a large circle representing the cell, there are two pairs of duplicated (sister-chromatid) chromosomes: two larger chromosomes (labeled as Chromosome 1, one darker/black and one lighter/gray, each drawn as an X-shaped pair of sister chromatids with a centromere dot) and two smaller X-shaped chromosomes (labeled as Chromosome 2, one darker and one lighter). To the right of the cell, a key shows a single darker chromosome labeled "Chromosome 1" and a single darker X-shaped chromosome labeled "Chromosome 2," identifying the chromosome-pair color/shape code used in the cell diagram.]
In a certain species of plant, the diploid number of chromosomes is 4 (2n = 4). Flower color is controlled by a single gene in which the green allele ($G$) is dominant to the purple allele ($g$). Plant height is controlled by a different gene in which the dwarf allele ($D$) is dominant to the tall allele ($d$). Individuals of the parental (P) generation with the genotypes $GGDD$ and $ggdd$ were crossed to produce $F_1$ progeny.
[Four empty circles are provided below part (c), each representing a cell, for the student to draw the chromosomes and alleles present in the four possible normal products of meiosis produced by the $F_1$ progeny.]
Construct a diagram below to depict the four possible normal products of meiosis that would be produced by the $F_1$ progeny. Show the chromosomes and the allele(s) they carry. Assume the genes are located on different chromosomes and the gene for flower color is on chromosome 1.
Predict the possible phenotypes and their ratios in the offspring of a testcross between an $F_1$ individual and a $ggdd$ individual.
If the two genes were genetically linked, describe how the proportions of phenotypes of the resulting offspring would most likely differ from those of the testcross between an $F_1$ individual and a $ggdd$ individual.
[Figure 1. Effect of exercise on blood prolactin levels in adult males. The data represent the means $\pm 2SE_{\bar{X}}$. Bar graph with y-axis "Blood Plasma Prolactin (nmol/L)" from 0 to 9, x-axis with two groups: "With Exercise" and "Without Exercise." Each group has two bars: an open/white bar labeled "T = 0 hour" and a gray/filled bar labeled "T = 1 hour," each with error bars. With Exercise: T = 0 hour bar is about 6.1 nmol/L (error bar spanning roughly 4.1 to 8.2); T = 1 hour bar is about 7.3 nmol/L (error bar spanning roughly 6.3 to 8.3). Without Exercise: T = 0 hour bar is about 6.4 nmol/L (error bar spanning roughly 5.4 to 7.3); T = 1 hour bar is about 6.1 nmol/L (error bar spanning roughly 4.8 to 7.3).]
Researchers conducted a study to investigate the effect of exercise on the release of prolactin into the blood. The researchers measured the concentration of prolactin in the blood of eight adult males before (T = 0 hour) and after one hour (T = 1 hour) of vigorous exercise. As a control, the researchers measured the concentration of blood prolactin in the same group of individuals at the same times of day one week later, but without having them exercise. The results are shown in Figure 1.
Justify the use of the without-exercise treatment as the control in the study design.
Using evidence from the specific treatments, determine whether prolactin release changes after exercise. Justify your answer.