Learn Extracted exam questions AP Biology 2014 Free Response
2014 Free Response
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Trichomes are hairlike outgrowths of the epidermis of plants that are thought to provide protection against being eaten by herbivores (herbivory). In a certain plant species, stem trichome density is genetically determined.
To investigate variation in stem trichome density within the plant species, a student counted the number of trichomes on the stems of six plants in each of three different populations. The student used the data to calculate the mean trichome density (numbers of hairs per square centimeter) for each population. The results are provided in the table below.
TRICHOME DENSITY IN THREE PLANT POPULATIONS (number of trichomes/$\text{cm}^2$)
| Population | Plant 1 | Plant 2 | Plant 3 | Plant 4 | Plant 5 | Plant 6 | Mean | Standard Error of the Mean (SEM) |
|---|---|---|---|---|---|---|---|---|
| I | 8 | 11 | 9 | 10 | 8 | 6 | 9 | 1 |
| II | 12 | 6 | 15 | 9 | 13 | 8 | 11 | 1 |
| III | 13 | 17 | 9 | 14 | 12 | 16 | 14 | 1 |
[Below the parts is a blank graph grid (approximately 18 columns × 22 rows) with no axis labels provided, for the student to create their own labeled graph.]
On the axes provided, create an appropriately labeled graph to illustrate the sample means of the three populations to within 95% confidence (i.e., sample mean $\pm$ 2 SEM).
Based on the sample means and standard errors of the means, identify the two populations that are most likely to have statistically significant differences in the mean stem trichome densities. Justify your response.
Describe the independent and dependent variables and a control treatment for an experiment to test the hypothesis that higher trichome density in plants is selected for in the presence of herbivores. Identify an appropriate duration of the experiment to ensure that natural selection is measured, and predict the experimental results that would support the hypothesis.
Mammalian milk contains antibodies that are produced by the mother's immune system and passed to offspring during feeding. Mammalian milk also contains a sugar (lactose) and may contain proteins (protein A, protein B, and casein), as indicated in the table.
MILK COMPONENTS IN DIFFERENT MAMMALS
| Character | Cat | Cow | Horse | Human | Pig |
|---|---|---|---|---|---|
| Lactose | + | + | + | + | + |
| Protein A | + | + | + | + | + |
| Protein B | $-$ | + | + | $-$ | + |
| Casein | $-$ | + | + | $-$ | + |
- indicates the presence of the character, and $-$ indicates the absence of the character
[Below the parts is a blank cladogram template: a horizontal trunk line branching rightward into an upper branch (which itself splits into two terminal branches) and a lower branch (which splits into two terminal branches, one of which further splits into two more terminal branches), for the student to label and annotate.]
Using the data in the table, construct a cladogram on the template provided to indicate the most likely evolutionary relationships among the different mammals. Indicate on the cladogram where each of the characters most likely arose in the evolutionary process, and justify the placement of the characters on the cladogram.
Describe FOUR steps in the activation of the mother's specific immune response following exposure to a bacterial pathogen. Predict how the mother's immune response would differ upon a second exposure to the same bacterial pathogen a year later.
Predict the most likely consequence for a nursing infant who is exposed to an intestinal bacterial pathogen (e.g., Salmonella) to which the mother was exposed three months earlier. Justify your prediction.
As part of a new suburban development, a sports complex consisting of athletic fields and buildings is constructed in a formerly wooded area.
Predict ONE ecological consequence on the local plant community that is likely to result during the site preparation and construction of the sports complex. Justify your prediction.
To maintain the playing fields, large quantities of water and chemicals are applied regularly to the grass-covered areas. Predict ONE effect on the local animal community that might result from regular use and maintenance of the playing fields. Justify your prediction.
Adult male guppies (Poecilia reticulata) exhibit genetically determined spots, while juvenile and adult female guppies lack spots. In a study of selection, male and female guppies from genetically diverse populations were collected from different mountain streams and placed together in an isolated environment containing no predators.
The study population was maintained for several generations in the isolated area before being separated into two groups. One group was moved to an artificial pond containing a fish predator, while a second group was moved to an artificial pond containing no predators. The two groups went through several generations in their new environments. At different times during the experiment, the mean number of spots per adult male guppy was determined as shown in the figure below. Vertical bars in the figure represent two standard errors of the mean (SEM).
[Line graph titled "Mean Number of Spots per Adult Male Guppy" vs. "Time (months)"; y-axis from ~8 (with a break symbol) to 14 in increments of 1; x-axis from 0 to 20, tick marks at 0, 10, 20. A vertical dotted arrow labeled "Population Separated into Groups" points to approximately month 6. Two data series with error bars (±2 SEM): "Predator present" (dashed line) starting at (0,10) with a very large error bar (from about 8.2 to 11.9), rising to a peak at (6,11.8), then declining to (10,10.5) and (20,9.3). "Predator absent" (solid line) starting at (0,10) with the same large error bar, rising to (6,11.8), continuing to rise to (10,12.5) and (20,13.2). Both lines coincide from month 0 to month 6, then diverge after separation into groups.]
Describe the change in genetic variation in the population between 0 and 6 months and provide reasoning for your description based on the means and SEM.
Propose ONE type of mating behavior that could have resulted in the observed change in the number of spots per adult male guppy between 6 and 20 months in the absence of the predator.
Propose an evolutionary mechanism that explains the change in average number of spots between 6 and 20 months in the presence of the predator.
Genetically modified crops have been developed that produce a protein that makes the plants resistant to insect pests. Other genetic modifications make the crops more resistant to chemicals that kill plants (herbicides).
Describe TWO potential biological risks of large-scale cultivation and use of such genetically modified plants.
For each of the risks you described in part (a), propose a practical approach for reducing the risk.
[Diagram titled "Cross Section of Spinal Cord and Skeletal Muscle Fiber": shows a hand/arm reaching toward a pin labeled "Stimulus" (arrow pointing to fingertip), with a second hand/arm shown pulling back labeled "Response" (arrow pointing to a retracting finger, with a pin shown moving away). A line labeled "Signal Direction" traces from the stimulus site down along a nerve fiber to a cross-section of the spinal cord (shown as a butterfly-shaped gray/white matter structure with several dark synapse points), then back up along a second nerve fiber (also labeled "Signal Direction" with an arrow) to a "Skeletal Muscle Fiber" (drawn as a striated cylindrical structure) connected back to the arm.]
Information processing involves complex neural pathways that require a certain amount of time between recognition of a stimulus and the resulting response. For some types of stimuli, a reflex arc replaces the typical stimulus-response pathway. A representation of a reflex arc is shown in the figure above.
Based on the figure, describe TWO ways that the reflex arc differs from typical stimulus-response transmission pathways. Provide reasoning to support the claim that reflex arcs help organisms avoid serious injury.
EFFECT OF ENVIRONMENTAL TEMPERATURE ON RATE OF OXYGEN CONSUMPTION
[Line graph: y-axis "Rate of Oxygen Consumption ($\text{mLO}_2$/g/h)" from 0 to 200 in increments of 40 (dashed gridlines at 40, 80, 120, 160, 200); x-axis "Environmental Temperature (°C)" from 0 to 30, tick marks at 0, 10, 20, 30. Data points: (10, ~28), (20, 80), (30, ~172), connected by a solid line that curves upward with increasing slope (line segment from 10 to 20 is nearly flat/slightly rising, then steeper from 20 to 30).]
Based on the graph, describe a specific method of thermoregulation used by the species of animal. Provide support for your answer using the data.
On the labeled axis provided below, draw a line to indicate the most likely relationship between body temperature and environmental temperature in the species.
[Blank grid provided: y-axis "Body Temperature (°C)" from 0 to 40 in increments of 10 with gridlines; x-axis "Environmental Temperature (°C)" from 0 to 40 in increments of 10 with gridlines, for the student to draw their predicted line.]
A research team has genetically engineered a strain of fruit flies to eliminate errors during DNA replication. The team claims that this will eliminate genetic variation in the engineered flies. A second research team claims that eliminating errors during DNA replication will not entirely eliminate genetic variation in the engineered flies.
Provide ONE piece of evidence that would indicate new genetic variation has occurred in the engineered flies.
Describe ONE mechanism that could lead to genetic variation in the engineered strain of flies.
Describe how genetic variation in a population contributes to the process of evolution in the population.