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Notes About the 2002 AP Biology Free-Response Exam Questions
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by Carolyn Schofield Bronston
Robert E. Lee High School
Tyler, Texas
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This question covered many aspects of biotechnology. Several questions on this topic have been asked in the past, so it was surprising that 43 percent of the books were blanks or earned zeros (and many of those zeros ran 2 to 3 pages). Several readers commented that students seemed to know a great deal about DNA, but not about the current technology involving it: others wished that the term RFLP analysis had been defined in the question or linked to gel electrophoresis. The mean was approximately 2.2 with zeros/blanks, about 3.4 without them.
Most of the students seemed to have had plasmid experience, but many had no comments on RFLPs or on PCR (I suspect that they may have known what polymerase enzyme was but could not explain the process). Most could not reconcile the sameness of the genetic coding sequences and the uniqueness of the DNA fingerprints (differences in mainly non-coding areas).
Common Mistakes/Misconceptions:
- many students talked about human or animal "cloning" rather than bacterial cloning
- codons were often equated with amino acids or proteins
- splice and cut were used synonymously
Suggestions to Teachers:
Biotechnology is a large part of the current state of our science. Talk to students not just about Lab 6, but also how these techniques are used in the real world. Ask them to apply what they have learned.
Question 2
This question was the most talked about question at the Reading! A fictional creature called a bombat had his activity level monitored over two days, and students were asked to describe and explain the activity patterns as well as design an experiment to test the effect of light on it. There were almost no blank books for this question, and the mean was about 4.4. Readers found it difficult to score, and slow to read because of its open-ended nature (especially with a fictional mammal) and internal point accounting constraints (internal "max's"). While many teachers disliked the construction of the question with its lack of depth in biological knowledge, others believed it was a true test of a students' ability to analyze new information and show an ability to do experimental design.
Common Mistakes/Misconceptions:
- students often made hypotheses based on the bombat being ectothermic rather than endothermic (and therefore were not awarded those points)
- though the graph clearly used time of day for the independent variable, students often jumped to the conclusion that the graph was one of temperature, which caused many problems in their answers
- many had no idea what a control group was when constructing a good experiment, and sample size or repetitions were not mentioned (many had a single bombat in the control group and a single one in the "experimental" group)
Suggestions to Teachers:
Spend more time on experimental design! Give the students a novel problem, let them make hypotheses, and then design appropriate ways to test them.
As one reader remarked, "'Design an experiment' is a perennial AP question. A teacher would be remiss in not preparing his students for this task!"
Question 3
This question involved important biological processes and the relevant structure that allowed three different animal phyla to accomplish them. This was the lowest mean question of the test at about 1.2 -- a score of 10 was very rare. In part A, students had to relate their structure description to a function statement to earn a point; many addressed one or the other but not both, so received no credit. As in past AP Exams, if a student selected their two processes, they had to carry through with those two for the entire answer -- those who switched to different processes received no credit for those responses. Elaboration points were given only if the initial structure/function point had been earned. Though the answers to this question were often the longest on the test (3 to 4 pages of writing), there was very little detail given!
Common Mistakes/Misconceptions:
- many students did not know much about Annelids or Cnidarians
- gills were thought to remove the oxygen from the water molecule itself
Suggestions to Teachers:
Make students practice writing! Help them learn to stay on task and on target. Help them with the idea of diffusion and osmosis, not just across cell membranes, but in relationship to nutrient, waste, and gas transport in organs. Encourage kids to focus on what they DO know. If they don't know about cnidarians, fine: talk about chordates. They could have 5 or 6 points if they had described the structures and functions well for chordates.
Question 4
This question had the highest mean at about 5.1, with most students writing something on this essay. Concepts were taken from AP Lab 1 on Diffusion. Students were asked to interpret results when a bag with 5 percent salt solution was placed in a beaker of distilled water. Graphing, prediction, and application were included.
Common Mistakes/Misconceptions:
- though students could graph fairly well, proper orientation of the independent and dependent variables was often reversed
- predictions were made but often not explained
- many students believed only water can diffuse -- even when the question stated the tubing was permeable to Na+, Cl-, and water
- many students thought that seawater decreases crop production because "salt comes into a plant's stomata and clogs the guard cells"
Suggestions to Teachers:
Diffusion, osmosis, and water potential are critical concepts both in cells and organ systems. Take the time to make sure your students understand the concepts, not just memorize them.
Form B, Question 1
This question showed a graph of bacteria growth over time and how it was influenced when bacteriophage were added.
Students did well on this question -- most students earned points for a description of what they saw illustrated in the graph and for viral attachment and lysis. They knew about HIV and knew it was an RNA virus that uses reverse transcriptase to make a DNA template. Many students spent much time contrasting the lytic cycle with the lysogenic cycle, which earned them no points.
Common Mistakes/Misconceptions:
- many students talked of the bacteria's recovery as a function of their immune system, and their ability to make antibodies again the virus [Note: the word immune was allowed, but only in the context of being resistant]
- Lamarck seemed alive and well as bacteria "acquired" a resistance to the virus and therefore survived
Suggestions to Teachers:
Use every opportunity to point out the underlying evolutionary ideas of how life adapts to new situations. Explain why immune response and inborn-resistance are very different situations. Keep doing a great job on AIDS and HIV.
Form B, Question 2
This question asked about the interactions of the respiratory, circulatory, and nervous systems during exercise. Students seemed comfortable with designing an experiment, and could construct a graph of their work. But rarely was any detail for a system's function given.
Common Mistakes/Misconceptions:
- "The heart needs to beat faster because the muscles need more blood." This type of answer does not earn any points! Students must give some detail as to what would make the heart beat faster or what the muscles receive when they get more blood.
- "The brain tells the heart to speed up." Again, no points were given unless the student explained what specific nerve or hormone is released that "tells" the heart what to do or describes specific sensors that alert the brain to increase heart rate.
Suggestions to Teachers:
Help students to be more concrete when answering AP questions. And though systems are often taught independently, showing their integration is important to overall understanding.
Form B, Question 3
Students were asked about structure and function of various biomolecules in living organisms. Students did well on nucleic acid composition, but often described protein synthesis in the "role" response, never addressing the actual functions of MRNA or tRNA. Chitin and tubulin were rarely chosen, indicating students did not know much about them. Students usually did not associate structure with function, though they could earn points independently on those sections.
Common Mistakes/Misconceptions:
- nucleic acid was often equated with nucleotide
- myosin was often mistaken for myelin
Suggestions to Teachers:
Help students to describe things factually and describe roles and functions specifically. Fluff and generalities do not belong in AP-level answers.
Form B, Question 4
This question addressed the three germ layers of embryos, development of a coelomate body plan, and comparisons of digestive systems in coelomate vs. acoelomate organisms. Approximately 50 percent of the scores were 0, 1, or 2. It was rare for a student to get all three layers correctly matched with potential fates (brain or kidneys or digestive lining). Though some students showed a complete understanding of body plans, many had no idea about the terms or could not describe why a pseudocoelomate was different from the others -- "a pseudocoelom is a false coelom" was often the extent of the explanation. Students did not do a good job of comparing.
Common Mistakes/Misconceptions:
- nerve cord was often confused with notochord
- students thought a particular organ was always from one germ layer (while many are lined with endoderm but also contain muscles, etc., from other layers)
Suggestions to Teachers:
Practice questions that ask students to compare and contrast. Be sure the students know what a coelom is (and why it is important) and what technicality makes some organisms "pseudos."
Carolyn has taught at Spring Branch's Memorial High School and Tyler's Robert E. Lee High School in Texas. Traveling as a consultant for the College Board since 1979, she also reads the AP Exam each June, authored the new Teacher's Guide -- AP Biology, created the AP Teacher's Corner, and is a member of the Biology Development Committee. Carolyn is also the biology content adviser for AP Central.
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