Study Guide
Field 010: Biological Sciences
Sample Constructed-Response Assignment
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The following materials contain:
- Test directions for the constructed-response assignment
- A sample constructed-response assignment
- An example of a strong and weak response to the assignment, and a rationale for each
- The performance characteristics and scoring scale
Test Directions for the Constructed-Response Assignment
This section of the test consists of one constructed-response assignment. You are to prepare a written response of approximately 300–600 words on the assigned topic. You should use your time to plan, write, review, and edit your response to the assignment.
Read the assignment carefully before you begin to write. Think about how you will organize your response.
As a whole, your response must demonstrate an understanding of the knowledge and skills of the field. In your response to the assignment, you are expected to demonstrate the depth of your understanding of the content area through your ability to apply your knowledge and skills rather than merely to recite factual information.
Your response to the assignment will be evaluated on the basis of the following criteria:
start bold PURPOSE: end bold the extent to which the response achieves the purpose of the assignment
start bold SUBJECT MATTER KNOWLEDGE: end bold accuracy and appropriateness in the application of subject matter knowledge
start bold SUPPORT: end bold quality and relevance of supporting details
start bold RATIONALE: end bold soundness of argument and degree of understanding of the subject matterThe constructed-response assignment is intended to assess subject matter knowledge and skills, not writing ability. However, your response must be communicated clearly enough to permit valid judgment of the scoring criteria. Your response should be written for an audience of educators in this field. The final version of your response should conform to the conventions of edited American English. Your written response must be your original work, written in your own words, and not copied or paraphrased from some other work.
Be sure to write about the assigned topic. You may not use any reference materials during the test. Remember to review what you have written and make any changes you think will improve your response.
Sample Constructed-Response Assignment
subarea roman numeral 1
Foundations of Scientific Inquiry
start bold Read the information below; then complete the exercise that follows. end bold
A researcher is interested in testing the effects of caffeine and ethanol on the heart rate of a species of start italics Daphnia end italics . start italics Daphnia end italics is a genus of small crustacean that is common in ponds and streams. The researcher obtains several start italics Daphnia end italics of the same species from a biological supply company. Individuals of the species average 1.5 mm long. The researcher keeps the start italics Daphnia end italics in small jars on a lab table until they are to be used. The researcher's proposed procedures are described below.
- Use a pipette to transfer one start italics Daphnia end italics and a drop of water from the storage jar to a clean microscope slide. Place a cover slip over the drop.
- Place the slide on a microscope, locate the start italics Daphnia end italics under low power, and then transfer to high power. Find the start italics Daphnia's end italics beating heart and count the number of beats per minute.
- Use a Pasteur pipette to apply a drop of solution containing caffeine to the edge of the cover slip. Use a piece of filter paper on the opposite side of the cover slip to draw water out from under the cover slip, which will help draw the caffeine solution under the cover slip.
- Wait one minute, then re-locate the start italics Daphnia's end italics heart in the field of view and measure the heart rate again.
- Use the same procedure described in step 3 to apply a drop of solution containing ethanol to the slide.
- Again, wait one minute, re-locate the start italics Daphnia's end italics heart in the field of view, and measure the heart rate.
- Repeat steps 1–6 with at least 10 more start italics Daphnia end italics .
Using your knowledge of the principles and procedures for conducting scientific investigations (e.g., sampling, data analysis, dependent and independent variables), prepare a response in which you:
- identify two weaknesses in the proposed procedures and explain why, from a scientific perspective, they are weaknesses;
- describe two modifications that should be made to the procedures that would address these weaknesses and explain how these changes would enhance the scientific validity of the investigation; and
- discuss an effective way to analyze or report the data that will be collected during this investigation.
Sample Strong Response to the Constructed-Response Assignment
start bold Please note: The sample response provided below is for review purposes only and should not be used in a response on an operational exam. Use of the exact words and phrases presented in this sample response will result in a score of "U" (Unscorable) due to lack of original work. end bold
There are several weaknesses in the described procedures. One significant weakness is the lack of an adequate control group. In this situation, there may be factors that would affect the start italics Daphnia's end italics heart rate other than exposure to the caffeine or ethanol. For instance, putting the start italics Daphnia end italics on a regular microscope slide rather than a depression slide could interfere with its heart's normal functioning. Also, heat generated by the light on the microscope could affect the heart rate, since metabolic rate tends to increase as temperature increases. Unless these or other factors can be ruled out, then the results of the entire investigation are likely to be challenged.
A second weakness is exposing a start italics Daphnia end italics to both drugs with no recovery time in between and always in the same order. There could be interactive effects between the caffeine and ethanol, which would skew the results. Any data collected on the effects of the ethanol specifically would be questionable because there might still be some caffeine present in the fluid surrounding the start italics Daphnia end italics , in the start italics Daphnia's end italics body, or both. Even assuming that all the caffeine was gone, it could still take a while for the start italics Daphnia end italics to recover physiologically from the effects of the caffeine.
To address the first weakness, the lack of an adequate control, some start italics Daphnia end italics should be observed under the same conditions (for example, same type of slide, same amount of time on the microscope) as the experimental subjects, except without addition of the chemicals. This allows the researcher to determine whether changes in the heart rate are due to factors other than the presence of the caffeine or ethanol. If the use of a proper control group rules out that other factors are influencing the results, then the researcher and other scientists can have greater confidence in the conclusions drawn from the investigation.
To address the second weakness, possible interactions between the caffeine and ethanol, the chemicals should be tested one at a time, with ample time between trials if the same start italics Daphnia end italics are to be reused. Having separate trials for each chemical would ensure that only one chemical is present at a time. Also, giving a start italics Daphnia end italics more time between trials with the different chemicals will allow it to recover physiologically from the effects of the first chemical before the second one is applied. Making this change to the procedures will reduce questions or concerns that other researchers might raise about unintended interactions between caffeine and ethanol. It will also strengthen the validity of any conclusions that are drawn based on the results of the investigation.
An effective way to report the data generated by this investigation would be to calculate the mean heart rates for three groups: the control group, the group exposed to caffeine, and the group exposed to ethanol. Mean values are a convenient way to summarize many data points into a single number for analysis and reporting. An appropriate statistical analysis could also be run on the data to determine if differences in the heart rates between the experimental groups and the control group are, in fact, statistically significant. For reporting purposes, the summarized data could be presented effectively in a table or in a histogram showing the mean heart rates for the three groups.
Rationale for the Sample Strong Response
Please note that the response is evaluated based upon the four performance characteristics of Purpose, Subject Matter Knowledge, Support, and Rationale. Please also note how the score point descriptions are based upon how the examinee attends to the performance characteristics. You should be very familiar with the CEOE performance characteristics and score scale and refer to them when reviewing this rationale.
The response fulfills the purpose of the assignment (refer to the instructions for the assignment) by accurately addressing all three bullets of the prompt. The first two paragraphs address the first bullet of the prompt by clearly identifying two significant weaknesses (i.e., the lack of adequate control group and the lack of recovery time between administration of test substances) and explaining why these are weaknesses, supporting these choices with accurate subject matter knowledge. High-quality and relevant examples of this support include the discussion of heat generated by the microscope light affecting heart rate, which must be ruled out for results to be valid. In addition, the discussion regarding the effects of relaxation time on heart rate, which indicates the possible physiological effects of caffeine retention, is another example of sound supporting evidence. Two modifications (i.e., heart rate measurements under identical conditions as before but without the addition of chemicals and increasing relaxation time between the two different chemicals) are described; appropriate evidence of the scientific validity of these modifications is shown by indicating the necessity for controlling all variables except the two independent variables being individually tested. The response provides a sound discussion of an effective way to analyze the data collected during this investigation (i.e., mean heart rates of the experimental and control groups are calculated for analysis, including statistical analysis to determine if mean heart rate differences are significant). Lastly, the writer explains that a "table" or "histogram" could be used to report this data. In summary, the purpose of the assignment is fully achieved, supporting evidence is sound, and the response demonstrates an ably reasoned comprehensive understanding of the topic.
Sample Weak Response to the Constructed-Response Assignment
This is a very useful experiment, but it should be modified in a few places.
The researcher has ignored any discussion of safety concerns, which may endanger either the workers or the start italics Daphnia end italics themselves. This can easily be fixed by having proper clothing; including: a mask, lab coat, and goggles. These safety items should be worn at all times. In addition, long hair and hanging clothing could cause the slide or cover slip to be contaminated, so these should all be pulled back. Sterile gloves must be worn to avoid exposure to skin oils and contaminates. Ethanol creates toxic vapors that may contaminate the area of the slide or cover slips. Ethanol must be used only in the fume hood.
A second major weakness is the lack of a control group because it is a requirement for every scientific experiment. Without a control group, no valid comparisons can be drawn. This is clearly needed to enhance the scientific validity of the start italics Daphnia end italics heart rate dependencies. A separate slide and cover slip without additive must be tested for each trial as well.
The start italics Daphnia end italics have very high heart rates so great care must be taken to record all the data from all of the different tests and write the values in a data table in your lab notebook. It must be clear that both sets of data be in individual columns and rows. A mean rate must be determined. Then a two color bar graph could be drawn with each additive given a different color.
Rationale for the Sample Weak Response
Please note that the response is evaluated based upon the four performance characteristics of Purpose, Subject Matter Knowledge, Support, and Rationale. Please also note how the score point descriptions are based upon how the examinee attends to the performance characteristics. You should be very familiar with the CEOE performance characteristics and score scale and refer to them when reviewing this rationale.
The purpose of this assignment (refer to the instructions for the assignment) is only partially achieved. Two weaknesses are identified (i.e., ignoring any discussion of safety concerns and the lack of a control group); however, very limited explanations with few relevant examples are given to support either of the identified weaknesses. The writer states, "Without a control group, no valid comparisons can be drawn"; however, the writer fails to provide any evidence to support this claim. A limited application of subject matter knowledge is shown in both the discussion of the weaknesses and their modifications. Lastly, there is no mention of the control group data in the data discussion. The weak subject matter knowledge demonstrated in this response combined with a lack of supporting evidence reflects a poorly reasoned understanding of the topic.
Performance Characteristics
The following characteristics guide the scoring of responses to the constructed-response assignment.
Scoring Scale
Scores will be assigned to each response to the constructed-response assignment according to the following scoring scale.