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Contributed by: Council of Chief State School Officers (CCSSO)
ME 402: Mold/Yeast
Item #1
Item Description: Students investigate the growth
of yeast. The procedures for this experiment, included in the test
booklet, are summarized in the following figure:
Students were then asked the following question: Describe
the difference between the contents of Test Tubes 1A and 2A, and
explain the purpose in having this particular difference.
Content Definition: Students are given the following
information:
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Yeast is a living one-celled organism that produces
carbon dioxide gas and alcohol. |
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BTB(bromothymol blue) is an indicator
that will turn light green or yellow in the presence of carbon
dioxide. |
Scoring Parameters: Response should contain
the following:
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Description of the difference between the contents
of Test Tube 1A and 2A (2A has sugar.) |
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Explanation of the reason for the difference between
tubes 1A and 2A. |
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Quality of the explanation. |
Score Level Descriptions:
| NS |
Blank or irrelevant response. The student did not
perform the experiment or does not discuss it. |
| 1 |
The response demonstrates minimal understanding
of the events in this experiment. Student states something other
than "sugar" as the difference between the two test tube contents.
For example:
- 1A had a yellow balloon and 2A had a blue balloon. We
put them like that so we can tell them apart.
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| 2 |
The response demonstrates some understanding of
the events in this experiment. Student correctly points out
that the difference is the the presence of sugar in 2A
but does not explain why they were designed to be different. |
| 3 |
The response demonstrates adequate understanding
of the experiment. Student correctly points out that the difference
is the presence of sugar in 2A and provides an explanation
for designing such a difference in the experiment, but the explanation
is brief. For example, the student points out that the difference
was designed into the experiment to see the effect of sugar
on carbon dioxide production level, but does not talk about
what the microorganism (yeast) does to sugar and where does
the carbon dioxide gas come from. |
| 4 |
The response demonstrates a high level of understanding
of scientific principles and experimental procedures involved
in this item. The student correctly and completely describes
and explains that the difference between the two test tubes
is the sugar and the role of this difference in the experiment
is pointed out with further explanations that might include
some information on sugar metabolism by yeast. Written expressions
are effective and free of major flaws. |
ME 402: Mold/Yeast
Item #2
Item Description: Students are given the following
to answer based on what they have learned from their experience. For
yeast cells that are growing in a sugar solution and producing alcohol,
Figure B below shows the relationship between the number of line yeast
cells per ml of solution and time.
Describe two conditions that could prevent the number of living
yeast cells per ml from increasing with time beyond point A.
Content Definition: The student must know or
deduce that some factors that limit the growth of living yeast cell
population are:
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Limit in resources (food, space, etc.). |
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Build up of harmful metabolic bi-products. |
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Environmental limits (temperature, etc.) |
Scoring Parameters: Responses should have the
following features:
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The two conditions mentioned above in the Content
Definition.
Students may name tow conditions within the same factor. |
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Quality of explanation. |
Score Level Descriptions:
| NS |
Blank or irrelevant response. Student does not
attempt to answer the question. |
| 1 |
The response demonstrates minimal understanding
of yeast and the conditions that effects its population growth
rate. Student presents a wrong answer. The following would be
an example:
- It is because of an outside supernatural force.
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| 2 |
The response demonstrates some understanding of
yeast and the conditions that effect its population growth rate.
Student provides one condition, with or with out explanation. |
| 3 |
The response demonstrates adequate understanding
of yeast and the conditions that affect its population growth
rate. Student provides more than one conditions and explains
two. The explanations are brief and may contain some inaccuracies.
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| 4 |
The response demonstrates a high level of understanding
of yeast and the conditions that effect its population growth
rate. Student provides at least two unique conditions and explains
both. The explanations are complete and effective with no inaccuracies.
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