Assessment of
Science Writing in
Biology
Name:
Teacher:
PRE
MID
POST
Introduction: One hundred samples of different plant parts were placed in seven different sealed containers of equal volume and size.
The amount of CO2 present in each of the containers at the beginning of the experiment was 200 ml. After two days, it was at the level
shown in the following table.
Container
1
2
3
4
5
6
7
Plant
Tulip
Tulip
Tulip
Tulip
Oak
Oak
Oak
Plant Part
Flower
Leaf
Leaf
Stem
Root
Leaf
Stem (trunk)
CO2/ml
250
100
50
200
300
150
325
Assume that the test conditions that are not listed are identical in all seven containers and that the test was repeated five times with
virtually identical results.
A scientist thinks that photosynthesis occurs throughout a plant. This is his/her argument:
Photosynthesis occurs in all parts of the plant because there is a change in carbon dioxide in each container after
two days. Photosynthetic activity is indicated by a change in the amount of carbon dioxide.
Directions: Examine the data table above and think about what you know about photosynthesis. Then, write an essay to convince the
scientist that photosynthesis occurs in the leaves of the plant. As you write your essay, remember to:
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Discuss the scientists argument and then provide evidence and/or other reasons to demonstrate why the claim is inaccurate;
Clearly state your claim and then provide adequate evidence and a sufficient rationale to support it;
Present your ideas in a clear and logical order, including an introduction, body, and conclusion;
Use a variety of words and well-constructed sentences to create tone and voice; and,
Use proper punctuation, capitalization, sentence formation and spelling.
You will have one class period (but no more than 60 minutes if your class if longer) to plan and write your essay.
A scientist claims that photosynthesis occurs throughout a plant. However, data collected from 100
samples of plant parts in 7 different sealed containers over two days indicates that photosynthesis occurs
only in the leaf of the plant.
During the process of photosynthesis, plants use light energy to convert carbon dioxide (CO2) and water
(H2O) into glucose (C6H12O6) and oxygen (O2). The experiment referenced by the scientist measured CO2
levels in each container before and after two days. Since plants convert carbon dioxide into oxygen and
glucose during photosynthesis, then a decrease in CO2 levels would be expected in containers where
photosynthesis is occurring. This only occurred in three of the seven containers, all of which contained
leaves. The other four containers, which contained flowers, stems, and roots, experienced either no
change in CO2 levels or an increase in CO2 levels.
If the scientist’s claim that photosynthesis occurs in all parts of the plant was valid, then we would
observe a decrease in CO2 levels in all of the containers. However, the containers holding stems/trunk
experienced either no change or an increase in the amount of CO2. The container holding flowers also
experienced a rise in CO2 levels. In addition, the container holding roots experienced an increase in the
amount of CO2 as well. This indicates that photosynthesis did not occur in any of these containers,
contradicting the scientist’s claim.
However, there was a decrease in CO2 levels in three of the containers, indicating that photosynthesis did
occur. All three of the containers where photosynthesis occurred contained leaves. Two containers
holding tulip leaves saw a drop in CO2 levels from 200 mL to 100 mL and 50 mL. The container which
held oak leaves saw a drop in CO2 levels from 200 mL to 150 mL. This indicates that photosynthesis does
occur in the leaves of plants. Since the evidence shows that photosynthesis does not occur in flowers,
stems/trunk, or roots, but it does occur in leaves, it would be appropriate to conclude that
photosynthesis occurs only in the leaves of plants.