Download Student Exploration: Forces, Friction, and Fan Carts

Name: _____________________________
Date: ________________________
Student Exploration: Plants and Snails
Vocabulary: bromthymol blue (BTB), indicator, interdependence
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
1. What important gas do we take in when we breathe?
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2. Why don’t we run out of the important gases that we need to stay alive?
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Background Information
In this activity, you will create and monitor closed ecosystems with aquatic snails and elodea
plants. The bromthymol blue (BTB) indicator in the test tubes will show carbon dioxide
concentrations by changing color. If there is a lot of carbon dioxide, the liquid turns yellow. If
there is little carbon dioxide, the liquid turns blue. Because plants convert carbon dioxide to
oxygen, you can infer that low carbon dioxide levels correspond to high oxygen levels.
Gizmo Warm-up
In the Plants and Snails Gizmo™, each of the test tubes
contains water and a small amount of bromthymol blue
(BTB). BTB is a chemical indicator. An indicator changes
color when the chemicals in the water change.
1. With the lights set to on, drag a snail into one test tube
and a plant into another. Press Play (
). After 24
hours, what is the color is the tube with the snail in it?
______________ What color is the tube with the plant
in it? __________________
2. Select Show oxygen and CO2 values. Place the O2/CO2 probe in each tube. The probe
will show you the levels of two gases, oxygen (O2) and carbon dioxide (CO2), in the tubes.
We call these amounts the gas levels.
A. When the water turns blue, which gas is most common? ______________________
B. When the water turns yellow, which gas is most common? _____________________
C. What does it tell you when the water is green? ______________________________
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3. Summarize:
Increased CO2 = ________________ Color
Decreased CO2 = ________________ Color
Increased O2 = ________________ Color
Decreased O2 = _________________ Color
Activity A:
Gases in and
gases out
Get the Gizmo ready:
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Click Reset (
).
Remove organisms from the test tubes.
Turn on Show oxygen and CO2 values.
Question: What gases do plants and animals take in and what do they give off?
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On the table below fill in the Initial Color of Water.
Under Predicted Final Color of Water, write your hypothesized color change for each test
tube in the experiment. (What do you think will happen?)
Now click play and record your observations of the Final Color of Water.
Tube
Contents
A – Light
1 Plant
B– Light
1 Snail
C– Light
2 Plants
D– Light
2 Snails
E – Dark
1 Plant
F– Dark
1 Snail
G– Dark
2 Plants
H– Dark
2 Snails
Initial Color of
Water
Predicted Final
Color of Water
Final Color of
Water
1. Analyze: Study your data on gases given off by plants.
A. What gas do plants give off in the light? ___________________________________
B. How about in the dark? ________________________________________________
2. Analyze: Study your data on gases given off by animals.
A. What gas do animals give off in the light? __________________________________
B. How about in the dark? ________________________________________________
C. How do these results compare to your plant results? _________________________
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3. Extend your thinking: What do you think would happen if plants and animals were put in the
same test tube? Explain your thinking. You will get an opportunity to test this in the next
Activity!
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Get the Gizmo ready:
Activity B:
Interdependence
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
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Click Reset.
Clear all of the test tubes.
Turn the light switch to on.
Check Show oxygen and CO2 values.
Question: How do plants and animals depend on each other?
1. Observe: Put one sprig of Elodea and one snail in a test tube with the lights on. Click Play.
A. Does the color of the water in the tube change? _____________________________
B. What happens to the O2 and CO2 levels? __________________________________
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2. Predict: Without using the Gizmo, predict what you think will happen to the gas levels in
each case listed below. (Leave the Actual result column blank for now.)
Tube
Prediction
Actual result
2 snails, 2 sprigs,
lights on
1 snail, 2 sprigs,
lights on
1 snail, 2 sprigs,
lights off
3. Run Gizmo: Now run the Gizmo to test your predictions. Record your findings in the table.
4. Generalize: Describe how plants and animals each contribute to the survival of the other.
(This type of cooperative relationship is called interdependence.)
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Analysis and Conclusions
Let’s relate what you learned in this lab to our study of photosynthesis and cellular respiration.
1. Which organism(s) were undergoing photosynthesis? _______________
2. Explain why you know your answer above, based on evidence from the lab simulation.
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3. Which organism(s) were undergoing cellular respiration? _______________
4. Explain why you know your answer above, based on evidence from the lab simulation.
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5. How are respiration and photosynthesis related to each other?
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