Name:
Date:
Problem: You are setting up a snail aquarium at home. Your aquarium kit contains a bag of snail eggs on an Elodea plant. The instructions say to pour the contents, including the Elodea into the aquarium, but you’re not sure why you need the Elodea. Why might Elodea plants be important in maintaining a healthy ecosystem? In this investigation, you will use snails and Elodea to explore a biological system. You will form a hypothesis about the relationship between snails and Elodea, and then design an experiment to test your hypothesis.
Materials: As you click on each item, a description will appear. Write down the importance or use of each item.
1. Beaker of Bromthymol Blue (BTB) Solution:
2. Pond Snails:
3. Elodea:
4. Test Tubes:
5. Grow light:
6. Test Tube Rack Cover:
7. CO2 – O2 Cycle Poster
8. Color Key
Hypothesis: Use the poster of the cycle between photosynthesis and cell respiration to answer the following question:
How does carbon dioxide cycle through an aquarium using snails and Elodea (plant)?
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***You must type something in the online notebook to move forward but you will not be printing, you must record your answer here****

Experiment:
Instead of designing your own experiment, I will help you with the set up. Remember you want to see why snails need elodea, and why elodea needs snails. Be sure to remember that when adding organisms to your test tubes.
Dependent Variable: The level of carbon dioxide in the test tubes is your dependent variable.
Operational definition: Determine the operational definition for the dependent variable. How will you measure the dependent variable?
In my experiment, I will measure the level of carbon dioxide by: (look back at your materials, what we you use to measure the amount of carbon dioxide, and what will you put in your tubes that will make carbon dioxide)?
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Independent Variable
Identify your independent variable.
Decide which condition you will test:
-the number of snails in a test tube.
-the number of Elodea plants in a test tube
 In my experiment, my independent variable will be:
* This is determined for you. You will be testing snails and elodea in tubes separately and together.*
Control: Determine your control. A control is a set-up against which the change in the dependent variable can be measured. Describe what is in the test tube for your control condition.
 The set-up for my control condition is:
The control will be the test tube with no organisms in it for both the light and dark parts of this experiment.
 Experimental Design:
You have 8 total tubes available for your experiment. Each of your test tubes will be filled with BTB solution. I will use ____8____ test tubes. At least one of the test tubes will be used for your control condition. The other test tubes will be used for your experimental conditions.
Determine the set-up for each tube:
Test Tube What to put in
1 BTB
2
3
4
BTB, 1 snail
BTB, 1 plant
BTB, 1 snail, 1 plant
1 (second set) BTB, 2 snails
2 (second set) BTB, 2 plants
3 (second set) BTB, 2 snails,
2 plants
4 (second set) BTB, 2 snails,
1 plant

Data: Record your data table with your predications and end results here.
Test Tube Contents
1 0 snails 0 elodea
Starting Color Predicted End
Color
2
3
1 snail, 0 elodea
0 snails,1 elodea
4
1 (second set)
2 (second set)
3 (second set)
4 (second set)
1 snail, 1 elodea
2 snails,
0elodea
0 snails,
2elodea
2 snails,
2elodea
2 snails,
1elodea
End Color
Click add stoppers
Add to the Light
Follow Direction to See Your Results
Analyze & Conclude: Use the bottom and back of this page to answer.
1.
Conclude: Look at your results, what do you notice about carbon dioxide production?
When is it at its highest? Why? When is it at a medium rate? When is it at its lowest? Why?
2.
Analyze: Why did the color of BTB change?
3.
Analyze: What was the importance of a control in your experiment?
4.
Infer: When you began the experiment was there carbon dioxide in the water? In the test tube that contained Elodea, where did the carbon dioxide go?
5.
Infer: Which gas did the snails release? What did you observe that supports this?
6.
Apply: Based on the results of your experiment, explain why you need to add the elodea to your snail aquarium.