Snails and Elodea Investigation

Investigating Photosynthesis and Cellular Respiration
To explore the relationship between snails and Elodea in a closed
biological system. To form a hypothesis and design an experiment to
test a hypothesis.
1. Launching the investigation and read the information in the
pop-up window (Problem).
2. Click on the items on the materials list to see what they are to
be used for. Record the materials in your journal.
3. Formulate a hypothesis to explain how CO2 cycles in aquarium
water through snails and Elodea. Record your hypothesis in
your journal.
4. As you follow the instructions in the virtual investigation when
you are required to record in the lab notebook you should also
record in your science journal. Be sure to include the following
 How you will measure the level of CO2
 Your independent variable
 Your controlled variable(s)
5. You will use all 8 test tubes. Record in your Science Journal
what you will have in each tube. Note: You cannot have more
than 2 snails or 2 Elodea per test tube.
6. Set up your experiment and record in your journal your
prediction of the outcome of each test tube.
7. Run the experiment
8. Record your results in your Science Journal.
9. Answer the question on the back in your Science Journal.
Analysis and Conclusion
1. What is the relationship between snails and Elodea?
2. Why did the color of the BTB change?
3. What was the importance of a control in your experiment?
What would you conclude if the color of the solution in the
control changed?
4. When you began the experiment, was there CO2 in the water?
In the test tubes that contained Elodea, where did the CO2 go?
5. Which gas did the snails release? What observation supports
this inference?
6. Based on the results of your experiment, explain why you
need to add the Elodea to your snail aquarium.
7. Write the balanced chemical equation for photosynthesis
(label reactants and products).
8. Write the balanced chemical equation for cellular respiration
(label reactants and products).