Name: ___________________
Carbon Transfer through Snails and Elodea – Virtual Lab
Directions to Virtual Lab – Use the link on my homepage to Virtual Photosynthesis and
Respiration Lab
(http://www.classzone.com/cz/books/bio_09/resources/htmls/virtual_labs/virtualLabs.html)
 Select Carbon Transfer Through Snails and Elodea
Background:
All organisms are dependent on a healthy carbon dioxide-oxygen balance. Photosynthesis and
cellular respiration are key processes in maintaining this balance. Plants, through the process of
photosynthesis, use energy absorbed from sunlight, water, and carbon dioxide to produce
carbohydrates and oxygen. Animals and plants through the process of cellular respiration, use
oxygen and sugars to produce carbon dioxide, water, and energy needed to maintain life.
Problem 1: Do plant do respiration, photosynthesis or both?
Materials: See Checklist on the Explore part of the virtual lab
Select each item in the lab. Read the description that appears for each item. Once
you have selected all the items, click procedure to start the lab.
Hypothesis: The Elodea plant will do ______________ (photosynthesis/respiration) when left
in the ____________ (light/dark ) and will do _______________ (photosynthesis/respiration)
when left in the ____________ (light/dark ).
Set up your experiment in the following manner:
You will use 4 test tubes in this set-up. Set-up the test tubes in the following way:
Rack 1 – place in the dark
 Test tube 1: only Bromthymol Blue (BTB) solution
 Test tube 2: 1 Elodea plant
Rack 2 – place in the light
 Test tube 1: only Bromthymol Blue (BTB) solution
 Test tube 2: 1 Elodea plant
Name: ___________________
Test Tube
Starting Color
Predicted End
Color
Actual End Color
1. Dark: only
Bromthymol
Blue (BTB)
solution
2. Dark
1 Elodea plant
1. Light
only
Bromthymol
Blue (BTB)
solution
2. Light
1 Elodea plant
Add stoppers
Place the test tube under the grow light and under the rack cover.
Click Start.
Record the final results in the table above
Analysis:
1. What happened when the elodea was keep in the dark? Did the color change? Why or
why not?
2. What happened when the elodea was left in the light? W Did the color change? Why or
why not?
When asked if you want to start a new experiment or continue to
analyze your results- CHOOSE NEW!!
Name: ___________________
Problem 2:
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 content, including the Elodea, into the
aquarium, but you are not sure why you need to Elodea. Why might Elodea plants be helpful in
maintaining a health ecosystem?
Purpose: To determine how carbon dioxide cycles through a biological system.
Procedure: Follow the steps to the lab given on the screen.
Hypothesis: If there is ______________ (Elodea/snail) then it will release ____________ (O2 /
CO2 ) and the _______________ (Elodea/snail) will take it in.
Set up your experiment in the following manner:
Dependent variable: Amount of carbon dioxide present
Operation Definition: Color of the solution
Independent variable: number of snails
Control: only Bromthymol Blue (BTB) solution
You will use 4 test tubes in this set-up. Set-up the test tubes in the following way:




Test tube 1: only Bromthymol Blue (BTB) solution
Test tube 2: 0 snails, 1 Elodea plant
Test tube 3: 1 snail, 1 Elodea plant
Test tube 4: 2 snails, 1 Elodea plant
Test Tube
1. only
Bromthymol
Blue (BTB)
solution
2. 0 snails, 1
Elodea plant
3. 1 snail, 1
Elodea plant
4. 2 snails, 1
Elodea plant
Starting Color
Predicted End
Color
Actual End Color
Name: ___________________
Add stoppers
Place the test tube under the grow light
Analysis and Conclusion:
1. What is the relationship between snails and Elodea
2. Why did the color of the Bromthymol Blue (BTB) solution 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 observations support this?
6. Based on the results of your experiment, explain why you need to add the Elodea to your
snail aquarium.