Carbon Transfer Through Snails and Elodea – Virtual Lab
From the Internet: Go to http://www.classzone.com/cz/books/bio_07/book_home.htm?state=NJ
Under Labs, select virtual labs.
Select Carbon Transfer Through Snails and Elodea from the list of labs.
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.
Purpose:
To determine how carbon dioxide cycles through a biological system via photosynthesis and cellular
respiration.
Materials:
Get from the 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 (8 total), click procedure to start the lab.
Procedure:
Follow the steps to the lab given on the screen until you complete all seven (7) steps.
You will use 8 test tubes in this set up. Set up the test tubes in the following way:
Test Tube 1a: only Bromthymol Blue (BTB) (light)
Test Tube 1b: only Bromthymol Blue (BTB) (dark)
Test Tube 2a:
(light)
0 snails, 1 Elodea Plant and BTB
Test Tube 2b: 0 snails, 1 Elodea Plant and BTB
(dark)
Test Tube 3a:
1 snail, 1 Elodea Plant and BTB (light) Test Tube 3b: 1 snail, 1 Elodea Plant and BTB (dark)
Test Tube 4a:
(light)
2 snails, 1 Elodea Plant and BTB
Test Tube 4b: 2 snails, 1 Elodea Plant and BTB
(dark)
Dependent Variable: _________________________________________
Independent Variables: (what changes/is manipulated in the test tubes?) _______________________
Control: (Which test tubes do you think are the controls? What are in them?)
__________________________________________________________________________________
Place the test tube “a” rack under the grow light and test tube “b” rack in the dark.
Data/Results:
Test Tube Contents
1a (light) BTB only
2a (light) 0 snails, 1 elodea,
BTB
3a (light) 1 snail, 1 elodea,
BTB
4a (light) 2 snails, 1 elodea,
BTB
Starting color Predicted color Ending color
Green
Green
Green
Green
Test Tube Contents
Starting color Predicted color Ending color
1b (dark)
BTB only
Green
2b (dark)
0 snails, 1 elodea, BTB Green
3b (dark)
1 snail, 1 elodea, BTB
4b (dark)
2 snails, 1 elodea, BTB Green
Green
Discussion:
1) Conclude. What is the relationship between snails and Elodea?
2) Infer. When you began the experiment, was there CO2 in the water?
3) Analyze. Why did the color of the Bromthymol Blue (BTB) solution change in test tube 2 under
light conditions turn blue?
4) Analyze. Why did the color of the BTB solution stay green in test tube 2 under dark conditions?
5) Analyze. What was the importance of the control in your experiment?
6) Infer. Which gas did the snails release?
What observation supports this inference?
7) Why did the BTB solution turn yellow in test tube 3 under dark conditions but stayed green under
light conditions?
8) Why did the BTB solution turn yellow in test tube 4 under both conditions?
Figure 1: Test tubes under “dark” conditions.
Test tubes under “light” conditions.