Name _________________________________ Date _____________ Period ______
Lab: Investigating Photosynthesis and Cellular Respiration
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 sugars and oxygen. Animals and plants, through the process of cellular respiration, use oxygen and sugars to produce carbon dioxide, water, and the energy needed to maintain life.
Purpose:
To determine how carbon dioxide cycles through a biological system by performing the “Carbon Transfer Through Snails and Elodea” lab activity.
Procedure:
1. Read through the background information and purpose. Create your own question for what you are investigating in this experiment.
a. Problem (in question form): How are photosynthesis and cellular respiration related?
2. Obtain 8 test tubes of equal size/volume and number the test tubes 1-8. Fill each test tube with approximately 30 mL of deionized water.
3. Add enough bromothymol blue (BTB) indicator to solution to each test tube to change the water to a green color (about 3 mL).
4. What is Bromothymol Blue? Why is the BTB in the test tube green (Hint: recall the teacher demonstration)?
Bromothymol blue is an indicator that changes color when carbon dioxide is present. Green in the test tube means a low carbon dioxide presence.
5. If snails use lungs to breathe, you can conclude that they release which gas into their environment as a result of respiration?
Carbon Dioxide
6. If Elodea is an aquatic plant, you can conclude that it releases which gas into its environment as a result of photosynthesis?
Oxygen
7. Next, place the following items in each appropriately labeled test tube.
Test Tube Number
Added Contents
#1 and #5
Water Only
#2 and #6
2 snails
#3 and #7
2 sprigs of Elodea
#4 and #8
2 snails and 2 sprigs of Elodea
8. Place test tubes 1-4 in a test tube rack and place the rack under a growth light.
9. What is the purpose of the growth light?
To synthesize sunlight for the plants
10. Place test tubes 5-8 in a test tube rack and place the rack under a test tube rack cover.
11. What is the purpose of the test tube rack cover?
To provide dark conditions
12.
Make your predictions below:
Test Tube #
Conditions
Contents of Tube
Predict Color and Explain
1
Light
Water only
Answers will vary
2
Light
2 snails
Answers will vary
3
Light
2 Elodea
Answers will vary
4
Light
2 snails and 2 Elodea
Answers will vary
5
Dark
Water only
Answers will vary
6
Dark
2 snails
Answers will vary
7
Dark
2 Elodea
Answers will vary
8
Dark
2 snails and 2 Elodea
Answers will vary
Predict - Explain how carbon dioxide (CO2) cycles in aquarium water through snails and Elodea. Complete the following statement to develop your own hypothesis.
If I add a snail and elodea to a test tube with bromothymol blue, then the water w...
