Carbon Dioxide and Ideal Conditions

Name: ______________________________________ Date: ________________________

Student Exploration: Photosynthesis Lab

Vocabulary: carbon dioxide, chlorophyll, glucose, limiting factor, nanometer, photosynthesis, wavelength

Prior Knowledge Questions (Do these BEFORE using the Gizmo.)

• To survive, what gas do we need to breathe in? ___________________________________

• Where is this gas produced? __________________________________________________

Gizmo Warm-up
During photosynthesis, plants use the energy of light to produce glucose (C6H12O6) from carbon dioxide (CO2), and water (H2O). Glucose is a simple sugar that plants use for energy and as a building block for larger molecules.

A by-product of photosynthesis is oxygen. Plants use some of the oxygen they produce, but most of it is released. In the Photosynthesis Lab Gizmo™, you can monitor the rate of photosynthesis by measuring oxygen production.

1. Observe the left pane closely. What do you think the bubbles are? ____________________

2. Select the BAR CHART tab. On the graph, notice the Oxygen production bar. Move the Light intensity slider back and forth. How does light intensity affect oxygen production?

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3. Experiment with the vertical Temperature slider (upper left) and the CO2 level slider.

A. How does temperature affect oxygen production? ___________________________

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B. How does CO2 level affect oxygen production? ______________________________

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C. How does oxygen production relate to the rate of photosynthesis? ______________

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|Activity A: |Get the Gizmo ready: |[pic] |
| |Be sure that the BAR CHART tab is selected. | |
|Ideal conditions |Turn on Show numerical values. | |

Question: In the Gizmo, what are the ideal conditions for photosynthesis?

1. Form hypothesis: During photosynthesis, light energy is used to synthesize carbon dioxide (CO2) and water (H2O) into glucose (C6H12O6) and oxygen (O2). The complex series of chemical reactions is summarized by the following formula:

6CO2 + 6H2O + light energy ( C6H12O6 + 6O2

In the Gizmo, what light intensity and CO2 level do you think will maximize the rate of photosynthesis? ___________________________________________________________

2. Experiment: Use the Gizmo to find the ideal conditions for photosynthesis. Use any method you like. When you think you have the answer, list the conditions below.

|Temperature |Light intensity |CO2 level |Oxygen production |
| | | | |

3. Revise and repeat: One way to test if you’ve found the ideal conditions is to change each variable slightly from the value that you recorded above. If the oxygen production decreases with each change that you make, it is likely you have found the ideal conditions. If a small change causes oxygen production to increase, continue to experiment.

If necessary, revise your numbers in the table above.

4. Think and discuss: Think about the process of finding the ideal conditions.

A. Why would it be hard to find the ideal light intensity if the temperature were very hot or cold? ____________________________________________________________ ___________________________________________________________________

B. Why would it be hard to find the ideal CO2 level if the light intensity were very low? ___________________________________________________________________ ___________________________________________________________________

|Extension: |Get the Gizmo ready: |[pic] |
| |Select the WHITE tab and the BAR CHART tab. | |
|Limiting factors |Turn on Show numerical values. | |

Introduction: Photosynthesis requires light, water, and CO2 to work. When one of these factors is in short supply, it is called a limiting factor. Temperature can also be a limiting factor when it is too hot or too cold for photosynthesis to work well.

Question: What is the effect of limiting factors on photosynthesis?

1. Observe: Set Temperature to 24°C, Light intensity to 50%, and CO2 level to 200 ppm.

A. Move the Temperature slider up and down. Were you able to increase oxygen production? _____________________ (Return the slider to 24°C when finished.) B. Move the Light intensity slider back and forth. Were you able to increase oxygen production? _____________________ (Return the slider to 50% when finished.) C. Move the CO2 level slider back and forth. Were you able to increase oxygen production? _____________________ (Return the slider to 200 ppm when finished.)

2. Analyze: In this situation, what was the limiting factor? _____________________________

How do you know? _________________________________________________________

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3. Challenge: In each of the situations below, use the Gizmo to find the limiting factor.

|Temperature |Light intensity |CO2 level |Limiting factor |
|25°C |60% |700 ppm | |
|15°C |20% |200 ppm | |
|30°C |50% |400 ppm | |

4. Think and discuss: Suppose you were a farmer trying to grow plants in a greenhouse. Why would it be important to know what the limiting factor is?

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