Waterweed Simulation Answer Key

Introduction: In this simulation, you will be looking at the production of oxygen as a plant photosynthesizes. This procedure can be accomplished by placing elodea plants in water with baking soda to provide carbon. The plant can then be exposed to varying intensities and colors of light. Oxygen is measured in the number of bubbles produced by the plant. This simulator addresses three factors that influence the rate of photosynthesis. Carbon dioxide availability, light intensity, and light color can all be adjusted in the simulator to determine how each of the factors affects the rate of photosynthesis.

Site: http://www.saddleworth.oldham.sch.uk/science/simulations/waterweed.htm

Affect of Light Color on the Rate of Photosynthesis

Set the simulator to 6.0 Light Level, and 6.0 CO2 Level. Adjust the colors to complete the table.

Light Color

Number of Bubbles
(Light = 6.0 | CO2 = 6.0)

1. Based on the data, what color of light results in the fastest rate of photosynthesis? Propose an explanation for these results.

White light results in the fastest rate of photosynthesis, this is because the chlorophyll absorbs both blue and red light, white contains both spectrums, when enables photosynthesis to run efficiently.

*answers may vary on table, simulation has some random elements

Red 13
Blue 16
Green 5
Colorless 19

Affect of Light Level on Photosynthesis

Set the simulator to colorless light and CO2 level to 6.0. Make adjustments to the level of light to complete the data table.

Light Level

Number of Bubbles
(Light = Colorless | CO2 = 6.0 )

2. Based on the data, what light level results in the fastest rate of photosynthesis? Propose an explanation for these results.

As light intensity increases, number of bubbles increases. Light is required to split water into hydrogen ions, the start of the light reaction.

 

Answers vary on table, simulation has random elements

1.0 4
2.0 7
3.0 11
4.0 13
5.0 16
6.0 21
7.0 22
8.0 24
9.0 25
10.0 30

Affect of CO2 Level on Photosynthesis

Develop an experiment to test how the level of CO2 affects the rate of photosynthesis. Construct a data table in the space below that shows the data you collected. Make sure to include information such as the color of light, light intensity, level of CO2 and the amount of bubbles produced. (Use the previous experiments as a guide)

Data Table

CO2 Levels

Number of Bubbles
(light intensity = 8, color = white)

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2. Based on the data, what CO2 level results in the fastest rate of photosynthesis? Propose an explanation for these results.

As you increase the level of carbon dioxide, the rate of photosynthesis also increases, this is because CO2 is used in the calvin cycle to synthezie glucose. Levels go up quickly but taper off, the limiting factor is light.

Answers will vary on table, also depend on which light intensity was used to test.

1.0 8
2.0 16
3.0 20
4.0 20
5.0 23
6.0 27
7.0 25
8.0 28
9.0 25
10.0 29

ANALYSIS

4. Based on the simulation experiments, what factors can affect the rate of photosynthesis in a plant? How do you know?

Light intensity, color of light, and levels of carbon dioxide all affect the rate of photosynthesis

5. Write the equation for photosynthesis (use your book or online resources if you don't know it).

6CO2 + 6H2O + Energy C6H12O6 + 6O2

6. What are the bubbles you are measuring in this lab? Why do the bubbles tell you how fast photosynthesis is occurring?

Bubbles are oxygen released during the light reaction of photosynthesis. As water is split, oxygen is produced as a waste produce.

7. Why is it important that you keep two variables constant (such as light level and color) while you're testing how a third variable (CO2 Level) affects photosynthesis? If you change the levels of the other variables, you will not know if the increase (or decrease) was caused by the variable you were testing.

8. What settings can you put the simulator on to get the MAXIMUM rate of photosynthesis? white light, intensity 1.0 and carbon levels at 1.0 produced 32 bubbles.