Photosynthesis Lab Gizmo Answer Key

Name: Ronnie Keith Date: 04-24-2022 Student Exploration: Photosynthesis Lab Directions: Follow the instructions to go through the simulation. Respond to the questions and prompts in the orange boxes. 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? Oxygen ● Where is this gas produced? Plants 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? Those Bubbles of Oxygen 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? As light intensity is decreased, oxygen generation declines. 3. Experiment with the vertical Temperature slider (upper left) and the CO2 level slider. A. How does temperature affect oxygen production? Oxygen is produced less when the temperature drops. B. How does CO2 level affect oxygen production? CO2 levels drop Reduced oxygen generation C. How does oxygen production relate to the rate of photosynthesis? Activity A: Ideal conditions Less Oxygen Production Photosynthesis proceeds slowly. Get the Gizmo ready: ● Be sure that the BAR CHART tab is selected. ● 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? Light Intensity - 37% CO2- 1000 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 24.0 81 1000 51.9 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? No matter how bright the light was, you would produce very little oxygen regardless of how hot or cold it was. B. Why would it be hard to find the ideal CO2 level if the light intensity were very low? Because if the light intensity was low, little oxygen would be produced, regardless of how high or low you set the CO2 level. Activity B: Colored light Get the Gizmo ready: ● Select the COLOR tab and the BAR CHART tab. ● Set the Temperature to 24°C, the Light intensity to 90%, and the CO2 level to 1,000 ppm. Introduction: Plants use a green pigment called chlorophyll to absorb light and convert its energy into a form that the plant can use. Chlorophyll gives plants their green color. Question: What color of light is the best for photosynthesis? 1. Observe: The color of a light wave is determined by its wavelength. On the COLOR tab, slowly drag the Light wavelength slider back and forth and observe the effect on oxygen production. How does the color of light affect the rate of photosynthesis? It has a big impact since it reflects some colors that it wouldn't use for energy and absorbs others so that the rate of photosynthesis doesn't drop. So, in order to maximize photosynthesis, it will employ the colors it requires. 2. Form hypothesis: Which color of light do you think will maximize the rate of photosynthesis? Red and Blue, in my opinion, would increase the rate of photosynthesis. 3. Gather data: Set the Light wavelength to 400 nm. (The symbol “nm” stands for nanometers. A nanometer is a billionth of a meter.) Visible light ranges from 400 to 700 nm. On the TABLE tab, click Record data. Then set the Light wavelength to 420 nm, and repeat. Continue recording data in the Gizmo every 20 nm until the wavelength is 700 nm. ✏️ 4. Make a graph: Select the GRAPH tab and select Wavelength. Sketch the graph in the space at right. A. Which colors were absorbed best by the plant? Red and blue B. Which colors were absorbed the worst? Green and yellow 5. Think and discuss: When we look at a leaf, we see the colors of light that are reflected off its surface. How does this explain the relatively low flow of oxygen in green light? It demonstrates that it reflects the necessary light. Additionally, some colors have a higher photosynthesis rate than green, which means that color doesn't have the highest photosynthesis rate. Extension: Limiting factors Get the Gizmo ready: ● Select the WHITE tab and the BAR CHART tab. ● 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.) Only a decline or a hold steady in oxygen production was possible; not an increase. B. Move the Light intensity slider back and forth. Were you able to increase oxygen production? (Return the slider to 50% when finished.) Only a decline or stability, not an increase, in oxygen production was possible. C. Move the CO2 level slider back and forth. Were you able to increase oxygen production? (Return the slider to 200 ppm when finished.) When the CO2 levels increased the oxygen production increased. 2. Analyze: In this situation, what was the limiting factor? The CO2 was the limiting factor How do you know? Because only changes in CO2 levels would have an impact on the generation of oxygen 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 light intensity 15°C 20% 200 ppm temperature 30°C 50% 400 ppm none 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? Knowing the limiting issue as a farmer can assist him or her decide what changes to make to encourage improved plant growth.