Name: Biology: Unit 5 Date: LAB: Observing the Consumption of Carbon Dioxide and Production of Oxygen in Photosynthesis Collecting Observations: Answer the following questions as you read pp. 97, 99, 102, 114 in your text. 1. What is the chemical equation for photosynthesis? 2. How is oxygen produced during photosynthesis? 3. What is carbon dioxide fixation? When does this occur during photosynthesis? 4. What is Elodea? Asking a Question: How does the presence of light affect the consumption of carbon dioxide and production of oxygen during photosynthesis? Hypothesis: The rate of carbon dioxide consumption and oxygen production will if Elodea is not exposed to light. Experiment: Follow the procedure below: Part A: Demonstration of carbon dioxide consumption by plants 1. Label one test tube “Light” and a second “Dark”. 2. Fill each tube two-thirds full with aquarium water. 3. Add 1ml of Bromothymol Blue Solution to each tube and mix thoroughly. 4. Add one drop of HCL solution to each tube and mix the solution by covering the tube opening with your finger then inverting the tube. Repeat this process until the color of the liquid is uniformly yellow (pH approximately 6.0). Once this color change has occurred, do not add any mote HCL. 5. Using sharp scissors, make a diagonal cut across the bottom of two healthy Elodea sprigs. Slowly place an Elodea sprig into each tube to avoid overflow. 6. Cork each tube and swirl the tubes to mix the contents. Record the initial color in Table 1. 7. Place the Light tube next to the light and the Dark tube in the dark for 30-40 minutes. 8. Observe the color of each tube after this time period. Record this in Table 1 Part B: Observing Oxygen Production From Photosynthesis 1. Add 1000ml of 5% baking-soda-water solution into your beaker. 2. Put two or three small Elodea sprigs in the beaker. Place the wide end of the funnel over the Elodea. You will need to hold it in place temporarily. 3. Fill a test tube with 5% baking-soda-water solution. Place your thumb over the end of the tube. Turn the tube upside down; making sure that no air gets into the tube. Hold the opening of the tube under the solution in the beaker and place the test tube over the small end of the funnel. Try not to let any of the solution leak out of the tube as you do this. 4. Place your beaker setup in the area assigned by your teacher. 5. Record that there was 0mm of gas in the test tube on day 1 in Table 2. Name: Biology: Unit 5 Date: 6. Measure the amount of gas in the test tube once a day for the next five days. 7. Make a line graph of this data and paste it over Table 2. Table 1 Table 2 Color of Liquid Days Amount of gas (mm) Test Tube Beginning of Lab After 30 minutes 0 Light Tube 1 Dark Tube 2 3 4 Drawing Conclusions: 1. Was your hypothesis supported by the data? 2. Explain why your hypothesis was supported or not supported. Viewing Conclusions in Context: 1. In Part A, why did the bromothymol solution turn from yellow to blue? 2. In Part B, why was baking soda added to the beaker? 3. In Part B, what gas was forming in the test tube? How do you know? 4. How did the absence of light affect photosynthesis in both Part A and Part B? 5. What may happen to the oxygen level if an animal such as a snail was put in the beaker with the Elodea sprig?
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