Photosynthesis cellular respiration lab key2 PDF

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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?

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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?

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To provide dark conditions

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12. Test Tube # 1 2 3 4

Make your predictions below: Condition Contents Predict Color and Explain s of Tube Light Light Light Light

5 6 7 8

Dark Dark Dark Dark

Water only 2 snails 2 Elodea 2 snails and 2 Elodea Water only 2 snails 2 Elodea 2 snails and 2 Elodea

Answers will vary Answers will vary Answers will vary Answers will vary

Answers will vary Answers will vary Answers will vary 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 will turn yellow in light conditions and/or dark conditions. Explain: Why do you think this outcome will occur? Snails will produce only carbon dioxide, while the Elodea will produce carbon dioxide and oxygen gas. I predict the snails and Elodea will produce more carbon dioxide, causing the water to turn yellow.

Read This: The independent variable in an experiment is the variable that will be altered by you, the scientist. In the case of this experiment, the independent variable will be the number of snails and/or number of elodea plants in each test tube. 1. Identify the dependent variable (what you, the scientist, will measure) in this experiment: change in carbon dioxide levels (using the BTB indicator)

Now you must wait 24 hours. (make sure you clean up your station!)

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Data/Results: Yesterday, you filled 8 test tubes with the following contents. Carefully remove your test tube racks from the light or dark conditions and complete the tables below with your observations. First Test Tube Rack – Placed under the growth light: Test Tube Independent Beginning Color with BTB Variables Color Prediction Green Varies Tube # 1 Water Only Tube #2 2 snails Green Varies Tube #3 2 Elodea Green Varies Tube #4 2 snails, 2 Elodea Green Varies Second Test Test Tube with BTB Tube # 1 Tube #2 Tube #3 Tube #4

Tube Rack – Placed Independent Variables Water Only 2 snails 2 Elodea 2 snails, 2 Elodea

under the test tube cover: Beginning Color Color Prediction Green Varies Green Varies Green Varies Green Varies

Color Result Green Yellow Green Yellow

Color Result Green Yellow Yellow Yellow

Conclusions: Complete the following sentences. 1. In the test tubes which contained only snails, the water changed to yellow because the snails produced lots of carbon dioxide. 2. In the test tubes which contained only Elodea under the light, the water stayed green because the Elodea performed both photosynthesis and cellular respiration and produced oxygen and carbon dioxide. 3. In the test tubes which contained only Elodea in the dark, the water changed to yellow because the Elodea performed cellular respiration and produced lots of carbon dioxide. 4. In the test tubes which contained both snails and Elodea under the light, the water changed to yellow because the snails and Elodea produced more carbon dioxide.

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Extension: 1. Conclude. What is the relationship between snails and Elodea? The snails perform only cellular respiration, while the Elodea perform both photosynthesis and cellular respiration.

2. Analyze. Why did the color of the Bromthymol Blue (BTB) solution change in certain test tubes? The levels of carbon dioxide changed, therefore the BTB solution changed color to indicate the presence of carbon dioxide.

3. Analyze. What was the importance of a control in your experiment? What would you conclude if the color of the solution in the control changed? The control allowed me to have a point of reference in which no change should have occurred. If the control solution changed color, I would conclude there were organisms in the water.

4. Infer. When you began the experiment, was there CO2 in the water? In the test tubes that contained Elodea, where did the CO2 go? Yes, the water was green. This indicates a low level of carbon dioxide. In the tubes that contained Elodea, the carbon dioxide was used in the photosynthesis process.

5. Infer. Which gas did the snails release? What observation supports this inference? The snails released both oxygen and carbon dioxide. This was indicated by the solution changing to yellow.

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6. Apply. Based on the results of your experiment, explain why you need to add the Elodea to your snail aquarium. Adding the Elodea creates a symbiotic environment in which the snails can obtain oxygen from the Elodea.

7. Assess. Write the balanced chemical equation for photosynthesis below (label reactants and products). Reactants Products 6 CO2 + 6 H2O + Sunlight (energy)    C6H12O6 + 6 O2 Write the balanced chemical equation for cellular respiration below (label reactants and products). Reactants Products C6H12O6 + 6 O2    6 CO2 + 6 H2O + ATP (energy)

Draw a diagram below of your results: Answers will vary. Diagrams should include drawings of the experiment setup and labels of what processes are happening in each area. (i.e. label snails and Elodea, include products and reactants of each process.)

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