Mini Virtual Lab Calculating GPP and NPP

Name: _________________________________________ Date: ________________________________Period: ____ Mini Lab: Calculating GPP and NPP Look at the diagram above. Write a caption/description for this diagram. Make it detailed-similar to what you see in your textbook figures. The diagram is communicating the movement of glucose from photosynthesis into being used for either cellular processes or biomass Open this Video and answer the questions while watching the video: 1. 2. 3. 4. Where and what is the sample of water used in this lab? Fish tank water filled with algae What is the dissolved oxygen (DO) reading of the water sample? 7.4 mg/L How many bottles are filled? 2 Why was the lid of the bottle put on under the water? To make sure there’s no air in the water that could mess up the reading and data 5. What plant is put in each bottle? Elodea 6. Describe the treatment to each bottle. (What was done differently to each bottle?) Why? Equal parts of elodea were placed in the bottle. One had black paper and a cup covering it while the other didn’t. It was so that the DO levels in each bottle could be measured Pause the video and use what you’ve learned about experimental design to answer these questions: 7. List 4 constants (the things that are the same for each bottle) in this lab: amount of water, plant type, plant size, same source of water 8. What is the independent variable? Water and elodea 9. What is the dependent variable? (What will we measure?) DO levels Play the video to get the results and answer these questions: 10. What is the DO level of the bottle that was in the light? 10.0 mg/L (ppm) Name: _________________________________________ Date: ________________________________Period: ____ 11. What is the DO level of the bottle that was in the dark? 5.3 mg/L (ppm) Fill in this chart: Initial Dissolved Oxygen (ppm) (both bottles) 7.4: light 7.4: dark Final Dissolved Oxygen in Dark Bottle (no photosynthesis, only respiration) 5.3 mg/L Final Dissolved Oxygen in Light Bottle (both respiration and photosynthesis) 10.0 mg/L 12. Calculating Respiration Rate: Only respiration (and not photosynthesis) can occur in a dark bottle. Respiration rate is the decrease in DO over time. To determine this for your sample, subtract the dark DO from the initial DO, then divide it by the time (usually in days). This will give an answer in mg O2/L/day. Use the formula below to assist you. In a water solution, ppm = mg/L R = (7.4-5.3)/2 R = 1.05mg/L 13. Calculating Gross Primary Productivity: Gross Primary Productivity (GPP) is the total amount of carbon that was fixed by organisms over a period of time. To determine this for your sample, subtract the dark bottle DO from the light DO values, then divide it by the time (usually in days). This will give an answer in mg O 2/L/day. Use the formula below to assist you. GPP = (10-5.3)/2 GPP = 2.35 mg/L 14. Calculating Net Primary Productivity: Net Primary Productivity (NPP) is the total amount of carbon that was fixed by organisms into living tissue minus that used for respiration over a period of time To determine this for your sample, subtract the respiration rate in mg O2/L/day from GPP in mg O2/L/day. This will give an answer in mg O2/L/day. Use the formula NPP = GPP - R (NPP + R = GPP) NPP = 2.35-1.05 NPP = 1.3 mg/L 15. You can also use the formula below to calculate the net primary productivity since the difference between the light bottle DO and the initial DO is essentially the same algebraic expression as GPP minus respiration rate. Name: _________________________________________ Date: ________________________________Period: ____ NPP = (10.0-7.4)/2 NPP = 2 mg/L In this lab, we measured the amount of oxygen which is proportional to the amount of carbon dioxide that was laid down into biomass. In other words, the amount of carbon dioxide that was turned into tissues on the bodies of the plant. In other productivity labs, we would grow and mass the producers and calculate the number of calories available for consumers as energy if they ate the producers. More Practice: 16. The gross primary productivity of an ecosystem is 3.5 kgC/m2/year, and the energy needed by the producers for their own respiration is 3.0 kgC/m2/year. What is the net primary productivity of such an ecosystem? NPP = 0.5 , NPP = GPP – R or NPP + R : 3.5-3.0 17. The net annual primary productivity of a particular wetland ecosystem is found to be 2,000 kcal/m 2. If respiration by the aquatic producers is 18,000 kcal/m2 per year, what is the gross annual primary productivity for this ecosystem, in kcal/m2 per year? 18,000 + 2,000 = 20,000 GPP 18. Energy flow in Lake Fremont (kcal/m2/year) Trophic Level Energy Consumed _ Waste Energy GPP _NPP _ Producer - 1,500,000 10,000 8,000 Primary Consumer 2,000 1,600 200 180 160 100 40 10 Secondary Consumer 19. In the community described in the table above, which of the following represents the respiratory energy (kcal/m2/year) used by autotrophic organisms (cf question #14)? a) 10 b) 200 c) 1,600 d) 2,000 e) 10,000 20. Reference pgs. 74-7 (Miller/Spoolman). Which 3 ecosystems have the highest productivity and which 3 have the lowest productivity? The highest net primary productivity in terrestrial environments occurs in swamps and marshes and tropical rainforests; the lowest occurs in deserts 22. Read the Core Case Study on p. 66 (Miller/Spoolman). What is happening to the net primary productivity of the tropical rain forests? Why? Each year, some 140,000 sq km of rainforests are destroyed. Rainforests are being felled for timber by logging companies and cleared by people for farming