Name _____________________________ AP Biology AP Lab 12--DISSOLVED OXYGEN & AQUATIC PRIMARY PRODUCTIVITY (LabBench)
Web address: http://www.phschool.com/science/biology_place/labbench Click on Lab 12: Dissolved Oxygen & Aquatic Primary Productivity
A. KEY CONCEPTS:
1. Dissolved Oxygen Availability in ponds and lakes. Using the following diagram describe the effect that each of the factors has on availability of oxygen and explain why.
a. Temperature: As water becomes warmer, its ability to hold oxygen decreases
b. Light & Photosynthesis: In bright light, aquatic plants are able to produce more oxygen.
c. Decomposition & Respiration: As organic material decays, microbial processes consume oxygen.
d. Mixing & Turbulence: Wave action, waterfalls, and rapids all aerate water and increase the oxygen concentration.
e. Salinity: As water becomes more salty, its ability to hold oxygen decreases.
2. Productivity: Define each of these terms in your own words.
a. Primary productivity: Both of photosynthesis and respiration
b. Gross productivity: Only photosynthesis
c. Net productivity: the subtraction of photosynthesis - respiration
3. Why do we use dissolved oxygen as a measure of productivity? Does productivity include more than oxygen?
- We use dissolved oxygen as a measure of productivity because it measured by photosynthesis and respiration. Productivity also includes water, carbon dioxide, solar energy, and glucose.
14. Using the diagrams below explain:
a. How does putting a sample of pond water and algae/freshwater plants in the light enable us to measure gross productivity?
- It enables us to measure gross productivity because it's photosynthesizing, which create O2.
b. How does putting a sample of pond water and algae/freshwater plants in the dark enable us
to measure respiration?
- It enables us to measure respiration by the O2 consumption.
c. How does subtracting the two enable us to indirectly measure net productivity?
- We can know the amount of O2 available by subtracting respiration from photosynthesis.
5. What are the three ways that primary productivity can be measured? Highlight the way will be used in this lab?.
a. Rate of O2 production
b. Rate of sugar formation
c. Amount of CO2 used in process
B. LAB PART 1: EFFECT OF TEMPERATURE ON DISSOLVED OXYGEN
We actually did this part of the lab already. Remind yourself of our experiment, our procedures, and our conclusions. We were investigating the effect of the physical factor of temperature on the percent dissolved oxygen in a body of water.
6. What is the relationship between water temperature and dissolved oxygen?
- If the water temperature decreases, then the amount of dissolved O2 increases.
7. Explain why this relationship exists.
- Molecules move slower in cold water than warm water that's why O2 is able to stay in colder water.
8. So, now explain why the fish in the aquarium (on the LabBench Web site) above the radiator died?
- The fish suffocated and died because of the temperature in water was too high causing the low amount of O2
C. A MODEL OF PRODUCTIVITY AS A FUNCTION OF DEPTH IN A LAKE
Now we are going to look at the biological factors that affect dissolved oxygen in a body of water. Look at the experimental design on the LabBench Web site (http://www.phschool.com/science/biology_place/labbench/lab12/model.html). We are taking a sample of pond water (with algae) and then modeling different depths in the pond by using screening to block out successive amounts of light. One hundred percent light for shallow depth, all the way to 0% light for deep ponds.
9. Why do we take an initial reading of dissolved oxygen? What purpose does this serve in the experiment?
- We take an initial reading dissolved oxygen to compare change at the end.
10. Click on the “closer look” magnifying glass on the “initial bottle”. Why does the animation show oxygen being diffusing out of the freshwater plants? What does this signify?
- The animation shows that because the plants are releasing oxygen, which signified photosynthesis process.
11. Click on the “closer look” magnifying glass on the foil- covered bottle. Why does the animation show oxygen diffusing into the freshwater plants? What does this signify?
- The animation shows that because oxygen is being used by plants, which signified respiration process
12. Click on the “closer look” magnifying glass on the 100% bottle under the light. Why does the animation show oxygen diffusing both into and out of the freshwater plants? What does this signify?
- The animation shows that because oxygen is being absorbed and released. This signified the respiration and photosynthesis process.
D. ANALYSIS OF RESULTS
Let’s look at the results that will allow you to calculate the different types of productivity.
13. Measuring Respiration: Remember that plants (producers) perform both photosynthesis and respiration. To measure the amount of respiration that is happening in the bottle, we measure the amount of dissolved oxygen in the initial sample and then the amount of oxygen in the bottle kept in the dark. As shown in the illustration below, you then subtract the amount of dissolved oxygen in the “dark bottle” from the amount of dissolved oxygen in the “initial bottle” to calculate the amount of oxygen consumed in respiration. I have added some possible measurements to help. Explain why this calculation works.
- This calculation works because we already have the initial amount of dissolved oxygen. Now we just have to measure the remaining amount of O2 after going to the darkness and respiration, then we'll able to find the amount of O2 during the process.
14. Measuring Gross Productivity: Remember gross productivity is the total amount of sugars and oxygen produced by the plants in an ecosystem. I don’t like how this Web site shows you how to calculate gross productivity. The equation is correct, but it is a short cut, so it makes it more difficult to understand. So follow me with the illustrations and the possible measurements below.
So the illustration shows us there was 10mg increase in dissolved oxygen in the jar as a result of photosynthesis in the last 24 hours and there was 5mg decrease in dissolved oxygen in the jar as a result of respiration in the last 24 hours. So the gross productivity (the full photosynthetic production in this ecosystem) of the algae in the bottle is the 5mg dissolved oxygen lost to respiration added back to the 10 mg dissolved oxygen accumulated in the bottle kept in the light. So what the algae really produced in the bottle was a total of 15mg dissolved oxygen, it just lost 5mg to respiration. And remember, the oxygen is an indirect measurement of the sugars produced in photosynthesis and lost in respiration.
Now, in your own words, explain why this calculation works.
- This calculation works because the gross productivity is done in this process. It's still productivity either we gain or lose oxygen, so to able to get the total amount of product we have to add them together.
15. Measuring Net Productivity: Remember net productivity is the amount of sugars and dissolved oxygen produced by the plants in an ecosystem once you subtract out what the producers have consumed in respiration. So we actually already calculated that in the last example; I just called it “net photosynthesis.” Explain why this calculation works.
- This calculation works because the net productivity is the remaining amount of oxygen after photosynthesis and to able to find that, the initial amount of dissolved O2 needs to get subtracted from the amount of dissolved O2 that have gone through photosynthesis process.
16. Print out the completed calculation table from Sample Problem page of the LabBench Web site, fill in your predictions on the graph as well, and attach it to this lab to show me that you have completed it.
17. Print out the Lab Quiz and attach it to this lab to show me that you completed it.
SUMMARY QUESTIONS
18. Would you expect the dissolved oxygen levels in water sampled from a stream entering a lake to be higher or lower than the dissolved oxygen levels in water sampled from the lake itself? Explain.
- I expected the O2 level from the stream entering to the lake to be more than the dissolved O2 level of the lake because when water moves, it aerates water by adding oxygen.
19. Would you expect the dissolved oxygen levels in water sampled from a lake at 7AM to be higher or lower than the dissolved oxygen levels in water sampled at 5PM? Explain.
- It expected the O2 level in the water sample from the lake at 7am to be higher than the oxygen level in sample at 5pm. Because normally, the weather is colder in the morning; therefore, oxygen stays in cold water much more than warm water.
20. One of the major sources of water pollution is the runoff from fertilizer used in agriculture and on suburban lawns as well as golf courses. In particular, the nitrogen and phosphorus nutrients in the fertilizer creates problems in the streams and ponds it flows into. They cause alga blooms and eutrophication in lakes.
a. Why do nitrogen and phosphorus promote a lot of plant/algal growth?
- Nitrogen and phosphorus promote a lot of plant/algal growth because nitrogen contains proteins, which is found in DNA and DNA, and phosphorus transports cells.
b. What is meant by algal bloom? (Look it up!)
- An algal occurs when a population of algae increase rapidly due to receiving high amount of sunlight and nutrients.
c. What problems do algal blooms cause in ponds & lakes? Why isn’t a lot more producers a good thing? (Look it up!)
- Algae blooms in ponds and lakes cause organism underneath couldn't absorb sunlight causing it difficult for those organisms to sustain life. More producers more oxygen in the atmosphere. It'd become harmful to organism that depend on O2 fro sustainability if there's too much O2.
d. What is meant by eutrophication? (Look it up!)
- Eutrophication means that there's too much nutrients in bodies of water. Nutrients are good for the ecosystem, but not when too much.
21. What depth—shallow or deep—will there be more primary productivity in a pond or a lake? Explain.
- There's more primary productivity in a shallow pond or lake because the producers are closer to the surface and receives more sunlight the ones in the deeper part of water.
22. In an experiment, why do we use the mean of class data to make conclusions rather than individual group data?
- Class data is better because we have more chance to get a greatest result by the average. More groups, more % of getting it right.
23. AP exam FRQ (2008). Consumers in aquatic ecosystems depend on producers for nutrition.
a. Explain the difference between gross and net primary productivity.
- The net productivity is remaining the amount of the product after going through photosynthesis. The gross productivity is the total amount of product in the whole process.
b. Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period.
- To determine the gross amount of the productivity, we need to find the amount of carbon used over the 24hr period and the amount of O2 that got produce in that time period. Finally, add those 2 together.
- To determine the net productivity in a fresh water pond over 24hr period, first record the initial amount of O2 in the pond, then after 24hr, record the amount of O2 again. Finally, subtract the initial amount of the O2 from the final amount of O2 to get the net productivity.
c. In an experiment, net primary productivity was measured, in the early spring, for water samples taken from different depths of a freshwater pond in a temperate deciduous forest. Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at different depths of the pond.
- This graph shows that the lower depth os water, the less primary production is occuring. When the water in the pond was around 25 meters, the primary productivity rate stayed constant. When the depth of water reached around 30 and up, there was no primary productivity.
d. Describe how the relationship between net primary productivity and depth would be expected to differ if new data were collected in mid-summer from the same pond. Explain your prediction.
- If the new data were collected in mid-summer from the same pond, then the primary productivity rate will increase. It'd increase in the mid-summer because there will be more sunlight around that time. Also, the warmer the temperature, the lower oxygen would be available in water.
Web address: http://www.phschool.com/science/biology_place/labbench Click on Lab 12: Dissolved Oxygen & Aquatic Primary Productivity
A. KEY CONCEPTS:
1. Dissolved Oxygen Availability in ponds and lakes. Using the following diagram describe the effect that each of the factors has on availability of oxygen and explain why.
a. Temperature: As water becomes warmer, its ability to hold oxygen decreases
b. Light & Photosynthesis: In bright light, aquatic plants are able to produce more oxygen.
c. Decomposition & Respiration: As organic material decays, microbial processes consume oxygen.
d. Mixing & Turbulence: Wave action, waterfalls, and rapids all aerate water and increase the oxygen concentration.
e. Salinity: As water becomes more salty, its ability to hold oxygen decreases.
2. Productivity: Define each of these terms in your own words.
a. Primary productivity: Both of photosynthesis and respiration
b. Gross productivity: Only photosynthesis
c. Net productivity: the subtraction of photosynthesis - respiration
3. Why do we use dissolved oxygen as a measure of productivity? Does productivity include more than oxygen?
- We use dissolved oxygen as a measure of productivity because it measured by photosynthesis and respiration. Productivity also includes water, carbon dioxide, solar energy, and glucose.
14. Using the diagrams below explain:
a. How does putting a sample of pond water and algae/freshwater plants in the light enable us to measure gross productivity?
- It enables us to measure gross productivity because it's photosynthesizing, which create O2.
b. How does putting a sample of pond water and algae/freshwater plants in the dark enable us
to measure respiration?
- It enables us to measure respiration by the O2 consumption.
c. How does subtracting the two enable us to indirectly measure net productivity?
- We can know the amount of O2 available by subtracting respiration from photosynthesis.
5. What are the three ways that primary productivity can be measured? Highlight the way will be used in this lab?.
a. Rate of O2 production
b. Rate of sugar formation
c. Amount of CO2 used in process
B. LAB PART 1: EFFECT OF TEMPERATURE ON DISSOLVED OXYGEN
We actually did this part of the lab already. Remind yourself of our experiment, our procedures, and our conclusions. We were investigating the effect of the physical factor of temperature on the percent dissolved oxygen in a body of water.
6. What is the relationship between water temperature and dissolved oxygen?
- If the water temperature decreases, then the amount of dissolved O2 increases.
7. Explain why this relationship exists.
- Molecules move slower in cold water than warm water that's why O2 is able to stay in colder water.
8. So, now explain why the fish in the aquarium (on the LabBench Web site) above the radiator died?
- The fish suffocated and died because of the temperature in water was too high causing the low amount of O2
C. A MODEL OF PRODUCTIVITY AS A FUNCTION OF DEPTH IN A LAKE
Now we are going to look at the biological factors that affect dissolved oxygen in a body of water. Look at the experimental design on the LabBench Web site (http://www.phschool.com/science/biology_place/labbench/lab12/model.html). We are taking a sample of pond water (with algae) and then modeling different depths in the pond by using screening to block out successive amounts of light. One hundred percent light for shallow depth, all the way to 0% light for deep ponds.
9. Why do we take an initial reading of dissolved oxygen? What purpose does this serve in the experiment?
- We take an initial reading dissolved oxygen to compare change at the end.
10. Click on the “closer look” magnifying glass on the “initial bottle”. Why does the animation show oxygen being diffusing out of the freshwater plants? What does this signify?
- The animation shows that because the plants are releasing oxygen, which signified photosynthesis process.
11. Click on the “closer look” magnifying glass on the foil- covered bottle. Why does the animation show oxygen diffusing into the freshwater plants? What does this signify?
- The animation shows that because oxygen is being used by plants, which signified respiration process
12. Click on the “closer look” magnifying glass on the 100% bottle under the light. Why does the animation show oxygen diffusing both into and out of the freshwater plants? What does this signify?
- The animation shows that because oxygen is being absorbed and released. This signified the respiration and photosynthesis process.
D. ANALYSIS OF RESULTS
Let’s look at the results that will allow you to calculate the different types of productivity.
13. Measuring Respiration: Remember that plants (producers) perform both photosynthesis and respiration. To measure the amount of respiration that is happening in the bottle, we measure the amount of dissolved oxygen in the initial sample and then the amount of oxygen in the bottle kept in the dark. As shown in the illustration below, you then subtract the amount of dissolved oxygen in the “dark bottle” from the amount of dissolved oxygen in the “initial bottle” to calculate the amount of oxygen consumed in respiration. I have added some possible measurements to help. Explain why this calculation works.
- This calculation works because we already have the initial amount of dissolved oxygen. Now we just have to measure the remaining amount of O2 after going to the darkness and respiration, then we'll able to find the amount of O2 during the process.
14. Measuring Gross Productivity: Remember gross productivity is the total amount of sugars and oxygen produced by the plants in an ecosystem. I don’t like how this Web site shows you how to calculate gross productivity. The equation is correct, but it is a short cut, so it makes it more difficult to understand. So follow me with the illustrations and the possible measurements below.
So the illustration shows us there was 10mg increase in dissolved oxygen in the jar as a result of photosynthesis in the last 24 hours and there was 5mg decrease in dissolved oxygen in the jar as a result of respiration in the last 24 hours. So the gross productivity (the full photosynthetic production in this ecosystem) of the algae in the bottle is the 5mg dissolved oxygen lost to respiration added back to the 10 mg dissolved oxygen accumulated in the bottle kept in the light. So what the algae really produced in the bottle was a total of 15mg dissolved oxygen, it just lost 5mg to respiration. And remember, the oxygen is an indirect measurement of the sugars produced in photosynthesis and lost in respiration.
Now, in your own words, explain why this calculation works.
- This calculation works because the gross productivity is done in this process. It's still productivity either we gain or lose oxygen, so to able to get the total amount of product we have to add them together.
15. Measuring Net Productivity: Remember net productivity is the amount of sugars and dissolved oxygen produced by the plants in an ecosystem once you subtract out what the producers have consumed in respiration. So we actually already calculated that in the last example; I just called it “net photosynthesis.” Explain why this calculation works.
- This calculation works because the net productivity is the remaining amount of oxygen after photosynthesis and to able to find that, the initial amount of dissolved O2 needs to get subtracted from the amount of dissolved O2 that have gone through photosynthesis process.
16. Print out the completed calculation table from Sample Problem page of the LabBench Web site, fill in your predictions on the graph as well, and attach it to this lab to show me that you have completed it.
17. Print out the Lab Quiz and attach it to this lab to show me that you completed it.
SUMMARY QUESTIONS
18. Would you expect the dissolved oxygen levels in water sampled from a stream entering a lake to be higher or lower than the dissolved oxygen levels in water sampled from the lake itself? Explain.
- I expected the O2 level from the stream entering to the lake to be more than the dissolved O2 level of the lake because when water moves, it aerates water by adding oxygen.
19. Would you expect the dissolved oxygen levels in water sampled from a lake at 7AM to be higher or lower than the dissolved oxygen levels in water sampled at 5PM? Explain.
- It expected the O2 level in the water sample from the lake at 7am to be higher than the oxygen level in sample at 5pm. Because normally, the weather is colder in the morning; therefore, oxygen stays in cold water much more than warm water.
20. One of the major sources of water pollution is the runoff from fertilizer used in agriculture and on suburban lawns as well as golf courses. In particular, the nitrogen and phosphorus nutrients in the fertilizer creates problems in the streams and ponds it flows into. They cause alga blooms and eutrophication in lakes.
a. Why do nitrogen and phosphorus promote a lot of plant/algal growth?
- Nitrogen and phosphorus promote a lot of plant/algal growth because nitrogen contains proteins, which is found in DNA and DNA, and phosphorus transports cells.
b. What is meant by algal bloom? (Look it up!)
- An algal occurs when a population of algae increase rapidly due to receiving high amount of sunlight and nutrients.
c. What problems do algal blooms cause in ponds & lakes? Why isn’t a lot more producers a good thing? (Look it up!)
- Algae blooms in ponds and lakes cause organism underneath couldn't absorb sunlight causing it difficult for those organisms to sustain life. More producers more oxygen in the atmosphere. It'd become harmful to organism that depend on O2 fro sustainability if there's too much O2.
d. What is meant by eutrophication? (Look it up!)
- Eutrophication means that there's too much nutrients in bodies of water. Nutrients are good for the ecosystem, but not when too much.
21. What depth—shallow or deep—will there be more primary productivity in a pond or a lake? Explain.
- There's more primary productivity in a shallow pond or lake because the producers are closer to the surface and receives more sunlight the ones in the deeper part of water.
22. In an experiment, why do we use the mean of class data to make conclusions rather than individual group data?
- Class data is better because we have more chance to get a greatest result by the average. More groups, more % of getting it right.
23. AP exam FRQ (2008). Consumers in aquatic ecosystems depend on producers for nutrition.
a. Explain the difference between gross and net primary productivity.
- The net productivity is remaining the amount of the product after going through photosynthesis. The gross productivity is the total amount of product in the whole process.
b. Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period.
- To determine the gross amount of the productivity, we need to find the amount of carbon used over the 24hr period and the amount of O2 that got produce in that time period. Finally, add those 2 together.
- To determine the net productivity in a fresh water pond over 24hr period, first record the initial amount of O2 in the pond, then after 24hr, record the amount of O2 again. Finally, subtract the initial amount of the O2 from the final amount of O2 to get the net productivity.
c. In an experiment, net primary productivity was measured, in the early spring, for water samples taken from different depths of a freshwater pond in a temperate deciduous forest. Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at different depths of the pond.
- This graph shows that the lower depth os water, the less primary production is occuring. When the water in the pond was around 25 meters, the primary productivity rate stayed constant. When the depth of water reached around 30 and up, there was no primary productivity.
d. Describe how the relationship between net primary productivity and depth would be expected to differ if new data were collected in mid-summer from the same pond. Explain your prediction.
- If the new data were collected in mid-summer from the same pond, then the primary productivity rate will increase. It'd increase in the mid-summer because there will be more sunlight around that time. Also, the warmer the temperature, the lower oxygen would be available in water.