AP Biology AP Lab 12--DISSOLVED OXYGEN & AQUATIC PRIMARY PRODUCTIVITY (LabBench)
Web address: 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: Warm
b. Light & Photosynthesis: Bright
c. Decomposition & Respiration: As organic material decays, microbial processes consume oxygen.
d. Mixing & Turbulence: As organic material decays, microbial processes consume oxygen
e. Salinity :When the ocean is saltier, the oxygen is less stored in the ocean
2. Productivity: Define each of these terms in your own words.
a. Primary productivity: A term used to describe the rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem
b. Gross productivity: plant's organic production of compounds in the ecosystem
c. Net productivity: The remaining of the organic compounds of a plant.
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 is the easiest thing to measure in respiration and photosynthesis. Other than oxygen, productivity also includes carbon dioxide.
4. 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?
Putting a sample of pond water and algae/freshwater plants in the light enable us to measure gross productivity because it enables us to measure oxygen after photosynthesis.
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 O2 after respiration
c. How does subtracting the two enable us to indirectly measure net productivity?
Subtracting both respiration and photosynthesis, it will enable us to measure the amount of O2 left.
5. What are the three ways that primary productivity can be measured? Highlight the way will be used in this lab?.
a. It enables us to measure gross productivity because it is photosynthesizing, which create oxygen. We can measure the oxygen after photosynthesis
b. It enables us to measure respiration by the oxygen consumption
c. By subtracting respiration from photosynthesis, it allows us to measure the remaining amount of oxygen available.
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?
When the temperature in the water decreases, then the amount of dissolved oxygen will increase in the water.
7. Explain why this relationship exists.
Warmer water has molecules that move faster, means the water can't hold any longer
8. So, now explain why the fish in the aquarium (on the LabBench Web site) above the radiator died?
The aquarium's water temperature got warmer, losing its ability to hold oxygen, killing the fish
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?
The amount of light available for photosynthesis drops off sharply with increasing depth in an aquatic environment
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?
Plant is releasing O2. It signifies photosynthesis.
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 the plants this signifies respiration
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 oxygen diffusing into freshwater plants. It signifies the process of photosynthesis not working in the dark.
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.
Calculating respiratory rate is done best when the patient is not aware you are watching them breathe, as they tend to change the rate of respiration when they become self-conscious. Respiration is counted as part of vital signs --temperature, blood pressure, pulse and respiration - and are usually taken right after pulse while the caregiver is still holding the patient's wrist.
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.
This calculation works because the gross productivity is the total amount of productivity done in this process therefore if you gain or lost oxygen, it is still productivity so you will have to add those two together to get the total amount of productivity
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.
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.10 mg oxygen gained 5 mg oxygen lost 15 mg oxygen as += from photosynthesis to respiration gross productivity
This calculation works because net productivity is the remaining amount of oxygen after photosynthesis and to find that, the initial amount of dissolved oxygen needs to get subtracted from the amount of dissolved oxygen that have gone through photosynthesi
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 expect the dissolved oxygen level form a stream entering a lake to be more than the dissolved oxygen 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.
I would expect DO levels in water at 7am to be higher than at 5pm., because it is cold in the morning, which will affect the temperature of the water to be colder. At 5pm, the water could have gone through the intense heat of the afternoon, causing the water to be warm, therefore making the water to hold less oxygen
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 algal blooms and eutrophication in lakes.
a. These nutrients promote plant and algal growth because most of these nutrients are found in unusable forms and must be changed into organic forms that can be used by the plants
b. An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system
c. In lakes, algal blooms will starve the animals below of oxygen and the vial nutrients that they may need in a process called eutrophication
d. Eutrophication is caused by an algal bloom, where it induces hypoxia on a body of water, which means that it reduces the oxygen levels in the water
21. At what depth—shallow or deep—will there be more primary productivity in a pond or a lake? Explain.
Shallow water will have more primary productivity, because there is plenty of sunlight in shallow water, and in deep water, there will be less light for organisms to go through photosynthesis
22. In an experiment, why do we use the mean of class data to make conclusions rather than individual student group data?
We use the mean of class data to make conclusions because it is less likely that there will have been an error in the experiment, and if you had done it individually, there would have been no way to tell if there was a mistake
23. AP exam FRQ (2008). Consumers in aquatic ecosystems depend on producers for nutrition.
a. Explain the difference between gross and net primary productivity.
Gross productivity is amount of oxygen use for photosynthesis. Net productivity is amount of oxygen used in respiration and released in photosynthesis
b. Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period
To determine the net productivity in a freshwater pond over a 24-hour period, first record the initial amount of oxygen in the pond, then after 24-hours, record the amount of oxygen. By subtracting the initial amount of oxygen from the final amount of oxygen,then the net productivity would be found. To determine the gross amount of productivity, you need to find the amount of carbon used over the 24-hour period and the amount of oxygen that got produce in that time period, then add those numbers together
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.
The data presented by this graph shows that the lower the depth of the water, the less primary production is occurring. When the water in the pond was around 25 meters, the primary productivity rate stayed constant. When the depth of the water reached around30 and up, there was no primary productivity
Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at different depths of the pond
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.
The relationship of primary productivity and depth would be that, lower depth will have at least no increase or decrease of productivity. Depths of 0 meters to 20 meters will have an even higher rate of productivity. Depths at 25 and lower will have a slight increase of primary productivity or have no change. In summer, sun is higher, which shines more light into ponds, lakes, oceans, etc. With more light shining, there is more of a chance for sunlight to get deeper into ocean, than in Spring, because sun in spring isn't at it's highest point, therefore having less of a chance for sunlight to get deeper into waters
Web address: 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: Warm
b. Light & Photosynthesis: Bright
c. Decomposition & Respiration: As organic material decays, microbial processes consume oxygen.
d. Mixing & Turbulence: As organic material decays, microbial processes consume oxygen
e. Salinity :When the ocean is saltier, the oxygen is less stored in the ocean
2. Productivity: Define each of these terms in your own words.
a. Primary productivity: A term used to describe the rate at which plants and other photosynthetic organisms produce organic compounds in an ecosystem
b. Gross productivity: plant's organic production of compounds in the ecosystem
c. Net productivity: The remaining of the organic compounds of a plant.
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 is the easiest thing to measure in respiration and photosynthesis. Other than oxygen, productivity also includes carbon dioxide.
4. 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?
Putting a sample of pond water and algae/freshwater plants in the light enable us to measure gross productivity because it enables us to measure oxygen after photosynthesis.
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 O2 after respiration
c. How does subtracting the two enable us to indirectly measure net productivity?
Subtracting both respiration and photosynthesis, it will enable us to measure the amount of O2 left.
5. What are the three ways that primary productivity can be measured? Highlight the way will be used in this lab?.
a. It enables us to measure gross productivity because it is photosynthesizing, which create oxygen. We can measure the oxygen after photosynthesis
b. It enables us to measure respiration by the oxygen consumption
c. By subtracting respiration from photosynthesis, it allows us to measure the remaining amount of oxygen available.
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?
When the temperature in the water decreases, then the amount of dissolved oxygen will increase in the water.
7. Explain why this relationship exists.
Warmer water has molecules that move faster, means the water can't hold any longer
8. So, now explain why the fish in the aquarium (on the LabBench Web site) above the radiator died?
The aquarium's water temperature got warmer, losing its ability to hold oxygen, killing the fish
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?
The amount of light available for photosynthesis drops off sharply with increasing depth in an aquatic environment
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?
Plant is releasing O2. It signifies photosynthesis.
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 the plants this signifies respiration
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 oxygen diffusing into freshwater plants. It signifies the process of photosynthesis not working in the dark.
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.
Calculating respiratory rate is done best when the patient is not aware you are watching them breathe, as they tend to change the rate of respiration when they become self-conscious. Respiration is counted as part of vital signs --temperature, blood pressure, pulse and respiration - and are usually taken right after pulse while the caregiver is still holding the patient's wrist.
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.
This calculation works because the gross productivity is the total amount of productivity done in this process therefore if you gain or lost oxygen, it is still productivity so you will have to add those two together to get the total amount of productivity
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.
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.10 mg oxygen gained 5 mg oxygen lost 15 mg oxygen as += from photosynthesis to respiration gross productivity
This calculation works because net productivity is the remaining amount of oxygen after photosynthesis and to find that, the initial amount of dissolved oxygen needs to get subtracted from the amount of dissolved oxygen that have gone through photosynthesi
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 expect the dissolved oxygen level form a stream entering a lake to be more than the dissolved oxygen 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.
I would expect DO levels in water at 7am to be higher than at 5pm., because it is cold in the morning, which will affect the temperature of the water to be colder. At 5pm, the water could have gone through the intense heat of the afternoon, causing the water to be warm, therefore making the water to hold less oxygen
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 algal blooms and eutrophication in lakes.
a. These nutrients promote plant and algal growth because most of these nutrients are found in unusable forms and must be changed into organic forms that can be used by the plants
b. An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system
c. In lakes, algal blooms will starve the animals below of oxygen and the vial nutrients that they may need in a process called eutrophication
d. Eutrophication is caused by an algal bloom, where it induces hypoxia on a body of water, which means that it reduces the oxygen levels in the water
21. At what depth—shallow or deep—will there be more primary productivity in a pond or a lake? Explain.
Shallow water will have more primary productivity, because there is plenty of sunlight in shallow water, and in deep water, there will be less light for organisms to go through photosynthesis
22. In an experiment, why do we use the mean of class data to make conclusions rather than individual student group data?
We use the mean of class data to make conclusions because it is less likely that there will have been an error in the experiment, and if you had done it individually, there would have been no way to tell if there was a mistake
23. AP exam FRQ (2008). Consumers in aquatic ecosystems depend on producers for nutrition.
a. Explain the difference between gross and net primary productivity.
Gross productivity is amount of oxygen use for photosynthesis. Net productivity is amount of oxygen used in respiration and released in photosynthesis
b. Describe a method to determine net and gross primary productivity in a freshwater pond over a 24-hour period
To determine the net productivity in a freshwater pond over a 24-hour period, first record the initial amount of oxygen in the pond, then after 24-hours, record the amount of oxygen. By subtracting the initial amount of oxygen from the final amount of oxygen,then the net productivity would be found. To determine the gross amount of productivity, you need to find the amount of carbon used over the 24-hour period and the amount of oxygen that got produce in that time period, then add those numbers together
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.
The data presented by this graph shows that the lower the depth of the water, the less primary production is occurring. When the water in the pond was around 25 meters, the primary productivity rate stayed constant. When the depth of the water reached around30 and up, there was no primary productivity
Explain the data presented by the graph, including a description of the relative rates of metabolic processes occurring at different depths of the pond
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.
The relationship of primary productivity and depth would be that, lower depth will have at least no increase or decrease of productivity. Depths of 0 meters to 20 meters will have an even higher rate of productivity. Depths at 25 and lower will have a slight increase of primary productivity or have no change. In summer, sun is higher, which shines more light into ponds, lakes, oceans, etc. With more light shining, there is more of a chance for sunlight to get deeper into ocean, than in Spring, because sun in spring isn't at it's highest point, therefore having less of a chance for sunlight to get deeper into waters