Ap Biology Lab 5 4a352l

5/7/10 AP 5 Abstract: The experiment consists of setting up a room temperature bath and a 10oC bath. Obtain 3 100-mL graduated cylinders. Fill the first with 50mL of water, drop 25 germinating peas in the cylinder, and determine the amount of water that was displaced. The second cylinder needs to be filled with 50mL of water, drop 25 dried peas into it, and determine the amount of water that was displaced. The last cylinder needs 50mL of water and 25 dried peas and add enough glass beads to attain a volume equivalent to that of the germinating peas. Now recreate all three cylinders for use in respirometer 4, 5, and 6. Obtain 6 vials with and attached stopper and pipette. Place a small piece of cotton in the bottom of each vial and moisten the cotton with 15% KOH. Place the first set of germinating peas, dry peas plus beads, and beads in vials 1, 2, and 3 respectively. Place the second set of germinating peas, dry peas plus beads, and beads in vials 4, 5, and 6 respectively. Insert all the stoppers to each vial, and place a weight on the end of each vial. Make a sling with masking tape across both baths. This is used to keep the pipette out of water during an equilibrium period of 7 minutes. Vials 1, 2, and 3 should rest in the room-temperature bath and vials 4, 5, and 6 should rest in the 10oC bath. After the equilibrium period, immerse all vials into their respective baths for 0, 5, 10, 15, and 20 minutes. Every 5 minutes for 20 minutes check the readings on the pipette of the waters position and record it in a table. To set up the baths, two tubs are needed and must be filled halfway with water. o The 10 C bath needs ice added to it continuously to keep it at the right temperature. Use a glass thermometer to measure and keep the water at a continuous temperature. Setting the rest of the experiment up requires 6 vials with an attached stopper and pipette. Use masking tape to create a sling across each bath to keep the pipette’s out of the water until equilibrium has been achieved. After about 7 minutes, remove the masking tape and immerse the pipette in the baths. The results should show that the room temperature germinating peas have the fastest rate of photosynthesis. The rate is .040 of O2 per minute while the 10oC bath yielded a rate of .001 O2 per minute. Emphasis: Data collection and analysis Objectives: Before doing this lab, you should understand: • Respiration, dormancy, and germination; • How a respirometer works in of the gas laws; • The general processes of metabolism in living organisms; and • How the rate of cellular respiration relates to the amount of activity in a cell. After doing this lab, you should be able to: • Calculate the rate of cell respiration from experimental data; • Relate gas production to respiration rate;

• •

Test the rate of cellular respiration in germinating versus nongerminated seeds in a controlled experiment; and Test the effect of temperature on the rate of cell respiration in germinating versus nongerminated seeds in a controlled experiment.

Problem: What variable increases the rate of photosynthesis? Data: Beads Alone Diff.

Germinating Peas

Time (Min)

Reading at time X

Reading at time X

Diff.

Corrected Diff.∆

Initial0

3.38

0-5

3.38

0

3.16

.19

.19

5-10

3.38

0

3.04

.31

10-15

3.38

0

2.93

15-20

3.38

0

2.57

Initial0

3.40

0-5

3.39

.01

3.20

.12

.11

5-10

3.38

.02

3.11

.21

10-15

3.38

.02

3.00

15-20

3.38

.02

2.95

Dry Peas and Beads Diff.

Corrected Diff.∆

3.46

.01

.01

.31

3.44

.03

.03

.42

.42

3.43

.04

.04

.78

.78

3.42

.05

.05

3.40

0

.01

.19

3.40

0

.02

.32

.30

3.39

.01

.01

.37

.93

3.38

.02

0

3.35

Reading at time X 3.47

3.32

3.40

1. In this activity you are investigating both the effect of germination versus nongermination and warm temperature versus cold temperature on respiration rate. Identify two hypotheses being tested in this activity. The rate of cellular respiration is higher in the germinating peas in cold than in the beads or non-germinating peas; the cooler temperature in the cold-water baths slows the process of cellular respiration in the both germinating and non-germinating peas. 2. This activity uses a number of controls. Identify at least three of the controls, and describe the purpose of each.

The constant temperature in the water baths yielding stable readings, the unvarying volume of KOH from vial to vial leading to equal amounts of carbon dioxide consumption, identical equilibration periods for all the respirometers, precise time intervals between measurements, and glass beads acting as a control for barometric pressure all served as controls. 3. Graph the results from the corrected difference column for the germinating peas and the dry peas at both room temperature and at 10 degrees C. For this graph, you will need to determine the following a.

The independent variable: Time Interval (minutes)

b.

The dependent variable: Oxygen Consumption Change

Rate of Oxygen Consumption with varying variables

Oxygen Consumption Change

4

Beads at room temperature

3.5

Beads at 10 degrees celsius

3 2.5

Germinating Peas at room temperature

2 1.5

Germinating Peas at 10 Degrees Celsius

1 0.5

Dry Peas and Beads at room temperature

0 0

5

10

15

20

Time Intervals (Minutes)

Dry Peas and Beads at 10 Degrees Celsius

4. Describe and explain the relationship between the amount of oxygen consumed and time. There was a constant, gradual incline in the amount of oxygen consumed over precise age of time 5. Condition Germinating Peas/ 10 oC

Calculations

Rate in mL O2/ minute

(3.40-3.38)

.001

20 min.

Germinating Peas/ Room Temperature

(3.35-2.57)

.039

20 min. Dry Peas/ 10 oC

(3.40-3.38)

.001

20 min. Dry Peas/ Room Temperature

(3.47-3.42)

.0025

20 min.

6. Why is it necessary to correct the readings from the peas with the readings from the beads? The beads served as a control variable, therefore, the beads experienced no change in gas volume. 7. Explain the effects of germination (versus non-germination) on pea seed respiration. The germinating seeds have a higher metabolic rate and needed more oxygen for growth and survival. The non-germinating peas, though alive, needed to consume far less oxygen for continued subsistence.

8. Graph 5.2 is a sample graph of possible data obtained for oxygen consumption by germinating peas up to about 8oC.

9. What is the purpose of KOH in this experiment? The KOH drops absorbed the carbon dioxide and caused it to precipitate at the bottom of the vial and no longer able to effect the readings. 10. Why did the vial have to be completely sealed under the stopper? The stopper at the top of the vial had to be completely

sealed so that no gas could leak out of the vial and no water would be allowed into the vial. 11. If you used the same experimental design to compare the rates of respiration of a 35g mammal at 10 oC, what results would you expect? Explain your reasoning. Respiration would be higher in the mammal since they are warm-blooded and endothermic. 12. If respiration in a small mammal were studied at both room temperature (21 o C) and 10 oC, what results would you predict? Explain your reasoning. Respiration would be higher at 21 degrees because it would be necessary for the animal to maintain a higher body temperature. The results would proliferate at 10 degrees because the mammal would be required to retain its body temperature at an even lower temperature in comparison to room temperature. 13. Explain why water moved into the respirometer pipettes. While the peas underwent cellular respiration, they consumed oxygen and released carbon dioxide, which reacted with the KOH in the vial, resulting in a decrease of gas in the pipette. The water moved into the pipette because the vial and pipette were completely submerged into the bath. 14. Design an experiment to examine the rates of cellular respiration in peas that have been germinating for 0, 24, 48, and 72 hours. What results would you expect? Why? Respirometers could be set up with respirometer 1 containing non-germinating peas, respirometer 2 holding peas that have been germinating 24 hours, 3 would contain the peas that germinated 48 hours, and 4 would hold the peas that germinated 72 hours. All the respirometers should have the KOH added to the bottom in the same manner as in lab described earlier. The respirometers should be placed in baths with the same temperature for all the respirometers. The seeds that have not begun germination would consume very little oxygen. The peas that have been germinating for 72 hours will have the greatest amount of oxygen consumption, while the other two samples will consume a medium (in comparison to respirometers 1 and 4 results) amount of oxygen. Conclusion: The highest recorded rate of O2 per minute was .039mL. I think that because the peas were germinating that they were more active already. The peas kept in the 10oC bath were much colder than room temperature so their molecules moved slower and thus there was little reaction to the variables. The peas in the 10oC bath both had a rate of .001mL O2 per minute. Discussion: In the lab, CO2 made during cellular respiration was removed by the potassium hydroxide and created potassium carbonate. It was necessary that the carbon dioxide be removed so that the change in the volume of gas in the respirometer was directly proportional to the amount of oxygen that was consumed. In the experiment, water will move toward the region of lower pressure. Oxygen was consumed and its volume was

reduced to a solid. The result was a decrease in gas volume within the tube, and a related decrease in pressure in the tube. The respirometer with just the glass beads served as a control, allowing changes in volume due to changes in atmospheric pressure and/or temperature.