Assignment: Rate of Photosynthesis
For many metabolic processes, like photosynthesis, it is often difficult to make meaningful observations without expensive laboratory equipment. You can look at a green plant and assume that photosynthesis is occurring, but there are few ways for you to observe the chemical reactions involved in this critical metabolic process.
On land, the gases involved in photosynthesis, carbon dioxide, and oxygen, would be exchanged by the plant without any notable indication. However, in certain aquatic plants, the situation is slightly different.
The waterweed, Elodea, undergoes photosynthesis while completely submerged in water. The oxygen that is produced by the plant is released as tiny bubbles. As a result, you can get a relative measure of the rate of photosynthesis by counting the release of gas bubbles.
In this assignment, you will investigate the relative rate of photosynthesis by quantifying the gas bubbles emitted by the waterweed, Elodea canadensis.
This assignment focuses on the graphical presentation of the data, your analysis, and a discussion to report your findings.
Complete the interactive activities embedded within the page prior to analyzing the data. These activities are designed to help you understand the scientific method and how it applies to this specific mock experiment.
Graph the data in the appropriate format. Make sure that you present the data in the format that best demonstrates the results.
Analyze the data, looking for trends and evidence that supports (or disputes) the hypothesis.
Prepare your discussion that focuses on the background science, the results, any relevant scientific concepts that can help explain the results, and further tests or new experiments to expand on what was learned in this experiment.
Methods
Although you do not have to perform this experiment, it is important to your analysis that you understand how it was executed by others. Review the procedure before continuing on with this assessment.
The test tube containing Elodea canadensis was placed 100 mm away from the light source.
The light source was turned to the on position.
A set time later, the number of bubbles released by the Elodea plant was counted for a total of 3 minutes. This number was used to calculate the average number of bubbles released per minute.
The process was repeated for each 10 mm increment between 100 mm and a final distance of 200 mm.
A total of three repeats were completed for this experiment.
Raw Data
Use the raw data to create a graph that best illustrates the overall trend in your results. You will need to calculate the bubbles per minute to complete the data collection.
Total Number of Bubbles in 3 Minutes
Total Number of Bubbles in 3 Minutes
Total Number of Bubbles in 3 Minutes
Distance (mm)
Trial #1
Trial #2
Trial #3
100mm
444
465
456
110mm
336
345
342
120mm
306
312
309
130mm
285
288
291
140mm
282
276
279
150mm
189
186
192
160mm
159
141
150
170mm
141
144
141
180mm
132
135
129
190mm
108
110
109
200mm
60
58
61
Use the data to calculate the number of bubbles per minute for each trail and the average number of bubbles per minute for each distance.
Create a table to show your calculated data.
Use the raw and calculated data to create a graph that illustrates your findings.
Formula
To calculate the number of bubbles per minute:
Number of Bubbles Per Minute=Total Number of Bubbles In 3 Minutes / 3 Minutes
To calculate the average number of bubbles per minute:
Average Number of Bubbles Per Minute=Trial #1 + Trial #2 +Trial #3 / 3
Note: For each distance, you must use the number of bubbles per minute you calculated for each trial to calculate the overall average number of bubbles per minute.
Communicating Your Results
Display your results in the appropriate tabular and graphic formats.
Analyze your results in the form of a discussion. Your discussion section should be in an essay format similar to what you would write in a lab report. Be sure to:
provide the basic science used in the lab
summarize your results, referring to table/graph and highlighting trends in data
use scientific concepts to explain results
suggest possible further tests
Note
You are not required to write a complete lab report for this assignment.
The only sections of the rubric that will be commented on are the Results and References items of the Communication category and the Application/ Discussion category.
Assessment Details
Your submission should include the following:
Your results and discussion
All in-text citations and reference lists in APA style for sources used in your final report