This lab activity demonstrates the process of photosynthesis through the production of oxygen in a plant leaf. The activity calls for fresh spinach leaves, but other leaf types may be tried.The technique is a leaf disk assay. Leaf disks are created, the air is evacuated from the disks by applying pressure and the disks are added to a cup of water.They sink. Then the disks are exposed to light and sodium bicarbonate. As photosynthesis occurs the leaf rises.
Type of Material:
Reference Material. Video.
Recommended Uses:
In laboratory class. As a tutorial for students or instructors on how to use this technique effectively.
Technical Requirements:
Web Browser
Identify Major Learning Goals:
The goal of this video is to respond to student requests for help in getting this assay to work. The video demonstrates how to set up and run the leaf disk assay.
Target Student Population:
High School, lower division college
Prerequisite Knowledge or Skills:
Basic understanding of photosynthesis.
Content Quality
Rating:
Strengths:
The technique is fully and accurately explained and demostrated
The correct steps of this lab procedure are explained
The process is demonstrated in a narrated video
Some aspects of the technique modeled in this video are not commonly mentioned, such as the use of soap and stirring the disks periodically
Concerns:
No discussion of model or concepts
Video assumes you already have lab instructions and have attempted without success
Errors are made in the procedure and discounted without an explanation
There is no mention of using a heat sink to avoid a confounding variable (temperature)
No warning is given about avoiding the application of too much negative pressure to the disks
There is no discussion of how to use this assay for an actual investigation or an inquiry lab, as opposed to a simple demonstration
Potential Effectiveness as a Teaching Tool
Rating:
Strengths:
The intent of the video is clearly stated and accomplished
The video is detailed
The goal of the video is met
Will help students complete the lab
Since some aspects of the technique are easier shown than described, this is an effective format for teaching the technique
The pacing is slow and clear
There is effective use of time (the video is 4:22 but shows a much longer demonstration)
Concerns:
Lacks an explanation of what concept the lab illustrates
This lesson or demo would be improved by providing suggestions on how to effectively use this assay, not simply on how to get it to work
Ease of Use for Both Students and Faculty
Rating:
Strengths:
Video runs without difficulty and works as intended
The narration is clear and easy to understand
The images are clear
All student needs to do is click on the start arrow
The videography is good
There is closed captioning
Concerns:
Video seems to end a bit abruptly and could use more explanation at the end
The closed captioning is machine generated and is not very accurate
Other Issues and Comments:
This video was created to respond to student requests and therefore may not have ever been intended as a comprehensive explanation or tutorial on this technique. There are many other, more complete examples of this technique on YouTube.
Creative Commons:
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