The Cell Lab: Working with Microscopes (Day 1 of 3)
Objective
Big Idea
Notes for the Teacher
This is a three day lesson series focusing on microscope skills and cell organelle identification and comparisons.
On Day 1, students review the different types of microscopes and why/when we use them. We then work through an online tutorial to build basic microscope skills. Standards: SL.9-10.1, RST.9-10.3
On Day 2, students practice their microscope skills using prepared slides of pond life. They then follow a simple procedure to create wet mount cheek cell slides and answer questions about cell types and organelles. Standards: SL.9-10.1, RST.9-10.3, XC-P-HS-1, XC-SF-HS-2, SP4, SP8
On Day 3, students look at onion cell slides they wet mount themselves and discuss the differences between plant and animal cells. Standards: SL.9-10.1, RST.9-10.3, XC-P-HS-1, XC-SF-HS-2, SP4, SP8
Every biology teacher does some sort of microscope introduction lab and in the past, I found that I was running around breathlessly to every station helping each individual lab pair to adjust their focus and work with their microscopes. Since I began to use the 15-20 microscope tutorial, this no longer happens. I highly recommend it the Virtual Urchin website microscope tutorial and other resources and am eager to hear your experiences using the online tutorial with your classes.
My goal here is for students to get a sense of how to use a microscope, what a cell actually looks like, and to attach basic cell and microscope vocabulary to their experience creating and viewing slides.
I extended this lab from two days to three to allow for the tutorial and for more time for discussion and comparison of the kinds of things lab pairs were doing and seeing on their individual microscopes. As an additional interest, I asked students to experiment with taking photos of their favorite cell slide field of view and send it to me to share with the class. This idea was inspired by our local public television's education webpage on the KQED website; I saw a short video clip there called The Amazing Life of Sand and thought it might be a nice to way to bring in appropriate student device use as a way to gather evidence of their work to share out as a class on Day 3. Students were highly engaged with this aspect of the activity and to make the photo session work, they had to really dig into the vocabulary of the microscope parts in order to give and act upon suggestions each of them had to enhance their photo taking abilities. I loved this unintentional positive side effect of introducing the photo angle to our straightforward lesson.
The Classroom Flow: Comparing and Contrasting Microscope Types
1. Start out by announcing that today will be the intoduction to a multi-day cell lab where students will have the chance to work with microscopes and view and create their own slides.
2. Review the cell theory (see powerpoint slide# 2) to get students oriented to today's work.
- Note: I always like to remind students that before every big shift in science thinking typically comes a technology breakthrough and that cell biology is no different--as microscopes improved, so did out ability to see, compare, and understand the organelles and processes happening inside cells.
3. Take out the two types of microscopes from the microscope cabinet: a compound light microscope and a dissecting microscope. Ask students to share out some differences they see between the two using a casual popcorn protocol.
4. Once you have gotten to the most basic differences (number of oculars, size and number of objectives, the location of the stage), you can begin to talk about the purpose for using each one. I typically describe dissecting microscopes as similar to binoculars and give examples as to when we would use them: to look at fruit fly eye color or wing shape, to see our skin/fingerprints, all macro/surface type examples and then contrast that to the compound light microscope we will be using: inside cells, inside hair protein, etc.
5. Once you have discussed the two types of light microscopes, introduce the concept of electron microscopes. Use the powerpoint slide show to demonstrate examples of what they look like (slide #5) and compare/contrast them to light microscopes specifically in these areas (slide #3-4):
Cost
Magnification
Preparation needed in order to view specimen
Reasons for choosing one type (light vs. electron) over another
Transmission vs. scanning electron microscopes
6. After you have discussed the differences and pros/cons, show students various pictures of organisms and ask them if they have been produced by a transmission or an electron microscope (slide #6, 10, 12, 16, 19).
- Note: Students love trying to figure out the type of microscope used and what the subject of the photo actually is, such as a mitochondrion, a paramecium, etc.
The Classroom Flow: Using the Online Microscope Tutorial
1. Announce that students will now be working with their lab partner to go through a microscope tutorial lesson using Stanford University's Virtual Urchin website materials.
2. Use your projection system to show the website and to indicate which icon to click on in order to access the tutorial.
3. Allow students 20 minutes to go through the tutorial with their lab partner.
4. As students work together, circulate and observe/listen for interesting questions or comments you may want to revisit together as a class at the end of the session. What students tell me is that this a good preparation activity before using the microscopes, which can be a frustrating experience if students don't feel like they understand the terminology or have been unwilling to engage in written directions. This interactive technology tutorial engages the students in such a way that since I began using it last year, I have very little to no student frustrations about how to use the microscope or questions about why they can't see their specimen on the slide once we get back to the lab.
Notes :
- I tend to hang back and let the students discover for themselves rather than immediately solve every dilemma they might have at any given moment during this 20 minute block of time. The website materials are geared for high school freshmen and sophomores and it is very rare to have students who are unable to follow the procedure and complete the tutorial.
- As I am closely observing and listening to students as they work on the tutorial, I am looking for a steady pacing. If I observe that a student is stuck on one screen for longer than it typical, I go over and ask questions like:
How are things going?
Are you finding the tutorial helpful?
What questions do you have that aren't getting answered so far?
Is it easy to use the web interface?
- Although I don't use a handout to track to student work using this tutorial primarily due to the short time frame involved and my observations that lab time is significantly more effective and productive since using the tutorial for the first time last year. My intentional observations throughout help me pinpoint any struggling students and ask more questions of them to determine if the difficulties they experience are related to the content, their reading ability, or their technology comfort level, In the future, I could see expanding this resource to include a written response form for the entire class or to use in pairs or with individual students needing additional support and directions.
The Classroom Flow: Wrapping it Up
1. For the last ten minutes of class, conduct a brief formative assessment of student knowledge of microscope vocabulary and use by asking questions while pointing to various parts of the microscope. Words to focus on: objective, diaphragm, stage, magnification, field of view, course. vs. fine adjustment
- Note: This check for understanding is very informal. I point to a part of the microscope and students popcorn out the name of it. When I see that the names are being correctly associated with the appropriate microscope component, I list them on the board. At that point I begin to point to a microscope part and describe its function and ask students for the name that goes with that function/visual reference. Each time we work with microscopes, I do a similar quick microscope check prior to the lab activity. I also include labeled microscope diagrams for students to refer to at their lab tables, along with a typed list of basic directions for using the microscope just in case students need a refresher of the basic microscope use information they explored in the online tutorial.
2. Remind students that they will be working with the microscopes and cells over the next two days to strengthen their understanding of microscopes and cells.
3. If you look at the student work sample for the microscope lab that starts tomorrow, you will see how today's activity helped to support student learning on questions 1-3 on page one that pertain to the parts of the microscope and how to use them.
And now on to Day 2!
