I sent links to The Wacky History of Cell Theory and the Amoeba Sisters video, Introduction to Cell, for kids to watch at home before class.
In class I did a short presentation on cells and cell theory, covering the same information that was in the videos but being a little more interactive. I showed drawings of both a plant and animal cell and asked the students to spot the differences – plant cells usually have one large vacuole (for storage) while animal cells may have many small ones. Students also spotted that the plant cell had chloroplasts – green organelles where photosynthesis takes place. The last major difference is that plant cells have a rigid cell wall, not just a cell membrane.
Before students could look at cells under the microscope, they labeled the parts of a microscope on a page from the Cells Interactive Notebook by Getting Nerdy with Mel and Gerdy. Students can either cut and paste the labels or write the answers in the boxes.
As students finished the worksheet and put it in their notebook, I gave them a handout on how to make a wet mount slide and how to look at it with a microscope. Then they came up to the table with the microscopes and slides and tried their hand at making a very thin slice of cork, mounting it on a slide and observing it under the microscope. The photo below was taken with my iPhone in a Carson Universal Smartphone optics adapter (there is a newer version available called the HookUpz 2.0 , though I’m thinking about trying this one by Celestron – I’ve heard its a bit more stable) and the microscope was on the lowest objective lens with a magnification of 40X.
This isn’t too different from what Robert Hooke saw and published in Micrographia: or some Physiological Descriptions of Minute bodies made by Magnifying Glasses (1665).
Students also made slides of small pieces of red onion. If they got a thin enough sample they can see individual cells as in the photo below which was taken at 100X.
To see the nucleus in the onion cells we stained one slide with methylene blue chloride. Here’s a short video showing how to stain cells on a slide.
Below is a photo of stained red onion cells at 100X. The dark oval in each cell is the nucleus. Its easiest to see in the lighter blue cells near the center of the photo.
Students learned how to use a microscope, the names of the different parts of a microscope and got to see some real cells. We had some extra time at the end of class so students looked at a few prepared slides of different plant parts, like bamboo stems, dandelion fluff and pollen.
I have a number of different microscopes but I’m really enjoying the convenience of the dual-head LED microscope that I bought this summer from Home Science Tools. The dual-head lets two kids look at once, or I can look while a student is trying to focus, or we can set up a smart phone on one eye piece and take photos while still using the other one.