Friday, February 12, 2016

Microbiology Class

This class is so awesome:

First class summary follows, courtesy of our teacher extraordinaire.  Photos from the microscope work can be found here:

What we did:

– – We opened with one of the essential questions of Biology: What is alive? I actually asked “what is alive in this room”? We decided we were alive, and there were the dogs and a plant. Someone said “the air?” and we talked about air containing oxygen and nitrogen, and yes, maybe microorganisms that we cannot see with the naked eye. When we sneeze, we release germs (bacteria and viruses) which are alive and float around in the air, waiting for their next victim.
– – I then brought out my “algae ponds”, which are three containers that I left outside to fill with rainwater and then sit in the sun for weeks until class started. There was some garden soil in the bottom to provide spores, eggs, and other dormant forms of our algae and protozoa, but other than that, I added nothing to the collected rainwater. We gave the kids hand lenses and flashlights to look at the ponds. I also had some test tubes and glass jars with water in them, and challenged the kids to try and figure out what it is about a magnifying lens that magnifies. We had some good guesses (the water, the clear glass), but then I showed them the glass jar with square and flat sides (and doesn’t magnify). I got a “the roundness of the glass!”, and so we were on the right track. More about microscopes and stereoscopes as we go on…
– – Now the compound microscope was set up, and I demonstrated how to make a wet mount slide with the algae from the pond bins. It sounds complicated, but is essentially placing a small drop of your sample on the slide, and then placing the cover slip (the small piece of glass that goes over the sample) at an angle to the drop so no air is trapped under the cover slip. Since we are trying to see live organisms under the scope, this is the classic method for keeping them motile and alive.
– – Our compound microscope is hooked up a big monitor so everyone can see the action (but we will need to come up with a system to ensure that everyone has a turn with the mechanical stage and focus knobs). And then everyone saw a paramecium moving across the screen in the middle of the algae!! So exciting! We then discovered that they can move very quickly and trying to keep up with them with the stage knobs is very difficult – they do not stay still. We then spent time looking through the slide to try and see more protists and we might have seen more paramecia (link to online pictures), a hydra (link to online pictures) and other ciliated flagellates (link to pictures).
– – There were also several stereoscopes, or dissecting scopes on the table for more wet mount observations of the algae in the bins.
– – We also learned that stereoscopes “see” in 3-D like our eyes, and are used at lower magnifications than compound scopes, which require very thin slices of tissue to be used at 400X and up. You can look at pennies or a live insect under a stereoscope, which you cannot do with a compound microscope. Wet mounts with a compound scope is cheating a little, since we are trying to use it as a stereoscope, but at a higher magnification than usual stereoscopes. Fortunately you can make a drop of water very flat (why you put the cover slip on top) so it works extremely well.

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