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Teaching Tips
by Larry Flammer

Looking for ways to bring greater impact to your lessons? Move out from the constraints of your projection screen. Try building big classroom models. The following examples grew out of my efforts to make my classroom very different from any other classroom, a place where weird things happen, a place where kids look forward to coming every day.

Classroom as a Cell: Every year, my high school biology classroom "became" a cell. A few big models of various organelles (made by former students) were hung from the ceiling - using thead or string. Current students were encouraged to fabricate their own versions of organelles (based on latest images, and using different media, e.g., papier maché, styrofoam, etc.) to add to "our cell." They get better and better every year. For additional precision (along with practice for scaling), require organelles to be within proper scale to the room (as the cell).

When students walk into your room, they are always walking into a living cell! Awesome! As topics referenced particular organelles during the year, we could just point to the modeled examples hanging from the ceiling. Lots of different media were used revealing the creative talents of students. Models earned a little extra credit (some got credit as projects for art class as well). Model makers were expected to share the particular functions of "their" models, including the pointing out of how the structures reflected those functions. The walls of the room represented the cell wall (therefore, students realized "our" cell was a plant cell). A student draped clear plastic sheeting on one wall to represent a portion of the cell (plasma) membrane (low-tech project!). Another student built a model of an enlarged view of that membrane, using Styrofoam balls and pipe cleaners for the phospholipid bilayer, and various other materials for embedded protein channels and various surface proteins. Whenever students walked into "our cell," they could "breathe easier" (due to all that fresh oxygen being generated by chrloroplasts). If a student looked tired (often 1st period, or after lunch), I"d hand that person a model mitochrondrion with the command "You need more ATP!" All is fun and informative, always there and accessible throughout the year.

Classroom DNA Model: I worked with a team of students who made a giant DNA model (eventually hung from the ceiling) with a nucleotide sequence that would actually translate into the name of our school (students were challenged to figure out what the amino acid sequence was by looking at the DNA sequence.) Go to: Scroll down to the Extensions and Variations section to the Big DNA Model item for the templates and directions.

Classroom Time Machine: This is detailed on the ENSI site at: This was always a hit every year. Be sure to scroll to the end of the lesson to get the PDF files of time scales and other items for the "trip." And check out the many links under "Extensions and Variations" and "Other Resources." Lot's of good stuff here.

Classroom Cladogram: Students prepare the components for building a Colossal Classroom Cladogram of vertebrate evolution, then put it together along a wall of the classroom, showing the gradual, mosaic accumulation of the traits which we, as humans, possess. A major purpose of this is to dramatize the evidence that we (and in fact all living things) didn't suddenly pop into existence, but clearly evolved as an accumulation of traits over vast periods of time. A follow-up discussion helps focus on these concepts. Get this lesson at

Deep Ignorance: A dramatic introduction to science for the first day of school, designed to give an overview of the course in a memorable and novel way, a way that would set the tone for the year, and also leave the clear impression that there's so much mystery, so much about the natural world that we still don't know. It deflates the popular illusion that "science knows it all," and lets students realize that there's still a lot to learn, and they can be a part of the search it if they are really curious about the world. It uses a totally darkened room as a metaphor for Deep Ignorance. See it at:

Classroom EM Spectrum: All along one side of my classroom was a row of windows with long dark darkening curtains above a counter. As part of my demo of why plants are green, I would close the curtains and turn off the lights, and tell the class that the curtain was the electromagnetic spectrum. I would demonstrate how the wavelengths at one end were very short and they ranged all the way down to verrrry loooong by taking teeny tiny quick steps near the front end of the curtain, then, moving alonside the curtain toward the low frequency end by gradually taking longer and longer steps, finally just saying that my steps would have to be several miles, and they don't stretch that far! For a good diagram, try a Google search-images. I like this one;

I would then show them examples of the different wavelengths, starting with that little break in the curtain (middle of the room) that let in a bit of visible light. I would then switch to a demo setup of a narrow slit slide in a slide projector (can you still get those?) projecting a beam of light through a glass prism, putting a rainbow on the wall or screen, showing how white light is actually composed of a range of wavelengths that we see as different colors, blending gradually from one to the other (see Chlorophyll below*)

Back to the curtain, just to the left of the visible light chink in the curtain, I would bring out an infra-red lamp and point it at students so the nearby ones could feel the heat, the infrared rays. Then I would shift to the left a bit and start up my microwave oven. A little more to the left, and I turn on a little TV set (UHF/VHF); next, I turn on a radio (preferably with a rock music station on), then I tune it to static at the lower end of the dial.

I shift back to the visible crack in the curtain, move to the right, and bring out a UV lamp, directing it to materials (minerals, shirts, teeth, etc.) that fluoresce in UV. A little more to the right and I bring out some X-ray photos (get some from your doctor or hospital), pointing out that these are NOT X-rays, they're actually film exposed to X-rays passing through someone's body (or hand, etc.). More to the right, and I turn up my geiger counter that is picking up gamma rays from a radioactive sample. Again, be sure students know that most of the demos are of instruments or materials that are sensitive to a particular wavelength of EM energy that we can't detect with our own senses, and translates that energy into something we can see or hear.

I had set up all the equipment and other materials before class, and pulled each out from behind the curtain as I talked about it.

* CHLOROPHYLL - SELECTIVE ABSORPTION: Something to show afterwards, or at a later time in connection with the specific energy used by chlorophyll, use a thin flat-sided battery jar (or other flatt-sided bottle) filled with chlorophyll extract (or even green food-colored water), moved into the projected path of light passing through the prism, blocks out just the non-green parts of the spectrum, allowing only the green light to come through to be seen on the screen. Vividly shows that green leaves absorb primarily the non-green parts of the spectrum - and don't absorb (or use) the green part. You can place the jar of green water in either the white light beam before the prism, or in the spectrum beam coming out of the spectrum - same result on screen.

By the way, don't fall for the "catchy" idea often perpetrated by some middle school, high school, and even some college science teachers. They may say something like "A green leaf isn't green, it's every color except green [supposedly because it does absorb the colors other than green]. But that's not right. Something IS the color we call it because it reflects that color to our eyes (and absorbs the other colors). But it's still tht color we call it, by definition. There's nothing wrong with the REASON it's that color (i.e., it absorbs the other colors), but it's still that color we recognize it by. You can be tactful about it. Just ask the student who brings this out "What color do you see here (holding up a red ball, for example)?" "Red" is the answer, and you say "Right. Why is it red?" And the student should say "Because it reflects only red light to my eyes (while absorbing or subrracting the other colors in the white light that are falling upon it)." "But is it still red?" The answer has to be "yes."