It was a pretty good lecture, as lectures go: brief and to the point, with interesting subject matter– the red blood cell! All other cells in the body depend on it to bring that life-giving substance, oxygen. It’s tough and stream-lined to perform its function–zipping through the blood vessels with its payload, bumping into the vessel walls and other blood cells, stacking into rouleaux which reduce wear and tear. Early on it loses its nucleus and organelles, including mitochondria, so it can transport oxygen with maximum efficiency, traveling by the bulk flow of the blood. I described its width–8 microns–and the fact that it can fold to fit through capillaries that are only 4 microns in diameter. A lovely little cell, admirable in every way!
And the next day the class remembered nothing! I could almost believe we were viewing each other from alternate universes, with no sound and no meaning bridging the gap in between. Over the summer I thought about it a lot, and finally I went shopping. In a pet store I found a flexible rubber frisbee. The fabric store yielded some stretchy red cotton knit and some batting to pad the edges. Then I went home and sewed a red blood cell, a handsome bi-concave disc, flexible yet strong.
In the new school year the day finally arrived when the lesson included blood cells. This time I tossed the disc to a kid in the middle of the room, asking “What is this?” They passed it around, looked at it, and came up with the answer. “Why do you think so?” “What characteristics do you notice?” “How can this 8-micron-wide red blood cell fit through capillaries only 4 microns in diameter?” “What could be the benefit of having no mitochondria?” At this point I added five minutes worth of further information. The next class meeting, the students could tell me a lot about red blood cells, without even checking their notes. Over time that one red blood cell grew to a collection of four, with black and white buttons to represent blood type antigens, plus an appropriately shaped sickle cell.
My conclusion: an object to hold in the hand, to observe, to bend, and even toss around the room, made quite a positive difference in kids’ receptiveness and retention! Probably any teacher reading this has already reached this conclusion for her/himself, and I knew this too, even before the red blood cell epiphany. However, after that I devised even more biology models, and I used them in a more determined and systematic way. Using them in an introductory lecture, then having students explain key concepts using them, and finally, bringing them out for review prior to tests–this is a powerful strategy to enhance student understanding and recall.
So when and how could a teacher use manipulatives?
- Introduce a topic: Bring out your biology models to lead into a lecture.
Question the students: What do you observe? What do you suppose it represents? What is its function? Comment on the surface area-to-volume ratio– is surface area increased by the way the object is shaped? How would that affect its function? How might it interact with what you studied before?
- In your lecture: Manipulate the biology model yourself as you discuss it.
- Pose a mystery: Hand out the model and have students examine it to find an answer. Ex: How does this red blood cell, 8 microns in diameter, pass through a capillary that’s only 4 microns wide?
- Have students use the object to explain its function to the class.
- For a powerful review: Put your biology models out in stations with question cards for the students to use, answering together as they move around the room.
- Comply with NGSS: NGSS calls for use of models. When there isn’t time for students to create their own, then bring out biology models you have made or purchased, and watch your students get engaged.