CSTA Classroom Science

Start Big!

By Peter A'Hearn


"The cell is the basic unit of life"


Oh to be a first-year teacher again! I had just spent four (ok five) years getting a degree in Biology and I was pretty sure I could teach everything I knew in one year of high school Biology. In talking to many other teachers and professors, this turns out to be a pretty common first-year teacher delusion. So I don’t feel so bad.

Of course, I followed the very logical path through Biology that the textbook laid out. Start with tiny things like atoms and molecules, go to slightly less tiny things like cells, and work my way from small to big. This made sense to my newly minted Biology major brain. Once students understand atoms, they can understand cells, which will explain organisms, which will make evolution and ecosystems perfectly clear. It was a beautiful and perfectly clear tapestry.

We finished “covering” cells and moved on to genetics. To start the unit I showed a video clip culminating in a single sperm fertilizing an egg. I said,“ That’s how you began! How did you get to where you are now?” Expecting students to apply their deep understanding of cells to the problem of bodies and come up with the concept of cell division. Instead, a student confidently answered, “I got bigger!” After deeper questioning, the student declared that he was a single cell! Half the class agreed! (oh crap- this job is harder than I thought!).


So it turns out that learning about the little parts was not the best way to get students to see the big picture. What was logical to me was baffling to my students. Instead of starting with the world that they knew, I had started with abstract things with bizarre names like mitochondria, endoplasmic reticulum, and phospholipid bi-layer. Brain research tells us that learning has a physical reality - it’s neurons building new connections and strengthening existing connections. Learning sticks when it connects to what we already know. (How People Learn, 2000) Atoms and hydrogen bonds and Golgi bodies are important pieces of the puzzle of how life works. They are, however, very abstract to students and unlikely to connect to what students know about the world. Turns out, that when teaching kids, the parts don’t add up to the whole. I needed a different approach.

Did I really need to sully the beauty of my subject to meet the needs of my students? Yes! Teaching is ultimately about the students. I love science and find it deeply beautiful, but the job is not to teach myself. To get the students to understand I needed to meet them where they were and remember that I got to where I was after “many years’ of Biology courses. My own understanding developed over time.

So I decided to start big. Start with bodies and how they work. Teenagers all have bodies and are deeply interested in how they work and how they are changing. If we dig down into bodies deep enough you will get to cells and all those parts that make them work. One example that comes out of some NGSS work I did a few years ago was to start with the problem of Kidney Dialysis as a route to understanding how membranes function and why they are important at many levels of the organization. Start with the patient and what they struggle with and start digging down to find reasons.

Perhaps you have heard the word phenomenon used when talking about NGSS. This is the idea that learning should start with a question or a problem in the real world that we need to learn science to understand. This needs to be a question that is compelling to kids and builds their curiosity.


Consider this: The history of biology didn’t start with cells and atoms. It started with bodies and how they were different, diseases and disorders and how to cure them, how to grow food, animals and plants and how they all lived and fit together. As scientists dug in deep and connected their studies to chemistry and physics and Earth sciences the grand picture of small to big came into focus. The modern scientific understanding of scale (my favorite Crosscutting Concept) was hard won, but we started with what we could experience- our own human scale, our observations and our problems. Your student’s learning can take the same path. It’s a path of curiosity and discovery instead of one of abstraction and confusion. Start Big!



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