by James Endres, Molecular and Cell Biology
Teaching Effectiveness Award Essay, 2003
Contemporary biology is an empirical endeavor. Thus, the crucial skills to impart to science majors are the ability to critique experiments, and the ability to extend experimental reasoning to new hypotheses, new predictions, and new experiments. Upper level courses are quite rightly presented as a narrative of past experiments which have led to the current understanding in the field. Too often, though, students are allowed to accept this narrative passively, without developing these critical skills. Worse still, exam questions are often crafted to test these abilities in courses where little coherent effort has been made to develop them. I enjoyed complete freedom to structure my weekly sections for Introduction to Neurobiology (MCB 160), so I decided to use those meetings to focus on these issues. At the first meeting I commanded rapt attention by announcing the secret to getting an A in the course. “If you understand the experiments presented in lecture,” I promised, “actively understand them, enough that you can change them to make and test novel predictions, you will get an A.”
Every week, section meetings were divided into two parts. First I distributed an outline integrating the preceding week’s three lectures, and we discussed critically the key experiments that had been presented. Then I distributed a problem set with a challenging experimental scenario. These problems required that students explain “what if” results, speculate about how the results might change with different experimental parameters, and finally design further experiments to address novel hypotheses. We compared solutions the following week.
A good example deals with the embryonic development of the nervous system. Various secreted protein factors “induce” undifferentiated cells to become neurons. We discussed experiments that demonstrated how an embryonic structure called the notochord induces overlying skin cells to become spinal neurons by secreting a protein called noggin that blocks the non-neuronal fate. The aim of the problem set was to apply the experimental concepts from lecture in a completely different context:
It was hypothesized more than one hundred years ago that the embryonic eye induces the overlying skin to become the lens structure of the mature eye. (1) Propose experiments that would confirm this hypothesis.
To this day the molecular identity of the factor that signals from eye to skin remains unknown! Propose a set of experiments (2) to identify this factor in vitro and (3) to confirm its role in lens induction in vivo.
Three remarkable results of assigning these problem sets convinced me they were effective. First and most obvious, only students who truly understood an experiment were able to extend it. They couldn’t deceive me, and they couldn’t deceive themselves. Second, students’ solutions were all different, but still correct, because (as in science as actually practiced) there is always more than one way to do it. Finally, the look on a student’s face at the triumphant moment when she saw the answer — another thing that can’t be faked — was continually gratifying to witness.
Simply by virtue of its being so interactive, this approach helped me build rapport with students. Once they trusted me they told me what worked (and what didn’t) right away. Still, I relied on more structured evaluation as well. First, I staged periodic “anti-quizzes” which served both as a gauge of competence and a form of feedback: “Explain one key concept that was clarified in section today. What concept remains unclear?” After reviewing the responses as a group, I collected them to help me tailor preparation for the next weeks. Second, official course evaluation results come after the semester is over, which is too late! So after each exam I distributed anonymous evaluations in section. The students knew what worked: they demanded even more focus on experiments. Third, we noticed that exam grades climbed as the semester progressed. Finally, I was correct about how to succeed in the course. I simply knew which students were going to get A’s — and so did they — even as they were turning in their final exams. They were the ones who had mastered the problem sets.