As you might have gathered, I’m a big believer in letting students develop their scientific skill set in my classroom. A big part of this involves working to provide my students with opportunities to try out that kooky, crazy, mixed-up endeavor of human experience that we call the “scientific method”. To that end, I’m always trying to find ways to have my students spend more time giving the process a shot. This week provided one such example, the subject of this post.
We are in the beginning of our metabolism unit, and this week was all about enzymes. One of the major labs that students do in AP Biology is a lab to investigate the effects of a variable on the rate of an enzyme-mediated reaction. The official College Board version of the lab (for another month or so) involves students investigating the effects of declining substrate concentration on the rate of the reaction (spoiler: the rate decreases). The official version is pretty much everything that I dislike about the “cookbook” style of laboratory experiment. Students are given a protocol for a particular assay, which is somewhat baroque in structure, and they work through a series of steps to accomplish that protocol. It takes a lot of effort on the part of the instructor to make sure that students really understand what they are doing and why they are doing it, and even then a lot of students don’t really “get” it. To conclude the process, the College Board lab manual has students fill in the blanks on a series of questions, construct some prescribed graphs and call it a day. It sucks.
There are many ways to bring more inquiry to labs. Lots of work has been done on the levels of inquiry, and lots of good people are writing about it with frequency. Often, I dwell pretty firmly in the realm of “guided inquiry” in my own labs (something that I have written about before). In a “guided inquiry” setting, the instructor gives the students a protocol and allows students to modify that protocol or apply it to a particular question of their own conception. I am a big fan of this approach, but here, at the halfway point of the year, I wanted to push my students a bit farther.
So, this year, with this lab, I decided to take a slightly different (read: vastly different) approach: I had students do everything. I told them that they were responsible for developing an experiment to test the effect of an environmental condition on the rate of an enzyme-mediated reaction. I gave them an “experimental planner” that noted a few, fundamental things (they would need to isolate an enzyme, use a reasonable protocol which generated quantitative data, and they should feel free to adapt any protocol that they found online to suit their purpose). I gave them a four days to do the necessary research before meeting with each group on Wednesday.
During our meetings on Wednesday, I discussed the experiments with each group. We determined if the experiment was feasible, what modifications might need to be made, and we established which materials they would be responsible for providing (enzyme and substrate, mostly) and which materials I would provide for them (lab equipment, pH buffers, heating and cooling apparatus, various other niche items for particular circumstances). Out of five lab groups, four were prepared enough at this point to advance. One had not done much research at all. This was discussed, expectations were reiterated, promises were made, and the benchmarks that would need to happen prior to that group being able to begin work on Thursday with the rest of the class were delineated. I imagine it was somewhat embarrassing being the only group who didn’t hit that checkpoint on time.
I reserved Thursday and Friday for running experiments. I felt that two days would be enough time. I figured that some groups would finish on Thursday (and could do other things on Friday—like begin the process of writing the lab report), some groups would make bad mistakes when running their protocol on Thursday and would need to modify or regroup to run it again on Friday, and some groups would need to do some testing and protocol modification on Thursday in order to run the lab on Friday. As it turned out, I had all three situations develop. Though, interestingly, the group that I had to talk to about preparedness was able to run their entire experiment (measuring the effect of pH on catechol oxidases in apples) on Thursday.
Moving to a structure like the one that I have described above takes a real shift on the part of the instructor (and the students). It is not something that happens over night, particularly when dealing with a population of science learners who have never been asked to work through the process in this fashion prior to walking in to your class, and it involves a lot of “different” sorts of uses of an instructor’s time. At various points during the week, I had to serve as a coach, working to get students to meet certain benchmarks at certain times, and as a collaborator, helping to offer advice on trouble-shooting of methods or explaining ways of doing certain things. I had to make sure that each group was not going to do anything in their specific circumstance that was dangerous, but I had to make equally sure that I did not prevent groups from making mistakes that they needed to make to learn the various lessons that we all learn as scientists (like “don’t use up all of your enzyme until you are sure your protocol is going to work”). I know that each group learned much more about how science works by going through the process than they ever would have if I had just told them what to do and how to do it. They certainly can tell you more about what they did and why they did it than they would if they had all done some procedure that I had given them. And they have a genuine experience that can now form the basis of a formal lab report that hopefully won’t feel like pulling teeth to write, read, or grade.
I also learned a ton about all sorts of experiments to accomplish the purpose that I gave my students that I would not have thought of if my students hadn’t brought them in to our classroom (here’s my favorite: measuring the effect of temperature on lactase activity by testing temperature-treated solutions of lactaid and milk using an electronic, “diabetes” glucose meter…incredible). This is the kind of approach that the AP curriculum is moving towards for all of its labs, and to my way of thinking it is vastly superior to the other mode. As long as you stop caring about having students accomplish a particular lab in a particular way, allowing students to demonstrate their ability to think like scientists is quite possibly the most fun you will ever have running labs for your kids.