Beyond Bean Counting: A New Laboratory to Teach the Concepts of Microevolution

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Categories: GSI Online LibraryTeaching Effectiveness Award Essays

by Sonja Schwartz, Biology (Home Department: Environmental Science, Policy, and Management)

Teaching Effectiveness Award Essay, 2012

It was my third time teaching Introductory Biology (Bio 1B), and I shuddered with the approach of the evolution lab section. Every semester, the students complained about how these labs were boring and failed to connect with the concepts they were learning in lecture. The worst offender was the dreaded microevolution lab which consisted of approximately two hours of counting beans drawn out of a jar and a hand-waving explanation of how this was an illustration of natural selection in populations of mice. Students who already understood the material got the point in less than ten minutes and quickly lost interest. Students who didn’t understand were hopelessly confused by the tedious calculations. Clearly there had to be a better way to present this material, so I rolled up my sleeves and started from the beginning.

I began by going through the lecture material and identifying four main processes that the students needed to be able to understand in order to have a full grasp of the concepts of microevolution. Starting from there, I broke the lab down into four modules to be carried out sequentially over the course of session, each building on the other to illustrate each of these processes. Each module consisted of a written introduction with pre-lab questions, a short lecture explaining the concepts and the lab exercise, a group activity, and finally a discussion of the results. I researched teaching and museum websites to design activities that were intellectually and physically engaging, yet conceptually sound. For example, to illustrate the concept of how gene flow and migration between populations make them more similar, I divided the students into two groups to represent two populations of lizards (red and blue) separated by a mountain range (a taped line on the floor). They then performed a random walk and rolled dice to see if they were allowed to cross the line. We periodically stopped to examine how the composition of populations on either side of the “mountain range” changed over time. To show the effects of allowing different levels of migration, this activity was repeated several times with different probabilities for crossing between regions

My goal for this laboratory was to engage students of all learning styles by using a combination of passive and active, visual and auditory, and conceptual and applied activities. By reinforcing the material this way, I wanted to get beyond endless bean counting to more effectively teach my students key concepts of evolution. In order to assess whether I was successful and gauge their comprehension, I gave them an individual homework assignment using web-based computer simulations of populations over time. From this, I could see if they could apply the material they learned in class to understanding long-term patterns in evolution. I also closely watched the behavior of the students during class and gave an anonymous survey on which they could provide feedback on any of the activities. I posted complete instructions and materials on the course GSI website so that other GSIs could also use these refinements

The results? A huge jump in grades on the homework assignment for even my more poorly performing students, strongly positive survey feedback, and most importantly, students that were engaged and excited, rather than looking for the earliest opportunity to bolt for the door.