A Flipped Inquiry Approach to Teaching Natural Selection
Biology Teacher, Friends Seminary
New York City, NY
Understanding natural selection can be a challenge. Even after direct instruction, students typically resort to thinking about evolution in a Lamarckian fashion. For instance, students might think giraffes have long necks because, at some point, their predecessors needed them. Notwithstanding the current developments in epigenetics, science teachers can have a difficult time getting students to internalize Darwinian natural selection.
So far, I have had success marrying direct instruction through flipped videos with inquiry processes to help students understand the concept. The template below shows how you can teach natural selection during each phase of the flipped learning cycle.
After a poll, discussion, and lab about antibiotic resistance, the learning cycle unit continues with an exploration: The Chips Are Down lab. In this lab, which is designed to simulate natural selection, students experience how populations change and generate a wealth of data for analysis (Fig. 1).
Students play the role of predators and exert a selection pressure on a population of butterflies (made of different colored construction paper).
Place the prey on a multi-colored cloth background (Fig. 2)—some of the butterflies are camouflaged on the background while others are easily spotted. The student predators take turns eating the prey by picking up the first butterfly they see. After the predators eat a certain number of prey, pause the game to allow the prey to reproduce. Rounds of predation are followed by recovery of prey. After a few rounds, butterflies of a certain color will decrease in number while others increase (Fig. 1). Students witness natural selection in action before receiving any direct instruction.
Figure 2 A multi-colored cloth background.
At the end of the exploration, I ask students to extrapolate from the experience how populations change in general, and which characteristics and occurrences cause changes. Students will eventually return to these hypotheses after completing future steps in the learning cycle.
Direct instruction via video
After an initial hypothesis, students take notes from a video outlining Darwin's theory of evolution by natural selection. The video walks them through a different example than they experienced in the exploration so that they can see the connection between the explanation and the lab.
Using the principles of natural selection learned through the video and experienced in the exploration, students complete a problem set to practice generating hypotheses about adaptations of different populations.
I then assign differentiated case studies based on level of difficulty. For example, advanced students may have to analyze contradictory and incomplete data in order to hypothesize why variations in skin color evolved among humans. Struggling students analyze straightforward data in order to hypothesize why some variants of clover have stripes and produce cyanide in some environments but not in others. These case studies, as well as many others related to biology, can be found on the National Center for Case Study Teaching in Science Web site.
After students apply their understanding of natural selection to different scenarios through the problem set and case studies, they revise their initial hypothesis from the exploration about how populations, in general, evolve.