Assessing and enhancing student understanding of carbon cycling in organisms

Scaffolding students’ understanding of how carbon is used to make energy available to organisms, the biological processes involved, and the effects those processes have on systems at many scales (e.g. cells, organisms, the biosphere), is important to helping them make informed decisions as citizens — from personal health to public policy. This research investigates two laboratory activities designed to enhance student understanding of carbon transformation in plants. The undergraduate students participating in this study were enrolled in the Introductory Biology course at the University of Maine in fall 2011. Student learning was compared among three laboratory sections using two sets of pre-post surveys containing diagnostic question clusters (DQCs). Students in the comparison lab section (Class 1) followed the standard inquiry- based laboratory procedures for the Cell Structure and Photosynthesis Labs. Students in the two other lab sections did the standard activity plus one or both of two additional activities designed to confront common misconceptions. The second group of students used a pH indicator, bromothymol blue (BTB) for visual evidence that an Elodea plant produces CO2 through cellular respiration. The third group of students did the BTB experiment and observed and reasoned about the feeding behavior of a photosynthetic sea slug (Elysia chlorotica). Students who engaged in supplemented instruction had the greatest learning gains on pre-post questions about the movement of carbon and energy through plants via photosynthesis, biosynthesis and cellular respiration. Students who experimented with BTB and Elodea (Class 2 and Class 3) were also better than Class 1 at the end of the semester, in terms of applying their understanding to reason about the loss of mass in plants, whether or not they observed the sea slug. Results suggest that students’ understanding of carbon and energy flow through plants via photosynthesis and cellular respiration can be enhanced through activities involving BTB with Elodea and a photosynthetic sea slug