Diagnostic question clusters: Differences in discourse in physical and life sciences can be confusing for ecology students

Background/Question/Methods

We sought to understand why students have a difficult time understanding the flow of matter and energy through ecological systems, as evidenced by their poor performance on Diagnostic Question Clusters. Students who take our ecology courses typically take introductory biology, ecology, chemistry and physics courses during their first two years of college. To explore whether the various and sometimes conflicting discourse about and explanations of matter and energy in these STEM subjects may contribute to confusion in ecology learners, we synthesized the research literature about student understanding of matter and energy, analyzed textbook treatments of matter and energy, and conducted interviews of biology, ecology, chemistry, and physics faculty.

Results/Conclusions

We found both similarities and differences regarding contexts and discourse practices among the four disciplines with respect to matter and energy. All the disciplines apply the laws of thermodynamics to constrain ideas about what is possible and not possible, but whether laws of thermodynamics are an explicit part of the course varies among disciplines. We found that delineation of system boundaries differs among disciplines. For example, in chemistry class, a student may implicitly be required to draw boundaries around a molecular reaction, while in biology, the boundary might be the body of an organism, and in physics the boundary might be the entire universe. Boundary delineation is important because it cues students to think about how far to trace matter and energy.  For example, if students look only at what is occurring within the body of an organism, they will fail to trace the energy that leaves the body as heat. We found that physical science faculty focus more on following movement of matter and energy, while life science faculty focus more on the processes (e.g. cellular respiration) that transform matter and energy. Finally, we found that many science textbooks are not organized in a manner that parallels or facilitates the teaching about the flow of matter and energy as a core concept.