Monday, August 3, 2009

PS 11-99: Using DQCs and active learning strategies to assess ecology students’ alternative conceptions about carbon cycling in ecosystems

Heather P. Griscom, James Madison University, April C. Maskiewicz, Point Loma Nazarene University, and Nicole T. Welch, Mississippi University for Women.


Diagnostic Question Clusters (DQC’s) are sets of questions that determine students’ common misunderstandings, and give instructors a formative tool to assess students’ progress and modify instruction.  Andy Anderson and colleagues at Michigan State University developed Biology DQCs and shared them with invited participants in the NSF-supported, 2008 ESA workshop, “Using DQCs to Improve Introductory Biology Teaching.”  As participants in this workshop, we used the DQC pre- and post-tests in combination with active learning techniques (e.g., informal discussion of conceptual questions) in our Fall 2008 ecology courses to assess students’ understanding of, and  alternative conceptions concerning, the transfer of matter and energy in ecosystems. Two courses, Ecology and Evolution (N=60) and General Ecology (N=22) were composed of ³50% biology majors. The other course, Ecology and Conservation (N=42), was composed of 100% non-science majors. While the students taking Ecology and Evolution and Ecology and Conservation were a mix of freshman to seniors, General Ecology consisted entirely of students holding junior and senior rank.  


The findings were similar at all three universities. On the pre-tests for all questions combined, only 8-12% of the students from the majors courses answered at the highest standard set in the response coding strategy, and 2% from the non-majors. On the post tests for all questions combined, 20-36% of majors and 29% of non-majors responded at the highest level. Student understanding of carbon cycling improved, following active-learning instruction, yet some alternative conceptions remained. When asked to trace carbon after decomposition, <4% of students did so correctly on the pre-test, but 62% made the appropriate connections on the post-test.  Students could, for the most part, trace carbon atoms but not the change in mass during decomposition.  Our findings suggest that active learning instruction improves some students’ alternative conceptions about carbon cycling. Using DQC’s to assess student learning has focused our attention on areas needing improvement in our introductory biology and ecology curricula.  This experience also made us think more critically about our teaching methods.