Supporting Development of Mechanistic Reasoning Across Chemistry and Biology.

While extensive research explores the difficulties undergraduate students face when learning chemistry or biology, less is known about how students learn across disciplines, especially when constructing mechanistic explanations. This study investigates (1) how undergraduate students explain differences in protein function, focusing on their use of conceptual resources and mechanistic reasoning, and (2) how task design influences their explanations. Using three different tasks with the same underlying mechanistic explanation, we analyzed responses from students who had completed a transformed cell and molecular biology course to determine what conceptual resources they use and how they connect those resources. Our findings show that, given a task with appropriate scaffolding, half of the students constructed mechanistic explanations. We also found that students rarely integrated ideas from both biology and chemistry, but when they did, they consistently constructed mechanistic explanations. Task design significantly influenced the conceptual resources students used and the frequency of mechanistic explanations. These findings highlight the need for careful instructional and curricular design to support cross-disciplinary learning and mechanistic reasoning in STEM education.