MACH: A model for explaining molecular and cellular mechanisms

Biologists use mechanistic explanations to understand behaviors of the immense complexity of molecular and cellular systems. In undergraduate biology courses, students are expected to explain molecular and cellular mechanisms, but teaching this skill presents many challenges due to the highly abstract, intangible nature of the cellular world, the influence of everyday language, and the tendency of students to overestimate how much they can explain. Therefore, across three studies this dissertation addresses these obstacles to teach undergraduate biology students to explain molecular and cellular mechanisms. The first step was to model how biology experts explain molecular and cellular mechanisms, and to test the validity of this model by examining how experts from different biology sub-disciplines explain a mechanism they study. A literature review was performed to develop an initial model and then to determine the model\u27s validity, it was tested against explanations made during interviews by life scientists who work on molecular and cellular mechanisms. The interview data were subjected to thematic analysis and four themes were found. Explanations of molecular and cellular mechanisms include: Methods (M) used in research to inform ideas about the mechanism, Analogies (A) such as representations, models, stories, and diagrams to illustrate the explanation, Contexts (C) to emphasize the social importance and biological setting of the mechanism, and How (H) the mechanism works to address the organization of biological entities and their activities. Biologists who are experts in their sub-disciplines integrated all four components to explain cellular and molecular mechanisms. These themes formed the components of the MACH model, which extends previous models of molecular explanations and identifies components to include when teaching students how to explain biological mechanisms. Then a teaching intervention using the MACH model was implemented in an introductory undergraduate biology course to find out: How does using the MACH model change the explanations written by life science students? Why do students think learning about the MACH model is useful, if at all? Student explanations collected before and after an intervention were subjected to content and statistical analysis. Student interviews were conducted and subjected to inductive analysis. Before the intervention, about 30% of responses included all MACH components; after the teaching intervention, the frequency rose to 90%. It was found that students used the model to monitor their understanding, to communicate completely and concisely, and to reveal gaps in their explanations. Results indicated a successful implementation of the model in the classroom, as well as, some unexpected problems. For instance, many students, unlike experts, struggled to integrate the MACH components in their explanations, and instead treated each component as a separate section. Written for biology instructors, the third study presents knowledge and resources for using the MACH model in a classroom setting, and in doing so, furthers an understanding of how to make the components of explanation comprehensible to students. We discover pedagogical content knowledge (PCK) for teaching with the MACH model by asking: How does one help instructors and students understand and include the components biologists use to explain molecular and cellular mechanisms? Along with PCK, we present teaching resources including a tetrahedral model, a teaching activity, and a rubric for evaluating how well students use the MACH components when explaining molecular and cellular mechanisms. As for the result of the three studies, a new framework for researching, teaching, and communicating molecular and cellular mechanisms has been developed. Future research will test the model against a large pool of explanations by scientists who study a variety of topics such as evolution or chemistry. Additionally, future studies will replicate the intervention presented, vary factors in more carefully controlled quasi-experimental studies, or study the development of explanatory skills without any intervention in naturalistic settings. Teachers may also develop new applications for teaching with the model across additional institutes, biological topics, student populations, and educational settings. The MACH model will further the scholarship of both research and teaching