Developing a learning progression in physiology to characterize how students reason about ion movement
Authors: Wenderoth Mary Pat , Scott Emily , Jackson Mallory , Cerchiara Jack , Moon Sungmin , McFarland Jenny , Doherty Jennifer 
Published: April 2020

To gain expertise in a field is to recognize, understand, and effectively use underlying disciplinary principles. Too often students rely on rote memorization to solve problems rather than apply the appropriate principles of physics that governs biological phenomena, that is, use principle‐based reasoning. Student who rely on memorization can students list the steps of generating an action potential or stomatal opening but cannot reason to a correct prediction when changes are introduced in the system, e.g. when a toxin is applied. A learning progression can help us understand how students’ use of key principles are developed, refined and strengthened over a curriculum. Our goal is to develop a learning progression to describe how students reason about the fundamental physiological principle of flux (movement of a substance is directly proportional to the size of the gradient and inversely proportional to the resistance) to explain ion movement.To develop our learning progression, we used interviews and short‐answer questions to solicit explanations and predictions in six contexts: plant tropism, plant transport, neuromuscular, renal, cardiovascular, and respiratory physiology. We interviewed 90 students and collected short‐answers from over 4,000 students ranging from freshman to seniors at both R1s and Community Colleges. We used a constant comparative approach to uncover emerging patterns of reasoning.We propose the following learning progression: Lowest level, L1: Students provide explanations that tell stories in a non‐principled or non‐mechanistic way that often contain teleological, “these are the steps” or “these things move like this naturally” ideas. L2: Students use limited mechanistic reasoning. They attempt to explain the “why” or “how” by using relevant course content, often accurately, in a limited way. For example, they use “high to low concentration” or “opposites attract” reasoning where appropriate. L3: Students use emergent principle‐based reasoning. In their explanations, students independently address ideas about chemical and electrical gradients, resistance, and ion species, or they make errors when integrating the components. L4: Students use principle‐based reasoning with incomplete consideration of the relationships among interacting components. They construct mechanistic causal explanations that accurately integrate some ideas about gradients, resistance, and multiple ions. Upper level, L5: Students use principle‐based reasoning with full consideration of the relationships among interacting components. They construct mechanistic causal explanations that cohesively integrate ideas about gradients, resistance, and multiple ions. Students reconcile the impact of opposing forces (e.g., electrochemical gradients) or opposing ion fluxes (e.g., Na+ and K+) by attending to key quantitative values (e.g., equilibrium potential).This learning progression will afford faculty insight into how students’ principle‐based reasoning develops in the context of ion movement. This insight can inform their physiology course design to better support students’ learning.Support or Funding InformationNSF DUE 1661263