TABLE 1.

The preliminary flux learning progression framework characterizing the patterns of reasoning students may exhibit as they work toward mastery of flux reasoning. The student exemplars are from the ion flux formative assessment question presented in Figure 4. The “/” divides a student’s answers to the first and second parts of the question. Level 5 represents the most sophisticated ideas about flux phenomena.

Level	Level descriptions	Student exemplars
5	Principle-based reasoning with full consideration of interacting components	Change the membrane potential to −100mV/The negative charge in the cell will put a greater driving force for the positively charged potassium than the concentration gradient forcing it out.
4	Emergent principle-based reasoning using individual components	Decrease the concentration gradient or make the electrical gradient more positive/the concentration gradient and electrical gradient control the motion of charged particles.
3	Students use fragments of the principle to reason	Change concentration of outside K/If the concentration of K outside the cell is larger than the concentration of K inside the cell, more K will rush into the cell.
2	Students provide storytelling explanations that are nonmechanistic	Close voltage-gated potassium channels/When the V-K+ channels are closed then we will move back toward a resting membrane potential meaning that K+ ions will move into the cell causing the mV to go from −90 mV (K+ electrical potential) to −70 mV (RMP).
1	Students provide nonmechanistic (e.g., teleological) explanations	Transport proteins/Needs help to cross membrane because it wouldn’t do it readily since it’s charged.