Red Onions, Elodea, or Decalcified Chicken Eggs? Selecting & Sequencing Representations for Teaching Diffusion & Osmosis

Diffusion and osmosis are important biological concepts that students often struggle to understand. These are important concepts because they are the basis for many complex biological processes, such as photosynthesis and cellular respiration. We examine a wide variety of representations used by experienced teachers to teach diffusion and osmosis. To help teachers select appropriate representations for their students, we briefly describe each representation and discuss its pros and cons. After teachers select representations, we offer recommendations for sequencing them. We recommend beginning with macroscopic-level representations that easily allow students to visualize the phenomenon, then moving to microscopic-level representations (cell-level), and finally exploring the phenomenon at the molecular level using virtual representations.