written or graphic representation appeared to support each other, opening up new paths of inquiry.

Students noticed similarities and differences among graphs and wondered whether plant growth was similar to animal growth and whether the growth of yeast and bacteria on a Petri dish was similar to that of a single plant. Students studying the growth of such organisms as plants, tobacco hornworms, and populations of bacteria noted that when they graphed changes in heights over a life span, all the organisms studied produced an S-shaped curve on the graph. However, making this connection required a prior understanding of a Cartesian coordinate system. In this case and in others, explanatory models and data models worked together to further conceptual development. At the same time, growing understanding of concepts led to increased sophistication and diversity of representational resources.

Current instruction often underestimates the difficulty of connecting representations with reasoning about the scientific phenomena they represent. Students need support in both interpreting and creating data representations that carry meaning. Students learn to use representations that are progressively more symbolic and mathematically powerful. Teachers need to encourage this process over multiple grades.

Let’s take a closer look at how children develop scientific representations. In the following case, also taken from the work of Lehrer and Schauble, we examine a group of fifth graders working on an investigation of plant growth. They are challenged to develop representations of their data in order to reach particular goals in communicating.

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