Another common approach in the research literature is to create opportunities for students to engage in other aspects of scientific activity, such as argumentation, explanation, and model building. As scientists investigate empirical regularities in the world, they attempt to explain these regularities with theories and models, and to apply those models to new phenomena. Furthermore, the scientific community reaches consensus through a process of proposing and arguing about their own and others’ ideas through talk and writing, using the particular discourse conventions of the discipline. Some instructional interventions have brought these activities into the K-8 classroom. As students conduct investigations to develop and apply explanations to natural phenomena, they develop claims, defend them with evidence, and explain them, using scientific principles.
With a focus on explanation, students attempt to produce evidence that supports a particular account or claim (McNeill et al., 2006; Sandoval, 2003; Sandoval and Reiser, 2004). An emphasis on scientific argument adds the element of convincing peers of the explanation, responding to critiques, and reaching consensus (Bell and Linn, 2000; Driver, Newton, and Osborne, 2000; Duschl and Osborne, 2002; Osborne, Erduran, and Simon, 2004). A focus on model building adds the element of representing patterns in data and formulating general models to explain candidate phenomena (Lehrer and Schauble, 2000b, 2004; Schwarz and White, 2005).
Several elements emerge as critical in these approaches to argumentation, explanation, and model building. In these approaches, units of study are framed to address a question or set of questions about the natural world. The question may arise from benchmark lessons that elicit curiosity, from observations of perplexing natural phenomena, from a problem situated in the real world that can be addressed with scientific evidence, or from questions that scientists themselves are currently struggling to answer (Blumenfeld et al., 2000; Edelson, 2001; Linn et al., 1999). For example, Linn and colleagues used a documented cases of frog mutation in particular ecosystems and an overall pattern of increased mutations nationwide to frame a middle school environmental science unit. In this case there was no definitive scientific explanation for the pattern of mutated frogs; instead, students were engaged in a genuine scientific quandary and explored several competing explanations, including two leading hypotheses in the scientific community. One leading explanation entailed a type of parasite that scientists believe can physically interfere with the natural development of frog limbs, and the other involved a pesticide which, with exposure to sunlight, may interfere with the hormonal signals that control limb development. Once questions are framed and students understand and buy into them, they conduct inves-