lar teachers’ interpretations of the materials. Some of these adaptations diverged from some of the important instructional characteristics intended by the designers. Yet it is not possible to script these interactions or to embed all possible alternatives in “teacher-proof” curriculum materials (Doyle and Ponder, 1977). Instead, these approaches call for careful attention to teacher learning, perhaps through researcher-teacher partnerships (as in the early design studies) in an approach, or in more formalized professional development programs as interventions develop (Blumenfeld et al., 2000; Marx et al., 1997). Teacher learning is discussed further in Chapter 10.

Sequencing Units of Study

As discussed above, science as practice frames meaningful problems that depict complex phenomena and require that students master and coordinate a range of concepts and practices. As students begin to wrestle with these problems, teachers and instructional materials necessarily provide an important sequencing function. Students cannot do everything at once from the start. After framing a complex problem and assessing students’ entering capabilities to work on it, the teacher must adjust instruction to focus on smaller pieces of the problem at hand. While students are always working in the context of a large, complex problem, throughout the unit instruction emphasizes smaller, manageable pieces in their daily classroom experiences.

Let us consider how sequencing works by briefly examining the BGuILE middle school Struggle for Survival unit, a 6- to 7-week classroom examination of core evolutionary concepts through an investigation (Table 9-1). In this unit, “students learn about natural selection by investigating how a drought affects the animal and plant populations on a Galapagos island. Students can examine background information about the island, read through field notes, and examine quantitative data about the characteristics of the islands’ species at various times and points to look for changes in the populations” (Reiser et al., 2001, p. 275).

While from the outset this unit frames the large-scale, complex problem of explaining the impact of a drought on plant and animal populations, it unfolds over four phases, which are sequenced to gradually ratchet up the demands of the learning experiences and the sophistication of students’ reasoning about core concepts. The first phase (10 classes) sets the stage for the study by discerning students’ entering knowledge of natural selection and providing requisite background knowledge (about ecosystems and the theory of natural selection) and building student motivation. In the second phase (5 classes), students learn background information specific to the Galapagos investigation. They learn about the Galapagos Islands and the methods scientists use to study ecosystems. They generate initial hypotheses,

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