smells associated with the water. Ms. Idoni probes the students about their observations and reminds them to make entries in their journals. What important aspect of the lake do they want to investigate? What kinds of human influences are of most interest? “Pollution” is the term Ms. Idoni hears first and most consistently. She thinks it is essential to clarify the students’ understanding of pollution and in particular the possible sources of human pollution in the city lake. She asks the students to discuss in small groups what they mean by pollution for the city lake.

Over several class periods, they struggle with the issue of normal change, what counts as pollution, and possible human influences. Ms. Idoni lets the students grapple with these issues, which seem to center on one major idea: as living and non-living elements of an ecosystem interact, they change. Any study of changes in an environment, such as the city lake, must begin with an analysis of the patterns of change under normal circumstances. Students realize they have to understand the natural functions of the interactive system before tackling the more complex question of the impact of human actions, in particular, their notion of pollution. At this point Ms. Idoni realizes she already has her final assessment: she will suggest that something has polluted the lake and the students will have to apply what they have learned to this new problem. But, for the time being, she must wait and let the students pursue their questions and investigations.

After hearing the results of small group discussions, Ms. Idoni facilitates a large group review of ideas and helps students identify an overarching question for the class to pursue in the investigation. The class decides on a general question: Is city park lake polluted? If so, how have humans influenced the pollution? The class decides to approach the inquiry by first establishing a baseline of data about city lake and then determine if the lake is polluted. Students realize that many factors affect water quality. With help from Ms. Idoni, they decide



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