Supporting the development of scientific understanding when constructing an evolving explanation

We explore how students developed an integrated understanding of scientific ideas and how they applied their understandings in new situations. We examine the incremental development of 7th grade students’ scientific ideas across four iterations of a scientific explanation related to a freshwater system. We demonstrate that knowing how to make use of scientific ideas to explain phenomena needs to be learned just as developing integrated understanding of scientific ideas needs to be learned. Students participated in an open-ended, long-term project-based learning unit, constructing one explanation over time to address, “ How healthy is our stream for freshwater organisms and how do our actions on land potentially impact the water quality of the stream?” The explanation developed over several weeks as new data were collected and analyzed. Students discussed evidence by revisiting scientific ideas and including new scientific ideas. This research investigates two questions: (1) As students engage in writing a scientific explanation over time, to what extent do they develop integrated understanding of appropriate scientific ideas? and (2) When writing about new evidence, do these earlier experiences of writing explanations enable students to make use of new scientific ideas in more sophisticated ways? In other words, do earlier experiences allow students to know how to make use of their ideas in these new situations? The results indicated statistically significant effects. Through various iterations of the explanation students included richer discussion using appropriate scientific ideas. Students were also able to make better use of new knowledge in new situations.