Graduation date: 2007Recent science education reforms have placed a large emphasis on inquiry-based teaching strategies as an effective way of improving conceptual understanding of science principles, comprehension of the nature of scientific inquiry, and development of the abilities for inquiry (NRC, 1996). To better understand the relationship between inquiry-based instruction and student learning, this study examined the nature of student reasoning about science concepts during Claims-Evidence Inquiry lessons. The Claims-Evidence approach to inquiry teaching was chosen as the context for this study, because it focuses student investigations on specific scientific concepts. It uses a deductive approach to question generation, in which scientific claims are used as springboards for student investigations (Gummer, 2002; Thompson, 2003; Briley, 2003). This study found that the Claims-Evidence Inquiry model provides a framework for encouraging student reasoning about science concepts by providing supports for the development of explanations. Students were encouraged to develop explanations and consider how science concepts related to their investigations. A number of instructional factors appeared to influence students’ development of explanations during Claims-Evidence inquiry. These included explicitly encouraging explanations, clarifying the connection between the claim and the investigation, the presentation of the claim, the nature of the claim, the development of science concepts, the design of the task, and the development of inquiry skills. Students were found to engage in discourse related to explanations during all four phases of the inquiry; forming a question or hypothesis, designing an investigation, collecting and presenting data, and analyzing results. Most of the verbal discourse related to explanations occurred when students were reasoning about hypotheses and most of the written discourse related to explanations occurred when students were reasoning about hypotheses and results. This analysis also identified three primary types of explanations utilized by students: analogical explanations, systems-based explanations, and concept-focused explanations. Analysis of the reasoning used in written explanations for results highlighted issues related to the application of the science concepts, explicit links between variables in the investigation and the science concepts, and the nature of the causal reasoning used in explaining results.