Islands and the methods scientists use to study ecosystems. They generate initial hypotheses, work with a small data set, and learn about the computer system they will use in the major investigation. These first two phases of the investigation illustrate how foundational knowledge is built on in the context of an investigation. Although from the very beginning students are presented with the challenge of explaining a shift in finch population, they do not dive immediately into collecting and analyzing data. Instead, they begin by building their understanding of the specifics of the case and key principles of biological evolution.

Only after completing these initial 15 lessons do the students begin to work with the natural selection data set. Having immersed themselves in the problem and having built the theoretical knowledge and skills they will need to advance the investigation, they begin the third phase of the unit (10 classes). In this phase, students explore the data set, generate explanations for observed patterns of change in the finch populations, and critique the explanations of their classmates. In the fourth phase (six classes), student teams prepare reports, present findings, and analyze key points of agreement and disagreement across reports.

Sequencing a Unit on Natural Selection

Four Phases of Learning

Phase 1

General Staging Activities

Determine what students know, provide background knowledge, build student motivation (10 classes).

Phase 2

Background for Investigations

Gather information, generate initial hypotheses, work with small data set (five classes).

Phase 3

Software Investigations

Investigate data, generate and critique explanations for observations (10 classes).

Phase 4

Presenting and Discussing Findings

Prepare reports, present findings, analyze key points (six classes).

Carefully sequenced experiences such as these provide a road map for students, and they build just-in-time skills and knowledge that allow them to work through complex problems for which their knowledge and skill have immediate application. Students experience important elements of scientific practice as they wrestle with evidence, consider different ways of looking at phenomena and interpreting evidence, and work collectively to determine what they understand and which interpretations they find compelling. Students are not sent off on an unguided exploration of a phenomenon or question but are presented with intentionally sequenced and supported experiences framed in a sustained investigation of a central problem. This allows them to build knowledge about core aspects of biological evolution while building their skills and ability to work with data, learn with their peers, and present arguments using scientific language conventions.

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