The Natural Selection unit described on this site was developed for use with 11th and 12th grade students. If implemented as described here it will require seven to nine weeks of daily 45 minute instructional periods. The main focus of this unit is the development, use, and extension of the natural selection model.
The materials for the Natural Selection unit are organized into four sections:
Nature of Scientific Arguments
Within each of these sections there are two or more instructional materials related to the main learning outcomes of that section. Our unit begins with an examination of the structure of scientific arguments. This is followed by an extended comparison of three historic models-those of Paley, Lamarck, and Darwin that were developed to account for the diversity of the earth's species and/or the adaptations possessed by organisms. As a result of this comparison, students understand that the Darwinian model is a foundation of modern evolutionary biology. From here they go on to develop an understanding of the model's components and then use it to explain realistic data. Finally, our unit concludes with two case studies that require students to extend their understanding of the natural selection model in response to data that seems to be anomalous. The case studies used in this unit are collections of information about the natural history of a particular organism. Photographs, habitat and predator information, mating behavior and success, and phylogenetic data are examples of the types of information that may be included in a given case.
2. Comparing Explanatory Models (Paley, Lamarck, and Darwin)