One 40-55 min. Two-sided handout of the lesson, giving background information, purpose, materials, procedure and discussion questions. Have materials in trays available for convenient student access, with one set for every two students, including hand lenses or access to microscopes. Have copies of the lesson and worksheet pages for all students. Distribute copies of the lesson and worksheet pages to all students.
Students are to read Introduction and answer the Check Questions.
Students continue with the lesson, working in pairs, getting the materials and following the procedure provided. All observations are to be recorded on the worksheet. Students are to complete their histogram using these class data. If necessary, this part can be completed as homework, to be collected the next class day. Observe and record active participation by all students 2.