7.1: Instructor Guidelines

Purpose 

In this lab, students will review and use the microscope skills they acquired from the previous lab to view various prokaryotic and eukaryotic specimens. By the end of the lab session, students should be able to distinguish prokaryotic and eukaryotic cells through the observation of their cellular differences under the microscope. This lab includes student preparation of wet mounts of Oscillatoria, students' human cheek cells, onion cells, and Elodea. 

Tasks 

Students will complete the following exercises during this lab:

• View and identify the three common shapes of bacterial cells.
• Prepare a wet mount of Oscillatoria and infer cell type and characteristics based on cell structures. 
• Prepare a wet mount of their own cheek cells, onion cells, and Elodea and identify major cell structures. 
• Compare and contrast prokaryotic and eukaryotic cells and determine cell function based on cell structure. 

The lab instructor should conduct a brief review of major differences between prokaryotic and eukaryotic cells, including cell structure, organelles, and examples of each. Students may need a brief reminder of how and when to use the oil immersion lens. 

Demonstrate the preparation of a wet mount and how to properly clean or dispose of the materials after each procedure. Used toothpicks, slides, and coverslips from the cheek cell wet mount should be disposed of in a beaker (or similar container) containing alcohol or bleach. Forceps, dissecting needles, slides, and coverslips are available in the biology kits next to each student's seat (usually in the top drawer closest to the student). 

Optional: have students review proper use of the ocular micrometer by include measurements (l x w) with each of their drawings (i.e., measuring individual cells). 

Although most experiments in this course are conducted in groups. This laboratory should be completed individually in order to allow students to maximize their time working with the microscope. Encourage students to discuss potential answers to each of the lab questions with one another.