Biology

Microscopic Examination of Cells

Objectives

• To learn how to use the microscope, an important basic laboratory skill that you will apply in Introductory Biology. • To investigate some of the properties, including size, of different cell types including bacteria, protozoa, animals and plants.

Pre-lab Preparation:

• Read this lab manual chapter. • Review chapter 6 (A Tour of the Cell) in your Biology textbook, especially the section on microscopy and size (pages 94-96).

Introduction Compound Microscope Techniques

Two types of microscopes are used in Introductory Biology: compound microscopes and dissecting microscopes. The compound microscope is the more complicated of the two and is the one you will probably use most often. Our compound microscopes are used to observe materials placed on glass slides. The dissecting microscopes have much weaker magnification and are used to observe larger objects that are not mounted on slides. The compound microscopes are high-quality, delicate instruments that cost thousands of dollars each. Please treat them with special care. It is important that you learn to use the compound microscope correctly. Incorrect use could damage the microscope, give you a headache, and prevent you from seeing the materials you are supposed to study.

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Some general rules of microscope use that you must always follow include: • Always lift the microscope with both hands, with one hand grasping the arm of the microscope and the other supporting the instrument from underneath. • Never adjust anything without knowing exactly what you are doing. • When starting to use a compound microscope, always start by adjusting the ocular lenses correctly for your eyes. • Always observe a new slide under the weakest (4x) objective lens first. Focus using the 4x lens, then flip to the next (10x) lens, and focus it. Then flip to the 40x lens, focus it, etc. • Never remove any lenses from the microscope. • Be especially careful that you do not rotate...