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Saddleback BIO 3A - Microscopes and Cells

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BIOLOGY 3A LABORATORYMicroscopes and CellsObjectivesIntroductionBio 3A Lab. Scopes & Cells Page 1 of 13 BIOLOGY 3A LABORATORY Microscopes and Cells Objectives • To learn the proper use and care of compound microscopes • To learn staining techniques used in light microscopy • To prepare a wet mount • To determine the magnification and size of the field of view • To use the microscope reticle to measure the size of objects in the field of view • To determine the depth of field • To differentiate between prokaryotic and eukaryotic cells • To learn the similarities and differences between plant and animal cells • To identify cellular structures Introduction The ability to magnify specimens has been around since 1000 B.C. The first simple compound microscope that utilized two lenses was not invented until the late 16th Century. It was the invention and modification of this microscope that changed the way scientists studied living organisms. It allowed scientists to study the structure of a living organism and to discover numerous species that were not visible to the unaided eye. Today there are numerous types of microscopes available to scientists that provide greater magnification and superior detail (resolution). Besides magnifying and resolving an object, the microscope also provides the contrast that is needed to distinguish detail between adjacent objects. Microscopes used in most biology laboratories magnify up to 1000X with a resolving power of 0.2 μM. The microscopes in this laboratory are compound, light microscopes. The light is transmitted through the specimen on the stage and through two lenses before it reaches the user. These are expensive pieces of equipment. Please handle them carefully. A. USING THE MICROSCOPE There are some basic rules that you need to adhere to when using microscopes. These are: 1. Always use two hands when moving your microscope. Use one hand to hold the arm and the other hand should support the base. NOTE: The scopes are heavy! 2. Use only LENS PAPER to clean the lenses. Do not use tissues, paper towels, Kimwipes, your shirt, etc. to clean the scope. Even though these items may feel soft, they can scratch the lenses. 3. The microscope must be on the lowest power objective lens: a. when starting to use the microscope. b. when you finish using the microscope. Before you return the microscope to its numbered slot: 1) make sure the objective lens is on the lowest power, 2) the power is off, 3) there is no slide on the stage and 4) the dust cover is in place.Bio 3A Lab. Scopes & Cells Page 2 of 13 4. NEVER use the course focus knob on high power; use ONLY the fine focus knob. These microscopes are parfocal. This means that when the image is in focus on one objective, the image will be in focus with the other objectives. You may need to fine focus the image for sharpness. Functional Parts of the Microscope: Materials: Microscope, lens paper, letter “e” slide, color thread slide, 1 mm gridline slide Procedure: 1. Remove the microscope from the scopes cabinet and return to your work area. 2. Make sure that you use both hands to support the microscope (arm and base). 3. Place the base securely on the lab bench with the arm towards you. 4. Identify the following parts of the microscope: a. The ocular lens or eyepiece is a 10X lens which is at the upper end of the tube. The scope that you are using is binocular; it has two eyepieces. b. Revolving nosepiece: the objective lenses are attached below the nosepiece. It allows the user to change the magnification. c. Objective lenses: our scopes will either have 3 or 4 objective lenses attached to a revolving nosepiece. The magnification is inscribed on each lens. The powers that you will use are: scanning (4X), low (10X) and high dry (40X). Most of our scopes also have an oil immersion objective lens (100X). You will not use this lens in this lab. d. Stage and stage clamp: the slide will rest on the stage and will be held in place with the stage clamp. The moveable portion of the stage clamp should only be touching one corner of the slide. e. Iris diaphragm lever: on the front edge beneath the stage is a small lever that is used to adjust the contrast by regulating the amount of light. f. Condenser and adjustment knob: the condenser condenses the light rays into a stronger beam. Use the adjustment knob located below and to the side of the stage to increase or decrease the light intensity. g. Coarse Adjustment Knob: On each side of the scope is a large knob use to move the stage up and down to focus the image. This knob is to be only used with the scanning and low power objective lenses. h. Fine Adjustment Knob: Located by the coarse adjustment knob, this knob allows for very small changes to the height of the stage. This knob is used to increase the sharp focus of an image and is the only knob to be used with high power. i. Slide Movement Knobs: To one side of the stage, there are two black or silver knobs that you will use to move the slide. One knob will move the slide to the left and right. The other knob will move slide towards and away from you. The scopes are parcentral. This means that when you have the object centered in the field of view on a lower power and then change to a higher power, the image will remain in the center of the field of view.Bio 3A Lab. Scopes & Cells Page 3 of 13 j. On/Off Knob/Switch: Located on side of the microscope (Nikon) or the top of the base in the front end of the microscope (Swift). Determining the Magnification or Power: The compound microscope utilizes two different sets of lenses to magnify an object. These lenses are the ocular and objective lenses. Procedure: 1. Determine the magnification for each of the following lenses by looking for the engraved magnification. 2. Calculate the total magnification of object being viewed by multiplying the magnification of the ocular lens and objective lens. Image Orientation and Brightness: Procedure: 1. Obtain a letter “e” slide. 2. Place the letter “e” on the stage so that you can read it normally. Use the stage clamp to hold it in place on the stage. 3. Adjust the letter “e” so that the light is transmitted through the letter. 4. Start with the scanning lens; bring the stage as close to the scanning lens as it will go. 5. Look into the eyepieces


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