Biology 1 Using the Microscope & Introduction to Cells Lab. Part 1: Introduction

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1 Biology 1 Using the Microscope & Introduction to Cells Lab Part 1: Introduction The microscope plays a fundamental role in almost every type biological research. Scientists in each field rely on it to study the fine structures cells and tissues things too small to see with the unaided eye. Were it not for the microscope, our understanding life would be far different from what it is today. In this lab, you will learn how to use a compound light microscope to observe structures too small to see with the unaided eye. You will also learn to prepare slides for viewing with a microscope and compare cells from two important types organisms: plants and animals. As review, here is a diagram the parts the microscope. Be sure to handle the scope with care. When carrying a microscope, you should place one hand under then base and another on the arm. You should never hold the microscope by the parts that move. You should also avoid touching the lenses and only clean them with lens paper or a lens cloth. This will help to avoid scratching.

2 The purpose the microscope is to magnify your specimen. Most microscopes use two lenses the ocular objective and another objective to magnify the image. The magnification is the number times the size an object is increased. If the magnification an object is 13X, it will appear 13 times larger than it really is. The magnification your microscope is equal to the product the separate magnifications the ocular objective and the objective being used on the rotating nose piece. Total Magnification = Ocular Objective Magnification X Objective Being Used 1. If the magnification the ocular objective is 10X, what is the total magnification your microscope when using the low power objective? 2. What is the total magnification your microscope when using the high power objective? Remember: Lower magnifications should be used first, to scan the field view for a good part the specimen to focus on. You should use the highest magnification that is appropriate/available for observations.

3 Part 2: Using the Scope Orientation The first thing you will prepare for observation under the microscope is the letter e. Prepare a wet mount the letter e by following the steps detailed below. How to prepare wet-mount slide: 1. Drop Water 2. Sample Interest 3. Cover Slip Place your prepared slide on the stage. Adjust the light source and the diaphragm to obtain enough light to see the slide. Use the low power objective to view the letter e. When the slide is in focus, switch to high power and refocus the slide. 3. What magnification is most appropriate for viewing the letter e? Why? 4. Do you see more or less the letter e when you switch to high power? Explain. 5. How does the letter e look compared to the way it appears when not viewed through the microscope? Describe the change in its orientation. 6. Move the slide to the left and right. Describe the way the slide appears to move (viewed with the scope) relative to the way that you are moving it. 7. Move the slide up and down (towards and away from you). Describe the way the slide appears to move (viewed with the scope) relative to the way that you are moving it. 8. What can you conclude about the way an image moves as compared to the way you are actually moving the slide? To learn how to see the depth a specimen, you will prepare a wet mount a piece thread. Obtain a colored piece thread about 1cm long. Place the thread in a drop water on a clean glass slide. You will not add a cover slip because you will only be asked to view the thread under low power. Cover slips protect the high power lens from touching the specimen. Focus up and down using the low power objective. 9. Why do only parts the thread appear clear (and in focus) at any given time? 10. What do you notice when you adjust the diaphragm settings as you view the thread?

4 Part 3: Microscopic Measurement You will now measure the diameter the low power field and calculate the field view for high power. Put a clear plastic ruler on the microscope stage so that one the millimeter markings is at the far left hand side the field view. See below. To determine the diameter the low power field view, count the number full millimeters that fit into the field and estimate the portion the last millimeter that is in the field view. The space between these 2 lines is 1mm. This field view is between 3mm and 4mm. 11. What is the field view the low power objective measured in millimeters? 12. Divide the high power magnification by the low power magnification. Record this number. 13. Now determine the diameter the high power field by dividing your answer for #11 by your answer for # 12 to get the answer for this question. Many specimens observed under the microscope are smaller than 1mm. Because this, measurements are ten expressed in micrometers. One millimeter contains 1,000 micrometers. 14. What is the diameter your low power field view in microns? 15. What is the diameter your high power field view in microns?

5 Part 4: Preparing Wet Mounts Plant and Animal Cells Next you will prepare two separate wet mounts. For the first wet mount you will use a piece onion skin. Using forceps, obtain the thinnest piece onion skin possible. Prepare a wet mount the small piece onion skin. In order to see the cells better, scientist ten use stains that are specific to the structures they are trying to observe. Remember that plants have cell walls made cellulose? Cellulose is a carbohydrate and iodine can be used to stain polysaccharides. Therefore we will use iodine as a stain for this wet mount. See the diagram below. How to prepare wet-mount slide: 1. Drop Water 2. Sample Interest 3. Drop Appropriate Stain 4. Cover Slip Observe the onion cells under low meduim and high powers. A great way to communicate your observations is to make a drawing. Drawings must be done in pencil and the magnicifation used should be labeled. 16. Sketch the onion cells under low and high power. 17. Estmiate the size a single onion cell. This measurement should be in microns. You can give a range. The next wet mount you will prepare is animal cells. Where could we possible find some animal cells? We ll get some from your cheeks. Use a cotton swab to gently collect come cells from the inside your cheek. Use the same procedure detailed above to create a wet mount these cells. The stain that you should use in called methylene blue. 18. Sketch the animal cells under low and high power. 19. What type cells are plant and animal cells? 20. What are the differences between plant and animal cells? Using specific structures in your answer.

6 Biology 1 Using the Microscope & Introduction to Cells Lab Name: Date: Hour:

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