LAB 6

.pdf

School

Chemeketa Community College *

*We aren’t endorsed by this school

Course

232

Subject

Biology

Date

Dec 6, 2023

Type

pdf

Pages

13

Uploaded by LieutenantSquirrel3921

Activity 1: Microscopes 1-1: Dissecting microscopes Dissecting microscopes, also known as stereo microscopes, are used during dissections to see a detailed view of the organs revealed during a dissection. These microscopes are most useful for observing the surface of specimens at a relatively low magnification. 1. o Place the metric ruler on the stage of the dissecting microscope and focus using the focusing knob on the side of the body. Use the magnification dial on the top or the side of the microscope to adjust to the lowest power (widest field of view). What power is the microscope at now? Record your measurement of the field of view diameter in mm in the table below. Now adjust the magnification to the highest power and measure the field of view diameter in mm. ' Convert the measurements to pum. 1mm=1000um View the letter “e” slide with the label in the upright position. View it in the dissecting microscope on the lowest power and the highest power. Add drawings to the provided spaces below. Use the dissecting scope to view the objects available at your table, on your person (like fingers, license, dollar bill), or collect items from around campus (leaves, bugs, flowers) to view under the dissecting microscope. Questions 1. Complete the table below. Magnification Diameter (field of view) | Diameter (field of view) " mm Hm Di ting Mi LowestPower | A0 5 e 00 UM e e L L J100n 2. Draw the letter “e” in the circles provided under section 1-3, accurately representing how much of the field of view the “e” takes up at the various magnifications. 1-2: Compound Microscope Overview Microscopes are fragile and expensive, and we want to maintain them in good working order. Your instructor will walk you through a tutorial on how to handle the microscope, understand its parts, and explain their functions. 1 Microscope Introduction a. Caring for the microscope and proper storage b. Parts and functions
c. Cleaning slides and lenses, situating the slide d. Locating objects at different magnifications Label OQ\) Make sure you can identify the following parts and explain what they do: e Arm Base Nosepiecej Stage / Stage clip (slide holder) ¥ Stage controls Course adjustmentj % Fine adjustment QQ‘(\(\S})‘\CD Ocular lenses (x2)¥ Objective lenses (x3) ¥ Condenser Lamp / Brightness adjusterJ o5 Questions 1. What kinds of things do you need to be aware of to make sure you don't damage your microscope? Weing 14 v ay i ¢ pose 2. When lookifg at a slide with*maximum magnification, the objective lenses should always be used in what order? (name the lens and give the magnification) Led i .0 \iQ\\DW A0 x Blue Hdx 3. What tools does the microscope have to regulate how much light passes through the specimen? bh%h n 0Y O\\m e oo d 56}: 4
Questions . Complete the drawings of the letter “e” below. *"”’\) e N | K S sk NS Dlssa;tmg microscope Naked eye S L e 40x total 100x total | 400x total magnification magnification magnification 2. What happens to the orientation (not the magnification) of the letter “e” when it is viewed in the compound microscope as opposed to with the naked eye? 11 oecornes ) ppe cl 1-4 Magnification, field of view, and depth of field You have already examined several differences in magnification by looking at the letter when you increase the magnification of an object, you can see less of that object. Or, in a more scientific term, your field of view decreases as magnification increases. Also notice that when you use a lower magnification, you can see most of the depth of the object in focus at the same time. When magnification is increased, only smaller depths of the object can be focused on at the same time. This means that the depth of field is decreased when magnification increases. We'll explore these phenomena further with this activity. ‘e”. You have seen that 1. Observe the magnification marked on the eyepiece and each of the three objective lenses. Record these values in the table below. Calculate the total magnification by multiplying the objective magnification times the ocular magnification.
2. To measure the field of view: use the 4x (scanning) objective. Place a clear metric ruler under the stage clip so you can see the markings on the metric side of the ruler and measure the diameter of the field of view in mm. Record the value in the table below. Now measure the field of view with the 10x objective and record that value as well. You will not be able to directly measure the field of view for the 40x objective. _ To calculate the field of view for the 40x objective, we can use this ratio between magnification and field of view diameter: ) Lower power maghification Higher power diameter Higher power magnification | gwer power diameter A For example, if we measured the 10x field of view diameter to be 3mm, we could solve for the 40x field of view diameter as shown below: 10x High power diameter 40x Simplify this .~ fraction 3%rim N 3mm x 0.25 = high power diameter 0.75mm = high power diameter Muiiiply both sides by 3mm 4. When usihg compound microscopes, it's more typical to use micrometers (um) to measure objects. Convert the field of view diameter to pm. 5. To observe how depth of field changes, we will use the crossed-threads slide. Use the 4x objective to focus on the point where the three threads cross. Can you see all three threads clearly? Refocus on this point using the 10x and the 40x objectives. Are all three threads still equally clear? Answer the questions below about the depth of field. Questions 1. Complete the table below: Name of lens Magnification Diameter (field | Diameter (field of view) mm of view) pm Objective Ocular Total Scanning A LO ¢ “0 0 00| HODOKM Lowpover__| 10 0, [109 _ [7.00mm [2000 High power V\O {O)g 4*100 O“@W\m 60@ \/\YY\ : A—
2. Without using a ruler, how could you use the above information to figure out how big in pm the “e” is from the previous activity? Use your drawmgs to ewte the snze of the letter “e” jn Compmre, e YYACA v e | k 3. Is it ‘as clear to focus on all three threads at the 400x total magnification as it is at the 40x total magnification? If not, why? /Ar\’ \o 0+ \{\ A ’/f O X O X, o Comn u.z oNn 1 \(\é/ +ho: »eigig oA o HODx 1ts W‘\Ove ddfr@&“ Pocosed 4. What is the order of the colored threads on the slide? Top v €c Middle | ,Ulow Bottom 0| v 5. What can you conclude about the size of the field of view in relation to magnification? e field view g solley e Wigheye g MOAANA caa 0N ety 6. What'can you conc ude about the depth of field in relation to magnification? } 0S mO\ Hecahon cjoes VP | \(éQ, N ACYEeas e _ Activity Observmg prepared and live specimens It is helpful to observe fresh specimens in order to view things that only happen in living cells. Some cells move through their environment. Others show a cycling of their cytoplasm. Still others show metabolic changes, particularly if effective dyes or indicators are used. “Prepared” slides that have been stored in a cabinet cannot show such behaviors. Prepared slides are useful when studying the structures of organisms or tissues. Keep in mind that when looking at prepared slides, these are often stained in order to make the cells or specimen visible. The color something appears in a prepared slide is not always its true color if it were living. Most cells are small and must be magnified 100x or more to be clearly seen. Additionally, it may be useful to use dyes or stains when looking at live specimens, otherwise the cells appear as gray blobs. Specific dyes are absorbed by certain parts of the cell. For instance, the cell nucleus often stains a dark color. This isn’t because the nucleus is darker than the rest of the cell, it just absorbs more of the stain, making it more visible. It is also helpful to regulate the light when looking at both live and prepared specimens. Use the light adjustment knob and the condenser knob to change the amount of light that comes through and the contrast of the image. This will make parts of the cell, like the cell wall, stand out. Cells Cells are the simplest individual units of life, and humans are made of several trillion of them working together - to create a functional organism. You will need to understand the structure of cells and functions of organelles forever, so learn them now. There are two major categories of cells: prokaryotic cells like bacteria are relatively small with a simpler internal structure, and gukaryotic cells which comprise protozoa, animal, plant and fungal cells. Eukaryotic cells are much larger and contain nuclei and membrane-bound organelles. Cells come in a surprising variety of shapes and sizes and carry out very diverse functions, yet are all made of the same core parts:
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help