Using the Microscope

Using the Microscope Laboratory 1 Biology 171

What did the invention of the microscope enable? • DUH…. to look at tiny stuff • Individual cells could be observed • Allowed scientists to see that all cells are very similar, but often take on different functions • Allowed us to see very small things • Typical cell = 0.02 mm • Our eyes can only see 0.2 mm • Invented around 1675; telescopes around 1605. • Fundamentally changed how we saw ourselves and nature. Dutch Inventor: Antoni van Leeuwennhoek

Today in Lab Exercise 1: The Compound Microscope Activity A: The parts of the Compound Microscope Activity B: Using the Compound Microscope Activity C: Depth of Focus Exercise 2: Observing Cells Activity A: Animal Cells Activity B: Plant Cells Exercise 3: The Stereoscopic Dissecting Microscope Activity A: The Parts of the Dissecting Microscope Activity B: Using the Dissecting Microscope Exercise 4: Observing an Animal Specimen Culture Microorganisms for Next Week…

Determining Total Magnification Multiply the magnification of each set of lenses: Total magnification = magnification of objective X magnification of eyepiece Scanning power: eyepiece ______x times objective _____x = _____x Low power: eyepiece ______x times objective _____x = _____x High power: eyepiece ______x times objective _____x = _____x Oil immersion power: eyepiece ______x times objective _____x = _____x 10 4 40 Page 4, lab manual

Magnification vs. Resolving Power • Magnification Def: ratio of image size to actual size; an apparent enlargement of an object. • Resolving Power - resolution Def: a microscope’s ability to distinguish between two objects that are very close together as separate; what allows us to see detail. Why don’t our microscopes have more and/or higher powered objectives?

Activity A: Parts of the Compound Microscope

Activity B: Using the Microscope ATTENTION! Important to follow these steps: • Plug in and turn on the light source. Adjust light source as needed. • Move the stage to its lowest position. • Make sure the lowest objective is in place (4x). • Place the slide on the stage and secure it with the slide clips/holder. • Use the stage controls to center the slide over the light source. Look at the slide from the side of the microscope, not through the eyepieces. • Looking through the eyepieces, use the coarse adjustment knob to bring the slide toward the objective. Soon you will see the image come into view. • After you get the image as clear as possible with the coarse adjustment, use the fine adjustment knob to further focus the image. • You may now go to a higher objective if you want, but be sure to ONLY use the fine adjustment knob to focus. (Also, be sure you are going to the next highest objective and NOT the oil immersion). The microscope objectives should be parfocal, as an image is focused with one objective, it will also be in focus in the other objectives.

Field of View We will be using a ruler to measure the field of view. What is the field of view in this image? 7 mm

Micrometer The images we will be looking at under the microscope are often too small to be measured in millimeters. Thus, we use the micrometer… 1 mm = 1000 µm 1 µm = 0.001 mm

7 mm = ? µm Remember our conversions: 1 mm = 1000 µm 1 µm = 0.001 mm 1 µm = 1 x 10-3 mm 7 mm (1000 µm/1 mm) = 7000 µm 7 mm (1 x 10-3 µm/mm)= 7000 µm

Activity C: Depth of Focus Def: the thickness of the specimen that can be seen in focus at any time

Preparing a Wet Mount

Activity A: Animal Cells Most structures in animals cells are too small to see. We will be able to see the plasma membrane and the nucleus today.

Oil Immersion • PLEASE be very careful!! Procedure: • After focusing in the high power objective, move the nosepiece half way between this and the oil immersion objective. • Place a small drop of oil on the coverslip. • Move the oil immersion objective into and through the oil and secure in position. • ONLY use the fine adjustment (and only a little bit) to focus

Oil Immersion cont. • After you are finished, be sure to wipe the oil immersion lens with LENS paper and LENS CLEANER to remove the oil. ONLY use lens paper or else you will damage the objectives. • Seriously. Use lens paper, not Kimwipes.

Cheek Cells • Stained with methylene blue • Only attaches to DNA, so only see nucleus • Fun fact: methylene blue may be a treatment for malaria, cancer, alzheimer’s and cyanide poisoning. http://waynesword.palomar.edu/lmexer1.htm#cheek

Activity B: Plant Cells In addition to the nucleus, we will also be able to see the cell wall and chloroplasts.

ElodeaLeaf http://waynesword.palomar.edu/lmexer1.htm#elodea

Elodeacytoplasmic streaming • http://www.youtube.com/watch?v=8edk6nGMwMs • Moves nutrients, genetic info, raw material throughout the cell.

Exercise 3: Stereoscopic Dissecting Microscope Use when your specimen is too large or thick to see using a compound microscope. Activity A: Identify the parts of the dissecting microscope Activity B: Using the dissecting microscope

Exercise 4: Observing an Animal Specimen • Observe a hydra on a depression slide (that you will prepare) • You will be feeding the hydra liver juice and Daphnia.

Hydra eating Daphnia http://youtu.be/G188PDx73i8

Culturing Microorganisms for next week… Purpose: We will be sampling microorganisms in from our environment and observing the effectiveness of antimicrobial agents. • Be creative! – The UC! Outside! Between your toes! • Find a unique area to sample • Or a few groups could sample the same surface and test the effectiveness of different antimicrobial agents Work in pairs  (not enough agar plates)

Using Antimicrobial Agents • Divide your plate in half – put an antimicrobial agent on half of the plate • Examples: listerine, vinegar, pine sol, mikro-quat disinfectant • Only need a little bit so it doesn’t diffuse over to other half of plate • Write on the BOTTOM of the plate (not on lid) and indicate what half has the antimicrobial agent

What to include on BOTTOM of plate Antimicrobial agent NO antimicrobial agent Names Lab Section Surface Sampled Date

Culturing Microorganisms • Procedure: • Wet a cotton swab with sterile water and swab the environmental surface • Inoculate an agar plate on both halves of the plate – do the side WITHOUT the antimicrobial agent FIRST • After innoculation… • Put the lid on the petri dish • Flip the whole dish upside down • Make sure your name and lab section (day) are on the bottom • Make a pile on the front desk

REMINDERS: • Work productively and efficiently • Think creatively, critically, and freely. ASK QUESTIONS! • Return materials in the same condition you found them • Take thorough notes, draw pictures, answer all questions in your lab notebook, and come up with two possible research questions on microorganisms or something you saw today. • Before you leave make sure your work station is in the same condition as you found it. • Also: be sure you have gotten an email from me, know how to access the website, and have spoken with me personally if you are concerned about your writing ability and the research paper.

Using the Microscope