Name: _________________
MICROSCOPE LAB---Biology 20
Outcomes: Unit 1: 2.1, 2.2, 2.3, 2.4
A.
B.
- this is a hand-in assignment
PREPARE A WET-MOUNT SLIDE
i)
Obtain a slide and cover slip. Always hold them by their edges. Clean the slide if
necessary, using water and paper towel.
ii)
Cut out a small piece of newspaper (not more than 4 mm sq.) containing a lowercase
letter 'e' from the text of a story. There should not be any printing on the back.
Place the 'e' in the center of the slide, right side up, print side up. Using an eyedropper, put a large drop of water on the 'e'.
iii)
Placing the cover slip. Skill is required to prevent air bubbles. Place one edge of
the slip on the slide and slowly and gently lower the cover slip, perhaps with a
dissecting needle or forceps. A gentle tap may remove any remaining bubbles.
iv)
Place the slide on the stage so that the letter is right-side-up. On LOW POWER,
focus on the letter. The objective lens should be about 1 to 2 cm from the slide.
ANSWER THESE QUESTIONS
1.
Draw the EXACT image that you see in the field of view on Low Power. Make
your drawing large. (please draw in the space provided below)
2.
Move the slide on the stage from right to left. Which way does the image move?
3.
Move the slide away from you. Which way does the image move?
4.
How does the image that you see differ from the actual position of the letter on the
slide?
5. Observe the letter on MEDIUM POWER and focus, then on HIGH POWER, without
changing the diaphragm. Is the brightness of the field of view greater or lesser on high
power?
C. STAINING TECHNIQUE
In this lab you will practice the proper technique of preparing and staining a wet-mount slide.
Materials:
iodine dropper bottle
1 slide
beaker of water with eye dropper
1 cover slip
1 toothpick
small piece of potato
eye dropper
paper towel
Observing Starch Grains
1.
Clean your slides.
2.
Place a small piece of potato in the center of the slide. Place the slide on the table and press
potato into the slide with a finger to squeeze out a little juice. Smear the juice on the slide
with the potato and then discard the potato.
3.
Add 1 to 2 drops of water and a cover slip.
4.
Examine the slide under low power, closing down the diaphragm to increase contrast.
Locate well-separated grains. Switch to medium, then high power.
Observe the shape of an individual starch grain.
5.
Return to low power and remove the slide. Stain the starch grains by placing a small drop
of iodine on the slide at one side of the cover slip. Place a small piece of paper towel in
contact with the water at the opposite edge of the cover slip. As water is absorbed, iodine
will be drawn under the cover slip. Stop when the iodine covers half of the slip.
*** BE CAREFUL NOT TO GET IODINE ON CLOTHING ***
6.
Under low power examine various regions of the slide to observe the effects of different
concentrations of iodine stain. Examine under high power.
Please answer the following questions:
6.
What colour are the starch grains exposed to high concentrations of iodine?
7.
What colour are the grains exposed to low concentrations?
8.
Below, draw a stained starch grain. Make your drawing large. (You do not need to calculate
magnification for this drawing).
Observing Cheek Cells
1. On a clean slide, place a small drop of Lugol’s Iodine solution.
2. Using a clean toothpick, gently scrape the lining of the cheek with the flat end of a toothpick.
3. Transfer this into the small drop of Lugol’s solution on the slide. Stir the material in the stain
so that the cells will not clump together.
4. Carefully apply a coverslip.
5. Examine the slide under low power.
6. Center a few cells and increase the power to medium and then high power.
7. Draw a 1-2 cheek cells. Follow the procedure for drawing biological diagrams. Calculate the
magnification. Be sure to title your diagram.
8. Label your diagram with the following terms. Nucleus, Cell Membrane, Cytoplasm
Please include a conclusion for this lab. (i.e. what have you learned; what concepts were
reinforced in this lab)
Please Hand – In:
 The completed handout
 Your biological drawing
You may include your conclusion here:
Biological Drawing Cheek
Cells  0—1—2—3—4—5
 Pencil ____
 Title ____
 Drawing
(Great, Good, Average, Cells not reflecting
actual slide, getting disorganized, more effort
for next time) ___


Labels _____
Cell Membrane
Cytoplasm
Nucleus
Labels lined up to one side ___
 Size of Drawing ____;
 Magnification calculations
(Good) (check calculations, check size
of drawing in micrometres, check step 1,
check step 2) ___;