IB BIOLOGY
INTRODUCTORY MICROSCOPE LAB
PURPOSE: 1. To become familiar with using a compound light microscope and practise
focussing using all three objective lenses.
2. To calculate the total magnification of the image using all three objective
lenses.
3. To learn how to prepare a wet mount slide.
4. To observe and record how the orientation of the image compares to the
orientation of the specimen on the slide.
5. To measure the diameter of the low power field and use it to calculate the
diameters of the medium and high power field diameters.
6. To observe and record how the diameter of field changes as the magnification
of the microscope increases.
7. To observe and record how the depth of field changes as the magnification of
the microscope increases.
8. To estimate the width of the crossbar of a letter “e” using all three objective
lenses. The crossbar is the straight line on the letter. The width of the
crossbar is essentially the width of the line that was used to form the letter.
9. To estimate the length of two protists using prepared slides.
10. To practice drawing lab diagrams of microscope observations.
MATERIALS AND APPARATUS: Refer to MacMillan Biology Laboratory Manual pp. 37-44
and pp. 73-76. In addition, threads of 3 different colours.
PROCEDURE:
Laboratory Skills 5 from pp. 37-44-all
In addition: 1. Use low, medium and high power even though the lab manual itself only
refers to low and high powers.
2. Prepare a slide of three threads of different colours crossed over each other
(similar to an asterisk). Observe the slide using all three objective lenses.
Measuring with a Microscope from pp 73-76-all
Make sure to observe at least two specimens from the prepared slides. You have been
provided with Paramecium and Euglena. Paramecium is the larger of the two types of
protists so it is best to try to observe them before trying to observe the Euglena. To make
them easier to see, the organisms have been dyed. Paramecium are most commonly dark
pink or purple; Euglena are most commonly green. There may be other colours but as a
general rule, anything that is almost colourless is probably not a protist.
OBSERVATIONS:
Laboratory Skills 5 from pp. 37-44
*Each diagram must follow the guidelines given on p. 18 of your lab manual.
1. 3 drawings of the letter “e”-one using each objective lens.
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2. 3 drawings of the three crossed threads-one using each objective lens
Measuring with a Microscope from pp 73-76-all
1. Diameters of all three fields of view. (Yes, I know the manual only refers to low power
and high power.)
2. One drawing of each of the specimens from the prepared slides. Choose the best view out
of the three magnifications. (Whole specimen, greatest amount of detail possible)
3. Estimations of the actual width of the crossbar of the letter “e”. Do this using all three of
the drawings that you made for Laboratory Skills 5.
4. Estimations of the actual sizes of the specimens you observed from the prepared slides.
5. Calculations of the drawing magnification of each of your drawings.
DISCUSSION: PLEASE USE COMPLETE SENTENCES.
Analysis and Conclusion pp. 42-43#3, 4
Critical Thinking and Application pp. 43-44 #1-3, 5
Analysis and Conclusion pp. 75-76#4, 5
Critical Thinking and Application p. 76 #3, 4
CONCLUSION:
Write statements regarding Purposes 2, 4-9.
WHAT NEEDS TO BE HANDED IN?
1. Observations: as outlined above.
*Each diagram should meet the criteria from p. 18 of the lab manual and include a
title, microscope magnification, actual size (when possible, if not, note the
impossibility and explain why calculating the actual size is impossible), and drawing
magnification. Include your calculations.
2. Discussion: as outlined above.
3. Conclusion: as outlined above.
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