question archive Introduction to Microscopy and Bacterial Shapes Pre-Laboratory Questions 1
Introduction to Microscopy and Bacterial Shapes Pre-Laboratory Questions 1
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Introduction to Microscopy and Bacterial Shapes
Pre-Laboratory Questions
1. What is the magnification of the eyepiece lens on your microscope?
2. What is the magnification of the lowest power objective lens on your
microscope?
3. Calculate the total magnification of an object viewed under the lowest power
objective on your microscope.
4. Describe the proper way to carry a microscope.
5. Describe the proper way to store a microscope slide.
6. List the three most common shapes of bacteria, and provide a brief description
of each.
7. What is the main difference between a spirillum and a spirochete?
8. Do bacteria live as single cells? In groups? Explain your answer.
9. Identify each bacterial shape in the image below.
A.
B.
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Observations
1. What are the magnification powers of the objective lenses on the microscope
you are using?
2. What happens when you adjust the iris diaphragm of the microscope?
3. When the slide was moved left, which direction did the "e" on the microscope
slide appear to move? When the slide was moved away from you, which
direction did the "e" appear to move?
4. Can you use the fine adjustment knob so that you can focus on all three threads
simultaneously when viewing them under high power? Why or why not?
Data Table
Using your bacterial types slide, identify the three types of cell shapes on the slide.
Describe and insert a photo of each cell shape.
Total Magnification = (eyepiece lens power) × (objective lens power) = _________
Smear Cell Shape Photo or Drawing
1
2
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Smear Cell Shape Photo or Drawing
3
Slide Photos
Insert your photos of the eight slides that you observed and indicate the total
magnification that you used for each slide below:
Letter "e"
Total magnification =
Intersection of the colored threads
Total magnification =
Tick
Total magnification =
Mite
Total magnification =
Bacterial types
Total magnification =
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Bacterial endospores
Total magnification =
Gram-negative spirillum
Total magnification =
Gram-positive bacillus
Total magnification =
Acid-fast bacteria
Total magnification =
Post-Lab Questions
1. Describe how you can quantify the size difference between the tick and the mite
using the microscope.
2. Why must specimens viewed with a compound microscope be thin or chemically
cleared?
3. Why are specimens viewed with a compound microscope sometimes stained
with dyes?
4. What are the advantages and disadvantages of using a compound microscope
versus a stereoscope?
5. Why is it important to adjust the light intensity when viewing a specimen with a
compound microscope?
6. How can depth of field affect your ability to find and examine a specimen?
7. Of the three bacterial cell shapes you observed, which is most likely to have
moved using flagella when living? Which shape is the least likely to have moved
with flagella?
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8. Some bacteria are harmful to humans, but most are not. Provide one example of
a harmful species and one example of a harmless species for each of the three
common bacterial cell shapes.
9. List three harmful bacteria that were NOT mentioned in your answer to question
8, along with the conditions they cause. Also, note the cell shape of each.
10.Describe the acid-fast staining technique. What dyes are used? What is the
technique commonly used for?
11.Describe the endospore staining technique. What dyes are used? What is the
technique commonly used for? Why would it matter if an organism is capable of
producing endospores?
12.Explain why some bacterial species are described as endospore-forming or acid-
fast.
13.Identify which slide you found the most interesting, and explain why.
