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BSC 196- Midterm Exam Guide - Comprehensive Notes for the exam ( 75 pages long!)


Department
Biological Sciences
Course Code
BSC 196
Professor
sakaluk
Study Guide
Midterm

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ISU
BSC 196
MIDTERM EXAM
STUDY GUIDE

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

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Microscopes have been used since 1665.
They are essential tools for magnifying and viewing small organisms, bacteria, viruses, cells,
molecules, and atoms.
Three major types are used by biologists:
Dissecting (light) microscope
Compound light microscope
Electron microscope
Resolving power (resolution) = the smallest distance that a lens can distinguish between very
close objects.
Dissecting < compound < electron scope
Passes beams of light through a specimen, which then pass through lenses that bend the light to
produce a magnified image.
Resolving power: 0.2 micrometers (μm), 1000 times more powerful than the human eye.
Compound light microscope: 4-40X magnification.
Has multiple lenses for magnification.
Also called a stereo microscope. 5X-50X magnification.
Used for specimens too large or bulky to be observed by the compound light microscope.
Has a single lens for magnification.
Magnifies objects by focusing electron beams at them.
Electrons pass through coil-shaped electromagnets and hit photographic film or form
pixels on a screen.
Resolving power: 2 nanometers (nm), 100 times more powerful than light scope.
Two types of electron microscopes:
Transmission electron microscope (TEM) Used to look at a thin section of a specimen
stained with heavy metals for contrast. Creates an image of the inside of the specimen.
Scanning electron microscope (SEM) Used to observe external features of specimens.
Creates a 3D iage of the specie’s outer surface with a great depth of field.
Grasp the microscope by its arm with one hand, and hold the base with the other hand.
Setup: rotate the lowest power (4X) objective lens into place (do this when putting the scope
away as well). Turn the illuminator light on.
Place slides under the slide holding bars to secure them. Move stage controls to adjust field of
view.
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Do not touch the coarse focus knob once you move to a higher power objective lens than 4X
the larger lenses could crack your slide.
You will not need the oil immersion lens (100X).
Field of view: the lit area you see when looking through the eyepieces (oculars).
It decreases as resolution increases.
Total magnification: objective magnification times ocular magnification (10X the objective lens).
Condenser: lens beneath mechanical stage, focuses light on specimen.
Condenser (iris) diaphragm: adjusts image contrast.
Working distance: the distance between the objective lens and the specimen you are viewing.
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