Microscopes & Cell theory
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Transcript of Microscopes & Cell theory
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Microscopes & Cell theory
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Microscope development:• Hans and Zacharis Janssen:
1590 –simple microscope; 2 lens in a tube
• Anton van Leeuwenhoek: early 1660’s- used microscope to observe nature & recorded it.
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Describe the properties of microscopes.
• Microscope: magnifies images
• Magnification: increase in size
• Resolution: increase in detail
• Two types:• Light microscopes • Electron microscopes
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Light Microscopes• Magnifies objects using
light• Simple microscopes:
have only one lens (magnifying glass)
• Compound light microscope: has two lenses
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Using the microscope:• Find total magnification: multiply power of eyepiece
(usually 10X) x power of objective lens• When focusing: always start with LOW POWER
objective• Move nosepiece all the way down and focus slowly
UPWARD using the coarse adjustment
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Electron Microscopes• 1940’s, uses electron beams
instead of light• Allows more detail, but
specimens are usually killed in the staining process
• Two types:• TEM: beam goes through
specimen• SEM: scans surface only
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Parts of a microscope• Ocular lens: lens near eye • Eyepiece: holds ocular lens• Objective lens: lens near specimen a. high power lens: longer, usually 40 X b. low power lens: shorter, usually 10 X• Nosepiece: holds objective lenses• Stage: platform supporting specimen• Diaphragm: regulates amount of light • Fine adjustment/coarse adjustment: used to focus on object• Arm: supports microscope• Illuminator: light source
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Robert Hooke discovered cells in 1665
a.Examined a wine cork(tree)
b.looked like his monastery cell so he named them “cells”
How did the Cell Theory come about?
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• Schleiden and Schwann (1838-1839) examined many types of cells
• Schleiden: botanist, discovered that all plant parts are made of cells
• Schwann: zoologist, discovered that all animals parts are made up of cells
• Both observed / different types of cells performed different functions
Schwann
Schleiden
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• Rudolph Virchow (1855)• Physician that stated all
living cells come only from other living cells
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The Cell Theory
• All organisms are made up of cells
• Cell is the basic unit of organization
• Cells come from pre-existing cells
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Stem Cell Research
http://www.sumanasinc.com/webcontent/anisamples/stemcells.html
Website-stem cell animation