Biological Tools : Biological Tools Biology I
Burrell High School
Mr. Mike
Microscopes : Microscopes All biologists use things such as balances, dissecting tools, and computers.
One of the most important tools is the MICROSCOPE.
History of Microscopes : History of Microscopes The HAND LENS has been around for over 600 years.
It was the first simple microscope
Lens – curved glass that bends light rays to enlarge an image.
History of Microscopes : History of Microscopes The first compound microscope was invented in 1595 by Zacharias and Hans Janssen.
Janssen's microscope consists of three draw tubes with lenses inserted into the ends of the flanking tubes.
The Janssen microscope was capable of magnifying images approximately 3x when fully closed and up to 10x when extended to the maximum.
No early models of Janssen microscopes have survived, but there is a candidate housed in the Middleburg Museum in Holland that some historians attribute to Janssen.
Janssen’s Microscope : Janssen’s Microscope
History of Microscopes : History of Microscopes Antony van Leeuwenhoek
Further developed the microscope to a different shape and magnification capabilities.
His microscope could magnify up to 300x.
He was the first to view protozoans and bacteria.
Leeuwenhoek’s Microscope : Leeuwenhoek’s Microscope
Factors That Affect Microscopes : Factors That Affect Microscopes Magnification:
Increase the size of the image
Represented by X – i.e. 10x or 10 times what the naked eye could see.
Resolution:
Measure of the amount of clarity and sharpness of the image.
A disadvantage is that as magnification increases, resolution decreases and vice-versa.
Compound Light Microscope : Compound Light Microscope The scopes that we use here at Burrell.
Called Light Microscope b/c it allows light to pass through the object that is being viewed.
Has 2 lenses
1) Ocular eyepiece – 10x
2) Objective lenses – 4/5x, 10x and 40x
Slide 10 :
Compound Light Microscope : Compound Light Microscope Total magnification
Eyepiece x Objective
Scanning Power 4x or 5x
Total: 4/5 x 10 = 40x or 50x
Low Power 10x
Total: 10 x 10 = 100x
High Power 40x
Total: 40 x 10 = 400x
Stereoscope : Stereoscope Has 2 oculars
Used to view 3-D objects (light cannot pass through)
10x – 60x
Electron Microscope : Electron Microscope Uses a beam of high speed electrons instead of light.
Particles bounce off the specimen and form an image on a TV screen or photographic plate.
First used in 1931.
Have better magnification and resolution than light microscopes.
Electron Microscope : Electron Microscope 2 kinds of EM’s
1) Transmission Electron Microscope
Object appears to be flat and thin
2) Scanning Electron Microscope
Objects appear to be 3-D and a sharp image in very good detail.
A huge disadvantage is that one cannot view live specimens b/c the staining technique kills living cells.
Electron Microscope : Electron Microscope