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Tools of the Biologist

Tools of the Biologist. The Microscope. History. Antonie von Leeuwenhoek —Born in Holland in 1632 First to observe living bacteria & drew them. Also looked at sperm, protists , blood 1 st simple scope Made over 500 " microscopes". History.

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Tools of the Biologist

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  1. Tools of the Biologist The Microscope

  2. History • Antonie von Leeuwenhoek—Born in Holland in 1632 • First to observe living bacteria & drew them. • Also looked at sperm, protists, blood • 1stsimple scope • Made over 500 "microscopes"

  3. History • Robert Hooke (1665) – Used compound scope to examine cork. • Coined the term “cell” referring to the many little boxes. • Actually saw dead plant cells.

  4. Types of Microscopes • Simple microscope – Hand lens(magnifying glass) • Only has 1 lens • 3-40 times magnification

  5. Types of Microscopes • Compound Light Microscope – The type we use in our labs • Has two sets of lenses – Ocular (eye piece) & Objective (near the object being viewed) • Most commonly used microscope • Uses lenses and light to magnify & view the specimen • Total magnification on our scopes = 40 – 1000 times • Total Magnification = Ocular (10X) x Objective (40X)

  6. Microscope Parts Ocular – eye piece. Magnifies 10x Neck – Supports the eyepiece. Objectives – 4 – 100x magnification Arm – Supports neck and objectives. Carry by this Stage and clips – Holds slide in place Adjustments – Coarse & Fine. Focuses image Diaphragm – Controls the amount of lightcoming through the stage Light – Electric light source Base – Bottom of scope. One hand goes underneath

  7. Making specimens visible • Since most of the specimens we observe will be clear to near clear, what could be done to enhance the image we view through the scope? • Adjust the diaphragm to allow less light to come through • Use a stain to make transparent specimens visible. Ie. Iodine, methyl blue • Specimens must be sliced very thin. Blood cells Morel spores Endospores Colon x section Phytoplankton

  8. Electron Microscopes • Uses electromagnets and streams of electrons to view a specimen • Limit of Resolution is 1000x finer than light microscope • 200,000 – 1,000,000 x magnification • Two types

  9. Transmission EM • Transmission Electron Microscope (TEM) 1931 (Germany) • Image is seen on a fluorescent screen • Specimen must be thinly slices and coated in carbon. • Gives a 2D of specimen • Specimen must be dead Staphylococcus Herpes simplex virus E. Coli aureus

  10. Scanning EM • Scanning Electron Microscope (SEM) – 1935 (Germany) • Gives a 3D image and coated in Au or Ag • Electrons scan around specimen • Shows only the outside of the specimen • Gives very clear details of surface structures Weevil Tick DiatomRadiolarian

  11. Limits of the Electron Microscope • Specimens must be very thin • Specimens must be stained or coated • Specimens must be dried out (Mounting chamber is vacuum sealed • Specimens must be dead • BLACK AND WHITE images only!

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