Types of Microscopes 1. Compound Light Microscope -Contains two lenses; the ocular lens and the objective lens. -Specimen must usually be transparent and stained. -Magnification usually from 40X to 400X

Images Taken by a Compound Light Microscope

2. Dissecting Microscope - Has 2 eyepieces. - Magnification of 6X to 50X. - Used to observe specimens that are small, but can be seen by the unaided eye. - Useful in performing dissections.

Image Taken From a Dissecting Microscope

3. Phase-Contrast Microscope Has made it possible to view unstained (staining kills cells), living cells. Live cells undergoing cell division have been studied with this microscope.

Images Taken by Phase-Contrast Microscope

4. Electron Microscope - Uses beams of electrons (rather than light) to produce an image. - Live specimens cannot be viewed - Two types: transmission and scanning

A. Transmission Electron -Magnifies between 250,000X – 2,000,000X -Allows biologists to view internal structures of cells.

Image Taken By Transmission Electron Microscope

B. Scanning Electron Microscope -Scans the surface of an object with a beam of electrons to produce a 3-dimensional image. -Magnifies objects up to 50,000X. -Has a very high resolving power which reveals fine details of the surface of the specimen.

Scanning Electron Microscope

Image Taken by Scanning Electron Microscope

Image Taken by Scanning Electron Microscope

Lab Techniques of a Biologist

1. Centrifuge -Separates material based on density. -Material is placed in a test tube and then into the centrifuge. -Centrifuge spins -The most dense particles fall to the bottom of the tubes -Can be used to separate parts of the cell from one another

-Growing cells outside of the body. 2. Tissue Culture -Growing cells outside of the body. -Cells are placed in a test tube/petri dish. -Scientists can learn how living cells react to different medications.

3. Micro dissection - Small instruments attached to a microscope. - These instruments can be used under a microscope to remove, add, or transfer cell parts.

4. Chemical Analysis/ Indicators - Determine chemical composition of a substance. Lugol’s Iodine – Turns from amber to blue/black in the presence of starch. Bromothymol Blue – Turns from blue to yellow in the presence of CO2 C. Benedict’s Solution - Turns from blue to orange/red upon heating in the presence of glucose.

5. Chromatography -Separates chemical mixtures into its components. A dot of the mixture is placed on filter paper. The filter paper is placed in a solvent. The solvent diffuses up the paper separating the components in the mixture.

Chromatography Finish Start

Plants contain other pigments besides chlorophyll.

6. Gel Electrophoresis -Separates mixtures of large charged molecules. Such molecules include DNA fragments and proteins. http://www.lpscience.fatcow.com/jwanamaker/animations.htm