Intro to Biology Feb, 2009
What is Biology? Biology is the branch of Science that deals with living organisms. What do Biologists study? “Umbrella Term” -ologists Examples?? Hydrologist, Cytologist, Pathologist, etc. Heavy vocabulary…but some clues to help! What is the most important tool used by Biologists?
Microscopes Anton van Leeuwenhoek ( ) was responsible for the first “microscope” as we know them today Due to his knowledge of lenses he was able to construct a piece of equipment that made things appear closer and larger. Today’s microscopes use 2 lenses to magnify specimens. (ocular/objective)
Types of MICROSCOPES Light vs. Electron Smallest size seen with the Naked Eye is…. 0.2mm = one ridge on your finger print (resolution OR resolving power) Light Microscopes can view mm Electron Microscopes can view mm (0.2 nm)
Compound Light Microscope Crudest of today’s microscopes Uses light passing through a medium of liquid to view a specimen Uses generally a 10X ocular lens in addition to a 4x, 10x, 40x objective lens Magnification = ocular x objective Limited in it’s magnification
Parts of the Compound Microscope – Fill in your sheet as we go!! quiz/# quiz/# quiz/#
Focusing a Microscope Always start with the low power objective (4X). Odds are, you will be able to see something on this setting. Use the Coarse Knob to focus. Once you've focused on low power, switch to Med Power (10X). Use the Coarse Knob to refocus. Again, if you haven't focused on this level, you will not be able to move to the next level. Now switch to High Power. (40X) If the specimen is too light or too dark, try adjusting the diaphragm.
Making a Wet Mount 1. Gather a thin slice/piece of whatever your specimen is. your specimen is too thick, then the coverslip will wobble on top of the sample like a see-saw, and you will not be able to view it under High Power. 2. Place ONE drop of water/dye directly over the specimen. If you put too much water, then the coverslip will float on top of the water, making it hard to draw the specimen, because they might actually float away. (Plus too much water is messy) 3. Place the coverslip at a 45 degree angle (approximately) with one edge touching the water drop and then gently let go. Performed correctly the coverslip will perfectly fall over the specimen
Finished with your Microscope? 1. Store microscopes with the scanning objective (4X) in place. 2. Wrap cords and cover microscopes. 3. Wash slides/slips in the sinks and dry them, placing them back in the slide boxes to be used later. 4. Carry with 2 hands (arm/base) 5. Put back in the correct location
Transmission Electron Microscope Uses electrons instead of light Capable of over X magnification Specimens that contain many layers of cells, such as blood vessels, cannot be examined A thick specimen would absorb all the electrons and produce a blackened image Only view thin sections encased in plastic
TEM cont..
Scanning Electron Microscope (SEM) Produces a 3-D image Provides even greater magnification than the TEM Takes “pictures” of surfaces Specimens are usually preserved, coated in a metal, dehydrated…so specimen being viewed is non-living.
Scanning Electron Microscope
SEM cont… Salt
Guess? Toilet Paper
Guess?? Staple going through paper
Guess?? Mascara Brush
Guess?? Mosquito Head
Rules for Biological Diagrams Unlined paper and a sharp pencil Leave an empty margin of about 1 cm all around your page When drawing cells, choose only one cell (unless otherwise required) and show the edge of neighbouring cells to show the connection Draw outline of your subject with clear and unbroken lines. Your drawing should be about ½ of the page Use Figure # and name as your heading Always indicate the magnification below your drawing Use stipples for darkened areas Always label to the right with a ruler
Biological Diagrams - Lab #2 Following all steps for biological diagrams complete the following: (Do two drawings on one page of plain paper) 1. Obtain a sample from the front and draw the specimen in the container (do not draw the bottle)