Biology-Mr.Willets Name__________________________
Lab-Scope #2
I. Microscopic Measurement
When we measure anything, we do so by comparing it to something whose size is known. In the case of your microscopes, we use the pointer.
The pointer has marks on it that represent various lengths. What we must do today is get used to using the pointer to measure things. If you wish to move the pointer to another part of the field, simply rotate the black eyepiece. Turn on your scopes and try this.
The smallest spaces on a metric ruler are millimeters. These are too big for use with a microscope. The units we use are called microns. One millimeter (mm) equals 1000 microns. Microns are very small. The symbol for micron is m There are 1 million microns in a meter.
As you look at the pointer, you see there are lots of lines. We will only use a few of them. The value of these is different depending on whether you are using low power or high power. The values you will need are listed on the card in the plastic box.
A. Paramecium
Get a slide of paramecium. This is a unicellular fresh water organism. I will have a slide on the video scope so you can see what it looks like. These have been stained so they are more easily seen. When they were alive, they were colorless. Find a paramecium using scanning power. Use one that is by itself and not with a bunch of others. Center your specimen and switch to low power. Use the pointer to estimate its length and width. Draw the basic shape of the paramecium as it looks using low power. Indicate the magnification the length and the width. Do not now or ever include the pointer
Center the paramecium in the low power field and switch to high power. Now use the pointer to again estimate the length and width of the paramecium. Draw the paramecium as it appears using high power. Indicate magnification, length and width.
B. Hair
Remove a piece of hair from you or your partner. Place 2 drops of water on a clean slide. Cut a small piece off of one end of the hair and put it into the water. Cut another small piece from the other end of the hair and put it in the water also. Cut a small piece from the middle of the hair and put it into the water. Add a cover glass and examine using low power. Compare the width of your hair to some part of the pointer . Estimate how wide a piece of your hair is.______________
Center one piece of hair in the field and switch to high power. Compare the width of your hair to some part of the pointer . Estimate how wide your hair is? _______________
Did you get the same answer both times? The actual answer is probably somewhere between your two estimates.
II. Location Using the Pointer
The pointer is used when you wish to ask about something you are looking at. You can move the slide and spin the eyepiece so that the pointer is touching the object in question. You can then me ask about "the object the pointer is touching" You may also use the "clock method" to ask about something. Think of the field as being a clock face. What number on the clock is the object nearest? That is how you can tell me which object you are asking about.
In the circle below which letter could be described as being "near 5 o'clock"?_____
How would you describe the location of letter D? _________________________
Which letter is between 2 o'clock and the center of the clock? ___________
Describe the location of the letter C____________________________________
III. Stereo Microscopes
Stereoscopes are used to examine specimens that are either too big or too thick for the compound scopes. These scopes magnify either 1OX or 2OX. Most of our stereoscopes have a black switch on the side to change magnifications. Two of our scopes work differently. I'll show you in class.
Most of these scopes have two lights. One to shine through specimens that are thin enough and one to shine down on thick specimens. You must decide which type of lighting is best for your specimen.
The two eyepieces can be moved apart to match your eye width. The focusing knobs are obvious.
Use these scopes to examine some objects available at the front of the room. You may also find your finger interesting. Jewelry and coins are good, also.
Because you use both eyes, the image can be three-dimensional which is what stereo means.
IV. Pond Water
Pond water contains many micro-organisms and a few that are a little larger. By examining pond water, we get practice in slide making and using the compound scopes. If you find a moving organism, you will also get practice in keeping it in the field of view.
Some micro-organisms are animal-like and tend to live in the mud at the bottom of ponds. Others are plant-like and need the sunlight available nearer the top.
Some of the larger micro-organisms in pond water are crustaceans and are related to shrimp, lobsters etc. If you see one of these, note its jointed legs, its large eyes and look for its heart beating (the body is often transparent).
Plant-like micro-organisms are green. Animal-like micro-organisms move around. Everything else is probably dirt or air bubbles.
Make a slide using a drop or two of pond water from the front of the room. Bring your own slide. Cover glasses will be available at the front desk. Get a little grunk from the bottom (but not too much). Add a cover glass and examine under low power. If you find something interesting, you can switch to high power but remember, that doesn't always give a better view.
There are sheets available at the front of the room showing drawings of what might be found in pond water. You can use these to try to identify what you find.