This lab page has many other pages off of it. You will need to go, in order, through the pages to get to everything. To help you do this, at the top and bottom of each page from this one, you will find a "next" and a "previous" button. I hope that helps. You will be able to link over to this lab assignment from BlackBoard.
You need to submit this lab to me by Tues, 3/5, at midnight (because we had a test last week that interrupted stuff). There are 2 submission forms for the 5 exercises. One is currently available, the other will be available tomorrow.
Learning Objectives for this lab:
Portions of this laboratory:
In this laboratory we will learn how to use one of the most valuable tools in the biologists toolbox: the microscope. You have learned that the smallest item that can still be considered living is a cell... and that some living organisms are composed of only a single cell! But cells are too small for us to see. Therefore, we need to magnify them to view them. That is what the microscope will do for us-- it magnifies biological material for viewing.
There are two basic types of microscopes that are used in biological studies: the compound light microscope and the electron microscope. The compound light microscope utilizes ordinary light as the medium of illumination and magnification. The electron microscope utilizes a stream of electrons to magnify an object. Although different in appearance, both of these microscopes perform the same function: to magnify objects. Because the compound light microscope uses light, and our eyes understand light, we can view material through it. However, our eyes cannot see electron beams, so those microscopes have to send their information to special screens and photographic paper for us to view.
The development of the microscope can be traced back to the first century A.D. Roman author and philosopher Seneca noted that a jar of water positioned properly would make writing appear clearer and larger in size. The ancients at Nineva, the Romans, Chinese, and Greeks may have used lenses for reading. In 1558, Swiss naturalist Conrad Gesner wrote of the use of magnification in biological investigation.
Perhaps the best known of the early microscopists was Antony van Leeuwenhoek. A master lens grinder, Leeuwenhoek spent most of his life observing and describing the then virtually unknown microscopic world (microscopic being any substance or structure too small to be viewed with the naked eye), with his simple microscopes making thousands of observations. His contributions include sketching: the three major groups of bacteria; capillary circulation in an eels tail; muscle fibers; insect anatomy; plant tissues. He was also one of the first people to view human sperm beneath a microscope. In addition, Leeuwenhoek made observations of tartar taken from his teeth, in which he described living beasties in this material (we know today that this is bacteria). In one of his poorer choices for observation, Leeuwenhoek viewed a small gunpowder explosion beneath one microscope. It is reported that this experiment left him blinded for several days!
Because the microscopes Leeuwenhoek used had only one magnifying lens, his microscopes were considered to be simple light microscopes. The appearance of a true compound microscope dates from the late 16th century when Zaccharias Janssens of Holland discovered that by combining lenses and manipulating distances between them, objects could be enlarged. Modern microscopes that use two or more lenses to magnify an object are called compound light microscopes.
A beautiful replica of a Leeuwenhoek microscope, made by Alan Shinn of Berkeley California.
You will be learning about microscopes because the basics of biology lie in cells, which are almost always too small to see with the naked eye. In order to view cells, you will need to magnify them. In this class, we will only be looking at larger cells, so a toy microscope will suffice. However, to look at any or all cells, you will find it easiest to use a better microscope, such as those we have at STCC. If you live in the vicinity of STCC, I will be inviting you later on to visit us on a Monday night to use our microscopes. I promise that the quality of what you will see will be worth the trip.
The microscopes you will be using are compound light microscopes. Even though they are toy microscopes, they are rather sophisticated instruments. They must be used with care to prevent any damage to them (you wouldn't want to have to buy a second one).
Only clean the lenses with lens paper. The optical parts of the microscope are precision lenses and scratch easily. The only acceptable method of cleaning them is through the use of lens paper. Lens paper has been included in your kit. DO NOT use paper towels, shirtsleeves, handkerchiefs, or Kleenex to clean lenses. Never remove oculars or other parts from the body tube of the microscope-- they will just get dirtier.
Field (Field of View) - The circular area that can be seen when looking through the ocular.
Depth of Focus - The thickness of an object which is all in sharp focus at the same time. So, the more you can see in tissue thickness at one time, the greater the depth of focus.
Working Distance - The space between the bottom of the objective and the top of the slide. Shown in the image to the right. It is simply measured by placing a ruler as close as you can and estimating the distance in millimeters.
Resolution - The minimum distance between two points that can be separated. Usually refers to how clearly you can see details in the microscope.
© 2006 STCC Foundation Press, content by Dawn A. Tamarkin, Ph.D.
Last changed: January 21, 2007