Compound Microscope

Plant Organs and Organ Systems

admin — Mon, 30 Jul 2007 10:06:20 +0000

Microscopes And The Study Of Cells

admin — Mon, 30 Jul 2007 10:04:10 +0000

Much of our knowledge of cellular organization has been made possi¬ble by the development of better and more powerful compound microscopes. In the detailed analysis of subcellular structure, three attributes of certain microscopes like compound microscopes are of particular importance: magnification, resolution, and contrast. Magnification of the microscope is a means of increasing the apparent size of the object being viewed. Resolution of the microscope is the capacity to separate adjacent forms or objects-to show them as distinct. Contrast of the microscope is important in distinguishing one part of a cell from another. (more…)

The Internal Structure of Cells

admin — Mon, 30 Jul 2007 10:01:07 +0000

THE NUCLEUS

Within the cells of most organisms (though not of bacteria and Cyano¬bacteria), the largest and one of the most conspicuous structural areas is the membrane-bounded nucleus. The nucleus plays the central role in cellular reproduction, the process by which a single cell divides and forms two new cells, as seen under a compound microscope. It also plays a crucial part, in conjunction with the environment, in determining the way the cell will develop and what form it will exhibit at maturity. And the nu¬cleus directs the chemical activities of the living cell. In short, it is the nucleus that the “instructions” that guide the life processes of the cell as long as it lives.

The cells of bacteria and Cyanobacteria differ from those of all other kinds of organisms in lacking a membrane-¬bounded nucleus (though they do possess genetic material that controls the cell’s activities). Similarly, these two groups lack many of the other subcellular structures found in other organisms. These differ¬ences, as studied under a compound microscope, are so fundamental that bacteria and Cyanobacteria are clas¬sified in a kingdom of their own (the Monera), and their cells are designated as procaryotic (”having a primitive nucleus”), whereas the cells of all other organisms are designated as eucaryotic (”having a true nucleus”). (more…)

Cells: Units Of Structure And Function

admin — Mon, 30 Jul 2007 09:57:41 +0000

Organisms are composed of a great variety of chemicals, some simple and some complex. But these chemicals do not of themselves possess the properties we recognize as life. This scientific fact strongly suggests that some kind of order is imposed on them, that they are not simply dispersed in random fashion in an aqueous medium. The components of living matter are indeed elaborately organized, as demonstrated when tissues are viewed under a compound microscope. The fundamental unit of organization is the cell. In the tradi¬tional view and using a compound microscope, cells consist of a substance called protoplasm, which is subdivided into two major areas: the nucleus, which is the control center of the cell, and the cytoplasm, which includes all the rest of the cell. What sort of substance is protoplasm? The standard definition, “living substance,” conveys remarkably little. (more…)

Soil Microbes

admin — Thu, 21 Jun 2007 13:04:54 +0000

There is a group of beneficial soil microbes, which are undesirable in water. These are the iron bacteria, which tend to become so numerous that they are called water-pest bacteria. Iron bacteria are a natural part of the environment. These microorganisms, when examined under a compound microscope, mix dissolved iron or manganese with oxygen and use it to develop rust-colored deposits. These bacteria, in the process, manufacture a brown slime that build up on well screens, pipes, and plumbing fixtures. They not only cause pipeline obstructions, but also increase the organic material in the water encouraging the abnormal growth of other microbes, as seen in a compound microscope.

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Microbes in the Dust and Air

admin — Thu, 21 Jun 2007 12:57:37 +0000

Franklin P. Adams, of Conning Tower fame, has two active indignations. If he is violent in the matter of numbering houses invisibly, he is still more so in the matter of dry sweeping. And those who follow his column closely may have noticed that his antipathy to the broom has increased markedly since the birth of his first child. That, of course, may be mere coincidence; but very probably it is not. For dry sweeping raises dust; dust is dangerous to health particularly to child health. Heywood Broun once scoffed at F.P.A’s aversion to breathing dust-laden air, citing him man’s natural and acquired resistance to the microbes floating therein. But Mr. Broun overlooked the fact that resistance, while an important factor in prevention of disease, is by no means the whole story, as we shall see later. Moreover, if he had consulted vital statistics or the warnings of experienced sanitarians, he would have learned, for instance, that workers in occupations involving a dust-laden atmosphere are much more prone to respiratory infections than workers in other lines.

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Microbes In The Air And Water

admin — Thu, 21 Jun 2007 12:55:34 +0000

AIR

In the light of present knowledge, we may be tempted to laugh at the old beliefs concerning the dangers lurking in air. Hippocrates tells us that the Athenians, believing that the plague derived from impure air, fought it by lighting huge bonfires. And Defoe, in his Journal of the Plague Year, tells us that the English, two thousand years later, still were using the methods of the Greeks. And to laugh a little at our own times, less than fifty years ago malaria and yellow fever still were attributed to miasmatic conditions a view still stoutly held by certain persons and organizations even today.

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