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Life in a Drop of Water
Nature Bulletin No. 259-A   March 4, 1967
Forest Preserve District of Cook County
Richard B. Ogilvie, President
Roland F. Eisenbeis, Supt. of Conservation

LIFE IN A DROP OF WATER
A drop of pond water appears clear and lifeless to the naked eye but within it are many queer creatures that can only be seen when viewed through a high-powered microscope. The first simple microscopes, magnifying ten times or less, were made by Dutch spectacle-makers in the 16th century. These aroused a great deal of wonder and it was considered particularly fascinating to watch live fleas with them. Thus they became known as "flea glasses". By 1674, the self-taught Dutch naturalist and lens-grinder, Leeuwenhoek, had made microscopes giving magnifications up to 270-power and had begun to tell about the multitude of very small living things he saw in water. A whole new world of life was revealed for the first time.

Since then, thousands of species of microscopic water plants and animals have been described and given scientific names. Common English names are rare. They can multiply at an enormous rate and are the most abundant living things in both fresh and salt water. A single quart of water may have more individuals in it than there are people in the world.

One of the better known creatures, one that often swarms in puddles and ponds, is the Paramecium or Slipper Animalcule which is barely visible to the naked eye. Seen under a microscope, its body is a single cell enclosed in an oblong flexible envelope covered by thousands of short hair-like "cilia" that actively row the animal about. Near the front end is a broad deep groove with a mouth opening at the bottom. Into this opening the cilia in the groove sweep bacteria, algae and other small life on which it feeds. The Paramecium multiplies by merely pinching itself into two parts. The front half grows a new back half, and the original back half grows a new front half with a groove and mouth opening. There is nothing left which can be called a parent. Neither are there males or females.

Another microscopic one-celled animal, the Ameba, looks like a bit of grayish jelly that seems to slowly melt and flow over submerged water plants, dead leaves and mud. It feeds by merely flowing around smaller organisms and, like the Paramecium, multiplies by merely dividing. Another, the Vorticella, forms colonies on underwater surfaces. Each animal is a bell-shaped "head" attached to a long stalk that jerks back like a coil spring when danger threatens. It gathers food with its ring of cilia around the lip of the bell. Noctiluca, a microscopic animal that swarms in sea water, produces a phosphorescent glow when disturbed by a breaking wave or a passing ship.

Microscopic water plants, like larger plants, contain green coloring matter, or chlorophyll, by which they manufacture their own food in sunlight. Single-celled plants -- Diatoms, Desmids and certain other algae which multiply by dividing like the Paramecium -- numbering into billions of individuals, produce the golden brown masses that cover the beds of streams and aquatic weeds, or the film of green "bloom" or "scum" on the surface of lakes and ponds. In water supply reservoirs, certain ones give a fishy, a bitter, or a cucumber taste to the water. In other kinds of algae, such as Spirogyra, the cells divide but remain attached to form long threads which, in masses, look and feel like slippery green hair.

There are also strange creatures that swim with long whip-like "flagella" and eat like animals, but which have green chlorophyll and behave like plants in Some ways. They straddle the boundary between the plant and animal kingdoms.

Such microscopic organisms, called "plankton", are the staff of life -- basic food -- for all animals that live in water.


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