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
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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Update: June 2012