Place plant material such as dry grass, hay, or leaves in a wide-mouthed quart jar. Fill the jar three-fourths full with tap water that has been standing for two days to allow the chlorine to evaporate. Cover the jar and set it in a well lighted place, but away from direct sunlight.

In two days, observe drops of the water under a microscope. The population and varieties of protozoa will increase for several weeks.

Protozoa include the most primitive form of animal life.

Place a culture of protozoa in a long test tube sealed with a cork or rubber stopper. Hold the test tube vertically. Using a hand lens, you will see that the animals become
evenly distributed in a short time.

Now place the base of the tube against an ice cube. You will find that the protozoa tend to move to the top of the tube; they sense cold and seem to avoid it.

Test the influence of heat and cold upon one-celled plants by placing cultures of them in locations with different temperatures.

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Protozoa can be found primarily in water. Although they can be collected from puddles of standing water almost anywhere, the best source is unpolluted ponds.

Collect jars of pond water, including some mud from the bottom. Let the water settle. After two days, stir the water without disturbing the mud, fill a medicine dropper
with the water, and place a few drops in a watch glass or test tube. Use a hand lens to observe the contents. You will see some of the larger protozoa such as the
paramecium.

Some protozoa cause diseases in people -- one causes malaria, carried by the anopheles mosquito; another causes sleeping sickness, carried by the tsetse fly. You might be interested in researching information on the prevention of such diseases.