Aubrey Messer, age 13, of Marshall, N.C., for his question:
What are protozoa?
Perhaps you thought the smallest animal on earth was a tiny mite, Just big enough to be seen. This is what everybody thought before the microscope was invented. Its magnifying lenses showed the tiny mite to he a giant ‑ at least when compared to the midget protozoa which are far, for too small for our eyes to see.
These tiny creatures share our world with us. They teem in every stream, and river. They swarm in the soil and even float and crawl in the deep ocean. They are remarkable for two qualities ‑ beauty and efficiency. Each tiny protozoon is but a single cell measuring perhaps one thousand or two thousand to an inch. Yet that one cell carries on all the functions of life, and even multiplies itself.
Mother Nature, it seems, likes to have beauty even in her smallest creatures. Every beautiful design you can imagine is used by some little protozoon. There are protozoa shaped like dainty bells, fans, arrows and fragile pom‑poms. There are protozoa shaped like coils and balls, like rods and branches, cups and elegant vases. Some 15,000 of them have been discovered and this is but a beginning. Our world is populated to overflowing with these busy little fellows called protozoa.
The word protozoa means first‑life. The pretty one‑celled creatures are rated in Phylum I, Protozoa. This gives them first place in the classification of the Animal Kingdom. They are the simplest of all creatures. All other animals have more than one cell, some having billions The protozoa were most likely first in another sense. They may have been the first of all creatures to live on the earth.
The protozoon, which is singular of protozoa, does not seem to be limited by his small, one‑celled body. He can move about from place to place. Some flow or creep like blobs of animated jelly. Some‑have hairs or lashes which they use for swimming through the water. Some hitchhike on or inside animals and larger plants. Some merely float in the sea.
Most protozoa have soft, jelly like bodies, maybe adorned with microscopic hairs or tiny tails. One group actually builds houses. These are sea dwellers and they cover their soft bodies in shells of calcium carbonate. These shells, too small for our eyes to see, may be ornamental boxes, midget globes or graceful coils.
There are always holes in the walls. Through these windows, the tiny creatures send out fine threads and nets to trap fragments of food. Our beds of chalk and limestone were built from the shells of these little window makers.
Most protozoa are harmless to us and many of them are friendly. A font are dangerous. A certain wriggly protozoon causes the dread sleeping sickness of Africa. Another wriggler causes malaria. Apart from a few criminals, the vast Phylum of Protozoa is content to share our world and wait to be admired under a microscope,