Think of the tiniest animal you’ve ever seen. The chances are that animal is millions of times bigger than the paramecium, the smallest earthly creature we can truly call an animal.
The paramecium is a one-celled organism found in pond and lake water or in damp earth. Like all one-celled animals, the paramecium is called a protozoan, or “first animal,” because these creatures probably appeared on earth before any other members of the animal kingdom.
A paramecium looks like a slipper-shaped piece of transparent matter. It has no legs or fins, but it does have tiny hairs growing out of its sides. These hairs wave to move it through the water.
To examine a paramecium, you’ll need a microscope, for these creatures are so small that it would take more than a hundred of them in a line to equal just one inch!
A paramecium is not an animal. By definition, an animal is multicellular, while a paramecium is single-celled. A paramecium is a protist. And it’s not the smallest protist; there are many protists smaller than a paramecium.