Paramecia are unicellular organisms belonging to the kingdom Protista, so they aren't exactly plants or animals. A paramecium can digest food, move through water by propelling themselves with cilia, and reproduce. As some of the oldest organisms on earth, they have evolved very simple methods of defense, genetic exchange, and mobility.

There are eight different species of paramecium, but all are ciliate protozoa. This means they use cilia to swim through water and their one complex cell, a eukaryote, conducts all of the organism's basic functions. It doesn't divide labor between different tissues or cells like an animal. Instead, each paramecium is capable of an aerobic exchange, similar to breathing, reproducing asexually, ingesting nutrients, and expelling waste.

With good vision, you can just make out the speck of a paramecium, since they are about .02 inches (.5 mm) long. They're better viewed under a microscope. Here, you'll see a slipper or kidney shaped cell. Lining the outside of its membrane are tiny, beating hairs called cilia. Cilia move in conjunction, like a line of oars on a ship, to move the paramecium through liquid. The eukaryote is smart enough to navigate around obstacles and towards food.

When a paramecium encounters food, it swivels to move the food into its gullet. The gullet is a small opening, like a mouth. It's lined with other cilia to help "swallow" the bits of organic or decaying matter it eats, like other unicellular organisms or bacteria. The food will continue down the gullet to get stored in food vacuoles until the cell needs energy.

You might be able to make out other rounded structures, called organelles, that sort of function like an animal's organs. Look for contractile vacuoles. The paramecium must keep osmotic equilibrium, which means the water pressure outside its skin and inside its body needs to be equal at all times. Contractile vacuoles pass water from inside the cell to outside, and vice versa.

Following the paramecium as it moves slowly through a viscous liquid, remind yourself that in the wild, out in freshwater ponds, it speeds along at a much quicker pace. Under most circumstances, they reproduce by splitting themselves down the middle and giving each new paramecium half of the organelles. This is called binary fission, and is a simple form of asexual reproduction. If you're lucky enough to see two paramecium meet each other, watch how they behave.

Occasionally, a paramecium will meet another and exchange genetic material during a kind of primitive sexual reproduction. The membranous skins combine to make one giant paramecium. Then the tiny micronuclei that hold all of the genetic material switch around. When it divides into four smaller paramecium, they now have new combinations of DNA.