What are the distinct features of Protozoan animals?

The simplest members of the animal kingdom are unicellular or single celled animals. Examples of such animals are the amoeba and the Paramecium.
The amoeba is found in the mud at the bottom of ponds. It can be seen with the naked eye as a whitish speck. It reaches a maximum length of about 1/100 inch. It is an irregular, jelly like mass. The name amoeba is derived from the Greek amoebe which means change. If the amoeba is examined under a microscope the shape is seen to be continually changing.
The Paramecium too is found in muddy pools and stagnant puddles. It is the same size of that of the amoeba. However it has a definite shape. It's shape resembles that of a slipper.
Both the amoeba and the Paramecium breathe through the surface of their body. They feed on bacteria and other microorganisms or decayed remains of plants.