Protozoan
A protozoan is a microscopic size animal composed of one cell. The cells that make up the higher animals help each other to form tissues and organs, and each has a certain function, while protozoa live in a single body because all the functions are done in one cell. Exercise can lead to flagella, cilia, or stomach, but it can not exercise. The shapes are very diverse, such as asymmetric, rounded, circular, thin, long, flat, and distant from the back. Breeding is mainly based on dichotomy and germination. These protozoa are very important for the feeding of aquatic animal larvae. In addition, most of the colonies in the polluted water play a role of purifying the water. In the floating species, the abnormal growth is sometimes caused to cause the red tide phenomenon, which causes serious damage to aquatic animals. Protozoons are now known more than 30,000 species globally and live in rivers, lakes, and oceans.