Protozoa are found almost everywhere, in water, in moist surface of the soil, in air and even within the bodies of other animals and plants. They exert far more influence on the worldly affairs. They are harmful as well as useful species.
Helpful in sanitation: Numerous biologic protozoa feed on putrefying bacteria in various bodies of water and thus help indirectly in purification of water. These Protozoa play an n important part in the sanitary betterment and improvement of water and keeping water safe for drinking purposes.
Planktonic Protozoa as food: Protozoa floating on the plankton of sea provide directly or indirectly the source of food supplies to man, fish and other animals. They form one of the first links in the numerous and complicated food chains that exist in the oceans of the world. Clams and young fish feed extensively on aquatic larvae, small crustaceans, worms, etc. all of which take Protozoa as food. Thus Protozoa indirectly form food of fish, clams and other animals, which in their turn are consumed by man.
Symbiotic Protozoa: Some Protozoan are found in symbiotic relationship with other organisms. This association is beneficial to both the partners. The two partners become so dependent on each other and their separation results in the death of both. Several intestinal Protozoan flagellates of termites and woodroaches are extremely vital for the very existence of their hosts. They digest cellulose into soluble glycogen substance for their hosts as well as for themselves.
Oceanic ooze and fossil Protozoa: the tiny skeletons of dead pelagic Foraminiferida, Radiolaria and Heliozoa sink to the sea bottom forming the soft mud or oceanic ooze. These tiny skeletons are made up of silica or calcium carbonate and over the years, deposited on the floor of the ocean, became solid and fossilized and converted into some important sedimentary rock strata found all over the world. These have been put to various commercial uses such as filtering agents, abrasives, chalk, building stones etc.
Protozoa in study: They are studied in the laboratories for the comprehension and application of biological principles. Due to their minute size and quick reproduction, they are studied by geneticists for heredity and variations. They are progenitors of metazoans so their study helps in understanding the probable beginning of organic matter and the origin and evolution of life. The study of physiology of Protozoa also contributed to know about the physiology of cell