Phylum Protozoa: Economic importance
Posted on : 26-11-2017 Posted by : Admin



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 help indirectly in purification of water by feeding on putrefying bacteria in various water bodies. These Protozoa play an important role in the sanitary betterment, 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 Protozoans 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.



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.

Soil Protozoa: several species of Protozoa, present in large numbers in soil feed upon the nitrifying bacteria and thus decline their activity and consequently tend to decrease the amount of nitrogen given to the soil by the nitrifying bacteria.

Water pollution: The Protozoa of faecal origin are responsible for water contamination or pollution. Some free living Protozoa also pollute water by producing aromatic and oily secretions with objectionable odors which render water unfit for human consumption. Some bioluminescent dinoflagellates living in sea multiply extensively to turn the water red with their bodies.

The phenomenon is known as blooming and is the cause of ‘red tides’ experienced in the sea. The red water often gives afoul and disagreeable small to the ocean water. Large concentrations of these flagellate Protozoans may even lead to destruction of fish and poisoning of edible mollusks such as clam, oysters, mussels etc. making them unfit for human consumption.

Pathogenic Protozoa: Protozoa causing diseases are called pathogenic Protozoa. They occur in all classes of Protozoa.

* Pathogenic Sarcodines: There are two common genera which live in the intestine of man and other animals. Two species of Entamoeba cause serious dysentery in man and in reptiles.

* Pathogenic flagellates: The parasitic flagellates include Leishmania, Trypanosoma, Histomonas, Trichomonas, and Giardia. Three different species of Leishmania severe disease in man. These are transmitted by sandflies of the genus phlebotomus. The parasitic species of Trypanosoma in mammals causes serious diseases.

Different Trichomonas species cause vaginal Trichomoniasis in humans, cattle, doves, pigeon, turkeys and chickens. Giardia intestinalis causes Giardiasis in humans.

* Pathogenic Sporozoans: This super class is exclusively of parasitic forms. Some genera like Plasmodium, Eimeria, Isospora and Babesia include pathogenic species. Four species of Plasmodium cause malaria in man. Different species of Plasmodium cause malaria in monkeys tree rats and jungle fowl.

Pathogenic species of Eimeria causes coccidiosis in chickens, rabbits, dogs, cats, cattle, sheep and goats. One parasitic species of Isospora infect intestine of man, others infect cats and dogs. Babesia is intra-erythrocytic parasite of various vertebrates and causes lethal fevers, malignant jaundice and anaemia in horses, rodents, cat’s goats etc.

* Pathogenic Ciliates: Balantidium coli are the only important intestinal parasites in man and also often found in frogs.

  1. "Protozoans are both useful and harmful". Write in support of the statement.
  2. Write about the protozoans which can be used as food.
  3. How do protozoans cause water pollution?
  4. Write about pathogenic protozoans.

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