Size : Range - 2.0 - 200 μm
Characteristics :
Protozoa are unicellular eukaryotic microbes that belong to the kingdom Protista. Protozoa are classified according to their means of locomotion, Amoebas move using extensions of their cytoplasm called pseudopodias. Other protozoa have flagella or numerous shorter appendages called cilia. They have a variety of shapes and live as free entities or parasites that adsorb or ingest organic compounds from their environments. Protozoa can reproduce asexually or sexually. Euglena, Leishmania, Entamoeba are some known examples of protozoa. In a nutshell the characteristics of protozoa can be shortlisted as :
* Protozoa are eukaryotic unicellular organisms.
* They are differentiated on the basis of morphological, nutritional and physiological characteristics.
* Some protozoa can be cultivated in laboratory media.
* Some of them are intracellular parasites eg. Plasmodium vivax.
* They reproduce by asexual and sexual process.
Practical Significance :
* They act as food for aquatic animals.
* Some protozoans cause diseases eg. Entamoeba histolytica- amoebic dysentery, Trypanosoma gambiensiae - Sleeping sickness etc.
* Many free living protozoa function as the principle hunters and grazers of the microbial world.
* Some protozoa are normal inhabitants of the intestinal tracts if animals, where they aid in diagram of complex material such as cellulose.