Protozoa
The Protozoa is a subkingdom of the kingdom Protista. However, in the classical system, they were placed in the kingdom Animalia. Protozoa are unicellular eukaryotic microorganisms having a membrane-bound nucleus and other organelles within their cells. Despite their small size, they are incredibly diverse and exist in various aquatic and terrestrial environments worldwide. More than 50,000 species are known, most of which are free-living organisms. Some common examples of protozoa are Amoeba proteus , Paramecium caudatum , Euglena gracilis , Plasmodium falciparum , and Trypanosoma brucei ....