Phylum Protozoa - General Characters and Classification

Protozoans are the simplest microscopic organisms, regarded as most primitive and first animals in the evolutionary history of Animal Kingdom.The term Protozoa is derived from two greek words 'Protos' means first, and 'zoan' means animal. The term 'Protozoa' was first suggested by Goldfuss. Though they are generally known as unicellular animals, Hyman regarded them as acellular or non-cellular. The study of protozoans is called as 'Protozoology'. The phylum has about 50,000 species. First discovered by the Dutch scientist Anton Van Leeuwenhoek, with his self assembled microscope. The first protozoan found by him was - ;Vorticella', in 1675. Later he found 'Volvox' a colonial protozoan, and many other organisms.