What Are Protozoan Protists of Kingdom Protista?

Protozoan Protists occur in various habitats like aquatic, land. They may be free living or act as a parasite. Leuwenhoek first studied it. Basically they are small, acellular organisms which occur in variety of forms. Their symmetry can be radial or bilateral. Their body organization is molecular. They are multinucleate. Holozoic is the main mode of nutrition. They excrete and respire through general body surface. They have contractile vacuoles for osmoregulation. Sexual and asexual methods of reproduction are present. Asexual reproduction occurs by fission and budding. Conjugation and syngamy constitute methods of sexual reproduction. Under not so favorable conditions they form cyst. They have different organelles for locomotion. These are flagella, cilia and pseudopodia. Based upon these organelles they are subdivided into different groups which are zooflagellate, sarcodina, ciliata and protozoa.