General characters of Protozoa


Leuwenhoek first described the protozoan animals under a microscope, he called them animalcules.In 1871 Gold fuss gave the name PROTOZOA The term protozoa means primitive animals. Protozoans are present from Precambrian period to recent times 50.000 species are included in this Phylum.


1. Protozoa Body all protozoans are unicellular Hyman called them accelular.
2. Protozoa Symmetry: will show radial symmetry in some organisms, bilateral symmetry in some organisms& some organisms are asymmetrical.
3. Protozoan’s may live singly or some are colonial.
4. Protozoa body wall: these animals body covered by cell membrane which contain proteins and lipids.
5. Some animals may be covered by Pellicle. Some animals covered by shell Ex : Elphidium.
6. Protozoa Osomo Regulation :In fresh water animals contractile vacuole is present. It is useful for osomo regulation. in marine and parasitic protozoans contractile vacuole is absent.
7.Food vacuole will work as temporary stomach.
8. Locomotion Protozoa: protozoa amimals will show locomotory organelles like flagella. pseudopodia.cilia etc.
9.Nutrition in protozoans is by holozoic, holophytic. saprophytic, coprozoicetc.. Some protozoans are parasites.
10. Respiration is by diffusion
11, Excretion is by diffusion
12. In Protozoa Asexual Reproduction is by binary fission, multiple fission, budding etc.,
13. In Protozoa Sexual Reproduction is by syngamy. Conjugation etc.
14. During unfavorable condition - the protozoa’s will develop cyst around themselves.
15. In some the life cycle is complicated with asexual and sexual phases