Characteristics of Kingdom Protista:

(i) They include unicellular, eukaryotic organisms.

(ii) They may be free-living or parasitic or symbiotic in nature. Some also exist in colonies.

(iii) They may be autotrophic (e.g. algae and diatoms) or heterotrophic (protozoans).

(iv) They may be uninucleate, binucleate or multinucleate.

(v) Some of these organisms use appendages such as hair-like cilia or whip-like flagellum.

(vi) They reproduce asexually by binary fission or multiple fission and sexually by conjugation.

The Kingdom Protista is further classified into Phylum Protozoa:

(a) This phylum contains unicellular, mostly aquatic organisms.

(b) The body is either naked or covered by pellicle or hard shells. The body shape may also be varied.

(c) The cytoplasm is differentiated into an outer ectoplasm and an inner endoplasm.

(d) Locomotion is through finger-like pseudopodia, flagella or cilia.

(e) The protozoa undergo asexual reproduction by binary fission or multiple fission and sexual reproduction is by conjugation.

Phylum Protozoa is further divided into five classes:

Class 1- Mastigophora

Example: Euglena

Class 2- Sarcodina

Example: Amoeba

Class 3- Sporozoa

Example: Plasmodium

Class 4- Ciliata

Example: Paramecium

Class 5-Suctoria

Example: Ephelota