What are the types of protozoa?

Protozoa are divided into four major groups based on the structure and the part involved in the locomotion:

1. Mastigophora or Flagellated protozoans:
They are parasites or free-living.
They have flagella for locomotion
Their body is covered by a cuticle or pellicle
Freshwater forms have a contractile vacuole
Reproduction is by binary fission (longitudinal division)
Examples: Trypanosoma, Trichomonas, Giardia, Leishmania, etc.

2. Sarcodina or Amoeboids:
They live in the freshwater, sea or moist soil.
The movement is by pseudopodia. They capture their prey by pseudopodia
There is no definite shape and pellicle is absent
The contractile vacuole is present in the amoeboids living in freshwater
Reproduction is by binary fission and cyst formation
Examples: Amoeba, Entamoeba, etc.

3. Sporozoa or Sporozoans:
They are endoparasitic.
They don’t have any specialised organ for locomotion
The pellicle is present, which has subpellicular microtubules, that help in movement
Reproduction is by sporozoite formation
Examples: Plasmodium, Myxidium, Nosema, Globidium, etc.

4. Ciliophora or Ciliated protozoans:
They are aquatic and move actively with the help of thousands of cilia.
They have fixed shape due to covering of pellicle
They may have tentacles, e.g. in the sub-class Suctoria
Contractile vacuoles are present
Some species have an organ for defence called trichocysts
They move with the help of cilia and the movement of cilia also helps in taking food inside the gullet
They reproduce by transverse division and also form cysts
Examples: Paramecium, Vorticella, Balantidium, etc.