General characteristics of phylum protozoa

1. They belongs to kingdom Protista.
2. They are acellular organisms.
3. Their body consists of only mass of protoplasm.
4. They are mostly aquatic.
5. They exhibit protoplasmic grade of organisation.
6. Their body is either naked or covered with a pellicle.
7. Their locomotory organ may be pseudopodia, or cilia, or flagella, or absent.
8. The mode of nutrition in them may be holophytic, or holozoic, or saprophytic, or parasitic.
9. Digestion in them is intracellular. 
10. Respiration in them occurs through the body surface.
11. Contractile vacuoles helps them in osmoregulation.
12. They reproduces asexually through binary fission or budding and sexually through syngamy or conjugation.

Classification of protozoa

Protozoa are generally classified into 4 types on the basis of their mode of locomotion, these are discussed below:

Class 1: Rhizopoda

i. Locomotory organ in them is pseudopodia.

ii.They are mostly free living, some may be parasitic.

iii. They reproduces asexually by binary fission and sexually by syngamy. 

iv. They does not reproduce through conjugation.          

v. Two examples are: Amoeba, Entamoeba.

Class 2: Flagellata (or Mastigophora)

i.  Locomotory organ in them is flagella.

ii.   They are free living or parasitic in nature.

iii. Their body is covered with cellulose, chitin, or silica.

iv. They reproduces asexually by longitudinal fission.

v. They does not reproduce through conjugation.

vi. Two examples are: Euglena, Trypanosoma.

Class 3: Sporozoa

i.  Locomotory organ in them is absent.

ii. They are endoparasitic organisms.

iii.Their body is covered with pellicle.

iv. Contractile vacuole is absent in them.

v. They reproduces asexually by fission and sexually by spores.

vi. Two examples are: Monocystis, Plasmodium.

Class 4: Ciliata

i. Locomotory organ in them is cilia.

ii. Their body is covered with pellicle.

iii. They reproduces asexually by binary fission and sexually by conjugation.

iv. Two examples are: Blantidium, Paramecium.

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