Phylum Protozoa : General Characteristics and Classification


(Gr., protos = first; zoon = animal)

General Characteristics

  1. Microscopic and acellular animals
  2. Solitary or colonial
  3. Body naked or covered by pellicle and provided with internal skeleton
  4. Great variety of shape : oval, spherical elongated and some are flattened
  5. Cytoplasm : outer ectoplasm and inner endoplasm
  6. Locomotary organs : Pseudopodia (in Rhizopoda), Flagella ( in Flagellata), Cilia (in Ciliata), and absent in Sporozoa
  7. Nutrition : Holophytic (plant-like), Holozoic (animal like), Saprozoic or Parasitic
  8. Respiration : Diffusion by general body surface
  9. Excretion through general body surface
  10. Reproduction : Sexual (copulaion/syngamy and conjugation) , Asexual ( Fission, Budding, Plasmotomy)
  11. Lifecycle exhibits alternation of generation
  12. No physiological division of Labour

Phylum Protozoa is divided into 2 sub-phyla and 5 classes

Sub Phylum : PlasmodromaSub phylum : Ciliophora
Class : Rhizopoda/SarcodinaClass: Mastigophora/ FlagellataClass: SporozoaClass : CiliataClass: Suctoria
Locomotion by Pseudopodia, Amoeboid locomotionLocomotion by 1 or more flagellaNo locomotory organellesLocomotion by cilia present throughout the bodyAdults lack cilia, cilia replaced by suctorial tentacles
Mostly free living but some are parasitesMostly free living but some are parasitesExclusively endoparasitesFree living or endoparasites—–
Body naked and without definite shapePellicles present so with definite body shapePellicles present so with definite body shapePellicles present so with definite body shape——
Eg: Amoeba, Entamoeba, Arcella etc.Eg: Euglena, Trypanosoma, Leishmania, Giardia etc.Eg : Plasmodium, Monocystis, Eimeria, Babesia etc.Eg : Paramecium, Vorticella, Balantidium, Opalina etc.Eg: Aceneta, Ephelota etc.

Binod G C

I'm Binod G C (MSc), a PhD candidate in cell and molecular biology who works as a biology educator and enjoys scientific blogging. My proclivity for blogging is intended to make notes and study materials more accessible to students.

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