Phylum Protozoa : General Characteristics and Classification

Protozoa

(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, Ph.D.

Binod G C, Ph.D., is a passionate cell and molecular biologist with a flair for science communication. Through his blog, he simplifies complex biological concepts, making study materials and notes more accessible and student friendly.

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