Question

Phylum protozoa is classified on the basis of

• A. Mode of reproduction
• B. Locomotory organelles
• C. Mode of nutrition
• D. None of the above

Answer 1

Answer: (B)

Locomotory organelles

Phylum protozoa is classified on the basis of locomotory organelles. It is classified into four groups:-

1. Mastigophora (Zooflagellata): They possess flagella for locomotion. They may be free living aquatics, parasites, commensals or symbionts. Zooflagellates are generally uninucleate, occasionally multinucleate. The body is covered by a firm pellicle. Trypanosoma, Giardia, Leishmania, etc., are the examples of zooflagellates.
2. Sarcodina (Rhizopoda): They develop pseudopodia which are temporary protoplasmic outgrowths. They are of four types- lobopodia (broad and blunt), filopodia (slender, unsupported, independent), axopodia (slender with axial support) and reticulopodia (slender, reticulate). Pseudopodia are used for locomotion and engulfing food particles. The body may be covered with plasmalemma or a shell. Amoeba, Entamoeba, etc., are examples of sarcodina.
3. Sporozoa: All sporozoans are endoparasites. Locomotory organelles are absent. The body is covered with elastic pellicle or cuticle. Plasmodium, Monocystis, etc., are examples of sporozoans.
4. Ciliata: They develop a number of cilia during a part or whole of the life cycle. Cilia are used for locomotion and driving food. There are definite regions for ingestion and egestion. Ciliates often possess minute ejectable trichocysts for defence. Paramecium, Opalina, etc., are the examples of ciliates.