Protozoa

• Proto - first, Zoa - animals

• Term ‘Protozoa’ was given by Goldfuss.

• Term ‘Protista’ was given by Ernst Haeckel

• Paramecium was discovered by John Hill

• Amoeba was discovered by Resenhof

• Study of protozoans is called protozoology.

• Protozoan is not included in animal kingdom

• Protozoa belongs to kingdom Protista

• Ernst Haeckel removed protozoa from kingdom animalia and included it in kingdom Protista.

• Leeuwenhoek: first studied in detail about protozoans that is why he is known as the father of protozoology. AKA father of microscopy.

• Von Siebold: established unicellular and parasitic nature of Protozoa

• Dobell: established acellular nature of protozoans. All life process takes place in a single cell.

CHARACTERISTIC FEATURES OF PROTOZOANS:

• Unicellular eukaryotes

• Acellular (mainly for viruses) {In questions, always give first priority to unicellular and then acellular}

• lowest grade of body organisation —> protoplasmic

• Nucleoplasm + cytoplasm = protoplasm

• Symmetry: mostly asymmetrical except giardia lamblia

• symmetry of giardia —> bilaterally symmetrical

• Solitary and colonial (eg: proterospongia which is the connecting link b/w Protozoa and Porifera)

• Some protozoans show nuclear dimorphism/ heterokaryotic (2 diff nucleus: mega & micro) —> Class: ciliata —> eg: paramecium

• Some protozoans have contractile vacuole.

  • Only found in freshwater protozoans.

  • Function of contractile vacuole is osmoregulation & excretion.

  • Absent in marine & parasitic protozoans.

  • When freshwater protozoans are transferred into marine water, contractile vacuole disappears.

  • When marine protozoans are transferred into fresh water, contractile vacuole appears.

  • When freshwater protozoans transfer into distilled water, contractile vacuole works faster.

• Some protozoans have shell. They are called shelled protozoans. The function of shell is protection. Eg: Arcella (shell made up of chitin), Difflugia (tiny sand particles), Radiolaria (silica), Foraminifera (CaCO3). Pyramid of Egypt is formed of limestone of shell of foraminifera.

• Some protozoans are free living or parasitic.

• Locomotion:

  • By cilia: class —> ciliata

  • By flagella: class —> flagellata

  • By pseudopodia: class —> rhizopoda/ sarcodina

  • Type of pseudopodia in amoeba is lobopodia

• Mode of nutrition:

  • Holozoic (eats food in solid form): paramecium, amoeba

  • Holophytic (photosynthesis): euglena (only in the presence of light)

  • Saprozoic: giardia, trypanosoma, euglena (in absence of light)

  • Parasitic (gains nutrition from host): parasitic protozoans

  • Mode of nutrition in euglena is mixotrophic (both)

• Digestion: intracellular

  • The medium of food vacuoles in protozoans (amoeba, paramecium) is acidic first then alkaline.

• Respiration: general body surface

• Excretion: general body surface

• Mode of excretion: ammonotelic

• Reproduction: asexual & sexual

  • Asexual:

    • By binary fission

      • Simple binary fission in amoeba

      • Transverse binary fission in paramecium

      • Longitudinal binary fission in class flagellata (euglena, Giardia, leishmania, trypanosoma)

    • By multiple fission/sporulation: Amoeba, plasmodium

    • By plasmotomy: opalina

  • Sexual:

    • Conjugation: paramecium

    • Syngamy: plasmodium

  • Encystment: in adverse conditions, protozoans form a resistant layer on the outside made up of protein. This is called cyst wall. Function is to overcome from the adverse environment. Eg: Amoeba

CLASSIFICATION OF PROTOZOA ON THE BASIS OF LOCOMOTORY ORGANELLES

Q) Which class of phylum Protozoa is not after the name of its locomotory organelle? Ans: sporozoa

Q) Which class of phylum Protozoa is exclusively endoparasite? Ans: sporozoa