Protozoa- Definition, characteristics, classification, examples

 

Protozoa- Definition, characteristics, classification, examples

Protozoa can be defined as "single or colonized, microscopic acellular animals without tissues and organs with one or more nuclei".

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Various Protozoans

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General characteristics of Phylum Protozoa are

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1. Approximately 50,000 Phylum Protozoa species are known.

2. Protozoans are primarily living in two life forms: free (aquatic, freshwater, marine water) and parasite (ectoparasites or endoparasites).

3. They are small, normally microscopic, and don't appear without a microscope.

4. You have a simple organization of the body. i.e. a protoplasmic organizational grade.

5.  The body is unicellular (no tissue and organ).

6.  They have one or several monomorphic or dimorphic nuclei.

7.  The body is naked or bound by a pellicle, but in certain ways, shells may be covered, often with an inner skeleton.

8.  They are solitary (alone/individual) or colonial (individuals are alike).

9.  Sphere-like, oval, elongated, or flattened body shape variables may be available. 

10. Body symmetry either none or bilateral or spherical symmetry.

11. The body form is usually constant, some of them varied, and many changes with environment or age.

12. Protoplasm is distinguished by an external ectoplasm and an internal endoplasm.

13. This unicellular body carries out all the fundamental and vital actions that characterize the animal organism; hence the physiological division of labor in subcellular only.

14. Locomotive organs are pseudopodia, flagella, hair cilia, etc. fingers.

15. Holozoic (animal-like), halophytic (plant-like), saprozoic, and parasitic nutrition may be eaten.

16.  Intracellular digestion occurs within the food vacuoles.

17.  Breathing occurs through the surface of the body.

18. Excretion takes place through the surface of the body, but in certain forms through the temporary opening in the ectoplasm or a permanent pore known as the cytopyge. 

19. Contractile vacuoles perform osmoregulation in freshwater forms and also help in removing excretory products.

20. Reproduction asexual (binary or multiple fission, budding, sporulation) or sexual (conjugation, game formation (syngamy)).

21. The life cycle often complicated with alternation of asexual and sexual phases (alternation of generation).

22. Encystment commonly occurs to resist unfavorable conditions of food, temperature, and moisture, and also helps in dispersal.

23. The single-celled individual not differentiated into somatoplasm and germplasm; therefore, exempt from natural death which is the price paid for the body.

24. Protozoans exhibit mainly two forms of life; free-living (aquatic, freshwater, seawater) and parasitic (ectoparasites or endoparasites). They are also commensal in habitat.

25. Examples: Euglena, Amoeba, Plasmodium, Paramecium, Podophyra, etc.