General characteristics of protozoa

protozoa - characteristics and classification - harmful and beneficial protozoans

1. GENERAL CHARACTERISTICS AND CLASSIFICATION OF PROTOZOA by, K.ThangaMallika I M.Sc., Microbiology

2. PROTOZOA Protozoa are a diverse group of unicellular eukaryotic organisms. The word “protozoa” by coined by GEORG AUGUST GOLDFUSS in 1818. They are heterotrophic organisms and they donot have chlorophyll. eg : Amoeba, paramecium, euglena.

3. CHARACTERISTICS A protozoan body consists of only mass of protoplasm, so they are called acellular or non-cellular animals. HABITAT - mostly aquatic, either free living or parasitic. SIZE - most protozoans are in the size of 1 to 10 micrometer long, but Balantidium coli may measure 150 micrometer.

4. BODY- body of protozoa is either naked or covered by a pellicle. LOCOMOTION- locomotary organ are pseudopodia or cilia or absent. NUTRITION - nutrition are holophytic (like plant) or holozoic (like animal) or saprophytic or parasitic. DIGESTION - digestion is intracellular, occurs in food vacoules .

5. RESPIRATION - respiration occurs through the body surface. OSMOREGULATION – contractile vacoules helps in osmoregulation . In most protozoa, the c ytoplasm is differentiated into ectoplasm (the outer, transparent layer) and endoplasm (the inner layer containing organelles). The structure of cytoplasm is mostly seen in species with projecting pseudopodia, such as amoebas.

6. REPRODUCTION - reproduction occurs by both sexual and asexual reproduction. Asexual - usually by binary fission. Sexual - happens by Conjugation . NUCLEUS - Nucleus may be compact with diffuse chromatin or vesicular with central or eccentric karyosome (DNA) and peripheral chromatin (RNA). RESPIRATION – respiration is mostly anaerobic.

7. CLASSIFICATION OF PROTOZOA

8. SPOROZOA Commonly parasitic on vertebrate animals. Locomotory organ and contractile vacuoles are absent. Body covered with pellicle. Exclusively endoparasites . Reproduction by means of asexual and sexual. Examples: Plasmodium, Monocystis .

9. CILIOPHORA Complex freshwater or saltwater protozoan. It swims by the coordinated beating of their cilia. Nuclei is of two types: micronucleus and macronucleus. Body is covered by pellicle. Examples: Paramecium, Voricella .

10. RHIZOPODA These are amoeboid organisms that produce false pseudopodia. It preys on fungi , other protists and small invertebrates. Reporduction by means of sexual and asexual. Mostly free living, some are parasitic. Examples: Amoeba, Entamoeba .

11. ZOOMASTIGOPHORA It is characterised by one or more flagella. Free living or parasite. Body covered with cellulose, chitin or silica. Sexual reproduction occurs by longitudinal fission. Examples : Trypnosoma .

12. ECONOMIC IMPORTANCE OF PROTOZOA Protozoans are classified into two types based on their activites . Harmful protozoa Beneficial protozoa

13. BENEFICIAL PROTOZOA Food - Protozoa provide food for insect larvae and worms, which are taken by fishes and crabs and which are eated by man. Insect control - Several protozoa control harmful insects by persisting their bodies. Helpful in Sanitation - A large number of protozoa living in polluted water feed upon organic matters and thus purify it.

14. Oil exploration - Petroleum is organic origin. The skeletal deposit of Forminifera and Radiolaria are often found in association with oil deposits. In this means, they help in the exact location of oil. Scientific study - Many protozoa are used in biological and medical researches.

15. HARMFUL PROTOZOA Pollution of water - Drinking water in natural condition is made unpalatable by the reproduction of some free living protozoa in it. Destruction of wooden articles - Some flagellater like Trichonympha and Colonympha live in the gut of termites and help in cellular digestion. Reduction in Fertility of soil - Protozoans feed on nitrogen fixing bacteria thus reduce the fertility of soil.