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Friday, 27 January 2017

Biological Classification : Protista


         Kingdom Protista includes Chrysophytes, Dinoflagellates, Eugleoids, slime mould and Protozoans.

(a)  It includes all unicellular and colonial eukaryotes.

(b)  Most of them are aquatic forming plankton.

(c)   Mode of nutrition may be photosynthetic, saprobic, parasitic or holozoic.

(d)  Flagella if present are 11 stranded with 9+2 arrangement of microtubules composed of tubulin.

(e)  Genetic material consists of 2 or more DNA molecules.


Chrysophytes

·  They includes diatoms and golden algae (desmids) found in fresh water as well as marine water.

·   In diatoms cell wall forms two thin overlapping cells which fit together as in soap box.

·   The siliceous indestructible cell wall pile up at the bottom of water reservoirs and form big heaps called diatomaceous earth. It may extend for hundred meter and used for polishing, filtration of oil and syrups. They are chief producer in oceans.


Dinoflagellates

  • They are basically unicellular motile, biflagellate and photosynthetic protists. 
  • Predominate colour is golden brown but yellow, green, red and even blue.
  • Some Dinoflagellates like Gymnodinium and Gonyaulax grow in large number in the sea      and make the water look red and cause the so called “red tide
Eugleoids

  • They are Euglena like unicellular flagellates which possess pellicle instead of cell wall which make their body flexible.
  • They have two flagella, one short and other long.
  • They are photosynthetic in presence of sunlight and act as predators in absence of sunlight. 
  • Example- Euglena, Peranema.

Slime Moulds

  • They are saprophytic protists and feeds on decaying twinges and leaves.
  • Under favorable condition, they form an aggregation called plasmodium which produce fruiting bodies bearing spores. 
  • The cell wall of spores bears cellulose.
  • Example- Physarum, Fuligo.
Protozoans

  • All protozoans are heterotrophs and live as predators of parasites. They are considered as primitive relatives of animals. 
  • Amoeboids move and capture food by pseudopodia. Some are parasitic also. Flagellated protozoans are free-living or parasitic. They have flagella.
  • Ciliated protozoans are aquatic and have cilia all over the body for movement.
  • Sporozoans includes organism that have infectious spore like stage in their life cycle.

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