In Protista, phagotrophic nutrition is found in (a) Protozoan protists (b) Some dinoflagellates (c) A few euglenoids (d) All of the above
Hint: These are unicellular organisms having no defined digestive system in them and all the metabolic activities occur inside the cell. They are very simple eukaryotic organisms that live in water, in moist terrestrial habitats, and also as parasites and other symbionts in the bodies of multicellular eukaryotes.
Correct answer: In Protista, phagotrophic nutrition is found in protozoan protists, certain dinoflagellates, and also in a few euglenoids. The engulfment of large food particles inside cells through the method of phagotrophic nutrition is known as phagotrophy. Phagotrophic nutrition includes digestion inside the cells. In phagotrophic mode of nutrition, the large particles of food are engulfed by the cell by forming a surrounding membrane all around the food particles and gradually taking it inside the cell. Now, inside the cell, the engulfed food particles get digested.
Additional Information: In Protozoan protists, the food particle is taken inside the animal body through the process of phagocytosis. Then the engulfed or ingested food particle is broken down into simpler form by the action of enzymes. After the breakdown of food particles, the digested food is absorbed by the cell and the undigested food particles or waste products are expelled out of the body through egestion. -The dinoflagellates and mostly marine plankton but are also common in freshwater habitats. They are generally known to be photosynthetic but a large fraction of these are in fact mixotrophic, combining photosynthesis with ingestion of prey that is the combination of phagotrophy and myzocytosis. Euglenoids are commonly found in freshwater and are unicellular protists. Two flagella are present at the anterior end of the body of euglenoids. The euglenoids attack their food and engulf via phagocytosis and the entrapment of food takes place by an outer membrane. They capture their food by phagocytosis only in the absence of light otherwise they prepare their food with the help of photosynthetic pigment chloroplast.
So, the correct answer is, All of the above.
Note: In Protozoan protists, the absorbed molecules after digestion are later used for various metabolic processes in the organism. The euglenoids are a connecting link between plants and animals as they bear both characteristics. Dinoflagellate cysts or dinocysts are the resting stage produced by some dinoflagellates.