Question

Describe the various modes of nutrition in protists.

Answer 1

Hint: Protists include solitary or colonial unicellular eukaryotic organisms that do not form tissues. These organisms possess nuclear membranes and mitochondria. They may be motile or non-motile.

Complete answer:
The organisms included in Protista represent diverse ways of life. Many are photosynthetic autotrophs, for example, unicellular colored algae and diatoms. They are collectively known as phytoplankton or microscopic, floating microorganisms. Many of these bear cell walls and some of them have flagella.
Few protistan organisms are predatory and they feed on other protists. They are included in protozoa and they lack a cell wall. They have animal like holozoic mode of nutrition i.e. they ingest their food.
Some protozoans are found in the gut and digestive tract of all other organisms.
Few organisms help in the decomposition of organic matter like otherwise indigestible cellulose found in cell walls of plants, as in termites and wood consuming cockroaches.

The important groups of protists along with their type of nutrition are:
>Chrysophytes- They have a heterotrophic mode of nutrition.
>Dinoflagellates- They include the phylum Pyrrophyta of algae and like diatoms they fucoxanthin in addition to chlorophyll so they are autotrophic in nutrition.
>Euglenoids- Some of them are green and have a holophytic mode of nutrition but few are non-green and saprophytic like fungi.
>Slime moulds- They lack chlorophyll and are saprophytic in nature,
>Protozoans- They are found as predators or parasites and have heterotrophic nutrition.

Note: The single cells of protists perform all the functions like growth, reproduction, maintaining homeostasis, etc. and for this they require energy that they obtain from food. As they have both plant like and animal like features so they show a great diversity in their mode of nutrition.