Question

According to five kingdom system, unicellular algae like Dinoflagellates, Diatoms and Euglenoids are included in kingdom
A. Monera
B. Protista
C. Plantae
D. Animalia

Answer 1

Hint:-In 1969, Whittaker proposed the five-kingdom classification in which he grouped organisms into kingdoms like Protists, Monera, Fungi, Plantae, and Animalia. He based his classification on certain criteria like the complexity of cellular structure and body organization, mode of nutrition, reproduction, and phylogenetic relationships.

Complete answer:
Dinoflagellates, diatoms, and euglenoids are different genera of algae. They are eukaryotic organisms as they contain a membrane-enclosed nucleus. They are mostly unicellular and autotrophic organisms.
Dinoflagellates are mostly unicellular eukaryotes possessing stiff cellulose plates like an armour around their body. Most species are photosynthetic while few are parasitic on fishes. They exhibit variations in colours due to the presence of different pigments in their body. They demonstrate the phenomenon of bioluminescence. Diatoms are unicellular or colonial forms of algae. They are found in all types of aquatic habitats. They have a cell wall which is hard and siliceous. These organisms when they die, form diatomaceous earth in the water bed. Euglenoids are plant-like organisms that lack a cell wall however, they possess a hard pellicle which is protein-rich. They are mostly photosynthetic but when there is no sunlight, they turn heterotrophic. Thus, dinoflagellates, diatoms and euglenoids have been classified together in the kingdom Protista.
Thus, the right option is B.

Additional information:-
The algal bloom of dinoflagellates results in red tides. These organisms produce a neurotoxin which affects both humans and aquatic life. Diatoms are the most abundant phytoplankton responsible for photosynthetic activity in water.

Note:- Protists have a very simple organization i.e. cellular grade of body organization yet form a diverse taxon. They include both single-celled or unicellular as well as multicellular organisms. They are important primary producers in an ecosystem.