Unicellular eukaryotic organisms, such as amoeba and paramecium, belong to the kingdom Protista in Whittaker’s five-kingdom classification system. This classification distinguishes them from prokaryotes and multicellular eukaryotes based on cellular structure and organization. The correct answer to the multiple-choice question is (C) Protista.​

Correct Answer

The correct option is (C) Protista. This kingdom houses mostly unicellular eukaryotes with a well-defined nucleus and organelles, including protozoans like Amoeba and algae like Chlamydomonas. Protista serves as a diverse group bridging simple prokaryotes and complex multicellular kingdoms.​

Option Explanations

(A) Monera

Monera comprises prokaryotic unicellular organisms like bacteria and cyanobacteria, lacking a true nucleus and membrane-bound organelles. These differ fundamentally from eukaryotes, so Monera does not include unicellular eukaryotic organisms.​

(B) Plantae

Plantae includes multicellular, photosynthetic eukaryotes such as mosses, ferns, and flowering plants with cell walls made of cellulose. Unicellular forms are absent in this kingdom, which focuses on structured, chlorophyll-bearing organisms.​

(C) Protista

Protista fits perfectly as it primarily contains unicellular eukaryotic organisms that may be autotrophic, heterotrophic, or mixotrophic. Examples include Euglena (flagellated) and Plasmodium (parasitic), showcasing diverse modes of nutrition and locomotion.​

(D) Animalia

Animalia consists of multicellular, heterotrophic eukaryotes without cell walls, ranging from sponges to humans. No unicellular representatives exist here, as this kingdom emphasizes tissue-level organization and motility.​