Question

Unicellular prokaryotic organisms are included in which kingdom?

Answer 1

In contrast to a multicellular organism, which consists of several cells, a unicellular organism, also known as a single-celled organism, is an organism that consists of only one cell. A prokaryote is a single-celled organism and lacks a nucleus that is surrounded by a nuclear membrane. Prokaryotes lack mitochondria and other membrane-bound organelles found in eukaryotes. The kingdoms of living organisms are classified into five categories.

Complete Explanation:
Based on the $5$-kingdom classification, since fungi, plants, and animals are all multicellular and have nuclei in their cells, these three kingdoms cannot be the answers. Even though many protists are unicellular, they are also eukaryotes. Unicellular prokaryotic species only exist in Monera.
Unicellular prokaryotic species, such as bacteria, are classified as "Monera" since they lack a nuclear membrane and are capable of both autotrophic (chemosynthetic and photosynthetic) and heterotrophic (saprophytic/parasitic) feeding. Although it was widely recognized that prokaryotes and eukaryotes could be distinguished by the existence of a nucleus, mitosis versus binary fission as a method of reproduction, size, and other characteristics, the monophyly of the kingdom Monera (and, for that matter, whether classification should be based on phylogeny) was debated for decades.

Additional Knowledge:
Bacteria and archaea reproduce asexually, most often by binary fission. While genetic exchange and recombination still occur, it is a type of horizontal gene transfer rather than a replicative operation, involving only the transfer of DNA between two cells, as in bacterial conjugation.

Note:
The cytoskeleton of prokaryotes differs from that of eukaryotes in that it is more primitive. Apart from homologues of actin and tubulin (MreB and FtsZ), flagellin, the helically organized building block of the flagellum, is one of the most important cytoskeletal proteins of bacteria, providing structural backgrounds for chemotaxis, bacteria's basic physiological response. Some prokaryotes have intracellular structures that can be thought of as primitive organelles.