- In the five-kingdom classification system, Monera includes all prokaryotic organisms, such as bacteria and cyanobacteria, which are exclusively unicellular. - Protista primarily consists of unicellular eukaryotic organisms, but some simple multicellular or colonial forms are also classified under Protista depending on the system. - Fungi includes both unicellular (like yeast) and multicellular organisms. - Plantae and Animalia consist entirely of multicellular organisms.