Five-kingdom classification and the three-domain system
R.H. Whittaker (1969) proposed a Five Kingdom Classification. The kingdoms defined by him were named Monera, Protista, Fungi, Plantae and Animalia. The main criteria for classification used by him include cell structure, body organisation, mode of nutrition, reproduction and phylogenetic relationships. the table below gives a comparative account of different characteristics of the five kingdoms.
Characteristics of the Five Kingdoms
| Characters | Monera | Protista | Fungi | Plantae | Animalia |
|---|---|---|---|---|---|
| Cell type | Prokaryotic | Eukaryotic | Eukaryotic | Eukaryotic | Eukaryotic |
| Cell wall | Noncellulosic (Polysaccharide + amino acid) | Present in some | Present with chitin | Present (cellulose) | Absent |
| Nuclear membrane | Absent | Present | Present | Present | Present |
| Body organisation | Cellular | Cellular | Multiceullar/loose tissue | Tissue/organ | Tissue/organ/organ system |
| Mode of nutrition | Autotrophic (chemosynthetic and photosynthetic) and Heterotrophic (saprophytic/parasitic) | Autotrophic (Photosynthetic) and Heterotrophic | Heterotrophic (Saprophytic/Parasitic) | Autotrophic (Photosynthetic) | Heterotrophic (Holozoic/Saprophytic etc.) |
The three-domain system has also been proposed that divides the Kingdom Monera into two domains, leaving the remaining eukaryotic kingdoms in the third domain and thereby a six kingdom classification. You will learn about this system in detail in higher classes.