Kingdom vs Domain
There have been many attempts of classification of organisms found on earth and till 1977; it was the kingdoms system that was universally accepted across the world. Starting from the two kingdoms system called the Linnaean system way back in 1758 when the life forms were divided into plants and animals, the world has come to recognize the three domain system as the most current and the most scientific system of classification of organisms. Though there are some similarities, the kingdom system of classification of organisms has now been relegated to having relatively little significance and the three domain system is the preferred on in all parts of the world. This article aims to find out the differences between the Kingdom and the domain system of classification of organisms.
In the old two kingdom system of classification, there were only two kingdoms, the plant kingdom and the animal kingdom. Linnaean system called all organisms that moved with anima (with a soul) and fungi got classified as plants. The system went on adding kingdoms and finally the five kingdom classification system was believed to be the complete system after the discovery of bacteria, algae and electron microscope. Today, five kingdom system that was first proposed in 1969 is believed to be the most updated system of classification though a broader system having six kingdoms is considered to be more accurate. The six kingdoms in this system are Plantae, Archaebacteria, Eubacteria, Protista, Animalia, and Fungi. The fifth kingdom called Monera has been divided into Archaebacteria and Eubacterea; thus, bringing the number of kingdoms to six. In all classifications, whether 5 or 6 kingdoms, a kingdom is further subdivided into phyla or divisions. It is animals that get subdivided into phyla while plants get divided into divisions.
Two scientists, Woese and Wolfe, in 1977, completely changed the system of classification of organisms in the world when they made use of 165 ribosomal RNA sequences. Till 1977, the world had come to accept the bifurcation of life forms into eukaryotes and prokaryotes. But it was the discovery of archaea, the microorganism that could live without oxygen, and reminded one of the ancient environment of earth that was devoid of oxygen, that forced scientists to conceive of a third category of organisms. Archaea was accepted as being different from the earlier two classifications, and thus the three domain system came into existence.
Kingdom vs, Domain
The world of organisms was classified as five kingdom system and well accepted by the scientists all over the world till 1977 when Woese and Wolfe proved the existence of Archaea, a third category of organisms that could live without oxygen besides the two accepted categories called eukaryotes and prokaryotes. Thus, the world of organisms got divided into three domain system rather than the earlier 5 kingdom system of classification.