The three domain system recognizes fundamental differences between the two groups of PROKARYOTES.
The three domain system refers to a biological classification, which divides all living organisms into three basic groups, which are: archaea, bacteria and eukaryotes. The system divides the prokaryotes into two groups, which are bacteria and archaea. These division was based on the differences in the 16S rRNA genes of these organisms. This system of classification was introduced by Carl Woese in 1990. The bacteria are made up of prokaryotes which lack membrane covered cell organelles while the archaea group is made up of prokaryotes which have a mono layer core of lipid in their membranes and specific nucleotide in their 16S RNA