There are three different domains of organism in the classification –
a) The Archaea – These are prokaryotic cells. Its membrane is made up of hydrocarbon chains which is connected to glycerol through ether. It containsrRNA. Archaea include methanogens, halophiles, and hyperthermophiles.
b) The Bacteria - These are prokaryotic cells. Its membrane is made up of unbranched fatty acid which is connected to glycerol through ester. It also has rRNA but it is distinctive to that of Archaea. Bacteria include mycoplasmas, Gram-negative bacteria, cyanobacteria, Gram-positive bacteria etc.
c) The Eukarya - These are Eukaryotic cells. Its membrane is made up of unbranched fatty acid which is connected to glycerol through ester. It also has rRNA but it is distinctive to that of both Archaea and bacteria. It consists of four kingdoms – Protista, Fungi, plantae, and animalia