In the year 1969 R.H. Whittakar an American taxonomist, proposed five kingdom system of classification system on the basis of mode of nutrition, phylogenetic relationship, cell structure, thallus organization and reproduction. The five kingdom viz- Monera, protista, fungi, plantae and animalia. Viruses, prions and bacteriophage do not have the classification property suggested by Whittakar, hence they are not included in five kingdom classification.