This classification was proposed by RH Whittaker in 1969.
Before 1969, the classification systems for the living
organisms had undergone several changes over time.
Whittaker created Fungi, as separate kingdom.
The main criteria for classification used by Whittaker
(i) Cell structure
(ii) Mode of nutrition
(iii) Thallus organisation
(iv) Reproduction
(v) Phylogenetic relationships
Merits of Five Kingdom
Classification System
Merits of five kingdom classification system are
(i) Euglena and other transition types which had been
included both amongst plants and animals are given
proper place under kingdom—Protista.
(ii) Fungi have their own biochemical, physiological and
structural organisation. They have never been related
to plants. In this system of classification, fungi are
separately placed.
(iii) A separate kingdom—Monera including prokaryotes
has been created. Monerans differ from all other
organisms in their cellular, reproductive and
physiological organisations.
(iv) The five kingdom classification system is based on
cellular organisation, the mode of nutrition and
complexity of structure. These were the basic factors
used in earliest two kingdom system of classification.
(v) The system shows the gradual evolution of early
organisms into plants and animals.
(vi ) The plant and animal kingdoms are more
homogenous than they were in the two kingdom
system of classification.
Demerits of Five Kingdom
Classification System
Demerits of five kingdom classification system are
(i) Animal protozoans have been included in
kingdom—Protista, which also includes unicellular
plants. They show different modes of nutrition.
(ii) Chlorella and Chlamydomonas, though unicellular
are included under the kingdom—Plantae.
They should be kept in Protista.
(iii) Euglena like organisms and slime moulds with
flexible life style may need the creation Of an
intermediate kingdom other than Protista.
(iv) Viruses and viroids are not kept in proper place in
this system.
(v) Lichens have also not been placed in this system.