Five kingdom system of classification
The two kingdom system of classification of organisms was introduced by Carl Linnaeus. The system recognized two kingdoms of organisms as - Plantae and Animalia. However, this system was found inadequate for classification of some organisms like bacteria, fungi, Euglena, etc.
Haeckel suggested the third kingdom Protista to include these organisms.
They system of classification proposed by R.H. Whittaker in 1969 is a five-kingdom system. This system shows the phylogenetic relationship between organisms. The five kingdoms are:
1. Kingdom Monera
2. Kingdom Protista
3. Kingdom Fungi
4. Kingdom Plantae
5. Kingdom Animalia
The criteria used by Whittaker in system include -
i) Cell organization - Whether the organism is prokaryotic or eukaryotic.
ii) Body organization - Whether the organism is unicellular or multicellular.
iii) Mode of nutrition - Whether the organism is autotrophic or heterotrophic.
iv) Life style - Whether the organism is producer, consumer or decomposer.