Two Kingdom system
Biologists divided the living world in to two kingdom: Plants and Animals. The two kingdom system of classification was also given by Linnaeus in 1758 and worked well for a long time.
Three kingdom system
A German biologist Ernst Haeckel (1866) suggested a third kingdom Protista. He included unicellular protozoa and algae in it.
Four kingdom system
Four kingdom was developed by Copeland (1956). They are Monera, Protista, Plantae and Animalia. Monera includes Prokaryotes (bacteria and blue algae).
Five Kingdom System
An American ecologist Robert H. Whittaker proposed that fungi differ enough from other microorganisms to justify calling them a separate kingdom. This led to a five kingdom scheme of classification comprising Monera, Protista, Fungi, Plantae and Animalia.
Five kingdom classification based on:
- Complexity of cell.
- complexity of organisms
- mode of nutrition and
- major ecological role.
Whittaker scheme is still widely accepted as a logical classification of living things.
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