Three Kingdom Classification :
It was propounded by Haeckel (1866) and for the first time a separate group was assigned for microorganisms.
The three groups are-
Kingdom – 1 = Protista
Kingdom – 2 = Plantae
Kingdom – 3 = Animalia
Four Kingdom Classification : It was propounded by H.F. Copeland (1938). He coined a new kingdom – Monera for blue green algae. Hence, the four kingdom are Monera, Protista, Plantae and Animalia.