. Who Propose the Three kingdom system of classification in which basis
i. Ernst Haeckel (1866), a German zoologist suggested that a third kingdom, Protista be created to include those unicellular eukaryotic microorganisms.
ii. Three kingdoms according to Haeckel are Protista, Plantae and Animalia.
iii. This solves the problem of assigning suitable kingdom to the organisms which have similarities with both plants and animals.