Explanation

Two kingdom system of classification was used till very recently. This system did not distinguish between the eukaryotes and prokaryotes. Unicellular and multicellular organisms and photosynthetic (green algae) and non-photosynthetic (fungi) organisms. Classification of organisms into plants and animals was easily done and was easy to understand, inspite, a large number of organisms did not fall into either category. Hence, the two kingdom of classification used for a long time, was found inadequate