Explain the basis for grouping organisms into five kingdoms.

The major characteristics which is considered for classifying all organisms into five major kingdoms are:

(a) On the basis of their structure and presence or absence of a well developed nucleus and membrane bound cell-organelles, i.e., prokaryotic and eukaryotic organisms.

(b) On the basis of presence of the number of cells which differentiates them into unicellular and multicellular organisms.

(c) On the basis of the presence of a cell-wall which differentiates them into plant cell and animal cell.

(d) On the basis of their mode of nutrition which differentiates them into autotrophs and heterotrophs.

(e) On the basis of their level of complexity of cell which categorizes them into cellular level of organization, tissue level of organization, organ level of organization and organ-system level of organization.