Kingdom-Protista include all unicellular eukaryotic organisms and colonial eukaryotes except some unicellular member of algae and fungi. The kingdom was created by Haeckel to include all those organisms which lack differentiation of tissues. Three major groups of unicellular eukaryotes, namely protozoan, protist, photosynthetic protistan algal (diatoms) and slime moulds are later on included in this kingdom.