What is the basis of distinction in each of the four steps?

This is the five kingdom classification given by scientist Whittaker (1969).This scheme was based on -

Structure of Cells - {prokaryotic or eukaryotic }

Structure of Organism - {unicellular or Multicellular}

Mode of nutrition - Photosynthesis in green plants, absorption in fungi and ingestion in animals.

The Kingdoms are further classified into sub groups at various levels as follows.


                          #Phylum/sub kingdom/*Division


(# Phylum for animals)'
(* Division for Plants)                                            Genus                            


 Thus by separating organisms on the basis of Hierarchy of characteristics into smaller and smaller groups we arrive at the basic unit of classification which is a species. Species include all organisms that are similar enough to breed and perpetuate. eg. all the house cats of the world belong to one species ( Felis domesticus) ; they may have some differences among themselves such as colour, height and lenght of the tail and yet they can inter breed.