Evolutionary relatiomship is one of the many criteria for defining evolutionary classification. All living organisms show variation in characters. Biological classification is arrangement of living organisms into groups based on similarities and differences observed among them. The smallest group or taxon is species which consists of individuals which can successfully reproduce with each other. It is observed that, generally, the organisms having close evolutionary relationship are placed together in a smaller taxon. As we go to higher taxon, the relatedness decreases. This is consistent with the evolutionary theory. Therefore classification helps to establish evolutionary relationship.