Implication of Five Kingdom Classification

The implication of classification is thus to reflect a degree of kinship. On this basis one should be able to trace the evolutionary history of any group. In order to do this it would be worthwhile to keep in mind two basic postulates: one, all species in any one group, if correctly placed, should have a common ancestor; and two, no living organism is the ancestor of any other living organism. The common ancestor may not be found today in the living state and might have become extinct, leaving behind its fossilized remains.

Figure: Homologus forelimbs of several representative vertebrates are compared with those of the suggested primitive ancestral type. In each instance, the individual hones have undergone modification, though they can still be traced to the ancestor. Since these limbs have the same embryological origin, they are said to be homologous. The most drastic changes can be observed in bird, horse, whale. Several individual bones have undergone reduction and in some cases fusion. Another obvious modification is seen in the greatly elongated finger bones of the bat.