The difficulties that will be faced if common fundamental features are not taken into account are as follows
(i) The interrelationship among different animals will not be traceable.
(ii)The picture of all animals at a glance will not be projected.
(iii) The development of other animal species will not be made.
(iv) There are numerous animal species which show great variety of life. The various common fundamental characters are taken into account for the classification of these animals. If this has not been done, it is not possible to deal with every living form separately at individual level. Therefore, a classification has to be based on the common fundamental characters to study the diversity properly.