Why are the classification systems changing every now and then?

Discuss how classification systems have undergone several changes over a period of time?

Natural system of classification is based on

Linnaean system of classification was based on

In Bentham and Hooker's system of classification the arrangement of three series of polypetalae reflects evolution from

Phylogenetic system of classification is base done

Four kingdom system of classification was given by

An amount of work w is done by a system and q amount of heat is supplied to the system. By which of the following relation the change in internal energy of the system can be expressed?-

Sexual system of classification by Linnaeus is based on:

Phylogenetic system of classification is used by

Polygenetic system of classification is based on :