The classification system for organisms has changed from seven levels to eight. this happened because

Because scientist found another criteria for classifying organisms such as their DNA composition

Evidences that Taxonomy uses to group or categorizes species range from 
1.       "Fossil Records 
2.       Comparative anatomy 
3.       Comparative embryology 
4.       Biochemical information 
5.       Cellular structure 
6.       Behavior" 
We also suggest that taxonomy has played various roles mainly in many aspects in Zoology, Botany, Anatomy and Physiology –aspects that include animal and human structures and functions. As the biotic community is so diverse it is classified to Biodiversity and the existence of properly assorting by set standard.