Question

Why are the classification systems changing every now and then?

Answer 1

From very early days till now biologists use several characters for classification system. These are morphology, anatomy, cytology, physiology, ontogeny, phylogeny, reproduction, biochemistry,etc. But day by day biologists are learning something new about organisms from their fossil records and using advanced study techniques such as molecular phyogeny, etc. So their point of view about classification keeps changing. Thus the system of classification is modified every now and then.