Why are the classification systems changing every now and then?
Classification systems are changing because human beings have always been interested in knowing more and more about various kinds of organisms and their relationships. As our understanding grows, classification systems need to be updated.
The basis of classification has evolved over time. The earliest classifications were based on the 'uses' of various organisms, but modern taxonomic studies now consider external and internal structure, cell structure, development process, and ecological information. Additionally, systematics has enlarged its scope to include evolutionary relationships between organisms, making classification more comprehensive.
Explanation
The textbook context explains that classification has evolved from being based on 'uses' of organisms to modern taxonomic studies that include multiple parameters like cell structure, development process, and ecological information. The scope of systematics was 'later enlarged' to include evolutionary relationships. This shows that classification systems change as human knowledge expands and new parameters are included for better understanding of organisms and their relationships.