The classification systems are changing every now and then primarily because millions of new species of plants, animals, and microorganisms are continually being discovered. These newly discovered species often have new or previously unrecognized characters, requiring scientists to develop new or revised classification systems to accurately group and categorize them. Additionally, ongoing evolutionary processes mean that species themselves keep changing, necessitating updates to existing classification frameworks to reflect these changes properly. Moreover, advances in scientific techniques, especially in molecular biology such as DNA sequencing, have provided new data that sometimes challenge or refine previous classification schemes based solely on physical characteristics. This leads to re-evaluation and modification of how organisms are classified to better represent their evolutionary relationships and genetic relatedness. In summary:

• New species discoveries with new traits require updated classification.
• Evolution causes species to change, influencing classification needs.
• Technological and scientific advances offer deeper insights, prompting system modifications.

These factors create the necessity for classification systems to be dynamic and periodically updated to remain accurate and useful in organizing the diversity of life.