Why do orginizams chande over millions of years?

Organisms change over millions of years primarily due to the process of evolution, driven by natural selection, genetic mutations, and environmental pressures. As species adapt to their changing environments, advantageous traits become more common in the population, leading to gradual changes in their physical characteristics and behaviors. Additionally, factors such as genetic drift and gene flow contribute to the diversity and adaptation of species over time. This long-term process results in the emergence of new species and the extinction of others, reflecting the dynamic nature of life on Earth.