Which term best describes the change of an organism over time?

The term that best describes the change of an organism over time is evolution. Evolution refers to the gradual process by which species undergo genetic changes over generations, leading to adaptations that help them survive and reproduce in their environments. These changes can result from various mechanisms, including natural selection, mutation, genetic drift, and gene flow.

Understanding evolution is fundamental to the study of biology, as it explains the diversity of life on Earth and how organisms are related through common ancestry. By studying evolution, scientists can gain insights into the development of traits and behaviors that enhance the survival of species over time.

Adaptation specifically refers to changes that improve an organism's ability to thrive in its environment, but it is a part of the broader process of evolution rather than a synonym for it. Extinction describes the end of a species and does not involve change over time in the way that evolution does. Speciation is the process by which a single species evolves into two or more separate species, which is a specific outcome of evolutionary processes.