What term describes an organism's ability to adapt to its environment over time?

The term that best describes an organism's ability to adapt to its environment over time is evolution. Evolution encompasses the gradual changes in the traits of a species across generations, driven by mechanisms such as mutation, genetic drift, and natural selection. This process leads to adaptations that allow organisms to survive and reproduce in their specific environments.

While adaptation refers specifically to the changes in an organism that enhance its fitness in its environment, and natural selection is the process that drives evolution by favoring beneficial traits, evolution itself encompasses the broader concept of how species change over time due to these and other factors. Species diversity refers to the variety of species within a given area but does not directly describe the mechanism of adaptation over time. Thus, evolution is the most comprehensive term relating to the long-term changes in organisms as they respond to environmental pressures.