What is evolution? what is evolution? a rare event a process that occurs as a result of differences in reproductive fitness a process that is constantly occurring at the same rate in all organisms a process that occurred only in the past?

The correct answer is that " a process that occurs as a result of differences in reproductive fitness".

Evolution is best described as the alternate within the heritable characteristics of biological populations over successive generations. Evolutionary procedures provide upward thrust to biodiversity at every degree of biological organisation, together with the ranges of species, character organisms, and molecules.