Evolution can be defined as the process of the change occurring in a population over a period of time through genetic variation. This genetic variation and the process of natural selection help a species to evolve by selecting the traits that helps it to better adapt to the environment. These genetic variations are inherited over time as the species continue to evolve.
Hence, the correct answer is 'change in population through genetic variation over time'.
Despite the humpback whale and whale shark being similar in size, they are not as closely related as the humpback whale is to the spider monkey, which is far smaller in size. This provides evidence that size of a specie is not a good indicator of its relationship to other species.
