Answer:
The mutations cause genetic differences in a population, which causes the genetic variability, since the population is no longer homogeneous.
Step-by-step explanation:
Mutations are random changes in DNA, which determine the appearance, behavior and physiology of organisms. These changes in DNA are primarily responsible for genetic variability between individuals in a population, and they occur most often in natural ways, when DNA does not replicate correctly. Changes in DNA can also be caused by having external sources, such as your exposure to chemicals or radiation.