Besides Genetics, variation within species can be caused by environmental factors.
EXPLANATION:
Variation means difference in cells or organisms of one species. It can be caused by genetic variations or by environmental variations like climate, food supply or even actions of organisms. These changes are not hereditary and may not necessarily be passed onto coming generations of that species.
Some individuals of the population might be able to survive the changes in the environment. These environmental factors affect the phenotype of the population and it is also called phenotypic variation. Height, weight, color of hair, etc. are phenotype of an organism.