What are the three main causes of variation?

The three main causes of variation are alleles that individuals have inherited, which are genetic causes such as hair and eye colour, the environment, such as the colour of the hydrangea bloom flowers depending on the pH of their soil, or language in humans, and other variation is caused by a combination of genes and environment such as height in humans, as some people have alleles to grow taller though they also need a sufficient amount of calcium for their bone to fully develop