Independent Variable the one the researcher controls. It is what you, the researcher, change to cause a certain effect. 
Dependent Variable the one you measure or observe. It's the effect of the researcher's change.
 If skin cancer is related to ultraviolet light, then people with a high exposure to UV light will have a higher frequency of skin cancer.
"if temperature affect leaf color change, then exposing the plant to low temperatures will result in changes in leaf color.