Let's us match some Medicine to biology. Body functions (physiology) in response to the external environmental impact. This is clearly seen in the white tourist after a long stay in the tropical zones. Their skin color will differ from those who remainsin Mediterranean climate. So do all the insects, birds, fishes you name them. The basis reason is simply adaptation. However we are concentrating only external print outs. In the boby has been given a little room for study. Example, in the body of a smoker, the bacteria found have to adopt to the chemicals consumed. The body organs itself combined with the hormones all are affected to change in structure and function respectively.