Phenotypic adaptation is a change in the structural and physiological properties of an organism in response to a genetic mutation or to a change in environment.
For example, when we go to hill station or places at high altitudes, very often we suffer from nausea, fatigue and heart palpitations. This is because there is low atmospheric pressure at high altitude in our body does not get enough oxygen. Our body adapts itself to this low oxygen availability by increasing red blood cell production, decreasing the binding capacity of haemo-globin and by increasing breathing rate.