Define phenotypic adaptation. Also give one example.

Hint: Adaptation is an ability of an organism to express different phenotypes depending on the biotic or abiotic environment. This involves regulatory genes that switch on structural genes given the appropriate stimulus.

Complete step by step answer:
- Physiological adaptations may take the form of inherited genotypic or acquired phenotypic variations in the morphological and functional or physiological status of the individual.
- The former is invariably indistinguishable from the latter, yet both result in advantageous variations in physiological functions.
- The changes in physiological function to be beneficial in order to qualify as an adaptation.
- Physiology adaptation is a change which reduces the physiological strain produced by a stressful component of the total environment.
- These changes in response to slow development or long maintained changes in the environment are phenotypic adaptation.
Example
- Thermally induced phenotypic adaptation is expressed through the reversible modifications of the morphological configuration e.g. the size of sweat gland, thickness of subcutaneous adipose tissue or functional changes in effector organ control that occur e.g. the threshold and gain of the shivering response.
- These thermal adaptations can occur in response to the naturally occurring, broad spectrum of environmental changes or acclimatisation, to deliberate artificial thermal exposures or acclimation or to changes in body temperature, induced through changes in metabolic heat production that is the
sum of metabolic rate and external work.

Note:
- The term adaptation can be defined as changes or adjustments, often hereditary, in the structure or habits of a species or individual that improve its condition in relationship to its environment.
- Adaptation can influence all the systems and states of a living organism and, in so doing, is fundamental to survival and prosperity.
- Human adaptation to hot and cold environments and the integrated physiological responses that accompany these adaptations, resulting in a more effective defence of body temperature in the presence of thermal challenges.