Define phenotypic adaptation. Give one example.

Ravi, who lived at sea level, had around $5$ million $RBC$ per cubic millimeter of his blood. Later when he lived at an altitude of $18,000 ft$, showed around $8$ million $RBC$  per cubic millimeter of blood. This is an adaptation because

Halophytes are

Emergent land plants that can tolerate the salinities of the sea are called.

Distinguish between the following:

$(a)$ Hibernation and Aestivation

$(b)$ Ectotherms and Endotherms