Explain about adaptation in detail.

Adaptation is any attribute of the organism (morphological,physiological,behavioural) that enables the organism to survive and reproduce in its habitat. Many adaptation have evolved over a long evolutionary time and are genetically fixed. In the absence of an external source of water, the kangaroo rat in North American deserts is capable of meeting all its water requirements through its internal fat oxidation (in which water is a by product).

Urine excreted is concentrated.

Many desert plants have a thick cuticle on their leaf surfaces and sunken stomata to minimize water loss through transpiration.

These plants have special photosynthetic pathway ($CAM$) in which stomata remains closed during day time.

In some plants like cactus(opuntia) leaves are transformed into spines and photosynthesis is performed by flattened stem.

Mammals from colder climates have shorter ears and limbs to minimize heat loss. This is called Allen's Rule.

In polar seas aquatic mammals like seals have a thick layer of fat called blubber, below their skin that acts as an insulator and reduces loss of body heat.

Altitude sickness is observed at higher altitude that includes symptoms like nausea, fatigue, heart palpitations due to less oxygen and atmospheric pressure. The person gradually get acclimatized ang stop experiencing altitude sickness. This is type of physiological adaptation.

A number of marine invertebrate and fish live in temperature always less than zero and some lives in great depth in ocean where pressure is very high by array of biochemical adaptations.

Some organisms like desert lizard lack the physiological ability that mammals have but deal with high temperature of their habitat by behavioral means. They bask in the sun and absorb heat and when their body temperature drops below the comfort zone, but moves in shade when the ambient temperature starts increasing.