Explain about adaptation in detail.

(A) Adaptation is any attribute of the organism (morphological,physiological,behavioural) that enables the organism to survive and reproduce in its habitat.
Many adaptations have evolved over a long evolutionary time and are genetically fixed.
For example,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).
Its urine is highly concentrated.
Many desert plants have a thick cuticle on their leaf surfaces and sunken stomata to minimize water loss through transpiration.
These plants have a special photosynthetic pathway $(CAM)$ in which stomata remain closed during the daytime.
In some plants like cactus $(Opuntia)$,leaves are transformed into spines,and photosynthesis is performed by the 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,which acts as an insulator and reduces the loss of body heat.
Altitude sickness is observed at higher altitudes,including symptoms like nausea,fatigue,and heart palpitations due to low oxygen and atmospheric pressure. The body gradually gets acclimatized,and the person stops experiencing altitude sickness. This is a type of physiological adaptation.
$A$ number of marine invertebrates and fish live in temperatures always less than zero,and some live at great depths in the ocean where pressure is very high,through an array of biochemical adaptations.
Some organisms,like the desert lizard,lack the physiological ability that mammals have but deal with the high temperature of their habitat by behavioural means. They bask in the sun to absorb heat when their body temperature drops below the comfort zone,but move into the shade when the ambient temperature starts increasing.