What is adaptation? Explain with examples how various organisms show adaptations to cope with specific environmental conditions.

(N/A) Adaptation is any attribute of an organism (morphological,physiological,or 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.
$1$. Physiological Adaptation: In the absence of an external source of water,the kangaroo rat in North American deserts meets all its water requirements through its internal fat oxidation (where water is a byproduct). It also has the ability to concentrate its urine,so it uses minimal water to remove excretory products.
$2$. Morphological Adaptation: Many desert plants have a thick cuticle on their leaf surfaces and have their stomata arranged in deep pits to minimize water loss through transpiration. They also have a special photosynthetic pathway $(CAM)$ that enables their stomata to remain closed during daytime. Some desert plants like $Opuntia$ have no leaves—they are reduced to spines—and the photosynthetic function is taken over by the flattened stems.
$3$. Allen's Rule: Mammals from colder climates generally have shorter ears and limbs to minimize heat loss. This is known as Allen's Rule. In polar seas,aquatic mammals like seals have a thick layer of fat (blubber) below their skin that acts as an insulator and reduces loss of body heat.
$4$. Acclimatization: Some organisms possess physiological adaptations that allow them to respond quickly to a stressful situation. For example,when visiting high-altitude places $(> 3500 \ m)$,one may experience altitude sickness (nausea,fatigue,and heart palpitations). This occurs because at high altitudes,atmospheric pressure is low,and the body does not get enough oxygen. However,the body compensates for low oxygen availability by increasing red blood cell production,decreasing the binding affinity of hemoglobin,and increasing the breathing rate.