Class 12 Biology Organisms and Populations Adaptation


Adaptation is morphological, physiological and behavioral attribute of the organism that enables the organism to survive and reproduce in its habitat.


Adaptation of animal in desert

  • 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.
  • Kangaroo rat has the ability to concentrate its urine so that minimal volume of water is used to remove excretory products.

Fig. kangaroo rat  

Adaptation of plants in desert

  • Thick cuticle on the leaf surfaces of the desert plants reduces transpiration.
  • Stomata is sunken to reduce transpiration.
  • Desert plants follow a special photosynthetic pathway called Crassulean acid metabolism (CAM), in which stomata remains closed during day time and open during night time.
  • In some plants like Opuntia , leaves are modifies into spines to reduce transpiration and photosynthesis takes place in flat green stem called as phylloclade

Fig. Opuntia  

Adaptation of animal in cold climate

  • Mammals from colder climates generally have shorter ears and limbs to minimize heat loss, called as Allen’s Rule.
  • 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.

Fig. a seal

Adaptation in high altitude

  • When a person moves to high altitude place, develops altitude sickness because in the low atmospheric pressure of high altitudes, the body does not get enough oxygen.
  • Symptoms include nausea, fatigue and heart palpitations.
  • The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding capacity of hemoglobin and by increasing breathing rate.

Fig. red blood cells carrying hemoglobin  

Behavioral adaptation

  • Desert lizards deal with the high temperatures of their habitat, by managing to keep their body temperature fairly constant by behavioural adaptation.
  • Desert lizards bask in the sun and absorb heat when their body temperature drops below the comfort zone and move into shade when the ambient temperature starts increasing.
  • Some species are capable of burrowing into the soil to hide and escape from the above-ground heat.

Fig. desert lizard   

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