Adaptations - Practice Questions & MCQ

• Adaptation is any attribute of the organism (morphological, physiological, behavioural) that enables the organism to survive and reproduce in its habitat.

Adaptations in Desert Habitat:

• 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). 
• It also has the ability to concentrate its urine so that a minimal volume of water is used to remove excretory products.
• Many desert plants have a thick cuticle on their leaf surfaces and have their stomata arranged in deep pits to minimise water loss through transpiration. 
• They also have a special photosynthetic pathway (CAM) that enables their stomata to remain closed during day time. 
• Some desert plants like Opuntia, have no leaves – they are reduced to spines–and the photosynthetic function is taken over by the flattened stems.

Adaptations in Colder Habitat:

• Allen's Rule states that certain extremities of animals are relatively shorter in the cooler parts of a species' range than in the warmer parts. 
• By "extremities" is mainly meant arms, legs, ears, and snout or nose. 
• Mammals from colder climates generally have shorter ears and limbs to minimise heat loss. 
• In the 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.
   

Physiological Adaptations:

• Some organisms possess adaptations that are physiological which allow them to respond quickly to a stressful situation. 
• People visiting high altitude places experience altitude sickness. 
• Its symptoms include nausea, fatigue and heart palpitations. 
• This is because in the low atmospheric pressure of high altitudes, the body does not get enough oxygen. 
• But, gradually they get acclimatised and stop experiencing altitude sickness. 
• The body compensates low oxygen availability by increasing red blood cell production, decreasing the binding capacity of hemoglobin and by increasing breathing rate.
• Microbes such as archaebacteria which can survive in very high temperatures are called thermophiles. 
• They can survive in deep-sea hydrothermal vents or hot springs due to their structural difference present in the properties of the lipid bilayer. 
• The compactness in their proteins and the presence of high levels of saturated fatty acids helps them to withstand temperatures far beyond 100 degree Celsius without denaturing the enzymes present inside them.
• The fishes are cold-blooded so their body temperature fluctuates with the surrounding temperature. In the cold region where the temperature is low, the body temperature goes down which creates the risk of freezing the blood which can lead to death. They have antifreeze compounds like glycerol which prevents the blood from freezing.
• A large variety of marine invertebrates and fish live at great depths in the ocean where the pressure could be >100 times the normal atmospheric pressure that we experience. 
• Marine invertebrates such as worms, crustaceans, and sea cucumbers, are not affected by this change in pressure as they lack gas-filled cavities or lungs.
• Fish have streamlined their shapes that helps them in reducing oxygen consumption, possessing higher concentration of the protein myoglobin, which binds oxygen in muscle tissue. 
• The cell membranes of these organisms have more number of unsaturated fatty acids to increase the fluidity and their enzymes have specific structure.

Behavioural Adaptations

• Some organisms show behavioural responses to cope with variations in their environment. 
• Desert lizards lack the physiological ability that mammals have to deal with the high temperatures of their habitat, but manage to keep their body temperature fairly constant by behavioural means. 
• They bask in the sun and absorb heat when their body temperature drops below the comfort zone, but 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.