Answer:
(a) (i) Adaptations of desert plants for reduced transpiration:
• Presence of thick cuticle on their leaf surfaces.
• A few and sunken stomata which are of scotoactive type.
• Crassilucean pathway of photosynthesis.
• Leaves are modified into spines e.g. Opuntia.
(ii) Adaptations of desert animals for reduced water loss:
• Skin is spiny and highly cornified in Phrynosoma (horned toad) and Moloch horridus.
• Body surface with waxy water-proof coat in desert insects.
• Expelling of highly concentrated urine in kangaroo rat and camel.
(b) (i) Some desert plants have succulent parenchymatous tissue to absorb and store water e.g. Opuntia, Aloe, etc.
(ii) Some plants are drought escapers and live only for a few weeks when the water is available and are called ephemerals. The dry period of the year is tide over in the form of drought-resistant seeds e.g. Argemone maxicana, Echinops echinata, etc.
(c) Behavioural adaptations:
(i) Desert lizards and crocodiles bask in the sun to absorb heat radiations and increase their body temperature in cold conditions.
(ii) Certain animals remain inside the burrows during day time and become active only during night when the percentage of moisture in their burrows and outside is equal.
(iii) Hibernation during winter months and aestivation during summer months in poikilothermal animals.
(d) Effect of temperature or water scarcity on adaptations of animals
In conditions of high temperature or water scarcity, the adaptations will be such that help the animals to
(i) reduce water loss from the body in breathing and excretion.
(ii) utilise water generated internally through metabolic activity.
In cold conditions, the adaptation would be such that will help the animal to
• Conserve body heat.
• Keep their body warm by developing thick fur.
• Insulating the body by depositing fat under the skin.
• Avoid cold conditions by migration or hibernation.
• Produce antifreeze proteins and solutes in excessive cold conditions.
(e) (i) Effect of temperature and adaptations in animals:
• The body appendages like snout, ears and legs of mammals like foxes and gazels of colder region are relatively shorter than those of warmer region (Alien's rule) so as to reduce loss of body heat.
• The birds (e.g. Antarctic penguin) and mammals (e.g. Polar bear) of cold regions are larger in size than those of warmer region as large body size reduces surface area per unit of weight which decreases heat loss (Bergman's rule).
(ii) Effect of water scarcity and adaptations in animals:
• Spiny lizard of Australia (Moloch horridus) has hygroscopic glands in its skin to absorb water from moist sand.
• Kangaroo rats feed upon dry seeds and depend upon metabolic water produced during cell respiration.
• Desert rabbits feed upon the succulent plants to draw water.
You need to login to perform this action.
You will be redirected in
3 sec
