Climatic Conditions: Extremely hot with unreliable and scarce rainfall
1. Plant life adapted to aridity.
2. Two general classes of vegetation- Perennials and ephemerals. Perennials succulants adjust to aridity by various avoiding mechanism:
(i) Extensive root system (phreaiophyte)
(ii) Transpiration reduction
a. dying back of leaves as in many grasses
b. shedding of leaves
c. Heavy cuticular and epidermal layers
d. Waxy coating on leaves
e. Sunken stomata
f. Very small, narrow sometimes scaly leaves
g. ridged stems
(iii) Aerial organs may become variously modified according to prevailing climatic conditions.
(iv) Leaf surfaces are generally shiny and glazed.
Ephemerals have short life cycle and may form a fairly dense stand after rainfall. They evade drought. Develop vigorously and produce large number of fruits and flowers during rain
Animals show various adaptations either by behavioural adaptation (they escape or retreat):
1. Escape involves aestivation or dormancy.
2. Seasonal migration.
3. Nocturnal habit:
i. Some xerocole rodents seek burrow and passively loose heat by pressing their bodies against the burrow walls.
ii. Some birds and humming birds and bats go into torpor.
4. Jackrabbits and kit fox have large ears.
5. Kangaroo rat seals its burrow by day to keep chamber moist:
i. Obtains water by own metabolic process and from hygroscopic water in food.
ii. Liberates concentrated urine
6. Camel- Low surface area to body size ratio and lower internal heat production result in slower accumulation of heat.
i. Excretes highly concentrated urine.
ii. Loses water from body tissues not blood.
iii. Fat accumulation in hump.
7. Marine birds utilise salt gland to help in maintenance of water.
8. Black throated sparrow zebra finch of Australia feed on dry seeds
9. Small snakes and sidewinder burrow.