Deserts

• Distribution: Deserts are hot and low rain areas suffering from water shortage and high wind velocity. They show extremes of temperature. Globally deserts occupy about 1/7th of the earth’s surface.
• Flora and fauna: Cacti, Acacia, Euphorbia and prickly pears are some of the common desert plants. Desert animals include shrew, fox, wood rats, rabbits; camels and goat are common mammals in desert. Other prominent desert animals are, reptiles, and burrowing rodents insects.
• Adaptations: Desert plants are hot and dry conditions.
  • These plants conserve water by following methods:
  • They are mostly shrubs. 
  • Leaves absent or reduced in size.
  • Leaves and stem are succulent and water storing.
  • In some plants even the stem contains chlorophyll for photosynthesis.
  • Root system well developed spread over large area.
• The animals are physiologically and behaviorally adapted to desert conditions.
  • They are fast runners.
  • They are nocturnal in habit to avoid the sun’s heat during day time.
  • They conserve water by excreting concentrated urine.
  • Animals and birds usually have long legs to keep the body away from the hot ground.
  • Lizards are mostly insectivorous and can live without drinking water for several days.
  • Herbivorous animals get sufficient water from the seeds which they eat

Deserts in India

• The Thar desert in Rajasthan is an extension of the Sahara deserts through Arabian and Persian deserts. They extend from Punjab, Haryana, Rajasthan to Gujarat state. Indian deserts are divided into four main types: hills, plains with hills, marshes and plains with sand dunes.
• The distinct Rann of Kutchch–Bhuj in Gujarat forms a separate zone with in Thar deserts due to its different climatic conditions. It represents vast saline flats. The region of sand dunes is most spectacular and covers an area of 100,000 sq. km nearly. It extends into Pakistan. The dunes are highly sandy and contain 0.12–0.18 mm size grain, 1.8 to 4.5 % of clay and 0.4–1.3% of silt.
• Since heat and light intensity are very high and sand dunes are shifting, these deserts cannot support vegetation. There are only some thorn forests and dry open grasslands. Indira Gandhi canal which carries water through Punjab and Haryana enters into Rajasthan supports some vegetation.
• The main crops of desert are bajra, millet, wheat, barley, maize, jowar, guwar. Medicinal plants found here are mehndi, hak, isabgole and gugal. 
• Indian deserts support many threatened species of birds and mammals, such as Asiatic lion, wild ass, bats, scaly ant eater, desert fox, Indian gazzel, four horned antelope , white browed Bushchat, Great Indian Bustard, Cranes and Sandgrouse.
• Gulf of Kuchch is distinguished by the presence of living corals, pearl oyster, sea turtles and a large number of migratory birds like kingfisher, cranes ibis and herons.

Tundra

• The word tundra means a “barren land” since they are found in those regions of the world where environmental conditions are very severe. There are two types of tundra- arctic and alpine.

Distribution

• Arctic tundra extends as a continuous belt below the polar ice cap and above the tree line in the northern hemisphere. It occupies the northern fringe of Canada, Alaska, European Russia, Siberia and island group of Arctic Ocean. On the south pole Anatarctica tundra in the south pole is very small since most of it is covered by ocean.
• Alpine tundra occurs at high mountains above the tree line. Since mountains are found at all latitudes therefore alpine tundra shows day and night temperature variations.
• Flora and fauna: Typical vegetation of arctic tundra is cotton grass, sedges, dwarf heath, willows, birches and lichens. Animals of tundra are reindeer, musk ox, arctic hare, caribous, lemmings and squirrel.