Arid Land/Deserts SS1 Biology Lesson Note

ARID LANDS [DESERTS]

These are areas of very low rainfall and high evaporation rates. They are the driest habitats, receiving less than 25cm of annual rainfall. Arid lands are of two types;

Hot deserts e.g. Sahara desert (North Africa), Kalahari desert (South Africa)

Cold deserts e.g. deserts in North America

   CHARACTERISTICS OF A DESERT

1. Water is very scarce
2. Temperature is very high by the day and very low by the night
3. Vegetation is very scanty
4. The soils are sandy or rocky
5. Strong winds occur frequently and sunshine is very intense
6. Presence of drought resistance plants (xerophytes)

PLANTS DISTRIBUTION AND ADAPTATION IN DESERTS

Desert plants include thorny bushes, cacti, scattered dwarf acacia, date palms, wiring grasses, baobab trees and euphorbia species. They adapt to this habitat in the following ways;

1. Plants have thin leaves to reduce transpiration
2. Cacti leafless have thorns to reduce transpiration and thick succulent stems to store water
3. Acacia (drought resistant) has deep roots which absorb underground water
4. The Baobab tree has waxy leaves which can be hairy or needle-shaped to reduce the rate of transpiration
5. Wiring grass has narrow and slender leaves to reduce transpiration.

ANIMAL DISTRIBUTION AND ADAPTATION IN SPORTS

The Desert animals include camel, rodents, lizards, snakes, zebras, desert tortoises, grasshoppers, wasps, ants etc. They survive in the following ways;

1. Most desert animals excrete solid wastes to conserve water.
2. Kangaroos, rats remain in burrows during the day to avoid excessive heat
3. Reptiles have scales to reduce water loss
4. Camels can survive several days without drinking water. They can withstand a wide range of body temperature up to 40oc.
5. Locusts have water-proof bodies and impervious cuticles

 FOOD CHAINS IN ARID LANDS

1. Plants → desert rats → snakes
2. Plants → ants → scorpions → snakes