2017-05-05 06:55:05
Desert & Tundra
Distinct CharacteristicsA desert is a biome that receives no more than 25 centimeters (10 inches) of precipitation per year. Deserts are found in both temperate and tropical areas. The largest deserts are found at about 30° north or south latitude due to the dry air masses over these latitudes. Deserts also occur in rain shadows. A rain shadow is a dry region on the leeward side of a mountain range (see Lesson 16.1). Examples of rain shadow deserts include Death Valley and the Mojave Desert, both partly in California. The dry air in deserts leads to extreme temperature variations from day to night. Without water vapor in the air, there are no clouds to block sunlight during the day or hold in heat at night. Desert soil is usually very poor. They tend to be sandy or rocky and lack organic content. Because of the low precipitation, minerals are not leached out and may become too concentrated for plants to tolerate. Plant cover is very sparse, so most of the soil is exposed and easily eroded by wind. The occasional rain tends to be brief but heavy, causing runoff and more erosion. Most desert plants have evolved adaptations to the extreme dryness. For example: Many plants have special water-storing tissues in leaves, stems, or roots. Some plants have very long taproots that can reach down to the water table. Some plants have wide-spreading roots that can absorb water over a large area. Plants may have small, spiny leaves that help reduce water loss. Most desert animals have adaptations to the extreme heat and bright sunlight. For example: Many small animals stay underground in burrows during the day and come out only at night. Most animals that are active in daytime spend as much time as possible in the shade of rocks or plants. Some animals have very large ears or other appendages, which help them lose heat to the environment, keeping them cooler. Many animals are light in color, which helps them reflect sunlight and stay cooler.



  • 2017-05-05 06:53:38
    2017-05-05 06:55:05
  • English
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  • Creative Commons License CC-BY-SA 3.0 / GNU FDL


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