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Chapter 7 Sections 1, 2 & 3 All deserts have one thing in common… very little rainfall. Rainwater moving through soil carries minerals deeper into the soil through a process called LEACHING Very little leaching occurs in deserts Upper levels of soil is rich in minerals Not a lot of organic matter = little topsoil If loose soil is removed, a lower layer of soil, called PAVEMENT is exposed Pavement is the desert floor The desert floor is made up of hard-baked sand and/or bare rock particles Cool Deserts Found on eastern side of Sierra Nevada and Rocky Mountains Main plant is the sagebrush Hot Deserts Found in south west, particularly Arizona, New Mexico and western Texas Main plant is the cactus Desert Climate Rarely get more than 25 cm of rain per year Precipitation is the limiting factor of the desert Most deserts receive less than 10 cm of rain Hot days and cold nights Desert Organisms(Plants) Cactus spines are actually leaves Cacti are SUCCULENTS, meaning they store water Aloe vera is also a succulent Desert Plants cont. Most plants have shallow roots but some have long roots, like the mesquite tree which has roots 20m deep. Desert Animals Insects, birds, reptiles, and mammals Insects and reptiles have an outer coating to reduce water loss Most animals are NOCTURNAL meaning they are active at night. Why? Deserts cover over 30% of Earth’s surface Deserts of the northern belt are found near the Tropic of Cancer (23ºN) Deserts of the southern belt are found near the Tropic of Capricorn (23ºS) Winds move from west to east As they move, moisture is drawn up The newly formed clouds then move up over the mountains and drop their moisture The air now is very dry (on the east side), resulting in the formation of a desert OR A SEMIARID region (not as dry as a desert) The drying of the eastern side is called the RAINSHADOW EFFECT The transformation of semiarid land into desert is called DESERTIFICATION How does this occur? The Tundra is cold, windy, dry region Tundra is located in Northern Hemisphere in Alaska, Canada, Greenland, Iceland, Scandinavia and Russia Takes up 10% of Earth’s Surface Lack of biodiversity makes Tundra unstable Tundra receives 25cm of precipitation per year Temp rarely reaches above 10ºC Temperature is limiting factor of Tundra Tundra soil has an ACTIVE ZONE, which may only be 8cm thick Below that, where the ground never thaws is the PERMAFROST Mosses and grasses cover the active zone in the summer Water cannot drain in Tundra This causes the formation of bogs, marshes, and small streams This gives mosquitoes and black flies chances to breed, keeping the food chain intact Tundra Plants Very small, grow close to ground Tundra Animals MIGRATION or seasonal travel brings in animals Birds, Arctic Fox, Caribou Musk oxen, coastal polar bears, and wolverines Finish Worksheets for Chapter 7
