Desert and Tundra Biomes Chapter 3

7.1 Deserts Objectives Describe the characteristics of a desert Explain how desert organisms adapt to live in their environment                                                                    Deserts are different, but they all receive very little rain.

Deserts continued Desert soil Rich in minerals Poor in organic materials Very little leaching Leaching a process where rainwater moving through soil carries minerals deeper into the soil Little rain -> little leaching -> upper desert soil rich in minerals

Deserts continued Lack of rainfall makes deserts dry Prevents many plants from living there Slows decay of organic material Not much topsoil Soil easily blown away Exposing the Pavement

Pavement The lower layer of the desert soil It is the desert floor Made mostly of Hard-baked sand Bare rock particles Or both

Types of Deserts in the US Cool Deserts - Sagebrush On eastern side of the mountains in western US Hot Deserts - Cactus In the southwest: Arizona, New Mexico and western Texas

Desert Climate Lack of precipitation is the limiting factor Less than 25 cm per year, most less than 10 cm Determines the types of plants Determines the types of animals Most rain during a few short storms Most water runs off due to compacted pavement

Desert Temperature Varies Greatly Moisture helps to stabilize temperature Acts like a blanket Absorbs heat in day Holds in warmth at night Without this moisture, desert temperature rise and fall dramatically within 24 hour periods              

Desert Biome Video

Desert Organisms Must be adapted to survive with Lack of water Extreme temperatures Despite these challenges, deserts are actually species-rich complex ecosystems                                                                                   

Desert Plants They Must Be able to absorb scarce water from ground Prevent water loss form tissues Cactus spines (leaves) reduce water loss by reducing surface area Succulents – have thick water filled tissue (cacti, aloe vera) An attractive source of food and water for desert animals Spines also help protect from being eaten by animals

Desert Plants continued Another adaptation is the roots Some shallow but covering a wide area Others grow very deep Both help to maximize the amount of water they can get

Desert Animals Many types Most get water from their food Most have adaptations to help reduce water loss Also adaptations to survive the heat Many are nocturnal – active at night, sleeping during the heat of the day

7.2 Formation of Deserts Objective Illustrate the processes that cause deserts to form.

Natural Desert Formation Two broad belts of deserts Northern one near Tropic of Cancer Southern near Tropic of Capricorn Around the equator (tropics) very moist air After moisture has fallen as rain air becomes dry Then flows towards poles becoming cooler and heavier Sinks back to earth as dry winds forming deserts

Rainshadow Effect Exact locations are determined by local geographic features such as mountains In U.S. Winds move from west to east Forces warm moist air over mountains Drops moisture on mountains Cool dry air reaches eastern side Picks up moisture from soil Soil becomes very dry forming desert

Life in the Desert Video

Desertification Deserts often bordered by semiarid regions with grasses and shrubs Human activity (raising livestock) has caused these semiarid regions to become deserts The process of changing semiarid land into desert as a result of human activity is called desertification

Human Impact on the Desert

7.3 Tundra Objectives Describe why the characteristics of the tundra make it a fragile ecosystem Compare the characteristics of tundra organisms with those of their relatives in warmer climates The tundra is a cold , windy, dry region.

Tundra Facts In northern hemisphere just south of polar ice caps in Alaska, Canada, Greenland, Iceland, Norway and Asia A large biome –10% of Earth’s surface Fewer types of organisms than any other biome Lack of diversity makes them fragile and unstable

Tundra Video

Tundra Climate Like a desert little precipitation A cold climate Less than 25cm per year A cold climate Usually below 10 degrees Celsius Most precipitation falls as ice or snow Temperature is the limiting factor

Permafrost Only the top layer, or active zone, of soil thaws in summer The active zone may be as thin as 8 cm The frozen soil beneath the active zone is called permafrost A dense mat of mosses, grasses, and other plant life keeps the ground insulated and prevents the permafrost from melting Any disruption of this mat affects the permafrost

Tundra Climate continued Tundra vegetation does not recover from disruption as quickly as in other biomes Rain in summer cannot penetrate the permafrost Water collects forming bogs,, marshes, ponds, and streams Creates a great breeding ground for mosquitoes and black flies (an important link in the food web) Permafrost is therefore important to the stability of a tundra ecosystem

Tundra Organisms Plants Short growing season Small and close to ground Ground warmed by radiant energy Roots close to surface Small trees (less than 1 meter) Lichens are very important producers

Tundra Animals Seasonal visitors (migrate south for winter) Safe place for breeding due to less predators Birds feed on mosquitoes and flies Predators feed on birds Caribou- large migratory mammal Thick coat big hooves Feed on lichen Fox, Bears, Wolverines don’t migrate

The End