Desert and Tundra Biomes

1. Desert and Tundra Biomes Chapter 7

2. 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.

3. 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

4. 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

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

6. 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

7. 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

8. 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

9. Desert Biome Video

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

11. 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

12. 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

13. 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

14. 7.2 Formation of Deserts Objective • Illustrate the processes that cause deserts to form.

15. 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

16. 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

17. Life in the Desert Video

18. 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

19. Human Impact on the Desert

20. 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.

22. 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

23. Tundra Video

24. Tundra Climate • Like a desert little precipitation • 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

26. 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

27. 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

29. 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

30. 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

32. The End