1. Desert and Tundra Biomes
Chapter 3

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 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

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