Transcript Environmental Science

Chapter 7
Sections 1, 2 & 3
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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
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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
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Cool Deserts
Found on eastern
side of Sierra
Nevada and Rocky
Mountains
Main plant is the
sagebrush
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Hot Deserts
Found in south
west, particularly
Arizona, New
Mexico and western
Texas
Main plant is the
cactus
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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
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Desert
Organisms(Plants)
Cactus spines are
actually leaves
Cacti are
SUCCULENTS,
meaning they store
water
Aloe vera is also a
succulent
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Desert Plants cont.
Most plants have
shallow roots but
some have long
roots, like the
mesquite tree which
has roots 20m deep.
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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?
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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)
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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
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The transformation of semiarid land into
desert is called DESERTIFICATION
How does this occur?
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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
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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
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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
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Tundra Plants
Very small, grow
close to ground
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Tundra Animals
MIGRATION or
seasonal travel
brings in animals
Birds, Arctic Fox,
Caribou
Musk oxen, coastal
polar bears, and
wolverines
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Finish Worksheets for Chapter 7