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Ecosystems
Chapter 31
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
31.6 The Sun and
Atmospheric Circulation
Tropics are warmer than temperate regions because
sunlight strikes perpendicularly providing more energy
This is the main
reason for the
diversity of climates
and thus the diversity
of ecosystems
Fig. 31.12 Latitude affects climate
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Near the equator, warm air rises, cools and shed
its moisture
Rainforests are formed
At about 30o N and S
latitudes, cool dry air sinks
and becomes reheated
Deserts are formed
At about 60o N and S
latitudes, air rises again,
cools and sheds its moisture
Fig. 31.13 Air rises at
the equator then falls
Temperate forests are formed
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
31.7 Latitude and Elevation
Temperature varies with latitude
It is higher in tropical ecosystems because
sunlight strikes the equator perpendicularly
Temperature also varies with elevation
At any given latitude, air temperature falls ~ 6o C
for every 1,000-meter increase in elevation
In North America, for example, the same
temperature drop is achieved by
A 1-km increase in elevation and an 880-km
increase in latitude
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 31.14 How elevation affects ecosystems
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Rain Shadows
A moving body of air is forced upward as it
encounters a mountain
As it cools, its moisture-holding capacity decreases
Rain falls on the windward side
Mount Whitney
The air descends and
warms on the leeward side
Its moisture-holding
capacity increases
Often produces
a desert
Death Valley
Fig. 31.15 The rain shadow effect
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
31.8 Patterns of Circulation
in the Ocean
Patterns of ocean circulation are determined by
atmospheric circulation and land masses
They are dominated by huge surface gyres
These move CW in the Northern Hemisphere
and CCW in the Southern Hemisphere
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Fig. 31.16 Oceanic circulation
Copyright ©The McGraw-Hill Companies, Inc. Permission required for reproduction or display
31.9 Ocean Ecosystems
Three-quarters of the earth’s surface is covered by
water
Fig. 31.18
The three main kinds
of ecosystems are
Shallow waters
Open-sea surface
Deep sea waters
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Shallow Waters
The world’s great commercial fisheries occur on
banks in the coastal zones
Intertidal region – Areas exposed to air when the
tides recede
Estuaries – Partly enclosed bodies of water,
often forming at river mouths and coastal bays
Intermediate salinity
Very fertile
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Open-Sea Surface
Upper, better-illuminated waters of the ocean
Rich with phytoplankton and zooplankton
Most occur in the top 100 meters
Some are photosynthetic
Responsible for ~ 40% of all
photosynthesis on earth
Populations able to increase rapidly
Nutrient turnover much more rapid than in other
ecosystems
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Deep-Sea Waters
Little light penetrates
beyond the top 300 meters
Relatively few, bizarre,
Fig. 31.20
organisms live there
Some fish have
bioluminescent
body parts
Sea anemones use
glass-sponge stalks to
catch falling particles
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Deep-Sea Waters
Hydrothermal vent systems (deepsea vents) support a broad array of
living organisms
Autotrophic prokaryotes obtain
energy by chemosynthesis
Fig. 31.20b
Extract energy from
hydrogen sulfide to
manufacture food
Live symbiotically
within the tissues of
heterotrophic animals
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31.10 Freshwater Ecosystems
Includes lakes, ponds, rivers and wetlands
Cover only about 2% of the earth’s surface
Strongly connected to land ecosystems
Some organisms can only live in freshwater habitats
Speckled darter
Giant waterbug
Eggs
Fig. 31.22
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31.11 Land Ecosystems
More than 90% of described species occur on land
A biome is a terrestrial ecosystem that occurs over a
broad area
Characterized by a particular climate and a
defined group of organisms
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The seven most
widely-occurring
biomes are
1) Tropical rain
forest
2) Savanna
3) Desert
4) Temperate
grassland
5) Temperate
deciduous forest
6) Taiga
7) Tundra
The seven other less
widespread biomes
are
1) Chaparral
2) Polar ice
3) Mountain zone
4) Temperate
evergreen forest
5) Warm, moist
evergreen forest
6) Tropical
monsoon forest
7) Semidesert
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Fig. 31.25 Distribution of the earth’s biomes
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Lush Tropical Rain Forests
Experience more than 250 cm of rain a year
Richest ecosystem on earth
Contain at least
half of the earth’s
species of
terrestrial plants
and animals
Unfortunately, they
are being destroyed
Fig. 31.26
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Savannas: Dry Tropical Grasslands
Rainfall is seasonal: 75-125 cm annually
Many organisms only active in rainy season
On a global scale,
savannas are
transitional between
tropical rain forest
and desert
Contain several
endangered species
Fig. 31.27
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Deserts: Burning Hot Sands
Dry places with less than 25 cm of rain a year
Vegetation is sparse
Plants and animals
have various means
of water conservation
Camels can drink
large quantities of
water and survive
long dry periods
Fig. 31.28
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Grasslands: Seas of Grass
Temperate regions found halfway between the
equator and the poles
Also called prairies
Often populated by
herds of grazing
mammals
Very rich
agricultural regions
Fig. 31.29
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Deciduous Forests: Rich Hardwood Forests
Mild climate with plentiful rains
Deciduous trees drop leaves in winter
Remaining areas
share animals and
plants that were
once widespread
Alligators only
found in China
and SE United
States
Fig. 31.30
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Taiga: Trackless Conifer Forests
Extends over vast areas of Asia and North America
Conifers are trees with needle-like leaves that are
kept all year long
Winters are long
and cold
Many large
mammals
Elk, moose,
bears
Fig. 31.31
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Tundra: Cold Boggy Plains
Found in the far north
Grasslands that are open, windswept and boggy
Little rain or snow
Permafrost, or permanent
ice, exists with a meter of
surface
Many large
mammals
Caribou, reindeer
Fig. 31.32
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Chaparral
Communities of
evergreen, often
spiny shrubs and
low trees
Fig. 31.33
Polar Ice Caps
Lie over the
Arctic Ocean in
the north and
Antarctica in
the south
Fig. 31.34
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Tropical Monsoon
Forest
Occur at slightly
higher latitudes
than rainforests
Or where local
climates are drier
Semidesert
Occur in regions
with less rain than
monsoon forests
but more rain than
savannas
Fig. 31.35
Fig. 31.36
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Mountain (alpine) zone
Similar to tundras
“Alive” in warm summer; little growth in winter
Temperate evergreen forests
Occur in regions where winters are cold and
there is a strong seasonal dry period
Warm, moist evergreen forests
Occur in temperate regions where winters are
mild and moisture is plentiful
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