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Biomes and Global Ecology
Chapter 48
PHYSICAL BASIS OF CLIMATE
48.1 Solar radiation, wind and ocean currents, and
topography determine the distribution of major climatic
zones on Earth.
• Climate: long-term average weather. Determined by:
– Solar radiation
– Global patterns of wind and ocean circulation
– Earth’s varying topography
SOLAR RADIATION
• Major determinant of Earth’s surface temperature: the angle at
which solar radiation strikes the surface.
• Earth climate: hot near the equator and cold at the poles; this
reflects incoming solar radiation.
• Sunlight strikes equatorial regions directly, but at higher latitudes,
Earth’s surface is tilted at an angle to incoming radiation.
• At higher latitudes, temperature is not only lower, it also exhibits
greater variation through the year.
• Seasonality: reflects a second feature of Earth
– Earth’s axis of rotation is not oriented perpendicular to incoming sunlight
but rather tilts at an angle of 23.5 degrees
– This is why most parts of globe show seasonal variation of temperature.
Climate
The
latitudinal
difference in
incoming
solar energy
density
explains why
Earth’s
surface is
hotter at the
equator and
cools
towards the
poles.
North
pole
At the equator, solar
energy strikes Earth
directly, resulting in high
influx of energy per unit
area.
60˚
30˚
~1000 km
0˚
Solar
radiation
30˚
60˚
South
pole
~2000 km
At high latitude, incoming solar
energy strikes Earth at an angle,
resulting in lower fluxes of energy
per unit area.
Annual Mean Temperature
TOPOGRAPHY
• Wind and ocean currents transport heat from
equator toward poles
• Topography: physical features of earth
– Also contributes to global temperature patterns
– Mountaintops: can be glaciated, even at low
latitudes
• Temperature declines with increasing elevation
– Mountains show a pattern in which climate and
biomes change as elevation increases
Rising and descending air organizes
the atmosphere into a series of cells
from the equator to the poles.
90˚ N
60˚ N
30˚ N
Easterlies
Westerlies
Trade winds
0˚
Equator
Trade winds
30˚ S
Westerlies
60˚ S
Easterlies
90˚ S
High temperatures warm air
near the equator. Because of
its lower density, the warm air
rises.
Cool
air
Sun
Warm
air
Hadley
cell
Equator
As air rises and
spreads outward
toward the poles,
it cools, eventually
becoming dense
enough to sink
back to the
surface.
Coriolis Effect
B
Equator
A
B
Equator
A
As Earth rotates
on its axis, a
point on the
equator moves a
greater distance
per time unit
than points at
higher latitudes.
On a rotating
globe, a point
traveling north
will also travel
east.
Because of Earth’s counterclockwise rotation , winds in No. Hemisphere deflect to the
right ; those in the So. Hemisphere deflect to the left
Ocean Currents
North Pacific
North Equatorial
North Equatorial
Equatorial Counter
North Equatorial
South Equatorial
Guinea
Equatorial
Counter
Antarctic Circumpolar
Antarctic Circumpolar (West Wind Drift)
Warm-water
current
Cold-water
current
Rainfall Patterns
Average Annual Precipitation, 1971-2000,
Washington
Precipitation (inches)
Cascade Range
Less than 10
10-20
20-30
30-40
40-60
60-80
80-100
100-140
140-180
More than 180
As air rises over the mountain, it
cools, releasing its moisture as rain.
Prevailing
winds
Warm Pacific
Ocean
Rainfall
Patterns
Once over the mountain,
the air descends,
warming and taking up
moisture.
• Mountains can have a regional pattern on climate because of rain shadow.
• Differing amounts of rain on the wind-facing and opposite sides of mountain
ranges.
Tundra
Temperate grasslands
Alpine
Desert
Taiga
Chaparral
Temperate coniferous forest
Savanna
Deciduous forest
Tropical rain forest
• Regional climate reflects the interactions among solar radiation, global patterns of
circulation, and Earth’s varying topography.
• Biomes, in turn, reflect these variations in climate.
Evapotranspiration
Biomes reflect the interaction of Earth and
life
Evotranspiration affected by:
• Amount of annual precipitation
• Sun intensity
Distribution of biomes reflects regional climates
Plant Convergence
Convergence: cacti in deserts of North America and in Africa look similar
because they most both conserve water; but they are NOT closely related
BIOMES
47.2 Biomes are broad, ecologically uniform
areas characterized by their climate, soil, and
plant/animal species.
 Temperate
•
•
•
•
Tundra
Alpine
Talga
Temperate Coniferous
Forest
• Deciduous Forest
 Grassland
 Desert
 Chaparral
 Savanna
 Rain Forest
Terrestrial Biomes
• Primary producers: mainly vascular plants
• Plants also provide a structure for these biomes
• Primary consumers: variety of animals; mammals, insects
• Secondary consumers: carnivorous vertebrates….lions, tigers, wolves
Tundra
•
•
•
•
•
•
Close to North Pole, above 65o degree N
Coldest biome
Permanent ice below soil
Low plant diversity…mainly mosses, lichen, herbs
Primary consumers: caribou, rabbits, birds
Secondary consumers: wolves, foxes
Alpine
•
•
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•
•
Similar to tundra, but lacks permanent ice below soil
Found throughout world at high altitudes (10,000 ft, but just below snow line)
Windy and cold
Low and slow-growing plants
Primary consumers: mountain goats, llamas, yaks
Taiga
•
•
•
•
•
Cool, moist forests at 50 -65 degree N
Plants are conifers
Soils deep with accumulated organic matter….acidic and poor in nutrients
Primary consumers: elk, moose, caribou, porcupines
Secondary consumers: bears, lynx, wolves, foxes
Temperate Coniferous Forest
•
•
•
•
•
Occur below 50 degrees N
Temperate with much precipitation
North America, northern Japan, parts of Europe, and continental Asia
Enormous conifers along Pacific coast of US; undergrowth is ferns
Insect and vertebrate diversity : higher than taiga forests
Deciduous Forest
•
•
•
•
•
•
Across much of North America, Europe and Asia
Moderate climate
Hardwood deciduous trees……maples oaks, poplar, birches
Human disturbance from agriculture and urban development
Much organic soil
Insects, birds and mammals are diverse; also snakes, lizards, and amphibians
Temperate Grassland
•
•
•
•
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•
Occupied most of Midwestern US prior to settlement
Mainly grasses
Fire maintains grass population
Soils accumulate nutrients; most productive agricultural lands in the world
Before colonization by humans: bison, horses, mammoths
Now, burrowing grazers such as prairie dogs are common
Secondary consumers: ferrets, badgers, foxes, birds of prey
Desert
•
•
•
•
•
•
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Around the world north and south of equator from 25o -35o.
Windy; little precipitation
Deep-rooted plants adapted to store water, i.e. cactus
Primary production is low;
Soils poor in nutrients, but high in salt
Primary consumers tend to be small….diverse lizards, rodents
Secondary consumers: snakes, coyotes, cat species, birds
Chaparral
•
•
•
•
•
•
Narrow range of climate conditions
Occurs on western edge of continents from 32o-40o north and south of equator
Limited rain and falls in 2-4 months
Plants are annual herbs, evergreen shrubs, and small trees
Drought resistant trees, fire resistant
Poor nutrients in soil
Savanna
•
•
•
•
•
•
•
Eastern Africa, southern South America, Australia
Tall, perennial grasses
Rain is seasonal
Scattered trees and shrubs
Animal diversity is high;
Primary consumers: antelopes, zebras, giraffes, kangaroos, large rodents
Secondary consumers: lions, other cat species, hyenas, wild dogs, dingoes, snakes
Tropical Rain Forest
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•
•
•
•
•
•
•
Moist, highly diverse forest
North and south of the equator from 10o N-10o S
Very hot and heavy rains
Huge tree diversity; very tall, epiphytic plants common
Decomposition rapid
Primary consumers: smaller primates, bats, rodents, birds, snakes, lizards
Insects are especially abundant and diverse
Ants make up 30% of animal biomass here
Latitudinal Diversity Gradient in Mammals
• Tropical biomes have more species than temperate biomes
• The number of mammal species decreases from equator to the poles.
• Known as Latitudinal Diversity Gradient
AQUATIC BIOMES
• Aquatic biomes:
–
reflect climate, availability of nutrients and oxygen but especially the depth to
which sunlight penetrates through water.
• In shallow aquatic environments such as lake margins and coastal
marine settings:
–
much plant, algal, and animal debris accumulates in sediments, supporting
luxuriant growth by bacteria.
• Grazers (such as snails and fish)
–
feed on marginal plants and algae, while single-celled protists and microscopic
animals called zooplankton consume phytoplankton that floats in the water.
• Secondary consumers such as other fish or squid feed on the
grazers.
• Because oxygen gas dissolves in water only to a limited extent,
surface waters directly beneath the atmosphere will have an O2
concentration about 20 times lower than that of the air.
• This forces larger animals to be moving constantly to keep their gill
systems well-oxygenated, or to live in places such as cold running
streams and rocky marine coastlines where currents naturally
produce well-oxygenated water.
Aquatic Biomes
Solar radiation
Oceanic
Neritic
system
system
Well-mixed Average
water depth 200m
Photic
zone
Pelagic
realm
Aquatic Biomes
• Only about 2.5% of water is fresh: lakes and rivers, glaciers, permafrost,
groundwater in soil
• 71% of Earth’s surface is seawater
• Ocean is the largest biome
Lakes
• Range in size from tiny pools to the Great Lakes (has more than 20% of all
freshwater)
• From equator to about 80 degrees N
• Primary producers: algae, cyanobacteria
• Zooplankton (heterotrophic or detritivorous organisms drifting in aquatic biomes):
small arthropods and rotifer protists
• Nekton (all aquatic organisms that can swim freely and independent of currents):
fish
• Secondary consumers: turtles and birds
Rivers
•
•
•
•
Freshwater biomes characterized by moving water
Primary producers: plants and large algae, phytoplankton
Primary consumers: insects, fish, turtles, birds
Salmon: spend lives in oceans, but swim up rivers to reproduce
Intertidal Zone
•
•
•
•
Lies along coastlines between high and low tides
Organisms are exposed to the atmosphere on a daily basis
Waves can cause mortality; so algae and animals securely attached to substrate
Consumers: sea stars, sea urchins, mollusks, barnacles, corals
Coral Reefs
• Best known reefs occur in shallow, tropical to subtropical saltwater environments
with little water movement
• Primary production: dinoflagellate algae that live within tissues of corals
• Free-living algae occur in reefs, but kept low by grazing fish
• Many species invertebrates also live in coral heads
• Fish diversity especially high
• Coral reefs also occur in deep sea, but build gradually since coral growth is slow
in absence of symbiotic algae
Pelagic Realm
• The part of the ocean neither close to shore nor close to seafloor: forms bulk of
ocean
• Organisms live within the water column: either as zooplankton (tiny arthropods)or
nekton(cephalopods)
• Upper region with sunlight: primary producers are diverse algae and cyanobacteria
• Secondary consumers: fish, squids , heterotrophic protists
Deep Sea
•
•
•
•
•
The deep seawaters: cold and dark
High species diversity
Primary producers: chemosynthetic bacteria
Primary consumers: bacteria, archeons; sinking detritus
Dense animal populations occur on deep seafloor in location of hydrothermal
vents
GLOBAL ECOLOGY
48.3 Biologically driven cycles of carbon and other
essential elements shape ecology and reflect
evolution.
• Biogeochemical cycles: cycles of carbon and
other biologically important elements as they link
organisms and their environments
Carbon Cycle
CO2
Photosynthesis
Aerobic
respiration
Grazing
Primary producers:
Autotrophs that fix
CO2 into organic
carbon.
Primary consumers:
Heterotrophs that
feed on primary
producers.
Aerobic
respiration
Secondary
consumers:
Heterotroph
s that feed
on primary
consumers.
Predation
Decomposers: Largely
fungi and bacteria in soil
that feed on organic
detritus.
Aerobic respiration
Anaerobic respiration
Fermentation
Ecology and biogeochemical cycling are interrelated processes
Nitrogen Cycle
Consumers
obtain N
from their
food.
N2
Nitrogen fixation
converts N2 to a
form that can be
used by plants.
Primary producers
assimilate biologically
usable N from soil or
symbiotic N-fixing
bacteria.
Denitrification
Assimilation
NO3–
Anammox
Chemoautotrophic
bacteria gain the
energy needed to
fix nitrogen by
oxidizing NH3,
using O2
(nitrification) or
NO2– (anammox).
•
•
•
•
Nitrogen
fixation
Nitrification
In anoxic environments, some
decomposing bacteria use NO3–
in respiration, a process called
denitrification because it
converts biologically usable N
back to N2.
NO2–
Ammonification
Nitrification
NH3
N and Ph limit primary production in most biomes
N in atmosphere is fixed by bacteria and archeons
Then cycles thru primary consumers and decomposers
Closely linked to C cycle
Decomposers
return N to soil
as ammonia.
Phosphorous Cycle
Primary producers
assimilate PO43–
from soil.
PO43
– in
rock
s
Weatherin
g
Consumers
get PO43–
from their
food.
Runoff
Tectonic
uplift
Decomposers release
PO43– to soil; some is
reincorporated by primary
producers, some is
leached.
In shallow oceans
PO43– is cycled
rapidly among
primary
producers,
consumers, and
decomposers.
Photic
zone
Upwelling
Deep
ocean
Sedimentati
on
Ph found mainly in rocks
Enters food web as phosphate ion by chemical weathering
Then cycles thru ecosystems, supporting primary production
GLOBAL BIODIVERSITY
48.3 Global patterns of biological diversity reflect
climate, history, and ecological interactions among
species.
• Latitudinal Diversity Gradient: species diversity
declines from equator toward poles
• Earth’s biomes: historical outcome of
environmental change and natural selection
Mammal Global Biodiversity
Tropical
regions have
a great
diversity of
different
kinds of
mammal,
representing
all of the
major groups
from
anteaters to
apes.
Number of mammal species
There are few
mammal species
near the poles,
mostly rodents
and their
carnivore
predators, plus
seals and
whales in the
sea.
Biodiversity Hotspots
Tropical
regions have
a great
diversity of
different
kinds of
mammal,
representing
all of the
major groups
from
anteaters to
apes.
Number of mammal species
There are few
mammal species
near the poles,
mostly rodents
and their
carnivore
predators, plus
seals and
whales in the
sea.