Download Chapter 58 Biosphere

The Biosphere
Chapter 58
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Outline
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The Sun and Atmospheric Circulation
Atmospheric Circulation & Climate
Major Biomes
Patterns of Ocean Circulation
Life in Oceans
Marine Ecosystems
Freshwater Habitats
Productivity of Freshwater Ecosystems
Human Activity & Biosphere Stress
– Global Warming
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The Sun & Atmospheric Circulation
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Biome distribution results from interaction of
features of the earth and:
– amount of solar heat reaching different parts of
the earth & seasonal variations
– global atmospheric circulation & resulting ocean
current patterns
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Relationships Between the Earth & Sun
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The Sun & Atmospheric Circulation
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Warm tropics
– Because earth a sphere, some regions receive
more solar energy than others
§ Sun’s rays hit almost perpendicular to equator
– Earth’s annual orbit around sun & its daily
rotation on its axis play important roles in climate
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The Sun & Atmospheric Circulation
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Major atmospheric circulation patterns
– Warm air hold more water vapor than cold air
– Warm, moist air rises at equator, cools,
condenses & falls as rain near equator & then
flows back toward the poles
§ Air masses descend & produce arid zones at
30o N & S latitudes
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§ rise again at 60 N & S latitudes
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Atmospheric Circulation
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Atmospheric Circulation and Climate
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Most major world’s deserts lie at 30o N & S latitude
– Other major deserts formed in interior of large
continents, or because of rain shadow effect
§ Mountain ranges intercept moisture-laden air
masses from sea
v air mass rises, cools & drops rain on
windward side
Ø leeward side often much drier
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Rain Shadow Effect
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Atmospheric Circulation & Climate
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Latitude
– no seasons in tropics à little variation in mean
monthly temperature in tropical ecosystems
§ away from equator, sunlight strikes earth at a
more oblique angle, thus less sunlight falls on a
given area
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Atmospheric Circulation and Climate
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Elevation
– Temperature progressively becomes colder as
you move up in elevation.
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§ 6 C for every 1000 m increase
Microclimate
– very localized climatic conditions
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Elevation and Latitude
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Major Biomes
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Biomes: major communities of organisms that have a
characteristic appearance (vegetation/plant) & are
distributed over a wide land area defined by regional
variations in climate
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Biome Distribution
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Major Biomes
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Biomes & climate
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Temperature & precipitation:
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key parameters determining biomes
Absence of geologic features/varying sea temperatures
each biome would form an even belt around the globe,
defined largely by latitude
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Predictors of Biome Distribution
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Major Biomes
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Tropical rain forests
– receive 140-450 cm annual rainfall
– contain at least half earth’s terrestrial plant &
animal species
Savannas
– seasonal rainfall (75-125 cm annually)
– dry tropical grassland transitioning from tropical
rainforests to deserts
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Major Biomes
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Deserts
– < 25 cm annual rainfall
– plants & animals adapted for water conservation
Temperate grasslands (prairies)
– highly productive temperate regions
– herds of grazing mammals
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Major Biomes
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Temperate deciduous forests
– mild climates & plentiful rain
– perennial herbs
Temperate evergreen forests
– cold winters & a strong, seasonal dry period
– nutrient-poor soils
– broad transitional zone
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Major Biomes
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Taiga
– long cold winter
– coniferous trees
Tundra
– open, windswept & boggy
– Permafrost (permanent ice) exists within a meter
of surface
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Patterns of Ocean Circulation
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Ocean circulation determined by
atmospheric circulation and location of land
masses.
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Patterns of Ocean Circulation
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El Nino southern oscillation
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Pacific Ocean normally fanned by constant
east-west trade winds
§ Pushes warm surface water away from eastern
coastal areas & allows cold, nutrient-rich, water
to well up
v If winds slacken, warm water moves back
inward, cutting off nutrient supply
Ø Commercial fishing off Peru & Chile
decreases dramatically
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El Nino Winter
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Marine Ecosystems
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O2 supply can be critical in ocean
– As water temperatures rise, amount of O2 that can be held
lowers
§ CO2 extremely plentiful
– uniform distribution of minerals
– patchy bottom environment may contribute to species
formation
90% of living species are terrestrial
– sharp habitat boundaries
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Marine Ecosystems
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Neritic zone
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< 300 m below surface along coasts of continental/island
§ Intertidal (littoral) region exposed to air as tides recede
§ Nutrient runoff from land near coastal regions
contributes to productive continental shelf fisheries
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Marine Ecosystems
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Pelagic zone
– Open sea: diverse biological community, primarily
plankton
§ most live in top 100 m
v light penetration
§ plankton ~ 40% of all photosynthesis on earth
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Marine Ecosystems
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Benthic zone
– Sea floor: thick mud layer composed of sediment
§ Sea floor at depths below 1000 m abyssal zone,
~ twice area of all land on earth
– Relatively recent discoveries: high diversity of marine life
living on sea floor near volcanic/deep sea vents
§ chemosynthesis
Pogonophoran (beard worms)
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Freshwater Habitats
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Inland lakes cover ~1.8% of earth’s surface
Running water ~ 0.3%
Ponds & lakes
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photosynthetic organisms: upper photic zone
heterotrophic organisms: lower disphotic/ aphotic zones
littoral zone - shallow area along shore
limnetic zone - surface water away from shore
profundal zone - below light penetration
limnology: study of life & processes in fresh water
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Freshwater Habitats
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Summer, warmer water forms layer over cooler water,
forming an abrupt thermocline
Autumn, surface water temperature drops until reaches
temperature of cooler water underneath.
§ upper & lower layers mix
v fall overturn
Fresh Water Stratification
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Productivity of Freshwater Ecosystems
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Lakes divided into two categories:
– eutrophic - rich in nutrients & organic matter
– oligotrophic - poor in nutrients & organic matter
§ often deeper than eutrophic lakes & very susceptible to
chemical pollutants
v cultural eutrophication
anthropogenic (human) input e.g. pollutants, high nutrients
eutrophic
oligotrophic
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Productivity of Freshwater Ecosystems
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Wetlands support a wide variety organisms
– definition: time period of standing water covering area
– play key ecological role by providing storage basins that
moderate flooding
§ many being disrupted by human activities
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Human Activity & Biosphere Stress
Pollution
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Widespread modern agriculture introduces large amounts of
chemicals into global ecosystem
§ Chlorinated hydrocarbons (DDT): severe environmental
problems due to biological magnification
v eggshell thinning in predatory bird spp (Robert
Risebrough)
§ Trichloroethane (TCE) runoff from Hill Air Force Base
leaching into groundwater (Clearfield)
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Acid Precipitation
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Sulfur introduced into upper atmosphere combines with water
vapor to produce sulfuric acid (H2SO4)
– Natural rain water rarely has a pH lower than 5.6:
northeastern US, rain with pH as low as 3.8
§ aquatic habitats/groundwater/forests damaged
v Solution: capturing emissions
Ø difficult & expensive
Forest in Tennessee
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Destruction of Tropical Forests
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> 50% world’s population lives in tropics, % rising
– In mid -1990’s, ~ 50% of original extent of tropical
rainforests existed in an undisturbed form
§ Current rates of clearing, all tropical rainforests will be
gone in 30 years
v loss of largely unknown levels of biodiversity as well
as ecological functioning
Sebastio Salgado
Amazon
Ecuador
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Ozone Hole
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Ozone thinning detected over Antarctica in 1975
– Major cause of depletion: chlorofluorocarbons (CFC’s).
– Stratospheric ozone protects life from UV rays
§ 1% drop atm ozone à 6% increase melanoma
Antarctica Ozone Hole
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Carbon Dioxide & Global Warming
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CO2 & other gases trap longer wavelength infrared light,
heat, radiating from surface of the earth
– greenhouse effect
§ Roughly 7X as much locked up in fossil fuels as
currently exists in atmosphere
v Estimated increases in atmospheric CO2 raise
average global temperature 1.5-4.5 o C by 2035
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Effects of Global Warming
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Ecosystems
– prehistoric climate change
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§ global temperature change up to 10 C in extremes
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- range shifts in contemporary species
life cycle changes
- Species
dispersal ability
reproduction cues
temperature-sensitive sex determination
1970
Mt. Kilamanjaro
Speckled wood butterfly
Parargreaegeria
1915-1939
2000
1970-1997
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Effects of Global Warming
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Humans
– rising sea levels
– climatic effects
§ extreme events
– agriculture
§ increased drought frequency
§ reduced crop yields
– human health
§ loss of safe drinking water
§ mosquito-borne diseases
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Summary
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The Sun & Atmospheric Circulation
Atmospheric Circulation & Climate
Major Biomes
Patterns of Ocean Circulation
Life in Oceans
Marine Ecosystems
Freshwater Habitats
Productivity of Freshwater Ecosystems
Human Activity & Biosphere Stress
– Global Warming
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