Transcript Understanding Our Environment

Biomes: Global Patterns of Life
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Outline
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Terrestrial Biomes
Marine Ecosystems
 Open Ocean
 Shallow Coasts
Freshwater Ecosystems
 Lakes
 Wetlands
Human Disturbance
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TERRESTRIAL BIOMES
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Biomes - Areas sharing similar climate,
topographic and soil conditions, and roughly
comparable communities.
 Temperature and precipitation are among
the most important determinants in biome
distribution.
- Most terrestrial biomes are identified by
the dominant plants of their
communities.
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Biomes
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Deserts
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Characterized by low moisture levels and
precipitation that is infrequent and
unpredictable from year to year.
Wide daily and seasonal temperature
fluctuations.
Soils are easily disturbed by human activities,
and slow to recover.
Plants exhibit water conservation
characteristics.
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Deserts
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Grasslands
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Communities of grasses, seasonal
herbaceous flowering plants, and open
savannas.
Few trees due to inadequate rainfall.
Large daily and seasonal temperature
fluctuations.
Frequent grass fires.
Historic grazing by roaming herds of large
ungulates.
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Grasslands
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Tundra
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Treeless, temperatures are below freezing
most of the year, only small hardy vegetation
survives.
Very short growing season, with cold harsh
winters.
Damage slow to heal.
 Arctic Tundra exhibits low productivity,
diversity and resilience.
 Alpine Tundra receives intense solar
radiation, hot daytime summer ground
temperatures, and potential droughts.
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Tundra
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Conifer Forests
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Cone-Bearing
Plants reduce water loss by evolving thin,
needle-like evergreen leaves with thick waxy
coating.
 Can survive harsh winters or extended
droughts and accomplish photosynthesis
even under poor conditions.
Fire often plays role in maintenance.
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Conifer Forests
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Boreal Forest - Northern Conifer Forest
 Broad band of mixed coniferous and
deciduous trees between 45° and 60° N
latitude.
 Moist and cool climate with abundant
streams and wetlands.
Taiga - Northernmost edge of boreal forest
 Species-poor. Harsh climate limits
productivity and resilience.
- Produce large peat bogs.
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Boreal Forest
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Conifer Forests
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Temperate Rainforest
 Wettest portion of coniferous forests of
Pacific Northwest.
 Mild temperatures, and very abundant
precipitation. (>250 cm)
- Canopy condensation is major form of
precipitation.
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Broad-Leaved Deciduous Forest
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Temperate regions support lush summer
plant growth when water is plentiful.
 Deciduous leaves an adaptation to
freezing temperatures.
Eastern half of US was covered with broad
leaf deciduous forest when European settlers
arrived. Much of that was harvested a
century ago for timber.
 Now large areas have re-grown and are
again approaching old-growth status.
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Temperate Deciduous Forests
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Mediterranean
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Characterized by warm, dry summers and
cool, moist winters.
Fires are a major factor in plant succession.
 Referred to as chaparral in California.
- Biodiversity hotspot.
 Referred to as thorn scrub in Africa.
- Landscape dominated by acacias and
other spiny plants.
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Tropical Moist Forests
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Humid tropical regions support one of most
complex and biologically rich biomes.
Ample rainfall and uniform temperatures.
 Cloud Forests - High mountains where fog
and mist keep vegetation continually wet.
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Tropical Moist Forests
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Tropical Rainforests - More than 200 cm
annual rainfall with warm-hot temperatures
year-round.
 90% nutrients tied up in living organisms.
 Rapid decomposition and nutrient cycling.
 Thin soil cannot support continued cropping,
and cannot resist erosion.
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Tropical Rainforests
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Tropical Seasonal Forests
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Semi-evergreen and partly deciduous forests
tending toward open woodlands and grassy
savannas.
 Characterized by distinct wet and dry
seasons with hot temperatures year-round
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MARINE ECOSYSTEMS
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Saltwater ecosystems cover vastly more total
area and contain much greater volume of
water than all freshwater bodies combined.
 Oceans hold bulk of world’s water.
Aquatic ecosystems are influenced by local
characteristics of climate, soil, and resident
communities, and also by adjacent terrestrial
ecosystems.
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Critical Characteristics
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Dissolved Substances
Suspended Matter
Depth
Temperature
Flow Rate
Bottom Characteristics
Internal Convective Currents
Connectivity to Other Aquatic Ecosystems
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Marine Ecosystems
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Vertical stratification is an important aspect of
many aquatic ecosystems.
 Organisms tend to form distinctive vertical
sub-communities.
- Benthic - Bottom sub-community.
 Low oxygen levels.
- Pelagic - Water column
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Light Penetration
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Shallow Coasts
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Coral Reefs - Accumulated calcareous
skeletons of colonial organisms (coral).
 Depth limited by light penetration.
 Among most endangered communities.
Mangrove trees grow in salt water.
 Occur along calm, shallow, tropical
coastlines.
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Tidal Environments
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Estuaries - Bays or semi-enclosed bodies of
brackish water that form where rivers enter
the ocean.
 Usually carry rich sediments.
- Fan-shaped sediment deposit (delta)
formed on shallow continental shelves.
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Barrier Islands
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Barrier Islands - Low, narrow, sandy islands
that form offshore from a coastline.
 Protect inland shores from surf.
 Prized for human development.
- Loss of vegetation triggers erosion.
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FRESHWATER ECOSYSTEMS
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Lakes
 Freshwater lakes have distinct vertical
zones.
- Epilimnion
- Hypolimnion
- Benthos
 Thermocline - Distinctive temperature
transition zone that separates warm
upper layer and deeper cold layer.
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Wetlands
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Land surface is saturated or covered with
water at least part of the year.
 Swamps - Wetlands with trees.
 Marshes - Wetlands without trees.
 Bogs and Fens - Waterlogged soils that
tend to accumulate peat.
Water usually shallow enough to allow full
sunlight penetration.
Trap and filter water, and store runoff.
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Wetlands
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HUMAN DISTURBANCE
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By some estimates, humans preempt about
40% of net terrestrial primary productivity.
Temperate broad-leaved deciduous forests
are the most completely human-dominated
biome. Tundra and Arctic Deserts are the
least disturbed.
About half of all original wetlands in the US
have been degraded over the past 250
years.
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Human Disturbance
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Summary
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Terrestrial Biomes
Marine Ecosystems
 Open Ocean
 Shallow Coasts
Freshwater Ecosystems
 Lakes
 Wetlands
Human Disturbance
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