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Transcript
Biomes
Ecology of Ecosystems
Biomes are large-scale, regional
ecosystems
• Biomes: the Earth’s ecosystems
– These ecosystems are dominated by their
forms of vegetation
– Boundaries are largely determined by climate
– The same biomes can occur on two different
continents and have different species; usually
the two regions will bear striking similarities
• Energy transfer in ecosystems
• Cycling of major elements
Ice
•
•
•
•
Water is frozen all year
No plants
Microscopic algae
Penguins, Polar bears,
etc.
• Threatened by global
warming
Tundra
•
•
•
•
•
•
At high altitude or latitude
Cold and dry
few or no trees
Short growing season
Low species diversity
Low productivity
Taiga (Boreal Forest)
• cold with much snow
• dominated by
evergreens
• Longer growing
season than tundra,
but still short
• birds immigrate
during summer and
emmigrate during
winter
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Tropical Rainforest
•
•
•
•
Warm and wet
low seasonality
highest diversity
evergreen
•
•
•
•
•
Moderate diversity
Brushy areas composed of shrubs
Mild winters and very dry summers
Poor in nutrients
Ecosystem depends on fire
Temperate Forest
•
•
•
•
moderate temperature and precipitation
high seasonality
deciduous trees
shaded understory
• good diversity
Temperate Grassland
Chaparral
• dominated by grasses
• dry and prone to fire
• seasonal in temperature
Tropical Savannah
•
•
•
•
scattered trees in grassland
high temperature and low rainfall
many herbivores
Impacted by grazing and fire
Mountains
• Tropical Montane forests:
– cool but constant year round.
– In Central America, dominated
by oaks.
• Alpine
– at an altitude of about 10,000
feet or more.
– just below the snow line of a
mountain.
2
Desert
•
•
•
•
•
Common at 30° N and S of equator
low rainfall, but may be cold to hot
many succulents
Spiny plants
Small rodents, lizards, snakes, jackrabbits, etc.
Determinants of the Ecosytem
• Temperature
–
–
–
–
Tilt of the Earth
Oceanic Circulation
Latitude
Altitude
• Precipitation
– Oceanic Circulation
– Mountain Shadows
Atmospheric circulation creates deserts.
Earth’s tilt creates seasons.
Latitudinal Patterns of Rainfall
3
Efficiency of Energy Transfer
• Energy is transferred between species ina
community by predation, herbivory or parasitism.
Decrease in energy available at
each level
• Organisms use about 90% of the energy in their
food for their functions:
• Cellular respiration
• Excretion
• Reproduction
– Only 10% can be transferred to another
species.
The 10% Rule
1
10
100
1000
Abundance of Elements in Living Things
• Applies to Biomass as well as energy
– There are many more
plants than herbivores
– There are more
herbivores than
carnivores
Producers
• Our composition does not reflect the abundance of
elements in the earth.
• We are mostly Carbon, Hydrogen, Oxygen, Nitrogen.
Elements in Living Things
– Carbon used as the basis for all biological
molecules
The
Carbon
Cycle
– Water is the solute for all of life’s reactions
– Nitrogen is used to build proteins and DNA
4
The Water Cycle
Transpiration
The Nitrogen
Cycle
• Nitrogen Fixation
– Bacteria convert N2 gas to NH3 (ammonia)
– Occurs in the roots of certain plants
• Nitrification
– Bacteria convert NH3 to NO3 (plant food)
• Denitrification
– Bacteria remove NO3 to N2 in the air
5