biomes: the earth’s ecosystems • energy transfer in...
TRANSCRIPT
• Biomes: the Earth’s ecosystems
• Energy transfer in ecosystems
• Cycling of major elements
Ecology of Ecosystems
Biomes
Biomes are large-scale, regional 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
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 immigrateduring summer and emmigrate during winter
Tropical Rainforest
• Warm and wet• low seasonality • highest diversity • evergreen
Temperate Forest• moderate temperature and precipitation • high seasonality • deciduous trees• shaded understory• good diversity
Chaparral• Moderate diversity• Brushy areas composed of shrubs • Mild winters and very dry summers • Poor in nutrients• Ecosystem depends on fire
Temperate Grassland• 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.
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
Earth’s tilt creates seasons.
Atmospheric circulation creates deserts.
Latitudinal Patterns of Rainfall
Efficiency of Energy Transfer • Energy is transferred between species ina
community by predation, herbivory or parasitism.
• 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.
Decrease in energy available at each level
1000100
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The 10% Rule
– There are many more plants than herbivores
– There are more herbivores than carnivores
Producers
• Applies to Biomass as well as energy
Abundance of Elements in Living Things
• 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
– Water is the solute for all of life’s reactions
– Nitrogen is used to build proteins and DNA
The Carbon
Cycle
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