Transcript Ecological Cycles

Ecological Cycles
Nitrogen, Carbon-Oxygen,
Phosphorus, Sulfur
The Nitrogen cycle
The Nitrogen Cycle

Nitrogen is used by living organisms to
produce a number of complex organic
molecules like amino acids, proteins, and
nucleic acids.
 78% of the world’s atmosphere is nitrogen
 Despite its abundance in the atmosphere,
nitrogen is often the most limiting nutrient for
plant growth. This problem occurs because
most plants can only take up nitrogen in two
solid forms: ammonium ion (NH4+ ) and the
ion nitrate (NO3- ) and CONNOT use raw
atmospheric nitrogen
Four processes participate in the cycling of
nitrogen through the biosphere:

nitrogen fixation
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atmospheric fixation by lightning
biological fixation by certain microbes
industrial fixation – making ammonia
decay (ammonification) – bacteria convert
dead matter and wastes into ammonia
 nitrification – bacteria convert ammonia into
nitrates and nitrites
 denitrification – bacteria return nitrogen to
the atmosphere
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Human Influence on Nitrogen Cycle
artificial nitrogen fertilization
 planting of nitrogen fixing crops
 N2O has risen in the atmosphere as a
result of agricultural fertilization, biomass
burning, cattle and feedlots, and other
industrial sources (N2O also destroys ozone)
 eutrophication
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Water Cycle
Water Cycle – Man’s Influence
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Tropical Rain Forest – deforestation
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Less trees = less tramsiration = less water
in atmosphere = less rain
Olalla Reservoir
Huge groundwater store in central U.S.
 Being depleted faster than replenished

Carbon Cycle
Carbon Cycle
O.03 carbon dioxide in atmosphere
 Plants take in CO2 and release O2 in
PHOTOSYNTHEIS
 Animals take in O2 and release CO2 in
CELLULAR RESPIRATION
 Decay also release CO2 into the
atmosphere
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Man’s Influence on Carbon Cycle
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Burning fossil fuels releases CO2 into
atmosphere
Cellulose in dead plant material is hard to
breakdown (too big)
Accumulates undecomposed over time
forming peat
Peat over time and under pressure forms fossil
fuels
When fossil fuels are burned – releases
carbon
Sulfur Cycle

Sulfur
Component of proteins
 Component of vitamins

Most sulfur is in rock and mineral slats
 Released naturally into atmosphere from
volcanoes and decomposition in
wetlands
 In atmosphere, SO2 reacts with water to
produce sulfuric acid

Man’s Influence
We release excess SO2 into the
atmosphere by:
 Burning fossil fuels
 Refining petroleum products
 Mining processes

Chemosynthesis
Ocean vents in trenches
 Bacteria use hydrogen sulfide H2S as
energy source

Phosphorus Cycle
Phosphorus important in
 DNA molecules
 ATP
 Cell membranes
 Bones
 Teeth
 shells
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Slow cycle
 Not much in atmosphere – but in soil,
rock, and water
 Big water component

Phosphorus Cycle