Transcript Biogeochemical Cycles

Biogeochemical Cycles
Where do macromolecules come from
&
Where do they go?
Elements transferred between compartments
(pools)
Active: accessible to living
things
Storage: inaccessible
Biogeochemical Cycle Overview
What is a Biogeochemical Cycle?
• Reuse of materials in ecosystem by living
organisms
• Biological components (biotic):
– Producers
– Consumers
– Detritivores (scavengers & decomposers)
• Geological components (abiotic):
– Atmosphere (gases & water vapor)
– Solid crust of the earth (minerals & chemicals)
– Earth’s water (oceans, lakes & rivers)
Biogeochemical Cycles
• Water – needed to make CARBOHYDRATES,
LIPIDS, PROTEINS
THE WATER CYCLE
Other Biogeochemical Cycles
• Water cycle
• Carbon – needed to make CARBOHYDRATES,
LIPIDS, PROTEINS, & NUCLEIC ACIDS
CARBON CYCLE
atmosphere
respiration
photosynthesis
biosphere
CARBON CYCLE
CARBON CYCLE
combustion
photosynthesis
respiration
atmosphere
biosphere
Other Biogeochemical Cycles
• Water cycle
• Carbon cycle
• Nitrogen – needed to make PROTEIN &
NUCLEIC ACIDS
gain
fixation
loss
atmosphere
biosphere
denitrification
Nitrogen Cycle
Nitrogen Cycle
• Despite abundance in the atmosphere (77% of
Earth’s atmosphere made of N2 gas) nitrogen is
actually a limiting factor to plant growth
• Most organisms cannot use elemental N2 and
must use nitrogen present in soil minerals
• N2 gas is “fixed” into these nitrogen compounds
mainly by bacterial processes
Stages of Nitrogen Cycle
• Ammonification
– Most soil nitrogen is result of decomposition of
nitrogenous compounds by bacteria (amino acids,
proteins, etc.)
– These bacteria release excess nitrogen in the form
of ammonia (NH3) or ammonium ions (NH4+)
Stages of Nitrogen Cycle
• Ammonification
• Nitrification (by nitrogen-fixing bacteria)
– Several species of bacteria able to oxidize
ammonia to get energy for metabolism:
2NH3 + 3O2  2NO2- + 2H+ + 2H2O
– Although nitrite (NO2-) is toxic, it is quickly
changed to nitrate (NO3-) by another group of
bacteria:
2NO2- + O2  2NO3-
NITRATE
– Most plants take up nitrogen in the form of nitrate
Stages of Nitrogen Cycle
• Ammonification
• Nitrification
• Assimilation
– Requires energy expenditure to attach ammonium
ions to carbon-containing compounds
– Amino acids produced:
Amino acids form PROTEINS
Loss of Soil Nitrogen
• Nitrates steadily lost from cycle by:
– Harvesting plants
– Soil erosion
– Fire
– Leaching
– Denitrifying bacteria – these break down nitrate
into N2 gas (in the absence of oxygen); usually
takes place in poorly drained soil
NITROGEN CYCLE ANIMATION
Other Biogeochemical Cycles
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•
•
•
Water cycle
Carbon cycle
Nitrogen cycle
Phosphorus – needed to make DNA & RNA
(nucleic acids) as well as ATP (the energy
currency of cells)
PHOSPHORUS CYCLE
Other Biogeochemical Cycles
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•
•
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Water cycle
Carbon cycle
Phosphorus
Sulfur – needed to make certain proteins
SULFUR CYCLE
Questions:
What would happen if a biogeochemical cycle
“slowed down” or “sped up?”
What might cause such a thing to happen?
Turn to your neighbor and explain.
Then write a summary of what you
both concluded.