Transcript Biogeochemical Cycles

Check In HW and
Set Up 5 Yeast Dilutions
Sentinel
Species?
Warwick E. Kerr
Sentinels of Global Warming?
Biogeochemical Cycles
How do biogeochemical cycles
reflect the 1st law of
thermodynamics?
Nutrient Cycles
• Materials necessary
to build tissues and
carry out essential life
functions
• Examples: Carbon,
Phosphorus, Nitrogen
HYDROLOGIC CYCLE
• Evaporation
• Condensation
• Powered by solar radiation
Primary Productivity v. Rainfall
Carbon Cycle
• Appx. 49,000 metric gigatons of carbon on
Earth and in atmosphere
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71% in ocean
22% fossilized
3% in dead matter
2% in live matter
1% in atmosphere
Mutualism & The Carbon Cycle
• Photosynthesis “fixes”
gaseous carbon (in
form of CO2) into a
more stable form
(glucose/C6H12O6)
• Cellular Respiration
releases carbon in
form of CO2
A Precarious Balance
• CO2 is only a small fragment of the
atmosphere (0.04%)
• Less than 2% of the world’s CO2 comes
from burning fossil fuels
• YET, the carbon cycle is rapidly becoming
unbalanced in its ability to absorb the
increases in CO2
NITROGEN CYCLE
• 78% of atmosphere is DIATOMIC
NITROGEN (N2)
• N2 is essentially useless to living
organisms as the triple covalent bonds
between nitrogen atoms make it
chemically inert
• To “liberate” nitrogen it must be chemically
reacted with other atoms
ABIOTIC NITROGEN FIXATION
• High energy reactions
like lightning and
vulcanism can break
the triple bonds of N2
• Liberated nitrogen
reacts with oxygen to
create Nitrate (NO3)
and Nitrite (NO2)
BIOTIC NITROGEN FIXATION
• Rhizobium bacteria
use the enzyme
nitrogenase to break
apart N2 in the
absence of oxygen
• To isolate themselves
from oxygen,
Rhizobium live in
nodules on legumes
Phosphorus & Algal Blooms
• Excess phosphorus in
aquatic ecosystems
allows for algal
populations to
increase drastically by
raising the carrying
capacity
• However, biological
oxygen demand
becomes too high and
system crashes