Transcript VI. Cycles in the Environment

VI. Cycles in the Environment
A. Carbon Cycle
1. Cycles the organic matter necessary
for all life
2. Bulk is preformed by life through
photosynthesis and respiration
a. 6CO2 + 6H2O + Energy 
C6H12O6 + 6O2
b. Most carbon is locked in life
because of this
3. As death and sedimentation occur,
atmospheric carbon gets trapped as rock
and fossil fuels.
4. Oceans also absorb CO2 from the air
and volcanic eruptions
a. This can combine with Ca to form
CaCO3 which makes shells of aquatic
life
5. CO2’s atmospheric concentration is
increasing
a. Burning of fossil fuels
b. Loss of plants that cycle
c. There is an undiscovered sink
though
B. Phosphorus Cycle
1. Key to production of membranes, DNA,
RNA, and ATP
2. Very small amount present in life and
negligible in the atmosphere
3. Vast majority locked in rock sand
released slowly by weathering
a. Dissolves in water which can:
1. precipitate back out to form
rocks
2. be absorbed by plants and
incorporated into the food web
a. This is the limiting
element in plant growth
4. Because amount limits growth, it is a
main component of fertilizers
a. Excess runs off, removing limitation
from plants and algae
1. these overgrow, using up
resources such as oxygen killing
themselves and other organisms
C. Nitrogen Cycle
1. N2 makes up 78% of atmosphere but is
inaccessible to most life.
2. Must be made biologically active by
nitrogen fixation
3. Several steps
a. Specially adapted nitrogen-fixing
bacteria combine it with H2 to make
ammonia (NH3)
1. live in the root nodules of
legumes
b. Ionized by water, NH4+
(ammonium) can be used by few plants
c. Other bacteria use nitrification to
convert ammonium in to more readily
usable NO2- (nitrite) and NO3- (nitrate)
1. also what is in fertilizers
d. Plants then pass N up the food web
e. Process can also by-pass N fixing
bacteria as lightning can produce
ammonia as well
4. As organisms decay, bacteria release
N2 back into air to start over
5. Along with phosphates, nitrates in
fertilizers have created dead spots in
several waterways.