Download When water vapor in the air cools (usually at night), it condenses on

Geochemical Cycles
Geochemical Cycles
Carbon Cycle
 Early atmosphere of Earth 95% CO2.
Photosynthetic plants removed some of the CO2
and added O2. Today’s atmosphere is 0.04%
CO2!
Carbon is found in the
 Reactions of photosynthesis and cellular
atmosphere
primarily
as CO
2
respiration couldn’t
take place
without
carbon.
These two reactions form a continuous cycle.
 Two important sources of Carbon are the ocean
(since
CO2 dissolves
easily
in H20)Respiration
and rocks :
Photosynthesis
:
Cellular
(suchtaking
as coal,
limestonetake
formed
fromand in
Plants
CO2ore
out andOrganisms
that sugar
organisms)
ofdead
the atmosphere
and
the process of burning energy
using it to produce
sugar.
release CO2 back into the
atmosphere.
And, another way to look at the carbon cycle:
Humans affect the Carbon Cycle
 Burning of fossil fuels, (oil, coal and
natural gas).
 Fossil fuels were formed very long
ago and is “fixed”: essentially
locked out of the carbon cycle.
 By burning fossil fuels the carbon is
released back into the cycle.
Humans affect the Carbon Cycle
 We presently release more carbon into the
air than can be reabsorbed by
photosynthetic organisms, thereby we have
a net INCREASE of carbon in the cycle.
 This atmospheric carbon has a role to play
in the warming of the atmosphere.
Geochemical Cycles




Nitrogen Cycle
Organisms require Nitrogen to form amino
acids for the building of proteins.
Lots of N2 in our atmosphere
Unfortunately, most organisms CANNOT
use atmospheric nitrogen.
Nitrogen-fixing bacteria CAN use N2 from
the atmosphere. Nitrogen-fixing bacteria convert
atmospheric N2 into ammonia
(NH4) which is a form of
nitrogen that plants CAN use.
Nitrogen Cycle Continued …
 Nitrogen-fixing bacteria live in the soil and in
roots of legumes.
 These bacteria also form nitrites (NO2) and
nitrates (NO3); which are compounds containing
N and O.
 Nitrate is the most common source of N for
plants.
 Animals get N from the proteins they eat.
 Decomposers return N to the soil in the form of
ammonia and the cycle repeats.
 So, oftentimes, the nitrogen cycle does not
require the N to be returned to atmospheric form!
Nitrogen Cycle Summary
 All living organisms require nitrogen – to
form amino acids to build proteins.
 Proteins are important for locomotion,
reproduction, defense, and structure.
 Nitrogen makes up 78% of atmosphere as
N2
 Nitrogen-fixing bacteria are very important N2 needs to be “fixed” before it can be used
by most living things.
NITROGEN CYCLE
N2
Fertilizer
Production
Lightning
Denitrification
(GAS
)
Nitrogen
Crops
Fixation
Sheep
Legume
Nitrogen-Fixing
Bacteria in
soil & roots
Decomposers
Ammonia
Nitrates
Nitrites
Humans affect the Nitrogen Cycle
 From the production and use of nitrogen
fertilizers to the burning of fossil fuels in
automobiles, power plants, and industries,
humans impact this cycle.
 Nitrogen is essential to living organisms and
its availability plays a crucial role in the
world's ecosystems.
 Excessive nitrogen additions can pollute
ecosystems
Humans affect the Nitrogen Cycle
 Increased global concentrations of nitrous
oxide (N2O), a potent greenhouse gas, in
the atmosphere
 Increased concentrations of nitric oxide,
(NO) that drive the formation of smog along
with N2O
 Losses of soil nutrients such as calcium and
potassium that are essential for long-term
soil fertility
Humans affect the Nitrogen Cycle
 Acidification of soils and of the waters
of streams and lakes
 Greatly increased transport of nitrogen
by rivers into estuaries and coastal
waters where it is a major pollutant.