Biogeochemical Cycles
Intro to Enviro Expo Part 3
Nutrient Cycles
Cycling maintains homeostasis
(balance) in the environment.
•4 cycles to investigate:
1. Water cycle
2. Carbon cycle
3. Nitrogen cycle
4. Phosphorus cycle
Water cycle•Evaporation, transpiration,
condensation, precipitation,
condensation, infiltration/percolation,
runoff
Water cycle-
Carbon cycle•Photosynthesis and respiration
cycle carbon and oxygen through
the environment.
Carbon/Oxygen Cycle
~ Photosynthesis and respiration cycle
carbon and oxygen through the environment.
O2
CO2
Carbon cycle-
Carbon Cycle
• In fact, carbon constitutes the very
definition of life
– Its presence or absence helps define whether
a molecule is considered to be organic or
inorganic.
• Every organism on Earth needs carbon
either for structure, energy, or, as in the
case of humans, for both.
Carbon Cycle
• Carbon is found in forms as diverse as:
– GAS
• carbon dioxide (CO2)
• Carbon monoxide (CO)
• Methane (CH4)
– SOLIDS
•
•
•
•
•
•
•
limestone (CaCO3)
Wood
Plastic
Diamonds
Plants
Graphite
Fossil Fuels
Carbon Cycle
• So what are some
ways Carbon can
get into the
atmosphere???
• So what are some
ways Carbon can
get out of the
atmosphere???
Carbon Cycle
• ON LAND - the major exchange of carbon
with the atmosphere results from:
– Photosynthesis
– respiration
and
Carbon Cycle
ON LAND - the major exchange of carbon with
the atmosphere results from
– During daytime in the growing season, leaves absorb
sunlight and take up carbon dioxide from the
atmosphere (photosynthesis).
– At the same time plants, animals, and soil microbes
consume the carbon in organic matter and return
carbon dioxide to the atmosphere (respiration).
Carbon Cycle
So can the amount of carbon in the
atmosphere change?
Yes!
During winter for instance, there are hardly any leaves
on the trees, so photosynthesis decreases, thus the amount of
CO2 being taken in by these leaves is decreased.
BUT…
At the same time animals are still respiring/exhaling the same
amount of CO2 that they were in all the other seasons
SO…
The amount of CO2 in the atmosphere during winter has
_____________________.
increased
Carbon Cycle
So can the amount of carbon in the
atmosphere change?
http://www.bbc.co.uk/cumbria/content/images/2007/02/06/winter_trees_
470x353.jpg
http://www.craiglauder.com/gallery/Limberlost/images/SUmmer_Trees_Lake.jpg
So an increase in CO2 in atmosphere during winter
in our Northern Hemisphere
Nitrogen cycle-
Nitrogen cycleAll organisms need N to build proteins
(which are used to build new cells).
Atmospheric nitrogen (N2) makes up nearly
78%-80% of air.
Organisms can not use it in that form.
Lightning and bacteria convert nitrogen into
usable forms.
Nitrogen cycleOnly certain bacteria and industrial
technologies can fix nitrogen.
Nitrogen fixation-convert atmospheric
nitrogen (N2) into ammonium (NH4+)
which can be used to make organic
compounds like amino acids.
N2
NH4+
Nitrogen cycleNitrogen-fixing
bacteria:
Some live in a
symbiotic
relationship with
plants of the legume
family (e.g.,
soybeans, clover,
peanuts).
Nitrogen cyclehttp://www.tokyomango.com/tokyo_mango/images/2007/10/0
5/super_mushroom.jpg
• Decomposers help by breaking up stored
Nitrogen (in wastes, leaves, decaying
plants/animals) (This is ammonification – NH4+)
and put Nitrogen back into the soil.
– Then bacteria (nitrobacter or nitrosomonas)
in the soil turn a small portion back into
Nitrogen gas and returns it to the
atmosphere – so that completes the cycle.
(This is called Dentrification).
Nitrogen cycle•Some nitrogen-fixing bacteria live free in the
soil.
•Nitrogen-fixing cyanobacteria are essential to
maintaining the fertility of semi-aquatic
environments like rice paddies.
Unicellular nitrogen-fixing
cyanobacteria, shown in this
light micrograph, play an
important role in the oceanic
nitrogen cycle.
(Credit: Washington University in St. Louis)
Lightning
Atmospheric
nitrogen
Nitrogen Cycle
Denitrification
by bacteria
Animals
Nitrogen
fixing bacteria
Decomposers
Ammonium
Nitrification
by bacteria
Plants
Nitrites
Nitrates
Phosphorus Cycle
Phosphorus cycle• Essential to form bones and teeth in animals,
also helps increase growth in plants
• Phosphorus cycle moves from the environment
to organisms, then back to environment again.
(so doesn’t really cycle through the atmosphere)
http://www.gonzaga.edu/campus+resources/sustainability/Images/waterfall_
web_environment.jpg
Phosphorus cycle• Enters soil when rocks erode
or
when decomposers break down the
remains of dead plants and animals.
• Plants then absorb phosphorus through
their roots and the cycle is complete.
How do Humans Affect the Nitrogen
and Phosphorus Cycles?
• Humans have increased the natural rate of
nitrogen and phosphorus, through the use
of chemical fertilizers.
- When excess nitrogen and phosphorus compounds
run off fields into bodies of water, they can cause an
overgrowth of algae blooms and aquatic plants.
- If abundance of aquatic plants, then
abundance of plant decay and abundance of decomposers,
which deplete oxygen that other aquatic organisms need to
survive.
Algal Blooms
http://serc.carleton.edu/images/microbelife/topics/red_tide_genera.v3.jpg
http://media.supereco.com/media/2009/02/02/320w/algae-bloom.jpg
http://www.waterencyclopedia.com/images/wsci_01_img0017.jpg