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APES
NDHS
Name: _____________________
Date: ______________________
Nutrient Cycles and Human Impact
Cycling of
in Ecosystems 
KEY PLAYERS 
– complete cycle
Types of Biogeochemical Cycles:
–
–
NUTRIENT RESEVOIRS:
WATER CYCLE
Reservoirs
The oceans contain
of the water in the biosphere.
is bound as ice, and
is in lakes, rivers, and
groundwater.
A negligible amount is in the atmosphere.
Key processes
CARBON CYCLE - base of
Reservoirs
The major reservoirs of carbon include
Key processes
by plants and phytoplankton
atmospheric
.
CO2 is added to the
by
of producers
and consumers.
add CO2 to the atmosphere.
NITROGEN CYCLE
Nitrogen is a component of
Biologically available forms
Plants and algae can use
Various bacteria can also use
Animals can use only
of nitrogen (
)
Reservoirs
The major reservoir of nitrogen is the atmosphere, which is
of lakes, rivers, and oceans.
in surface water and groundwater.
Nitrogen is stored in
.
Key processes
Nitrogen enters ecosystems primarily through
Some nitrogen is fixed by
by bacteria decomposes organic nitrogen.
In
, bacteria convert NH4+ to NO3−.
In
, bacteria use NO3− for metabolism instead
of O2, releasing N2.
- important symbiosis:
PHOSPHOROUS CYCLE
Part of
Biologically available forms
, plants absorb and use to synthesize organic
compounds.
Reservoirs
of marine origin.
Key processes
of rocks gradually adds phosphate to soil.
and incorporated into organic
Absorbed by
material.
It is returned to soil or water through
biomass or
of
.
Decomposition rates largely determine the rates of nutrient
cycling.
Decomposition takes an average of
years in
temperate forests, while in a tropical rain forest, most organic
material decomposes in a
.
The difference is largely the result of
and
more abundant
in tropical rain forests.
The rate of decomposition increases with actual
– wet and warm
Human Impact on Ecosystems and the Biosphere
The human population moves nutrients from one part of the
biosphere to another.
Human activity
in nutrient cycles.
1)
in the form of
:
- can exhaust the
2) Introduce
:
- excess
in air  atmospheric problems
(
)
- excess Nitrates in

of
water ways,
, tainted
,
3) Excess
:
– depletes standing
4) Increase
– fossil fuels
Acid precipitation:
The burning of fossil fuels releases
that react with water in the atmosphere to produce
and return as
Acid precipitation is a
than a local one.
problem, rather
Acid precipitation lowers the
soil chemistry of terrestrial ecosystems.
With decreased pH,
soil.
and affects the
leach from the
The resulting nutrient deficiencies affect the
and limit their growth.
Freshwater ecosystems are very
affects species directly
Climate Change:
Since the Industrial Revolution, the concentration of
–
Increased
is one consequence of increasing
CO2 levels.
Rising atmospheric CO2 levels may have an impact on
Earth’s
.
When light energy hits the Earth, much of it is
off
the surface.
CO2 and other gases cause the Earth to
that would ordinarily escape the atmosphere.
This phenomenon is called the
.
If it were not for this effect, the average air temperature on
Earth would be
.
A number of studies predict that by the end of the 21st
century, atmospheric CO2 concentration will have doubled
and average global temperature will rise by
.
If increased temperatures caused the polar ice caps to melt,
sea levels would rise by an estimated
, flooding
coastal areas
from current coastlines.
A warming trend would also alter geographic distribution of
, making major U.S. agricultural areas much
drier.
Human activities are depleting atmospheric ozone.
Life on earth is protected from the damaging affects of
ultraviolet radiation (UV) by a layer of
, or ozone, that
is present in the
.
Studies suggest that the ozone layer has been gradually
“
” since 1975.
The destruction of ozone probably results from the
accumulation of
—chemicals used in
, as propellant in
, and for certain manufacturing
The breakdown products from these chemicals
Subsequent reactions liberate the
, allowing it to
react with other
in a catalytic chain
reaction.
The result of a reduction in the ozone layer may be increased
levels of
that reach the surface of the Earth.
Some scientists expect increases in
, as
well as unpredictable
5) Add
to environment
- Toxins can become concentrated in successive
levels of food webs.
by organisms and can
accumulate in the
of animals and
become more concentrated in successive
Magnification occurs because the
Thus,
carnivores tend to be the organisms
most
by toxic compounds in the
environment.
- Many toxins cannot be
by microbes and
persist in the environment for
.
- Other chemicals may be converted to
by reaction with other substances or by the metabolism of
microbes.
Ex: mercury was routinely expelled into rivers and oceans in
an
.
Bacteria in the bottom mud converted it to
, an extremely
compound that
in the tissues of organisms, including humans who
fished in contaminated waters.