This document summarizes several nutrient cycles that are essential for life. It describes the nitrogen cycle, in which nitrogen is fixed from the atmosphere by lightning and bacteria, taken up by plants, and recycled through organisms and the soil with the help of bacteria. It also outlines the carbon/oxygen cycle of photosynthesis and respiration, the water cycle of evaporation and precipitation, and the phosphorus cycle of weathering and plant uptake. It notes how human activities like fossil fuel use, deforestation, septic systems, and phosphorus pollution can disrupt these natural cycles.

1. How Ecosystems Work
Ch. 5, Section 2: The Cycling of
Materials
Standards: SEV3a, b, c

2. How are substances recycled
through the ecosystem?
• Chemicals oscillate
between biotic
organisms & abiotic
reservoirs
• Abiotic reservoirswhere chemical is
“stockpiled” outside
organism.
– Ex: air, water, soil,
fossil fuels

3. Why is NITROGEN important to
your survival?
• Comes from:
proteins you eat in
meat, eggs, dairy
• Purpose: broken
down by body to
build new proteins,
enzymes, & repair
cells

4. NITROGEN CYCLE
Even though 78% of atmosphere is nitrogen, can’t get nitrogen by breathing in air. Blood
has no ability to remove nitrogen from air you inhale.
1.
2.
3.
4.
5.
6.
7.
Lightning can bond with nitrogen
gas in the air and add solid
nitrogen to soil.
NITROGEN FIXATION- Nitrogen
fixing bacteria on roots of legumes
(clover) take nitrogen gas out of
the air and turn it into usable form
for plants.
ASSIMILATION- Plants store
nitrogen in their body tissues
Animals eat plants and obtain
nitrogen. Nitrogen is used to make
proteins throughout body.
Plants & animals defecate or die
and bacteria return nitrogen to the
soil.
DENITRIFICATION- Other
bacteria in soil return nitrogen to
the air.
BACTERIA are the most important
“movers” of nitrogen!

5. How are humans altering the
nitrogen cycle?
1. Eutrophication:
a. Chemical fertilizers from farms
or feces from feedlots overload
nitrogen in soil or water
b. causes algae to grow and
create algal bloom.
c. algae overpopulate, compete, &
die
d. dead algae decompose
e. decomposers that are
decomposing algae use up
oxygen in water
f. fish die
2. Acid Rain:
a. Nitric acid released from
burning fossil fuel
b. Combines with water in
atmosphere & makes acid rain.

6. Why is CARBON & OXYGEN
important to your survival?
• Comes from: C6H12O6
(sugar made by
plants)
• Purpose: used as
energy source in
body. Oxygen
inhaled & used to
break down C6H12O6

7. 1.
2.
3.
4.
5.
CARBON/OXYGEN CYCLE
Plants and algae convert carbon
dioxide (CO2) from the air or water
into organic compounds (C6H12O6 which is food) during
photosynthesis. Oxygen is also
released.
Animals eat plants and get the
carbon from C6H12O6 into their
bodies. This carbon provides the
body with energy. Oxygen from
plants is also inhaled by animal &
used to break down C6H12O6.
Carbon is returned to the air or
water when animals &
decomposers exhale CO2.
Carbon is returned to soil when
decomposers break down feces
and dead bodies.
Carbon sinks include:
a.
b.
c.
Ocean
Shells & bones of ocean animals
Fossil fuels

8. How are humans altering the
Carbon/Oxygen Cycle?
1. burning EXCESS
fossil fuels=
more CO2 in air.
2. cutting down
trees= less CO2
removed from
air.
3. More CO2= more
heat retained=
Global warming

9. Why is HYDROGEN & OXYGEN
important to your survival?
• Comes from: from
H2O (water)
• Purpose: used in
chemical reactions
in body.

10. HYDROLOGIC CYCLE
1.
2.
3.
4.
5.
Water enters the atmosphere via
a. Evaporation
b. Transpiration thru plants (plants
giving off water as by-product of
photosynthesis)
c. Cellular Respiration- water is
given off as a by-product of breaking
down food to store energy.
Condensation- water cools and forms
clouds
Precipitation- clouds build and
release liquid in form of rain, snow,
sleet, or hail.
Run Off- Water rolls off land into a
body of surface water (lake, pond,
stream)
Infiltration- Water percolates thru soil
and recharges/refills aquifer

11. How are humans altering the
Hydrologic cycle?
1.
2.
Cutting down trees,
decreases
transpiration, may
change rainfall patterns
Septic tanks store
waste water for some
homes instead of sewer
pipes. Water stored in
septic tank is not
immediately returned to
river.

12. Why is PHOSPHORUS important
to your survival?
• Comes from: from
various foods you
eat
• Purpose: used to
make ATP (energy
storage molecule)

13. PHOSPHOROUS CYCLE
1. Phosphorus (P) stored
in rocks
2. Weathering of rocks
adds P to soil.
3. Plants take up P thru
roots
4. Animals eat plants
5. Decomposers return P
to soil.
6. Cycle starts over @ #3.
7. Only cycle that DOES
NOT have an
atmospheric stage.

14. How are humans altering the
phosphorus cycle?
1.
Overflowing sewers can
increase phosphorus
levels which leads to
death of water
ecosystem via
eutrophication.
2. Cheaper detergents may
contain phosphorus, if
leakage occurs,
eutrophication can
occur (see nitrogen
cycle)