Transcript Nutrient Cycles and Human Impact

Bell Ringer 12.1
• Describe the three main trophic levels.
• What does the 10% Law?
• Compare food chains to food webs.
• What are the three types of pyramids we
discussed yesterday? What information can you
get from each?
Nutrient Cycles and Human
Impact
What is Nutrient Cycling?
• BIOGEOCHEMICAL CYCLES: passage of
matter from one organism to another in the
biosphere.
• Nutrients are finite (not like the sun which
supplies constant energy), so they must be
(re)cycled through various parts of nature.
▫ Relies heavily on DECOMPOSERS and
MOVEMENT through the cycle (not getting
“stuck” in one area)
• Major Biogeochemical Cycles:
▫ Carbon, Water, Nitrogen
If elements are to be recycled in nature, which
organism must be present?
A.
B.
C.
D.
Decomposers
Predators
Herbivores
Parasites
Carbon Cycle
• Carbon cycles through the ecosystem mainly
by…
▫ PHOTOSYNTHESIS: takes carbon out of the
atmosphere in the form of CO2 (performed by
plants)
▫ RESPIRATION: puts carbon into the
atmosphere in the form of CO2 (performed by all
living organisms)
Photosynthesis
O2+ C6H12O6
H2O + CO2
Respiration
In the carbon cycle, carbon is transferred from
animals to plants by which of the following?
A.
B.
C.
D.
Carbon dioxide
Oxygen
Sugars
Water
Besides photosynthesis, why is it important to
have CO2 in the atmosphere?
• Many gasses found in Earth’s atmosphere help
trap HEAT
• Works like a greenhouse, so is called the
GREENHOUSE EFFECT
• Important because Earth
would be too cold for life
without it.
• CO2 is important to
have in the atmosphere
because it is one of the
gasses that contribute
to the greenhouse
effect.
Human Impact on the Carbon Cycle
• Combustion of fossil fuels: burning of coal,
oil, and natural gas add extra CO2 to the
atmosphere
• Deforestation: cutting down large areas of
trees reduces the amount of photosynthesis
leaving more CO2 in the atmosphere.
What is the main suspected environmental
problem associated with the burning of fossil
fuels?
A.
B.
C.
D.
Depletion of fresh water
Depletion of ozone
Global cooling
Global warming
Why should we be concerned about adding
more CO2 to the atmosphere?
Too much CO2 can cause changes in climate by
making the Earth too warm.
Why should we care if Earth is getting
warmer?
Even if Earth warms by only a few degrees, there
will be big impacts on weather and ecosystems all
over the planet.
DROUGHT
FLOODING
POLAR ICE
MELTING
How else do the actions of humans affect
the atmosphere and Earth’s ecosystems?
COMBUSTION OF FOSSIL FUELS releases sulfur
and nitrogen into the atmosphere in addition to
CO2
The sulfur and
nitrogen combine
with water in the
atmosphere to form
ACID RAIN
Effects of Acid Rain:
• Damages soil,
roots, and leaves
of trees
• Changes the pH of
rivers/streams
and may kill
plants & animals
in the water
• Damages
buildings, statues,
and bridges
Volcanic eruptions may
also affect the atmosphere
and Earth’s ecosystems.
• Releases sulfur into the
atmosphere which helps
to form acid rain
• Extremely large
eruptions may release
enough ash to block
sunlight  global
cooling
The Water Cycle
MAJOR PLAYERS:
• Precipitation
• Evaporation
• Transpiration
• Run-off
• Groundwater
How Humans affect the Water Cycle
• Humans use water:
▫
▫
▫
▫
Agriculture
Dams and deforestation
Urbanization (living in cities)
Overuse of aquifers (groundwater)
 Saltwater intrusion (ocean)
 Subsidence (lend to collapse)
• Clean water supply
▫ 1 billion people (16%) do not have any
access to clean water
▫ Can cause outbreaks of disease
 Examples: cholera, hepatitis, mosquito
breeding
• Acid Rain
▫ Hurts plants, animals, and buildings
When deforestation occurs in an area, what
immediate effect does this have on the water
cycle?
A.
B.
C.
D.
More precipitation is formed.
There is less runoff water.
More water is returned to the atmosphere.
Less water is returned to the atmosphere.
The Nitrogen Cycle
IMPORTANCE:
• 78% of the air is nitrogen
• All organisms need nitrogen
• Nitrogen is present in DNA and RNA and in
amino acids (proteins)
• The food chain largely moves nitrogen around
• Bacteria and lightning take nitrogen gas and
puts it into a useable form
▫ Process called NITROGEN FIXATION
▫ Some bacteria have mutualistic relationships with
plants and live on their roots
Which of the following statements about the
nitrogen cycle is true?
A. Although nitrogen is the most abundant
atmospheric gas, plants cannot use it from the
air.
B. Adding man-made fertilizers to farm fields will
take needed nitrogen from the cycle.
C. The occurrence of lightning takes extra
nitrogen molecules from the atmosphere and
the cycle.
D. Bacteria located in the soil trap excess
atmospheric oxygen and help it enter plant
roots.
How Humans affect the Nitrogen Cycle
• Humans contribute extra nitrogen in the cycle
due to fertilizers and animal waste (hog
lagoons) runoff into the lakes and rivers.
• Excess nitrogen can cause eutrophication which
encourages extra algae to grow (algal bloom)
lowering levels of oxygen causing fish kills.
Remember, energy
flows as nutrients
cycle!
1. What benefit does the carbon cycle provide to
ecosystems?
2. What problems can carbon dioxide cause?
3. Describe what contributes CO2 to the
atmosphere.
4. Describe what pulls CO2 from the atmosphere.
5. Where is the majority of CO2 stored?
6. How does fossil fuels/deforestation affect the
carbon cycle
7. How is the nitrogen cycle beneficial for plants?
8. How do decaying plants contribute to the
nitrogen cycle?
9. What role do bacteria play in the nitrogen cycle?
10. How would the absence of bacteria affect the
nitrogen cycle?
11. What consumer is essential for the function of
the nitrogen cycle?
12. Explain the water cycle.