How do ecosystems work Part 2

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How do ecosystems work? Part 2!
Chapter 41
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How does increased CO2 cause global warming?

• Greenhouse effect
• Certain gases in the atmosphere (water vapor,
  methane, CO2 ) absorb heat.
• More greenhouse gases ? more trapped heat
• Earth does need some greenhouse gases!
• Without any heat-absorbing molecules, the earth
  would be too cold for life!
• But we are now overheating the earth

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Some potential impacts of global warming

• Melting of ice ? sea level rise
• Some low-lying islands have already been
  inundated
• Changes in weather patterns
• Droughts in some places, floods in others
• Shift in agricultural centers (loss of some, gain
  of others)
• Increased hurricane intensity
• Shifts in species distribution
• Example 1 Mosquitoes that carry Plasmodium (the
  malaria parasite)
• How have they shifted? (Think about logically,
  considering they are found in warm climates)
• Example 2 Penguins in the Antarctic

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Focus Antarctic penguins
Gentoo penguins (Photo B. Grunewald)
Chinstrap penguin (Photo Shir Goldberg
Adelie penguins (Photo K. Haberman)
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Shift in penguin species on the Antarctic
Peninsula
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What can you do???

• Overall, reduce use of fossil fuels.
• Buy energy efficient appliances.
• Line dry your clothes.
• BUY LOCALLY!
• Shipping of products around the world uses a
  great deal of fossil fuels.
• Buy certified organic food (minimal use of
  fertilizers that use fossil fuels to make.)
• Invest in alternative, renewable energy.
• Vote wisely

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Nitrogen cycle (preview)
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Nitrogen cycle Nitrogen fixation

• The atmosphere is earths major nitrogen
  reservoir
• N2 gas not directly usable by producers
• Nitrogen fixation converts N2 to usable nitrogen
  forms (ammonia and nitrate)
• Lightning fixes nitrogen
• Bacteria fix nitrogen
• Humans fix nitrogen via chemical processing to
  make fertilizers or by burning fossil fuels.

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Nitrogen cycle Cycling through food webs

• Primary producers take up ammonia and nitrate
• Convert to organic nitrogen (part of protein
  DNA molecules)
• Consumers feed on producers
• Gain organic molecules with nitrogen
• Bacteria decompose dead organisms
• Convert back into inorganic forms that can be
  taken up by producers

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Nitrogen cycle Denitrification

• Denitrifying bacteria convert nitrates and
  ammonia back into atmospheric nitrogen

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Nitrogen cycle (review)
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Phosphorous cycle (preview)
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Phosphorous cycle How does phosphorous enter
ecosystems?

• Phosphorous comes from rocks (reservoir for
  phosphorous)
• Weathering of rocks and runoff moves phosphorous
  into ecosystems
• Human-synthesized phosphorous (as phosphates) are
  also applied to crops

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Phosphorous cycle Cycling through food webs

• Primary producers take up phosphorous
• Convert inorganic phosphates to organic
  phosphorous (part of protein, lipid DNA
  molecules)
• Consumers feed on producers (arrow missing in
  diagram!)
• Gain organic molecules with phosphorous
• Bacteria decompose dead organisms
• Convert back into inorganic forms that can be
  taken up by producers

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Phosphorous cycle Loss of phosphorous from
ecosystems

• Phosphorous ends up in aquatic sediments (such as
  deep ocean)
• Will only be reintroduced with uplifting of
  mountains!

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Phosphorous cycle (review)
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Phosphorous and aquatic ecosystems

• Agricultural and domestic runoff puts excessive
  amounts of phosphorous into aquatic ecosystems
• Intense blooms of phytoplankton
• Often these are toxic species Why?
• Dead zones Too much phytoplankton at once ? All
  dies at once? bacterial decomposition of excess
  phytoplankton reduces oxygen ? animals die
• Clean Water Act (1977)
• Reduction of phosphate-based detergents has
  decreased this problem in some places