2.2 Nutrient Cycles in Ecosystems p.68-91

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Chapter 2

• 2.2 Nutrient Cycles in Ecosystems p.68-91
• Words to Know
• cellular respiration photosynthesis
• denitrification sedimentation
• nitrification weathering
• Nutrients

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2.2 Nutrient Cycles in Ecosystems

• Nutrients - chemicals needed for plant and animal
  growth.
• Nutrient cycles the flow of nutrients IN and
  OUT of the land, ocean, atmosphere and deep rock.
• The health of our ecosystems depends on the
  balance of
• Carbon, Nitrogen, Phosphorous, Hydrogen and
  Oxygen
• C N P
  H O

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Nutrient Cycle Diagram
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Nutrient CyclesThe Carbon Cycle

• CARBON CYCLE
• A. Carbon Facts
• Carbon is an element found in the molecules of
  all living and dead things.
• It is important for plant growth.
• Places carbon is found are called stores or
  sinks.
• Short-term Stores Long-term Stores
• living things in water and on land underground
  (oil, gas, natural
• rotting tissue of plants and animals gas and
  coal)
• atmosphere (air) sedimentary rock (limestone)
• ocean (dissolved in the water) ocean floor (old
  shells)

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• How Carbon Changes Form
• 1. Photosynthesis (in plants, algae and
  cyanobacteria)
• CO2 H2O sunlight ? C6H12O6 O2
• 2. Cellular respiration (in cells of all living
  things)
• C6H12O6 O2 ? CO2 H2O ENERGY
• (energy is used for growth, repair etc.)
• Decomposition (rotting)
• cellulose ? CO2
• Only done by bacteria and fungi

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• Ocean Processes
• Ocean mixing moves CO2 around the world
• CO2 sinks in cold ocean waters ? flows to the
  warm equator and evaporates into the air.

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• Combustion (burning, engines, volcanoes, forest
  fires)
• fossil fuels O2 ? CO2 H2O ENERGY
• (oil, gas, natural gas, coal)

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CARBON CYCLE DIAGRAM
See page 76
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Nutrient CyclesThe Carbon Cycle (continued)

• Human Activities Have Increased CO2 in the
  atmosphere.
• Burning Fossil Fuels.
• CO2 in atmosphere has increased 30 in past 160
  years (since Industrial Revolution began).
• In the 160,000 years before that, it only
  increased 1-3.
• Carbon is being removed from long-term storage
  more quickly than it naturally would as we mine
  coal and drill for oil and gas.
• CO2 is also a greenhouse gas, which traps heat in
  the atmosphere.

See page 77
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• Removing Trees.
• Large trees and shrubs absorb CO2 from the
  atmosphere, so when they are cut down, there is
  more CO2 in the air.
• Crops that replace the trees dont remove as
  much CO2

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Nutrient CyclesThe Nitrogen Cycle

• Nitrogen Cycle
• Nitrogen Facts
• Makes up DNA and proteins (muscle function).
• Help plants grow.
• Where Nitrogen is Found
• Atmosphere (78 is N2)
• Oceans
• Organic matter in soil
• Lakes, marshes, organisms

See page 78
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• How Nitrogen Changes Form.
• N2 is not usable by plants or animals, so it has
  to be converted to other forms.
• Plants can use NO3- (nitrate) and NH4 (ammonium)
• Nitrogen Fixation
• Lightning changes N2 (nitrogen gas) ? NO3-
  (nitrate).
• Rain washes nitrate into soil. This only fixes
  a tiny amount of nitrogen.
• Bacteria in soil (rhizobium) and cyanobacteria in
  water
• change N2 (nitrogen gas) ? NH4 (ammonium).
• This processes fixes most nitrogen.
• Rhizobium live on the roots of legumes (peas,
  alfalfa, beans) and alder trees.

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Nutrient CyclesThe Nitrogen Cycle (continued)

• Nitrification
• NH4 (ammonium) ? NO2- (nitrite) ?
  NO3- (nitrate)
• This is done by nitrifying bacteria.
• Uptake
• NO3- is sucked into plants and used for growth.
• Herbivores eat the plants and use the Nitrogen
  for making proteins and DNA.
• Denitrification
• NO3- ? N2 done by denitrifying bacteria
• N2 is also returned to the atmosphere through
  volcanic eruptions.

See pages 78 - 79
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Nitrogen Cycle
See page 81
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Nutrient CyclesThe Nitrogen Cycle (continued)

• Human activities affect the nitrogen cycle.
• The amount of nitrogen in the ecosystem has
  doubled in the last 50 years due to
• Burning fossil fuels and sewage treatment.
• NO and NO2 are byproducts
• Land-clearing by burning.
• acid rain is formed which contains nitric acid
  (HNO3).
• Overfertilization
• excess NH4 and NO3- leach into the soil and
  waterways.
• This promotes huge growth in aquatic algae
  eutrophication
• These algal blooms use up all CO2 and O2 and
  block sunlight, killing many aquatic organisms.
• The algal blooms can also produce neurotoxins
  that poison animals.

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Nutrient CyclesThe Phosphorous Cycle

• Phosphorous Cycle
• Phosphorous Facts
• Phosphorous is a part of the molecule that
  carries energy in cells (ATP).
• Phosphorous helps root growth, stem strength and
  seed production.
• In animals, phosphorous is important for strong
  bones.
• Where Phosphorous is Found
• Not in atmosphere, but in phosphate rocks (PO43,
  HPO42, H2PO4) and sediments on the ocean floor.

See pages 83 - 84
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• How Phosphorous Changes Form.
• 1. Weathering (breaking down rock into smaller
  pieces).
• a) Chemical weathering
• acid rain or lichens releases phosphates
  (PO43- )
• b) Physical weathering
• wind, water and freezing release the
  phosphates.
• Uptake
• plants suck up PO43- for growth, then are eaten
  by animals.

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• Decomposition (rotting)
• Bacteria break down dead plants and animals and
  phosphorous is returned to soil.
• Geologic Uplift
• when rocks under the ground are pushed up ?
  mountains ? weathering.

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The Phosphorous Cycle
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• C. Human activities affect the Phosphorous
  Cycle.
• 1. Mining
• Increases P in ecosystems quickly. Natural
  stores are not replaced.
• 2. Slash-and-burn forest practices.
• Turns P into ash, which runs into waterways.

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How Changes in Nutrient Cycles Affect
Biodiversity

• To Review
• Any significant changes to any of these nutrients
  (C, H, O, N or P) can greatly impact
  biodiversity.
• Carbon cycle changes ? climate change and global
  warming.
• Too much nitrogen can allow certain plant species
  to out-compete other species.
• Decreased levels of phosphorous ? slow
• growth of algae (important producers).

Take the Section 2.2 Quiz