Biogeochemical Cycles

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Biogeochemical Cycles

• Biology 20

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Chemicals Cycle

• Inorganic nutrients are cycled through natural
  ecosystems repeatedly.
• Biogeochemical cycles are the pathways by which
  chemicals circulate.
• Water Cycle
• Phosphorus Cycle
• Nitrogen Cycle
• Carbon Cycle
• ?Chemicals Cycle, Energy Flows

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Water Cycle

• Saltwater evaporates from suns energy producing
  fresh water in clouds leaves salt in the ocean
• Water vapor cools and condenses to precipitation
  over oceans and land.
• Runoff forms fresh water lakes, streams, ponds,
  ground water, and is held in plants and
  transpired.

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Water cycle

• Gravity returns water to oceans but some moves
  slowly through water table and porous aquifers
  between rock layers.
• Although the water cycle shows water to be a
  renewable resource, the 3 of water that is fresh
  may be polluted or inadequate for human
  populations concentrated in specific areas.

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Percolation
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Acid Deposition and the Water Cycle

• Sulfur dioxide is released by the burning of
  substances that contact sulfur such as fossil
  fuels and metal ores.
• Nitrous oxides are produced by the burning of
  fossil fuels.
• These combine with water droplet in the air to
  produce acid rain, which can be 40X more acidic
  than acid rain.
• Minimized in Alberta because of the limestone
  from the mountains

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Acid Deposition
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Phosphorus Cycle

• Weathering of rocks makes phosphates ions
  available to plants through soils.
• Runoff returns phosphates to aquatic systems and
  sediments called a sedimentary cycle.
• Widely used in organisms for phospholipids, ATP,
  teeth, bones, etc

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Human Influence

• Humans Influence the Phosphorus Cycle
• We mine phosphate ores for fertilizers, animal
  feed supplements, detergents
• Detergents, untreated human and animal waste,
  fertilizers from crops, all add excess phosphates
  to water often causing algae blooms. When the
  algae die it increases the bacteria in the water.
  The bacteria then consume large amounts of
  oxygen, decreasing oxygen levels in the water.

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Phosphorus Cycle
Spring runoff of nitrogen and phosphorus
fertilizers promotes the growth of algea.
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Nitrogen Cycle

• Atmospheric nitrogen gas (N2) is unavailable to
  plants.
• Plants therefore depend on various types of
  bacteria to take up nitrogen gas and make it
  available to them in the form of nitrates. This
  is done in four ways

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Nitrogen Cycle

• The first way is Nitrification which is the
  production of nitrates.
• In soil, bacteria convert ammonium to nitrate in
  a two-step process
• First, nitrite producing bacteria convert ammonia
  to nitrites
• The nitrate producing bacteria convert nitrite to
  nitrates.
• These two groups of bacteria are called
  nitrifying bacteria.

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Nitrogen Gas becomes Nitrates

• The second way is Nitrogen gas becomes fixed
• Nitrogen fixation occurs when nitrogen gas is
  reduced and nitrogen is added to organic
  compounds
• Atmospheric nitrogen is converted to ammonium
  (NH4) by some nitrogen-fixing bacteria in the
  nodules on roots of legume plants.
• The ammonia is then converted to nitrates to be
  used by plants.

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Nitrogen Gas becomes Nitrates

• The third way is by the use of fertilizers.
• The fourth way is Nitrogen gas is converted to
  nitrates by lightning in the atmosphere.
• Denitrification is conversion of nitrates to
  nitrogen gas, which is returned to the atmosphere
  by denitrifying bacteria.

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The Carbon Cycle

• Relationships exist between photosynthesis and
  respiration
• Respiration releases carbon dioxide, which is
  used in photosynthesis
• Photosynthesis releases oxygen used in
  respiration
• Therefore animals depend on green organisms for
  organic food, energy and oxygen

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Carbon Cycle

• In the carbon cycle, organisms exchange carbon
  dioxide with the atmosphere
• On land, plants take up carbon dioxide, via
  photosynthesis, incorporate it into food used by
  themselves and heterotrophs
• When organisms respire, a portion of the carbon
  is returned to the atmosphere as carbon dioxide

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Carbon Cycle

• Inorganic carbon is found in three places the
  atmosphere, the oceans and the earth crust
• Organic carbon is held in the bodies of living
  things.
• The organic carbon may eventually be converted to
  fossil fuels

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Humans and the Carbon Cycle

• Humans burning of fossil fuels and wood has
  increased amount of carbon dioxide released into
  the atmosphere.
• Increased CO2 may increase the greenhouse effect,
  where such gases allow the suns rays to pass
  through to earth where it is absorbed and emitted
  as heat, but heat is then reflected back to
  earth, causing global warming.

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Greenhouse Effect
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Human Impacted Ecosystems

• Natural ecosystems tend to be stable.
• Size of populations are held in check by
  competition, predation, etc
• Energy input-output is balanced cycles are
  sustainable
• Pollution, and undesirable change in the
  environment harmful to humans and life does not
  normally occur.

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Good or bad??

• Human beings replace ecosystems with their own.

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The Solution

• ?