Energy Flow and Nutrient Cycles

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Energy FlowandNutrient Cycles

• Within Ecosystems

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How did it all get started?

• The concept of ecology was first developed in the
  19th century by Ernst Haeckel.
• The environment consists of two parts
• 1. biotic (living) environment
• ie. organisms
• 2. abiotic (non-living) environment
• - considered to the living space
• - ie. temperature, soil, wind,
• precipitation, land masses, water

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What is ECOLOGY?

• the study of the interactions among organisms and
  between organisms and their abiotic environments

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Energy Flow in An Ecosystem

• All organisms require energy (ATP) and nutrients
  in order to carry out essential life activities
  such as growth, respiration, and reproduction.
• In nearly every ecosystem on Earth radiant energy
  provides the energy that powers life.
• CO2 H2O chlorophyll yields C6H12O6 H2O
  O2
• This energy requirement begins at a cellular
  level (ie. cellular respiration).
• C6H12O6 O2 yields ATP
• Nutrients (ie. carbon, nitrogen, phosphorous,
  water) enter the ecosystem from the abiotic
  environment (ie. atmosphere, earth, sea, etc.).

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Solar Energy...essential, limitless source of
energy!!

• Plants (photoautotroph) convert radiant energy
  into chemical energy (glucose)...
• THAT energy is then grazed upon and transferred
  to herbivores...
• THAT energy is then consumed by and transferred
  to carnivorous scavengers...
• THAT energy is then decomposed by and
  transferred to bacteria that break down the
  remains of the organism to obtain the last bits
  of energy available.

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Energy Loss...

• As energy flows from plants and then finally to
  decomposers, each organism along the way releases
  part of the energy they capture as heat to the
  atmosphere.
• So as the chemical energy moves through the food
  chain, it is slowly diminished.
• However, energy is re-infused back in the system
  by the Sun...again and again.

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Measuring Primary Productivity

• The amount of life (biomass) an ecosystem can
  support is determined by the amount of chemical
  energy generated by autotrophs (phototrophs,
  chemotrophs) producers.
• photoautotroph uses light to make energy (ie.
  plants)
• chemoautotroph uses chemicals w/in the
  environment to make
• energy (ie.
  bacteria)
• net primary productivity
• total E that producers make available to
  other
• members of the community
• Overall the primary producers in all the
  Earths ecosystems use solar energy and nutrients
  to
• produce an impressive 170 billion tons of
  organic
• material per year.

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Primary Productivity (continued)

• - influenced by environmental variables
• (temperature, available sunlight, water,
  nutrients)
• ie. tundra
• limited by temp range availability of
  sunlight
• ie. desert
• limited by water nutrients
• ie. temperate wetlands AND tropical rainforest
• radiant energy nutrients are abundant
• (productivity is HIGH)

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Trophic Levels

• Ecologists categorize living things according to
  their role in the flow of energy through an
  ecosystem (beginning with producers and through
  several levels of consumers) each category
  forms a trophic level
• first trophic level grasses, giant redwoods
• second trophic level
• caterpillars, grasshoppers, elk (primary
  consumers)
• herbivores
• third trophic level
• flesh-eating spiders, birds, lions (secondary
  consumers)
• carnivores who eat herbivores
• fourth trophic level
• bears, eagles, humans (tertiary consumers)
• carnivores who eat other carnivores

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Food Web
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Decomposers and Detritivores

• Liberate nutrients for reuse (convert larger
  polymers into monomers, molecules and elements).
• Small and some are microscopic (live on molted
  exoskeletons, fallen leaves, wastes, and dead
  bodies).
• Include worms,
• insects, and
• aviary vultures.

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Decomposers (continued)

• In some ecosystems, more energy passes through
  the detritus feeders and decomposers than through
  the all the consumers combined.
• If the detritus feeders and decomposers were to
  disappear suddenly, communities would gradually
  be smothered by accumulated wastes and dead
  bodies.
• ALSO, molecules such as carbon dioxide, water,
  nitrogen, and phosphorus wouldnt be available
  for sustained plant life.
• AS A RESULT energy would cease to enter the
  community and the higher trophic levels dependent
  on the energy captured by plants would disappear
  as well.

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Energy Flow Through Trophic Levels
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The 10 Law

• The energy transfer between trophic levels in
  most ecosystems is roughly 10 efficient.
• SO...the energy stored in primary consumers
  (herbivores) is only about 10 of the energy
  stored in producers...the energy in secondary
  consumers possess roughly 10 of the energy
  stored in primary consumers...
• The most abundant organisms are going to be those
  that are lower on the food chain
  (producers)...while those that are higher on the
  food chain are much less abundant (tertiary
  consumers).
• SO...the lower the trophic level utilized, the
  more food energy available to human populations
  (far more people can be fed on grain than on
  meat).

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Nutrients Essential to Life

• Unlike solar energy, the nutrients essential to
  life are limited.
• The Earth only has so much carbon, phosphorus, or
  nitrogen available for living organisms.
• If biological processes such as cellular
  respiration didnt return most of this captured
  carbon back to the atmosphere, life as we know it
  on Earth would rapidly end.
• So in order for life on Earth to continue,
  nutrients must be constantly recycled by the
  Earths ecosystems.
• ie. water cycle, sulfur cycle, carbon cycle,
  nitrogen cycle,
• phosphorus cycle

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The WATER CYCLE
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The NITROGEN CYCLE
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The CARBON CYCLE
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The PHOSPHORUS CYCLE
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The SULFUR CYCLE