Food Chains

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Food Chains Thermodynamics
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Goal

• To develop an understanding of the
  interdependence of all organisms and the need for
  conserving natural resources

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Concept

• Concept Living organisms share in a variety of
  complex interrelationships which are based on
  interdependence.
• Concept Objective To understand that energy does
  not cycle within an ecosystem

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Energy changes in the ecosystem

1. First law of thermodynamics
2. Second law of thermodynamics

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1st Law of Thermodynamics

• Rub hands together
• Place on face
• What happened?

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1st Law of Thermodynamics

• The First Law of Thermodynamics states that
  energy cannot be created or destroyed but only
  changes forms.
• In the introductory activity chemical energy in
  our bodies was changed to mechanical energy in
  our arms.
• Friction caused some of this mechanical energy to
  be changed to noticeable heat energy in our
  hands.
• We also felt some of the heat move to our cooler
  faces.

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1st Law of Thermodynamics

• The First Law of Thermodynamics states that
  energy cannot be created or destroyed but only
  changes forms.
• A practical ecological consequence of this law is
  that all living things must have a source of
  energy.
• The ultimate source of energy for most living
  things is the sun.

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2nd Law of Thermodynamics

• The Second Law of Thermodynamics states that at
  every energy transfer some portion of the
  available energy is degraded to heat which moves
  to cooler objects.
• We felt the heat in our hands move to our cooler
  face.

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2nd Law of Thermodynamics
http//www.epa.gov/mercury/exposure.htm

• Producers are the only organisms that are able to
  take the radiant energy from the sun and change
  it to chemical energy in food, glucose sugar.
• In the process of photosynthesis producers use
  carbon dioxide and water, in the presence of
  chlorophyll and light, to make sugar and oxygen.
• In the "light" phase of photosynthesis
  energy-rich adenosine triphosphate (ATP)
  molecules are formed.
• In "dark" phase a variety of substances required
  to build and maintain tissues are produced.
• Plants may convert as much as 75 percent of the
  light received into chemical energy in glucose
  sugar.
• Organisms in the environment have very poor
  efficiency in converting the energy they receive
  into usable energy or into energy which is stored
  and eaten by the next link on a food chain.

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• On average vertebrates use about 98 of
  assimilated energy for metabolism, leaving only
  2 for growth and reproduction. This is largely
  because they are regulating their temperature
• On average, invertebrates use only 80 of
  assimilated energy for metabolism, and thus
  exhibit greater net production efficiency (20)
  than do vertebrates.
• Plants have the greatest net production
  efficiencies, which range from 30-85.

http//www.globalchange.umich.edu/globalchange1/cu
rrent/lectures/kling/highertrophic/trophic2.htmlt
ransfer
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• 300 trout are needed to support one man for a
  year. 
• The trout, in turn, must consume 90,000 frogs,
• that must consume 27 million grasshoppers
• that live off of 1,000 tons of grass.  -- G.
  Tyler Miller, Jr., American Chemist (1971)
• Only a fraction of the energy available at one
  trophic level is transferred to the next trophic
  level. (which law of thermodynamics is this?) The
  rule of thumb is 10, but this is very
  approximate. 
• Typically the numbers and biomass of organisms
  decrease as one ascends the food chain.

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REVIEW

1. Can energy be created or destroyed?
2. This is a statement of what law?
3. Which living things are able to convert radiant
   or solar energy into usable chemical energy?
4. As food moves through an ecosystem is all the
   energy converted into usable energy?
5. This is a statement of what law?

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REVIEW

• 1. Can energy be created or destroyed? (No)
• 2. This is a statement of what law? (First Law of
  Thermodynamics)
• 3. Which living things are able to convert
  radiant or solar energy into usable chemical
  energy? (Producers or plants)
• 4. As food moves through an ecosystem is all the
  energy converted into usable energy? (No)
• 5. This is a statement of what law? (Second Law
  of Thermodynamics)

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Radiant energy to chemical energy

• Photosynthesis
• 6H2O 6CO2 ----------gt C6H12O6 6O2
• Light phase solar energy is harvested and
  transferred into the chemical bonds of ATP can
  occur only in light.
• In a series of reactions the energy is converted
  (along an electron transport process) into ATP
  and NADPH.
• Water is split in the process, releasing oxygen
  as a by-product of the reaction.

http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
BioBookPS.html
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Radiant energy to chemical energy

• Dark phase carbon dioxide from the atmosphere
  (or water for aquatic/marine organisms) is
  captured and modified by the addition of Hydrogen
  to form carbohydrates

http//web.mit.edu/esgbio/www/ps/dark.html
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Radiant energy to chemical energy

• B. Energy conversions happened with
• Phosphorylation
• Oxidation-reduction reactions

http//www.emc.maricopa.edu/faculty/farabee/BIOBK/
BioBookPS.html
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Release of energy

• Movement of energy to other organisms
• Energy moves through the ecosystem as consumers
  eat and as decomposers decay other organisms.
• The energy stored in glucose may be released when
  organisms burn food in their cells during
  respiration. (Note respiration occurs in the
  cells of producers, consumers, and decomposers.)
  These energy releasing reactions usually occur in
  the cell mitochondria.
• Oxygen is combined with glucose forming water and
  carbon dioxide with the release of energy. This
  is just opposite of the photosynthesis reaction.
• For example exercise vigorously for a few
  minutes. Observe the rapid breathing, increased
  heart rate, skin changes, and other evidence of
  increased respiration

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Release of energy

• In the cytoplasm is glycolysis
• In the mitochondria is cellular respiration
• Under aerobic conditions there are 2 reactions
  the Krebs cycle and electron transport
• In the Krebs cycle the small chain carbons are
  completely oxidized and a small amount of energy
  is the result (ATP, NADH)
• Electron transport is where more energy in the
  form of ATP is produced through oxidative
  phosphorylation
• Note oxidation-reduction reactions are a
  reaction in which electrons are transferred from
  a donor (the reducing agent) to an acceptor
  molecule (the oxidizing agent).   

image is from http//www.biosci.uga.edu/almanac/bi
o_104/notes/jun_4.html.
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Release of energy

• B. Power for life processes
• The energy released by respiration is used to
  power the life processes of organisms including
• movement, growth, chemical synthesis, movement of
  materials in the organism, reproduction, and
  others.
• Much of the energy released in respiration is
  lost to the environment as heat.

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Loss of chemical energy

• Use of energy by organisms Energy moves through
  the ecosystem as consumers eat and as decomposers
  decay other organisms.
• Loss of heat energy Much of the energy released
  in respiration is lost to the environment as
  heat.
• The energy stored in glucose may be released when
  organisms burn food in their cells during
  respiration.
• (Note Respiration occurs in the cells of
  producers, consumers, and decomposers.)
• These energy releasing reactions usually occur in
  the cell mitochondria.
• C. Stored Energy next slide

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Loss of chemical energy

• C. Stored energy (glucose)
• There are in general many more producers
• Limiting numbers on a pyramid because of the loss
  of stored energy as you move up the food chain.

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In Summary

• The energy released by respiration is used to
  power the life processes of organisms including
  movement, growth, chemical synthesis, movement of
  materials in the organism, reproduction, and
  others.

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Review

1. What happens to the amount of energy available as
   you move to higher levels on a food pyramid?
2. On the average, it decreases how many times as
   you move up one level?
3. How many times would the energy decrease if you
   moved up two levels?, three levels?, four levels?

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Review

1. What happens to the amount of energy available as
   you move to higher levels on a food pyramid? (It
   decreases)
2. On the average, it decreases how many times as
   you move up one level? (10)
3. How many times would the energy decrease if you
   moved up two levels? (100), three levels? (1000),
   four levels? (10,000)