Chapter 3 Ecosystems and Energy

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Chapter 3Ecosystems and Energy
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Overview of Chapter 3

• Ecology
• Energy
• First Law of Thermodynamics
• Second Law of Thermodynamics
• Photosynthesis and Cellular Respiration
• Flow of Energy Through Ecosystems
• Producers, Consumers Decomposers
• Ecological Pyramid
• Ecosystem Productivity

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Ecology

• Ecology
• eco house logy study of
• The study of interactions among and between
  organisms in their abiotic environment
• Broadest field in biology
• Biotic- living environment
• Includes all organisms
• Abiotic- non living or physical environment
• Includes living space, sunlight, soil,
  precipitation, etc.

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Ecology

• Biology is very organized
• Ecologists are interested in the levels of life
  above that of organism

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Ecology Definitions

• Species
• A group of similar organisms whose members freely
  interbreed
• Population
• A group of organisms of the same species that
  occupy that live in the same area at the same
  time
• Community
• Al the populations of different species that live
  and interact in the same area at the same time
• Ecosystem
• A community and its physical (abiotic)
  environment
• Landscape
• Several interacting ecosystems

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Ecology

• Biosphere contains earths communities,
  ecosystems and landscapes, and includes

• Atmosphere- gaseous envelope surrounding earth
• Hydrosphere- earths supply of water
• Lithosphere- soil and rock of the earths crust

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Energy

• The ability or capacity to do work
• Chemical, radiant, thermal, mechanical, nuclear,
  electrical
• Energy exists as
• Stored energy (potential energy)
• Kinetic energy (energy of motion)

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Thermodynamics

• Study of energy and its transformations
• System- the object being studied

• Closed System- Does not exchange energy with
  surroundings (rare in nature)
• Open System- exchanges energy with surroundings

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Laws of Thermodynamics

• First Law of Thermodynamics
• Energy cannot be created or destroyed it can
  change from one form to another
• Ex organisms cannot create energy they need to
  survive- they must capture it from another source
• Focus is on quantity
• Second Law of Thermodynamics
• When energy is converted form one form to
  another, some of it is degraded to heat
• Heat is highly entropic (disorganized)
• Focus is on quality

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Photosynthesis

• Biological process by which energy from the sun
  (radiant energy) is transformed into chemical
  energy of sugar molecules
• Energy captured by plants via photosynthesis is
  transferred to the organisms that eat the plants

6 CO2 12 H2O radiant energy
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Cellular Respiration

• The process where the chemical energy captured in
  photosynthesis is released within cells of plants
  and animals
• This energy is then used for biological work
• Creating new cells, reproduction, movement, etc.

C6H12O6 6 O2 6 H2O
6 CO2 12 H2O energy
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Energy Flow

• Passage of energy in a one-way direction through
  an ecosystem
• Producers
• Primary consumers
• Secondary consumers
• Decomposers

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Food Chains- The Path of Energy Flow

• Energy from food passes from one organisms to
  another
• Each link is called a trophic level

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Food webs represent interlocking food chains that
connect all organisms in an ecosystem
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Ecological Pyramids

• Graphically represent the relative energy value
  of each trophic level
• Important feature is that large amount of energy
  are lost between trophic levels to heat
• (Second Law of Thermodynamics)
• Three main types
• Pyramid of numbers
• Pyramid of biomass
• Pyramid of energy

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Pyramid of Numbers

• Illustrates the number of organisms at each
  trophic level
• Usually, organisms at the base of the pyramid are
  more numerous

• Fewer organisms occupy each successive level
• Do not indicate the biomass of the organisms at
  each level or the amount of energy transferred
  between levels

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Pyramid of Biomass

• Illustrates the total biomass at each successive
  trophic level
• Biomass measure of the total amt of living
  material

• Biomass indicates the amount of fixed energy at a
  given time
• Illustrates a progressive reduction in biomass
  through trophic levels

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Pyramid of Energy

• Illustrates how much energy (kilocalories/meter2)
  is present at each trophic level and how much is
  transferred to the next level
• Most energy dissipates between trophic levels

• Explains why there are so few trophic levels
• Energy levels get too low to support life

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Ecosystem Productivity

• Gross Primary Productivity (GPP)
• Total amount of energy that plants capture
  (photosynthesis) and assimilate in a given
  period of time
• Net Primary Productivity (NPP)
• Plant growth per unit area per time
• Represents the rate at which organic material is
  actually incorporated into the plant tissue for
  growth
• GPP cellular respiration NPP
• Only NPP is available as food to organisms

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Ecosystem Productivity

• Only NPP is available as food to organisms
• Most energy is used for cellular respiration for
  muscle contraction
• Avoid predation and secure prey

• Secondary productivity
• Remaining energy that can be used for growth and
  reproduction

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Variation in NPP by Ecosystem
AQUATIC
TERRESTRIAL
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Human Impact on NPP

• Humans consume more of earths resources that any
  other animal (Vitousek 1986)
• Humans use 32 of land-based NPP!
• Humans represent 0.5 of land-based biomass
• This may contribute to loss of species
  (extinction)
• We compete with other species needs (a factor
  driving extinctions)
• Humans high consumption represents a threat to
  planets ability to support both human and
  non-human inhabitants

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Human appropriation of NPP
We need to share NPP with other organisms more
efficiently to operate sustainably