Chapter Four

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Chapter Four

• systems a theoretical framework

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The Biosphere the biosphere includes air,
rocks, water and life

• Atmosphere a mixture of nitrogen (78), oxygen
  (21), and carbon dioxide (1)
• Hydrosphere the water on Earth in all its states
  and the elements dissolved in it
• Lithosphere the thin crust between the mantle
  and the atmosphere (rocks)
• Ecosphere made up of all living organisms
  temporary accumulators and sources of pollutants

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Types of Systems

• Open System exchanges matter and energy with its
  surroundings
• Closed System exchanges energy but not matter
  with its environment
• Isolated System exchanges neither matter nor
  energy with its environment

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Closed System

• Closed systems are very rare on earth the earth
  itself can be almost considered a closed system

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Open System

• Most systems are open systems all ecosystems are
  open

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Isolated System

• Isolated systems do not exist naturally, yet it
  is possible to picture the entire universe as an
  isolated system

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Laws of Thermodynamics

• First Law
• energy is neither created nor destroyed
• Second Law
• the entropy of an isolated system not in
  equilibrium will tend to increase over time
• Energy conversions are never 100 efficient

Entropy the spreading out or dispersal of energy
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Equilibrium

• Steady-State Equilibrium a characteristic of
  open systems where there are continuous inputs
  and outputs of energy and matter, but the system
  as a whole remains more-or-less constant
• Static Equilibrium there is no change over time
  when disturbed, it will adopt a new equilibrium
• Systems can also be stable or unstable

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Feedback

• Positive Feedback ?
• When students respond positively to teaching
  methods through learning and showing interest
• Negative Feedback ?
• When students respond negatively to teaching
  methods through distraction, indifference or
  dissent

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Positive Feedback in Global Warming
Higher Temperature
Land and Sea Temperatures Rise
More Heat Trapped By Atmosphere
Wetter Atmosphere
Increased Evaporation
More Water Vapor
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Transfers and Transformations

• Transfer Occurs when the flow does not involve a
  change of form or state
• Transformation Occurs when a flow does involve a
  change of form or state

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Transfers and Transformations
Transfers Transformations
Movement of material through living organisms Matter to matter
Movement of material in a non-living process Energy to energy
Movement of energy Energy to matter
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Flows and Storages

• Both energy and matter flow (as inputs and
  outputs) through ecosystems but, at times, they
  are also stored (as storage or stock) within the
  ecosystem
• When one organism eats another, the energy is
  flowed between them as stored chemical energy
• Energy flows through a system in the form of
  carbon-carbon bonds within organic compounds
• Matter cycles around the system as minerals

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General Flows in An Ecosystem
Atmosphere
Weathering
Rock cycle Elements locked in sinks
Respiration
Elements combined in animal tissue
Feeding
Elements combines in plant tissue
Volatile Gases
Death and Decomposition
Sedimentation and Fossilization
Absorbed
Nutrient elements in soil and water
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Energy Flow and Flow of Matter Through an
Ecosystem
heat
heat
Producers
Consumers
SUN
Inorganic Nutrient Pool
Decomposers
heat
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Complexity and Stability

• Most ecosystems are very complex systems that
  include feedback links, flows, and storages
• Primarily, a high level of complexity makes for a
  more efficient and stable system
• i.e. tundra ecosystems are quite simple therefore
  populations within this ecosystem tend to
  fluctuate such as the lemming population
  (unstable)

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Models of Systems

• Simplified models of systems can help predict
  changes in the system by modeling reality...
• A model can take many forms
• A physical model (i.e. an aquarium)
• A software model (i.e. of climate change)
• Mathematical equations
• Data flow diagrams

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Gaia

• Alfred Russel Wallace described the atmosphere as
  the Great Aerial Ocean
• In 1979, James Lovelock published his Gaia
  hypothesis in Gaia A new look of life on Earth
• Argued that the Earth is a planet-sized organism
  and the atmosphere is its organ that regulates it
  and connects all its parts
• Argued that the biosphere keeps the composition
  of the atmosphere within certain boundaries by
  negative feedback mechanisms

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Lovelocks Argument Was Based On

1. The temperature of the Earths surface is
   constant even though the sun is giving out 30
   more energy than when the Earth was formed
2. The composition of the atmosphere is constant
   with 79 nitrogen, 21 oxygen, 0.03 carbon
   dioxide. Oxygen is a reactive gas, but its
   proportion does not change
3. The oceans salinity is constant at about 3.4
   but rivers washing salts into the sea might be
   expected to increase this

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Lovelocks Work

• Although many people rejected his hypothesis
  Lovelock defended it for 30 years with the
  support of Lynn Margulis
• He developed Daisyworld as a mathematical
  simulation that depicted how feedback mechanisms
  can evolve from activities of self-interested
  organisms

James Lovelock
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• In 2006, Lovelock wrote The Revenge of Gaia, in
  which he argues that Earth is an older woman,
  more than half-way through her existence as a
  planet and not as able to bounce back like before
• He says that we will be entering a stage of
  positive feedback where the stable equilibrium
  will become unstable and thus result in the shift
  to a new and hotter equilibrium state
• The human population will survive but with a
  90 reduction in numbers

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The End!