Systems and Models

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Systems and Models

• IBES

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System Defined

• A system is an assemblage of parts and the
  relationships between them, which together
  constitute an entity or whole.
• The components are connected through
• Transfer of energy
• Transfer of matter
• What is the system at SVHS? Where are there
  transfers?

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Examples

• Particles
• Atoms
• Molecules
• Cells
• Organs
• Organ system
• Community

• Ecosystem
• Biome
• Earth
• Solar System
• Galaxy
• Universe!

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System consists of

• Storages (of matter or energy)
• Flows (inputs into system or outputs out)
• Processes (which transfer or transform energy or
  matter)
• Feedback mechanisms that maintain stability and
  equilibrium.

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We can model systems

• To allow scientists to predict simplify complex
  systems
• Can change inputs/outputs without having to wait
  for real events
• BUT, may oversimplify
• Different interpretations of the same events
  same input different result on different models

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For exampleA tree a systemboxstorage,
arrowflow
Water oxygen CO2 light heat heat
Tissue to other trophic level

• OR

Litter to soil
Nutrients Water
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Three Types of Systems

• 1. Open System
• Both matter and energy are exchanged
• Open systems are organic (living) and so must
  interact with their environment to take in energy
  and new matter and remove waste
• Can you think of an example? Draw it..

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The Biosphere

• Humans and all living things are part of the
  biosphere of earth
• It includes
• Atmosphere
• Lithosphere
• Hydrosphere
• Ecosphere

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2. Closed System

• Energy but not matter is exchanged.
• They do not occur naturally on Earth
• Can you think of an example?
• Draw a picture
• Biosphere II is an experiment to model he Earth
  as a closed system.
• www.pearsonhotlinks.com 2630P act1.3

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Design your own Biosphere

• The sun is the primary energy source
• Ten people must live in your dome for more than 3
  years.
• The door is sealed after the people enter,
  nothing enters or leaves
• Design and describe

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Examples

• Atoms
• Molecules
• Mechanical systems
• The Earth

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3. Isolated System

• Neither energy nor matter is exchanged across the
  boundary
• This system does not exist naturally
• We could think of the entire universe as an
  isolated systemmaybe!
• Draw it!

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Energy of a system

• The energy in a system is defined by the TWO laws
  of thermodynamics
• 1st energy cannot be created or destroyed, only
  change forms
• therefore, all energy that enters a system can
  be accounted for
• the transfer of energy is not 100 efficient, in
  each conversion, there is less usable energy.
• For example plants only convert 1-2 of the
  suns energy into glucose
• And herbivores only assimilate 10 of plants
  energy, the rest is lost in metabolic processes
  and ultimately released as heat.

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Energy in a System

• 2nd law of Thermodynamics energy goes from a
  concentrated form (sun) to a dispersed form
  (ultimately heat)
• Aka there is a dispersion of energy available for
  work.
• Therefore, an isolated system is not possible,
  there must always be an input of good energy
• Entropydisorder a system without equilibrium
  ALWAYS increases entropy

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Entropy
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Storage and release of potential energy
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Steady-State Equilibrium

• Common property of most open systems
• There are constant input and output of energy,
  but the overall system is stable
• If there is an unbalance, the system has the
  ability to regulate itself back to equilibrium
• Homeostatic mechanisms in animals (temperature
  controls, etc)

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Stable and unstable equilibriums

• If a system is stable, it will return to its
  original equilibrium after a disturbance
• If it is unstable, it will form a new equilibrium
• We could draw these two equilibrium like this
• Can you think of an example of this?

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In order to achieve an equilibrium

• FEEDBACK!
• Changes in the processes in a system lead to the
  changes in the level of output
• Two types positive negative

OUTPUT
FEEDBACK
PROCESS
INPUT
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Positive Feedback

• When a change in the state of a system leads to
  additional and increased change
• So, a change that increases the input, therefore
  increases the output, and so on.
• Positive feedback amplifies the change, which
  leads to an exponential deviation from equilibrium

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Positive Feedback example

• An increase of births in a population leads to a
  higher total population, which increases the
  births, etc

BIRTHS


TOTAL POPULATION
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Negative Feedback

• Reducing the effect of one of the systems
  components
• Maintains equilibrium, counteracts instability
• Examples
• humans temp increase?vasodilatation?
  sweat?evaporation from skin?cools body
• Wind in rainforest blows down tree?gap in the
  canopy?more light is let in?new tree can grow
  faster to fill in gap
• http//www.planetseed.com/node/15236

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What about the teacher/student relationship??

• How could Mrs. D teaching be feedback to your
  equilibrium of environmental science?
• The reaction is knowledge acquisition
• Firstdraw the interaction as a system, (you are
  the tree)
• Then, how does the input (knowledge) affect your
  equilibrium?

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As energy moves through a system

• Energy can either be transferred or transformed
• Transfer movement (change of location), but not
  change of state
• Ex water evaporate, condense, precipitate
• Transformchange of state (ie solar energy to
  chemical energy, glucose)
• Ex photosynthesis, respiration
• SO is your knowledge acquisition a transfer
  process or transform??

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Gia Hypothesis

• James Lovelock, 1968
• Our planet is one large system.
• More later