2.systems and models new

Models and the
behavior of systems
BY
GURU

GURU

IBESS/GURU/SYSTEMS & MODELS

Syllabus Statements
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1.1.1: Outline the concept and characteristics of a
system
1.1.2: Apply the systems concept on a range of scales
1.1.3: Define the terms open system, closed system,
isolated system
1.1.4: Describe how the first and second laws of
thermodynamics are relevant to environmental systems
1.1.5: Explain the nature of equilibria

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Syllabus Statements
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1.1.6: Define and explain the principles of positive and
negative feedback
1.1.7: Describe transfer and transformation processes
1.1.8: Distinguish between flows (inputs and outputs),
and storages (stock) in relation to systems.
1.1.9: construct and analyze quantitative models
involving flows and storages in a system
Evaluate the Strengths and limitations of models

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Vocab
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Entropy
Equilibrium
Feedback
Negative Feedback
Positive Feedback
Model
Stable Equilibrium
Steady State Equilibrium

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System
Closed System
Isolated System
Open system


Systems
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A system is a set of components that…
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2.

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Function and interact in some regular, predictable
manner.

Can be isolated for the purposes of observation
and study.


Systems on Many Scales
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Ecosystem – The everglades in South FL
Biome – Tropical Rainforest
The entire planet – Gaia hypothesis

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Coral Reef
Ecosystem
Most diverse
aquatic ecosystem
in the world
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Open systems
exchange matter
and energy with
the surroundings
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Closed systems exchange energy but not
matter. – don’t naturally occur on earth

Biosphere II Built as self sustaining closed system in 1991 in Tuscon, AZ
Experiment failed when nutrient cycling broke down
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Nutrient cycles Approximate closed
systems as well

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Isolated systems exchange neither matter nor
energy with the surroundings
Only possible though
unproven example is
the entire cosmos

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Components of systems
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Inputs = things entering the system  matter,
energy, information
Flows / throughputs = passage of elements
within the system at certain rates (transfers and
transformations)
Stores / storage areas = within a system, where
matter, energy, information can accumulate for a
length of time (stocks)
Outputs = flowing out of the system into sinks
in the environment

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Discharge of untreated
municipal sewage
(nitrates and phosphates)

Nitrogen compounds
produced by cars
and factories
Natural runoff
(nitrates and
phosphates
Inorganic fertilizer runoff
(nitrates and phosphates)

Discharge of
detergents
( phosphates)

Discharge of treated
municipal sewage
(primary and secondary
treatment:
nitrates and phosphates)
Lake ecosystem
nutrient overload
and breakdown of
chemical cycling
Dissolving of
nitrogen oxides
(from internal combustion
engines and furnaces)

Manure runoff
from feedlots
(nitrates,
phosphates,
ammonia)

Runoff from streets,
lawns, and construction
lots (nitrates and
phosphates)

Runoff and erosion
(from cultivation,
mining, construction,
and poor land use)

To assess an area you must treat all levels of the system
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Individuals work as well

Water
0.000002 ppm

Phytoplankton
0.0025 ppm

Herring gull
124 ppm

Herring gull eggs
124 ppm

Zooplankton
0.123 ppm

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Lake trout
4.83 ppm

Rainbow smelt
1.04 ppm

Types of Flows: Transfer vs.
Transformation
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Transfers  flow through the system, involving a
change in location
Transformation  lead to interactions in the
system, changes of state or forming new end
products
-Example: Water processes
Runoff = transfer, Evaporation = transformation
Detritus entering lake = transfer, Decomposition
of detritus is transformation
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Condensation

Transpiration
from plants

Precipitation
Precipitation
to ocean

Rain clouds

Transpiration
Precipitation

Evaporation
Surface runoff (rapid)

Evaporation
From
ocean

Runoff
Infiltration and
percolation

Surface runoff
(rapid)

Groundwater movement (slow)

Ocean storage

Groundwater movement (slow)

What type of System is this?

Name the inputs, outputs, transfers and transformations

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Systems and Energy
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We see Energy as an input, output, transfer, or
transformation
Thermodynamics – study of energy
1st Law: Energy can be transferred and transformed
but it can never be created nor destroyed
So…
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All energy in living systems comes from the sun
Into producers through photosynthesis, then consumers up
the food web

Energy at one level must come from
previous level
Sun

Producers (rooted plants)
Producers (phytoplankton)
Primary consumers (zooplankton)
Secondary consumers (fish)

Dissolved
chemicals

Tertiary consumers
(turtles)

Sediment
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IBESS/GURU/SYSTEMS & MODELS (bacteria and fungi)
Decomposers

Using the first law of thermodynamics explain why the energy
pyramid is always pyramid shaped (bottom bigger than top)
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2nd Law: With every energy transfer or transformation
energy dissipates (heat) so the energy available to do
work decreases
Or in an isolated system entropy tends to increase
spontaneously
Energy and materials go from a concentrated to a
dispersed form The concentrated high quality energy is
the potential energy of the system
The system becomes increasingly disordered
Order can only be maintained through the use of
energy

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First Trophic
Level

Third Trophic
Level

Fourth Trophic
Level

Producers
(plants)
Heat

Second Trophic
Level

Primary
consumers
(herbivores)

Secondary
consumers
(carnivores)

Tertiary
consumers
(top carnivores)

Heat

Heat

Heat

Solar
energy

Heat Heat
Heat

Heat

Detritivores
(decomposers and detritus feeders)

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Heat

What results from
the second law of
Thermodynamics?

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Feedback loops
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Self regulation of natural systems is achieved by the
attainment of equilibrium through feedback systems
Change is a result of feedback loops but there is a
time lag
Feedback occurs when one change leads to another
change which eventually reinforces or slows the
original change.
Or…
Outputs of the system are fed back into the input
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Positive feedback
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A runaway cycle – often called vicious cycles
A change in a certain direction provides output that further
increases that change
Change leads to increasing change – it accelerates deviation
Example: Global warming
1. Temperature increases  Ice caps melt
2. Less Ice cap surface area  Less sunlight is reflected away
from earth (albedo)
3. More light hits dark ocean and heat is trapped
4. Further temperature increase  Further melting of the ice
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Solar
radiation

Energy in = Energy out
Reflected by
atmosphere (34%)

Radiated by
atmosphere
as heat (66%)

UV radiation

Absorbed
by ozone

Lower stratosphere
(ozone layer)
Visible
Greenhouse
light
Troposphere
effect
Heat

Absorbed
by the earth
Heat radiated
by the earth

Earth
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Negative feedback
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One change leads to a result that lessens the original
change
Self regulating method of control leading to the
maintenance of a steady state equilibrium
Predator Prey is a classic Example
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Snowshoe hare population increases
More food for Lynx  Lynx population increases
Increased predation on hares  hare population declines
Less food for Lynx  Lynx population declines
Less predation  Increase in hare population

Remember hare’s prey and other predators also have an effect
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Most systems change
by a combination of
positive and negative
feedback processes
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Which of the populations show positive feedback?
Which of the populations show negative feedback?
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Positive or Negative?
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If a pond ecosystem became
polluted with nitrates,
washed off agricultural land
by surface runoff, algae
would rapidly grow in the
pond. The amount of
dissolved oxygen in the water
would decrease, killing the
fish. The decomposers that
would increase due to the
dead fish would further
decrease the amount of
dissolved oxygen and so on...

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A good supply of grass for
rabbits to eat will attract
more rabbits to the area,
which puts pressure on the
grass, so it dies back, so the
decreased food supply leads
to a decrease in population
because of death or out
migration, which takes away
the pressure on the grass,
which leads to more growth
and a good supply of food
which leads to a more rabbits
attracted to the area which
puts pressure on the grass
and so on and on....


End result? Equilibrium…
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A sort of equalization or end point
Steady state equilibrium  constant changes in all
directions maintain a constant state (no net change) –
common to most open systems in nature
Static equilibrium  No change at all – condition to
which most natural systems can be compared but this
does not exist
Long term changes in equilibrium point do occur
(evolution, succession)
Equilibrium is stable (systems tend to return to the
original equilibrium after disturbances)

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Equilibrium generally maintained by negative
feedback – inputs should equal outputs

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You should be able to
create a system model.
Observe the next two society
examples and create a model
including input, flows, stores
and output
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High Throughput
System Model

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Inputs
(from environment)

System
Throughputs

Output
(intro environment)

Low-quality
heat
energy

High-quality
energy

Unsustainable
high-waste
economy
Waste
matter
and
pollution

Matter

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Low Throughput
System Model

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Inputs
(from environment)
High-quality
energy

Matter

System
Throughputs

Outputs
(from environment)
Low-quality
energy
(heat)

Sustainable
low-waste
economy

Pollution
prevention
by
reducing
matter
throughput

Pollution
control
by
cleaning
up some
pollutants

Recycle
and
reuse

Energy Feedback

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Matter
output

Matter
Feedback

Waste
matter
and
pollution

Easter Island

What are the statues and where are the trees? A case
Study in unsustainable growth practices.
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Evaluating Models
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Used when we can’t accurately measure the real event
Models are hard with the environment because there
are so many interacting variables – but nothing else
could do better
Allows us to predict likelihood of events
But…
They are approximations
They may yield very different results from each other
or actual events
There are always unanticipated possibilities…
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Anticipating Environmental
Surprises
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Remember any action we take has multiple unforseen
consequences
Discontinuities = Abrupt shifts occur in previously
stable systems once a threshold is crossed
Synergistic interactions = 2 factors combine to produce
greater effects than they do alone
Unpredictable or chaotic events = hurricanes,
earthquakes, climate shifts
http://www.nhc.noaa.gov/archive/2008/FAY_graphic
s.shtml

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What can we do?
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Develop more complex
models for systems
Increase research on
environmental thresholds
for better predictive
power
Formulate possible
scenarios and solutions
ahead of time

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Define objectives

Systems
Measurement

Data
Analysis

Identify and inventory variables
Obtain baseline data on variables

Make statistical analysis of relationships among variables
Determine significant interactions

© 2004 Brooks/Cole – Thomson Learning

System
Modeling

Construct mathematical model describing
interactions among variables

System
Simulation

Run the model on a computer, with values
entered for different variables

System
Optimization

Evaluate best ways to achieve objectives

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Other systems
examples

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Uranium
mining
(95%)
Uranium
100%

Uranium processing
and transportation
(57%)

95%

Waste
heat

Power Transmission
plant of electricity
(31%)
(85%)

Waste
heat

14%

17%

54%

Waste
heat

Resistance
heating
(100%)

Waste
heat

Electricity from Nuclear Power Plant

Sunlight
100%

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Passive Solar

90%

Waste
heat


Energy
Production

14%

sun
EARTH

Economic
Systems

Natural
Capital
Air; water,
land, soil,
biodiversity,
minerals,
raw materials,
energy
resources,
and dilution,
degradation,
and recycling
services

Production

Heat

Depletion of
nonrenewable
resources

Degradation and
depletion of renewable
resources used faster
than replenished

Consumption
Pollution and waste
from overloading
nature’s waste disposal
and recycling systems

Recycling and reuse
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Economics
& Earth

Energy Inputs

System

Outputs
9%
7%

41%
84%

U.S.
economy
and
lifestyles

43%
8%
4%
4%

Nonrenewable fossil fuels
Nonrenewable nuclear

Biomass

Petrochemicals

Unavoidable energy
waste
Unnecessary energy
waste

Hydropower, geothermal,
wind, solar
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Useful energy

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Thank you

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By

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Guru

GURU


2.systems and models new

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