Models and the Models and the behavior of behavior of

systemssystemsIB syllabus: 1.1.1– 1.1.8IB syllabus: 1.1.1– 1.1.8

Videos – The Story of StuffVideos – The Story of Stuff

Ch. 3Ch. 3

Syllabus StatementsSyllabus Statements

1.1.1: Outline the concept and 1.1.1: Outline the concept and characteristics of a systemcharacteristics of a system

1.1.2: Apply the systems concept on a 1.1.2: Apply the systems concept on a range of scalesrange of scales

1.1.3: Define the terms open system, 1.1.3: Define the terms open system, closed system, isolated systemclosed system, isolated system

1.1.4: Describe how the first and second 1.1.4: Describe how the first and second laws of thermodynamics are relevant to laws of thermodynamics are relevant to environmental systemsenvironmental systems

1.1.5: Explain the nature of equilibria1.1.5: Explain the nature of equilibria

Syllabus StatementsSyllabus Statements 1.1.6: Define and explain the principles of 1.1.6: Define and explain the principles of

positive and negative feedbackpositive and negative feedback 1.1.7: Describe transfer and transformation 1.1.7: Describe transfer and transformation

processesprocesses 1.1.8: Distinguish between flows (inputs and 1.1.8: Distinguish between flows (inputs and

outputs), and storages (stock) in relation to outputs), and storages (stock) in relation to systems.systems.

1.1.9: construct and analyze quantitative models 1.1.9: construct and analyze quantitative models involving flows and storages in a systeminvolving flows and storages in a system

Evaluate the Strengths and limitations of modelsEvaluate the Strengths and limitations of models

VocabVocab

EntropyEntropy EquilibriumEquilibrium FeedbackFeedback Negative FeedbackNegative Feedback Positive FeedbackPositive Feedback ModelModel Stable EquilibriumStable Equilibrium Steady State Steady State

EquilibriumEquilibrium

SystemSystem Closed SystemClosed System Isolated SystemIsolated System Open systemOpen system

SystemsSystems

A system is a set of components A system is a set of components that…that…

1.1. Function and Function and interactinteract in some regular, in some regular, predictable manner.predictable manner.

2.2. Can be isolated for the purposes of Can be isolated for the purposes of observation and study.observation and study.

Systems on Many ScalesSystems on Many Scales

Ecosystem – The everglades in South Ecosystem – The everglades in South FLFL

Biome – Tropical RainforestBiome – Tropical Rainforest The entire planet – Gaia hypothesisThe entire planet – Gaia hypothesis

Coral Reef Ecosystem

Most diverse aquatic

ecosystemin the world

-------

Open systemsexchange exchange

matter and matter and energy with energy with

the the surroundingssurroundings

Closed systemsClosed systems exchange energy exchange energy but not matter. – don’t naturally but not matter. – don’t naturally

occur on earthoccur on earth

Biosphere IIBiosphere II Built as self sustaining closed system in 1991 in Tuscon, AZExperiment failed when nutrient cycling broke down

Nutrient cycles Nutrient cycles Approximate closed systems Approximate closed systems

as wellas well

Isolated systemsIsolated systems exchange neither exchange neither matter nor energy with the matter nor energy with the

surroundingssurroundings

Only possible Only possible though unproven though unproven

example is the example is the entire cosmosentire cosmos

Components of systemsComponents of systems

Inputs = things entering the system Inputs = things entering the system matter, energy, informationmatter, energy, information

Flows / throughputs = passage of Flows / throughputs = passage of elements within the system at certain elements within the system at certain rates (transfers and transformations)rates (transfers and transformations)

Stores / storage areas = within a Stores / storage areas = within a system, where matter, energy, system, where matter, energy, information can accumulate for a information can accumulate for a length of time (stocks)length of time (stocks)

Outputs = flowing out of the system Outputs = flowing out of the system into sinks in the environmentinto sinks in the environment

Discharge of untreatedmunicipal sewage

(nitrates and phosphates)

Nitrogen compoundsproduced by cars

and factories

Discharge of treatedmunicipal sewage

(primary and secondarytreatment:

nitrates and phosphates)

Discharge of detergents

( phosphates)

Manure runofffrom feedlots

(nitrates,phosphates,

ammonia)

Dissolving of nitrogen oxides

(from internal combustionengines and furnaces)

Runoff and erosion(from cultivation,

mining, construction,and poor land use)

Runoff from streets,lawns, and construction

lots (nitrates andphosphates)

Lake ecosystemnutrient overload

and breakdown of chemical cycling

Natural runoff(nitrates andphosphates

Natural runoff(nitrates andphosphates

Inorganic fertilizer runoff(nitrates and phosphates)

To assess an area you must treat all levels of the system

Water0.000002 ppm

Phytoplankton0.0025 ppm

Zooplankton0.123 ppm

Rainbow smelt1.04 ppm

Lake trout4.83 ppm

Herring gull124 ppm

Herring gull eggs124 ppm

Individuals work as well

Types of Flows: Transfer Types of Flows: Transfer vs. Transformationvs. Transformation

Transfers Transfers flow through the system, flow through the system, involving a change in locationinvolving a change in location

Transformation Transformation lead to interactions in lead to interactions in the system, changes of state or forming the system, changes of state or forming new end productsnew end products--Example:Example: Water processes Water processes

Runoff = transfer, Evaporation = Runoff = transfer, Evaporation = transformationtransformation

Detritus entering lake = transfer, Detritus entering lake = transfer, Decomposition Decomposition

of detritus is transformationof detritus is transformation

Precipitation

Precipitationto ocean

Evaporation

EvaporationFromocean

Surface runoff(rapid)

Ocean storage

Condensation

Transpiration

Rain clouds

Infiltration andpercolation

Transpirationfrom plants

Groundwater movement (slow)

Groundwater movement (slow)

RunoffRunoff

Surface runoff (rapid)Surface runoff (rapid)

Precipitation

What type of System is this?

Name the inputs, outputs, transfers and transformations

Systems and EnergySystems and Energy We see Energy as an input, output, We see Energy as an input, output,

transfer, or transformationtransfer, or transformation Thermodynamics – study of energyThermodynamics – study of energy

11stst Law: Energy can be transferred and Law: Energy can be transferred and transformed but it can never be created transformed but it can never be created nor destroyednor destroyed

So…So… All energy in living systems comes from the sunAll energy in living systems comes from the sun Into producers through photosynthesis, then Into producers through photosynthesis, then

consumers up the food webconsumers up the food web

Sun

Producers (rooted plants)

Producers (phytoplankton)

Primary consumers (zooplankton)

Secondary consumers (fish)

Dissolvedchemicals Tertiary consumers

(turtles)

Sediment

Decomposers (bacteria and fungi)

Energy at one level must Energy at one level must come from previous levelcome from previous level

Using the first law of thermodynamics explain why the energy

pyramid is always pyramid shaped (bottom bigger than top)

22ndnd Law: With every energy transfer or Law: With every energy transfer or transformation energy dissipates (heat) so transformation energy dissipates (heat) so the energy available to do work decreasesthe energy available to do work decreases

Or in an isolated system entropy tends to Or in an isolated system entropy tends to increase spontaneouslyincrease spontaneously

Energy and materials go from a Energy and materials go from a concentrated to a dispersed form The concentrated to a dispersed form The concentrated high quality energy is the concentrated high quality energy is the potential energy of the systempotential energy of the system

The system becomes increasingly The system becomes increasingly disordereddisordered

Order can only be maintained through the Order can only be maintained through the use of energyuse of energy

Heat Heat Heat Heat

Heat

Heat

Heat

First TrophicLevel

Second TrophicLevel

Third TrophicLevel

Fourth TrophicLevel

Solarenergy

Producers(plants)

Primaryconsumers(herbivores)

Tertiaryconsumers

(top carnivores)

Secondaryconsumers(carnivores)

Detritivores(decomposers and detritus feeders)

Heat Heat

What results from the second law ofThermodynamics?

Feedback loopsFeedback loops

Self regulation of natural systems is achieved Self regulation of natural systems is achieved by the attainment of equilibrium through by the attainment of equilibrium through feedback systemsfeedback systems

Change is a result of feedback loops but there Change is a result of feedback loops but there is a time lagis a time lag

Feedback occurs when one change leads to Feedback occurs when one change leads to another change which eventually reinforces or another change which eventually reinforces or slows the original change.slows the original change.

Or…Or… Outputs of the system are fed back into the Outputs of the system are fed back into the

inputinput

Positive feedbackPositive feedback

A runaway cycle – often called vicious cyclesA runaway cycle – often called vicious cycles A change in a certain direction provides A change in a certain direction provides

output that further increases that changeoutput that further increases that change Change leads to increasing change – it Change leads to increasing change – it

accelerates deviationaccelerates deviationExample: Global warmingExample: Global warming

1.1. Temperature increases Temperature increases Ice caps melt Ice caps melt

2.2. Less Ice cap surface area Less Ice cap surface area Less sunlight is Less sunlight is reflected away from earth (albedo)reflected away from earth (albedo)

3.3. More light hits dark ocean and heat is trappedMore light hits dark ocean and heat is trapped

4.4. Further temperature increase Further temperature increase Further melting Further melting of the iceof the ice

Solarradiation

Energy in = Energy out

Reflected byatmosphere (34%)

UV radiation

Absorbedby ozone

Absorbedby the earth

Visiblelight

Lower stratosphere(ozone layer)

Troposphere

Heat

Greenhouseeffect

Radiated byatmosphere

as heat (66%)

Earth

Heat radiatedby the earth

Negative feedbackNegative feedback

One change leads to a result that lessens the One change leads to a result that lessens the original changeoriginal change

Self regulating method of control leading to Self regulating method of control leading to the maintenance of a steady state the maintenance of a steady state equilibriumequilibrium

Predator Prey is a classic ExamplePredator Prey is a classic Example Snowshoe hare population increasesSnowshoe hare population increases More food for Lynx More food for Lynx Lynx population increases Lynx population increases Increased predation on hares Increased predation on hares hare population hare population

declinesdeclines Less food for Lynx Less food for Lynx Lynx population declines Lynx population declines Less predation Less predation Increase in hare population Increase in hare population

Remember hare’s prey and other predators also have an effect

Most systems Most systems change by a change by a

combination of combination of positive and positive and

negative negative feedback feedback processesprocesses

Which of the populations show positive feedback?

Which of the populations show negative feedback?

Positive or Negative?Positive or Negative? If a pond ecosystem If a pond ecosystem

became polluted with became polluted with nitrates, washed off nitrates, washed off agricultural land by agricultural land by surface runoff, algae surface runoff, algae would rapidly grow in would rapidly grow in the pond. The amount the pond. The amount of dissolved oxygen in of dissolved oxygen in the water would the water would decrease, killing the decrease, killing the fish. The decomposers fish. The decomposers that would increase that would increase due to the dead fish due to the dead fish would further decrease would further decrease the amount of dissolved the amount of dissolved oxygen and so on... oxygen and so on...

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

End result? End result? Equilibrium…Equilibrium…

A sort of equalization or end pointA sort of equalization or end point Steady state equilibrium Steady state equilibrium constant constant

changes in all directions maintain a changes in all directions maintain a constant state (no net change) – common to constant state (no net change) – common to most open systems in naturemost open systems in nature

Static equilibrium Static equilibrium No change at all – No change at all – condition to which most natural systems condition to which most natural systems can be compared but this does not existcan be compared but this does not exist

Long term changes in equilibrium point do Long term changes in equilibrium point do occur (evolution, succession)occur (evolution, succession)

Equilibrium is stable (systems tend to Equilibrium is stable (systems tend to return to the original equilibrium after return to the original equilibrium after disturbances)disturbances)

Equilibrium generally maintained Equilibrium generally maintained by negative feedback – inputs by negative feedback – inputs

should equal outputsshould equal outputs

You should be You should be able to create a able to create a system model.system model.

Observe the next two Observe the next two society examples and society examples and

create a model create a model including input, flows, including input, flows,

stores and outputstores and output

High ThroughputSystem Model

High-qualityenergy

Matter

SystemThroughputs

Output(intro environment)

Unsustainablehigh-wasteeconomy

Low-qualityheat

energy

Wastematter

andpollution

Inputs(from environment)

Low Throughput System Model

High-qualityenergy

Matter

Pollutionprevention

byreducing

matterthroughput

Sustainablelow-wasteeconomy

Recycleand

reuse

Pollutioncontrol

bycleaningup some

pollutants

Matteroutput

Low-qualityenergy(heat)

Wastematter

andpollution

MatterFeedback

Energy Feedback

Inputs(from environment)

SystemThroughputs

Outputs(from environment)

Easter IslandEaster Island

What are the statues and where are the trees? A caseStudy in unsustainable growth practices.

Evaluating Models Evaluating Models

Used when we can’t accurately measure the Used when we can’t accurately measure the real eventreal event

Models are hard with the environment Models are hard with the environment because there are so many interacting because there are so many interacting variables – but nothing else could do bettervariables – but nothing else could do better

Allows us to predict likelihood of eventsAllows us to predict likelihood of events But…But… They are approximationsThey are approximations They may yield very different results from They may yield very different results from

each other or actual eventseach other or actual events There are always unanticipated possibilities…There are always unanticipated possibilities…

Anticipating Environmental Anticipating Environmental SurprisesSurprises

Remember any action we take has Remember any action we take has multiple unforseen consequencesmultiple unforseen consequences

DiscontinuitiesDiscontinuities = Abrupt shifts occur in = Abrupt shifts occur in previously stable systems once a previously stable systems once a threshold is crossedthreshold is crossed

Synergistic interactionsSynergistic interactions = 2 factors = 2 factors combine to produce greater effects than combine to produce greater effects than they do alonethey do alone

Unpredictable or chaotic eventsUnpredictable or chaotic events = = hurricanes, earthquakes, climate shiftshurricanes, earthquakes, climate shifts

http://www.nhc.noaa.gov/archive/2008/FAY_graphics.shtml

What can we do?What can we do?

Develop more Develop more complex models for complex models for systemssystems

Increase research on Increase research on environmental environmental thresholds for better thresholds for better predictive powerpredictive power

Formulate possible Formulate possible scenarios and scenarios and solutions ahead of solutions ahead of timetime

SystemsMeasurement

DataAnalysis

SystemModeling

SystemSimulation

SystemOptimization

Define objectives

Identify and inventory variables

Obtain baseline data on variables

Make statistical analysis of relationships among variables

Determine significant interactions

Construct mathematical model describing interactions among variables

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

Evaluate best ways to achieve objectives

© 2

004

Bro

oks

/Co

le –

Th

om

son

Lea

rnin

g

Other systems Other systems examplesexamples

Uranium100%

Electricity from Nuclear Power Plant

14%

Resistanceheating(100%)

90%

Wasteheat

Passive Solar

Sunlight100%

Wasteheat

14%

Transmissionof electricity

(85%)

17%

Wasteheat

Power plant(31%)

54%

Wasteheat

Uranium processingand transportation

(57%)

95%

Wasteheat

Uraniummining(95%)

Energy Production

sunEARTH

NaturalCapital

Air; water, land, soil, biodiversity,minerals, raw materials, energy resources, and dilution, degradation,and recyclingservices

EconomicSystems

Production

Consumption

Heat

Depletion ofnonrenewableresources

Degradation and depletion of renewable resources used faster than replenished

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

Recycling and reuse

Economics& Earth

Energy Inputs System Outputs

U.S.economy

andlifestyles

84%

8%

4%4%

9%

7%

41%

43%

Nonrenewable fossil fuels

Nonrenewable nuclear

Hydropower, geothermal,wind, solar

Biomass

Useful energy

Petrochemicals

Unavoidable energy wasteUnnecessary energy waste