Chapter FourChapter Foursystems: a theoretical systems: a theoretical frameworkframework

The BiosphereThe Biosphere… … the biosphere includes air, rocks, water and lifethe biosphere includes air, rocks, water and life

• AtmosphereAtmosphere: a mixture of nitrogen : a mixture of nitrogen (78%), oxygen (21%), and carbon dioxide (78%), oxygen (21%), and carbon dioxide (1%)(1%)

• HydrosphereHydrosphere: : the water on Earth in all the water on Earth in all its states and the elements dissolved in itits states and the elements dissolved in it

• LithosphereLithosphere: : the thin crust between the the thin crust between the mantle and the atmosphere (rocks)mantle and the atmosphere (rocks)

• EcosphereEcosphere:: made up of all living made up of all living organisms; temporary accumulators and organisms; temporary accumulators and sources of pollutantssources of pollutants

Types of Systems:Types of Systems:

• Open System: Open System: exchanges exchanges mattermatter and and energyenergy with its surroundings with its surroundings

• Closed System: Closed System: exchanges exchanges energyenergy but but not matternot matter with its environment with its environment

• Isolated System: Isolated System: exchanges exchanges neither neither matter nor energymatter nor energy with its environment with its environment

Closed System:Closed System:• Closed systems are very rare on Closed systems are very rare on

earth; the earth itself can be almost earth; the earth itself can be almost considered a closed systemconsidered a closed system

Open System:Open System:• Most systems are open systems; all Most systems are open systems; all

ecosystems are openecosystems are open

Isolated SystemIsolated System

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

Laws of ThermodynamicsLaws of Thermodynamics

• First Law:First Law:– ““energy is neither created nor energy is neither created nor

destroyed”destroyed”

• Second Law:Second Law:– ““the the entropyentropy of an isolated system not of an isolated system not

in equilibrium will tend to increase over in equilibrium will tend to increase over time”time”•Energy conversions are never 100% efficientEnergy conversions are never 100% efficientEntropy: the spreading out or

dispersal of energy

Equilibrium:Equilibrium:• Steady-State Equilibrium: Steady-State Equilibrium: a characteristic of a characteristic of

open systems where there are continuous inputs open systems where there are continuous inputs and outputs of energy and matter, but the and outputs of energy and matter, but the system as a whole remains more-or-less system as a whole remains more-or-less constantconstant

• Static Equilibrium:Static Equilibrium: there is no change over there is no change over time; when disturbed, it will adopt a new time; when disturbed, it will adopt a new equilibriumequilibrium

*** *** Systems can also be Systems can also be stablestable or or unstableunstable

FeedbackFeedback

• Positive Feedback Positive Feedback – When students respond positively to When students respond positively to

teaching methods through learning and teaching methods through learning and showing interestshowing interest

• Negative Feedback Negative Feedback – When students respond negatively to When students respond negatively to

teaching methods through distraction, teaching methods through distraction, indifference or dissentindifference or dissent

Positive Feedback in Global WarmingPositive Feedback in Global Warming

Higher Temperature

More Water Vapor

More Heat Trapped By Atmosphere

Wetter Atmosphere

Land and Sea Temperatures Rise

Increased Evaporation

Transfers and TransformationsTransfers and Transformations

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

•Transformation:Transformation: Occurs when a Occurs when a flow flow doesdoes involve a change of form or involve a change of form or statestate

Transfers and TransformationsTransfers and Transformations

TransfersTransfers TransformationsTransformationsMovement of Movement of

material through material through living organismsliving organisms

Matter to matterMatter to matter

Movement of Movement of material in a non-material in a non-

living processliving process

Energy to energyEnergy to energy

Movement of energyMovement of energy Energy to matterEnergy to matter

Flows and StoragesFlows and Storages

““Both energy and matter flow (as inputs and outputs) Both energy and matter flow (as inputs and outputs) through ecosystems but, at times, they are also stored through ecosystems but, at times, they are also stored

(as storage or stock) within the ecosystem”(as storage or stock) within the ecosystem”

• When one organism eats another, the energy is When one organism eats another, the energy is flowed between them as stored chemical energyflowed between them as stored chemical energy

• Energy flows through a system in the form of Energy flows through a system in the form of carbon-carbon bonds within organic compoundscarbon-carbon bonds within organic compounds

• Matter cycles around the system as mineralsMatter cycles around the system as minerals

General Flows in An EcosystemGeneral Flows in An Ecosystem

Atmosphere

Nutrient elements in

soil and water

Elements combines in plant tissue

Rock cycle Elements locked in

sinksElements

combined in animal tissue

Sedimentation and

Fossilization

Weathering

Respiration

Volatile Gases

Feeding

Absorbed

Death and Decomposition

Energy Flow and Flow of Matter Through an Energy Flow and Flow of Matter Through an EcosystemEcosystem

Producers

InorganicNutrient

Pool

Decomposers

Consumers

heat

heat heat

SUN

Complexity and StabilityComplexity and Stability

• Most ecosystems are very complex systems Most ecosystems are very complex systems that include feedback links, flows, and that include feedback links, flows, and storagesstorages

• Primarily, a high level of complexity makes Primarily, a high level of complexity makes for a more efficient and stable systemfor a more efficient and stable system– i.e. tundra ecosystems are quite simple therefore i.e. tundra ecosystems are quite simple therefore

populations within this ecosystem tend to populations within this ecosystem tend to fluctuate such as the lemming population fluctuate such as the lemming population (unstable)(unstable)

Models of SystemsModels of Systems

““Simplified models of systems can help Simplified models of systems can help predict changes in the system by predict changes in the system by

modeling reality...”modeling reality...”

A model can take many forms:A model can take many forms:

• A physical model (i.e. an aquarium)A physical model (i.e. an aquarium)

• A software model (i.e. of climate change)A software model (i.e. of climate change)

• Mathematical equationsMathematical equations

• Data flow diagramsData flow diagrams

GaiaGaia• Alfred Russel Wallace described the Alfred Russel Wallace described the

atmosphere as the “Great Aerial atmosphere as the “Great Aerial Ocean”Ocean”

• In 1979, James Lovelock published In 1979, James Lovelock published his “Gaia hypothesis” in his “Gaia hypothesis” in Gaia: A new Gaia: A new look of life on Earthlook of life on Earth– Argued that “the Earth is a planet-sized Argued that “the Earth is a planet-sized

organism and the atmosphere is its organism and the atmosphere is its organ that regulates it and connects all organ that regulates it and connects all its parts”its parts”

– Argued that “the biosphere keeps the Argued that “the biosphere keeps the composition of the atmosphere within composition of the atmosphere within certain boundaries by negative feedback certain boundaries by negative feedback mechanisms”mechanisms”

Lovelock’s Argument Was Based On…Lovelock’s Argument Was Based On…

1.1. The temperature of the Earth’s surface is The temperature of the Earth’s surface is constant even though the sun is giving out constant even though the sun is giving out 30% more energy than when the Earth was 30% more energy than when the Earth was formedformed

2.2. The composition of the atmosphere is The composition of the atmosphere is constant with 79% nitrogen, 21% oxygen, & constant with 79% nitrogen, 21% oxygen, & 0.03% carbon dioxide. Oxygen is a reactive 0.03% carbon dioxide. Oxygen is a reactive gas, but its proportion does not changegas, but its proportion does not change

3.3. The oceans’ salinity is constant at about The oceans’ salinity is constant at about 3.4% but rivers washing salts into the sea 3.4% but rivers washing salts into the sea might be expected to increase thismight be expected to increase this

Lovelock’s WorkLovelock’s Work

• Although many people rejected his Although many people rejected his hypothesis Lovelock defended it for hypothesis Lovelock defended it for 30 years with the support of Lynn 30 years with the support of Lynn MargulisMargulis

• He developed “Daisyworld” as a He developed “Daisyworld” as a mathematical simulation that mathematical simulation that depicted how feedback mechanisms depicted how feedback mechanisms can evolve from activities of self-can evolve from activities of self-interested organismsinterested organisms

James Lovelock

• In 2006, Lovelock wrote In 2006, Lovelock wrote The The Revenge of GaiaRevenge of Gaia, in which , in which he argues that Earth is an he argues that Earth is an “older woman”, more than “older woman”, more than half-way through her half-way through her existence as a planet and existence as a planet and not as able to bounce back not as able to bounce back like beforelike before

• He says that we will be He says that we will be entering a stage of positive entering a stage of positive feedback where the stable feedback where the stable equilibrium will become equilibrium will become unstable and thus result in unstable and thus result in the shift to a new and the shift to a new and hotter equilibrium statehotter equilibrium state– ““The human population will The human population will

survive but with a 90% survive but with a 90% reduction in numbers”reduction in numbers”

The End!The End!