Systems and Models

What is the common thread?

System is… individual components working together. Look at this bicycle:

…when apart no longer a system You will never get anywhere if you just have the seat or the wheels!

Synergy This is the concept of synergy where the whole is greater than the sum of its parts.

Even if you know all the parts of a system, you can’t predict what will happen when they work together A good example of this is Table salt or Sodium Chloride: Sodium is highly reactive and has massive reactions with water. Chlorine as a gas can kill you. Put the two together and it forms something essential for our body and very important for life in general!

The Synergetic Effect Environmental systems, ecosystems, ecological systems all follow the laws of synergy. That the whole, the entire process, is far more important than the individual parts of it.

Environmental Systems and Societies Interrelationships among climate, geology, soil, vegetation, water and animals, including humans.

System A collection of interdependent components Each perform a function Connected through transfer of energy and matter.

Characteristics of systems Components Reservoirs, storages, stocks, accumulation Processes Flows, transformations, transfers, reactions, photosynthesis, respiration Feedback mechanisms Equilibrium and stability

Systems terminology and symbols Flows – Inputs and outputs - ARROWS energy or matter

Systems terminology and symbols Storages - represented by boxes Areas in which energy or matter can accumulate for various lengths of time before being released. Remember there is always a fixed time line!

The Tree as a System light O2 H2O Heat CO2 Tissue to other trophic levels Tree Biomass Litter to soil Nutrients H2O

Apply the systems concept on range of scales Scales range from small to large: You ESS Class CIS Bangkok Thailand SE Asia Local ecosystem Biome Gaia

Scales Biological ecosystems include levels of complexity beginning with atoms and molecules and broadens up to the biosphere.

Gaia James Lovelock 1960’s Earth is an organism Atmosphere as regulation and connection Gaia video The Gaia hypothesis compares Earth to a living organism in which feedback mechanisms maintain equilibrium. It describes how the living and non-living components of the global biosphere regulate the conditions for life on Earth. Daisyworld can be used to illustrate this hypothesis…..

Lets study this through Daisyworld Daisyworld is a very simple planet that has only two species of life on its surface -- white and black daisies. The planet is assumed to be well-watered, with all rain falling at night so that the days are cloudless. The atmospheric water vapour and CO2 are assumed to remain constant, so that the greenhouse of the planet does not change. The key aspect of Daisyworld is that the two types of daisies have different colours and thus different albedos. In this way, the daisies can alter the temperature of the surface where they are growing. Lets study this through Daisyworld

Types of Systems Open Closed Isolated Differences depend on how matter and energy move in and out of the system

Open System Open Systems: exchange matter and energy with its surroundings. In forest ecosystems plants fix energy from light entering the system during photosynthesis. Nitrogen is fixed by soil bacteria. Herbivores that live within the forest canopy may graze in adjacent ecosystems such as a grassland, but when they return they enrich the soil with faeces. After a forest fire top soil may be removed by wind and rain. Mineral nutrients are dissolved out of the soil and transported in ground water to streams and rivers. Open system exchange both matte and energy with their surroundings e.g ecosystem

Closed Systems Closed Systems: exchange energy but not matter. Rare in nature. Biosphere 2 was a human attempt at creating a habitable closed system on Earth. Video Closed systems exchange only energy with their surroundings e.g. the Earth

No natural closed systems exist on Earth but the planet itself can be thought of as an “almost” closed system. Light energy in large amounts enters the Earth’s system and some is eventually returned to space a long wave radiation (heat).

Isolated Systems Neither matter or energy is exchanged across the system No such systems exist (with the exception of the entire cosmos).

How are the 1st and 2nd laws of thermodynamics related to ESS First law – Conservation of Energy Energy is neither created nor destroyed In the food chain above the energy enters the system as light energy, during photosynthesis it gets converted to stored chemical energy (glucose). It is the stored chemical energy that is passed along as food. No new energy is created it is just passed along.

Energy Flow Energy absorbed from the previous trophic level 100 Energy lost as heat Energy lost to detritus 10 65 25 Energy passed on to the next trophic level So energy is conserved!!!

Second Law - Entropy Entropy is a measure of the amount of disorder, chaos or randomness in a system; the greater the disorder the higher the level of entropy. The energy in systems is gradually transformed into heat energy due to inefficient transfer, thereby increasing disorder (entropy). In any isolated system entropy trends to increase spontaneously – so ultimately…….. Energy is needed to create order. Less energy available then disorder increases. So universe is seen as an isolated system and our entropy is steadily increasing so eventually in billions of years there will be no more energy present.

What’s the relevance to environmental systems? Energy flows through ecosystems. Energy enters as sunlight and is converted to new biomass and heat. The energy entering the system equals the energy leaving it (1st Law) Energy is inefficiently moved through food chains in the process of respiration and production of heat energy (2nd Law).

Continued…. Initial absorption and transfer of energy by producers is also inefficient due to reflection, transmission light of the wrong wavelength and inefficient transfer of energy in photosynthesis (2nd Law) Light energy starts the food chain but is then transferred from producer to consumer as chemical energy. As a result of the inefficient transfer of energy, food chains tend to be short.

Equilibrium A system needs to be in equilibrium If not, entropy will increase so much the system will destroy itself by becoming too disordered There a 4 kinds of equilibrium: Static Steady State Stable unstable

Static Equilibrium State of the system time Note: this is not realistic – it could only occur in an isolated system

Steady State Equilibrium State of the system time

Stable Equilibrium State of the system time Weebles wobble but they don’t fall down! State of the system disturbance time

Unstable Equilibrium State of the system time He’s going down! disturbance time

Equilibrium in action

Feedback Mechanisms This is a way that the INPUT is affected by the OUTPUT In a stable equilibrium, feedback returns the equilibrium to its original state In an unstable equilibrium, feedback returns the equilibrium to a different state Feedback can be POSITIVE – input changes to bring the system to a new equilibrium NEGATIVE – input changes in order to bring the system back to its original equilibrium

Negative Feedback Your (stable) equilibrium body temperature is 37oC Sensors in the skin detect your skin temperature is rising (you are in Phuket on the beach) Show what happens in a system diagram

Positive Feedback Your (stable) equilibrium body temperature is 37oC Sensors in the skin detect your skin temperature is decreasing (you are locked in a freezer) Your body is unable to maintain its stable equibilibrium and therefore you enter a state of hypothermia Show what happens in a system diagram

Living systems 3 characteristics Functionality: ability to perform a task or serve a purpose. Sustainability: capacity to endure; how systems remain intact, productive and diverse over time. Evolution: change over time

Transfer and transformation processes Matter (material and energy move or flow through ecosystems Transfer Transformations

Transfers Flow through systems Change in location

Transformations Interaction within a system in the formation of a new product or change of state. Matter to matter (Glucose to starch) Energy to energy (light to heat by radiating surfaces) Matter to energy (burning fossil fuels) Energy to matter (photosynthesis)

Transfers and transformations can occur at the same time Water runoff (transfer) and evaporation (transformation) Decaying dead organic matter entering a lake (transfer) but the decomposition process is transformation

Flows and Storages Energy and matter flow as inputs and outputs through the system Can be storages or stocks

Energy flows …….. Energy flows from one compartment to another Energy that moves is stored as chemical energy Black arrows flow of energy Red arrows flow of matter

Matter cycles…….. Matter cycles around the system as minerals Black arrows flow of energy Red arrows flow of matter

Case Studies predator-prey equilibria