1.2 Systems & Models

Kristin PageIB ESS2015-2016

Significant Ideas• A systems approach can help in the study of complex environmental issues.

• The use of models and systems simplifies interactions but may provide a more holistic view than reducing issues to single processes.

Applications & Skills• Construct a system diagram or a model from a given set of information.

• Evaluate the use of models as a tool in a given situation, eg for climate change predictions

Knowledge and Understanding:• A systems approach is a way of visualizing a complex set of interactions which may be ecological or societal.

• These interactions produce the emergent properties of the system.

• The concept of a system can be applied on a range of scales.

• A system is compromised of storages and flows.

• The flows provide inputs and outputs of energy and matter.

• The flows are processes and may be either transfers or transformations.

• In system diagrams, storages are usually represente3d as rectangular boxes, and flows as arrows with the arrow indicating the direction of the flow. The size of the bos and the arrow may represent the size/magnitude of the storage or flow.

• An open system exchanges both energy and matter across its boundary while a closed system exchanges only energy across its boundary

• An isolated system is a hypothetical concept in which neither energy nor matter is exchanged across the boundry.

• Ecosystems are open systems. Closed systems only exist experimentally although the global geochemical cycles approximate closed systems.

• A model is a simplified version of reality and can be used to understand how a system works and predict how it will respond to change.

• A model inevitably involves some approximation and loss of accuracy.

What is a system?• On your notebook paper, brainstorm as many

examples of systems that you can think of from your every day life. Be ready to share.

• Round Robin

• Looking at these examples, how could we define a system?

SYSTEM• Is an organized collection of interdependent

components that perform a function and which are connected through the transfer of energy and/or matter

• All the parts are linked together and affect each other.

Reductionist vs Holistic Approach•Reductionist Approach: Looking at each individual part

•Holistic Approach: looking at how everything works together

• This course will focus on both!

We Can Discuss Systems on A Range of Scales:

Largest Scale Universe as a system

Earth as a system

A specific biome as a system (ex: Rainforests)

A specific ecosystem as a system

(ex: Amazon rainforest)

River bank within Amazon rainforest

Plant on river bank on Amazon

Small Scale Leaf of a plan on the river bank on the Amazon

GAIA HYPOTHESIS – JAMES LOVELOCK• James Lovelock

• Mid 1960’s

• Proposed that plant Earth is a single living system (global system)

• Earth maintains homeostasis (temperature, climate, ocean salinity)

https://www.youtube.com/watch?v=xVGuRX0xNaI

3 Types of Systems•An open system exchanges matter and

energy with its surroundings (for example, an ecosystem).

3 Types of Systems

• A closed system exchanges energy but not matter;

• “Biosphere II” experiment was an attempt to model this. closed

• Do not occur naturally on Earth, but all the global cycles of matter, for example, the water and nitrogen cycles, approximate to closed systems.

BIOSPHERE II• Two year (1991 - 1993) experiment

• 3 acre sealed greenhouse containing many different biomes including a rain forest, a desert, an ocean with a coral reef, a mangrove swamp, a savanna, and a small farm involving over 3800 different species of living things

• 8 people lived in the closed system for 2 years recycling water, sewage, and producing 80% of their food within the system

• In the end the CO2 levels were elevated significantly and many would say it was a failed experiment.

• What do you think? Can an experiment fail? What is the purpose of an experiment?

https://www.ted.com/talks/jane_poynter_life_in_biosphere_2?language=en

3 Types of Systems• An isolated system exchanges neither matter nor

energy. • No such systems exist • The universe as we know it is sometimes considered a

isolated system

SYSTEM DIAGRAMS• Used to visually represent a system

• Boxes show storage of matter or energy

• Arrows show the flow of matter or energy• Inputs = arrows into the storage• Outputs = arrows out of the storage

• Processes get labelled on the arrow (ex: photosynthesis, respiration, diffusion, consumption, etc)

Carbon Dioxide(CO2)

Biomass to Next Trophic Level

Water(H2O)

Waste

Oxygen(O2)

Biomass to Decomposers

Nutrients (Food)

Water(H2O)

ConsumptionDigestion

YOU TRY - FORMATIVE• Choose a system from our list created

earlier or a new one you have thought of and create a system diagram to show the stocks and flows in your system.

• Be prepared to share your system with classmates

FLOWS or PROCESSES CAN BE EITHER TRANSFERS OR TRANSFORMATIONS

•Transfers: matter and energy moving through a system without changing form or state.

•Usually involve a change of location

•Examples:•Movement of materials through a food chain (one animal eats

another)•Movement of materials in a non-living process (water carried to

the ocean)•Movement of energy (ocean current or wind transfers heat)

FLOWS or PROCESSES CAN BE EITHER TRANSFERS OR TRANSFORMATIONS

•Transformations: when matter or energy change form or state moving through a system.

• Leads to an interaction within a system in the formation of a new end product or involves a change of state.

• Examples:•Solar energy is transformed into glucose through photosynthesis (energy to

matter)•Burning fossil fuels (matter to energy)•Water evaporating off the Earth’s surface (matter to matter)• Light energy to electrical energy in a solar panel (energy to energy)

MODELS: Benefits

• System diagrams are one type of model

• Models are used in science to show concepts on a scale that is manageable

• They allow us to simplify complex systems in order to study them more closely

• They allow us to make predictions about future events

• They allow us to look at different scenarios so that we can look at the impacts to different changes to the system

• They allow us to discuss and consult with other experts

POSSIBLE PROBLEMS WITH MODELS

•Models can be oversimplified to the point that accuracy is lost•Models and predictions depend on the skills and experience of people making them•Models can be interpreted differently•Different models of the same system may predict different outcomes•Data may not be accurate so models could be used to manipulate for financial or political gain. http://wps.prenhall.com/wps/media/objects/439/449969

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HOMEWORK• Read section 1.2 pp 17 – 26 and complete all To Do Boxes