1. Systems and Models

2. Try this
Think of any system that is cyclical and draw it as a model. For example, the seasons.

3. System
An assemblage of parts, working together, forming a functioning whole.
May be small or large
May be open, closed, or isolated
Take a minute and write down 3 examples of a system.

4. Parts of a System Input- energy or matter enters a system.
Output- something produced at the end of a system
Storage- areas where energy or matter is accumulated inside a system
Flow- movement of energy or matter within a system
Boundaries- outside/edge of a system

6. Examples of Systems Pond Biome Atmosphere Ocean Island School
Ecological
Other Types
Pond
Biome
Atmosphere
Ocean
Island
School
Political
Family
Examples of Systems

7. Ecosystem We look at how each system interacts
A specific geographical area that takes into account all biotic and abiotic factors that interact:
Ex: Biosphere = atmosphere (air) + lithosphere (rocks) + hydrosphere (water)+ ecosphere (life).
We look at how
each system interacts
and not individual parts

8. Name a few factors that affect the interactions in this ecosystem
Sunlight, precipitation, temperature, flora, fauna, number/type of species, biomass

9. Open Systems Exchanges matter and energy with its surroundings
Any examples?
All ecosystems
Forests
Marine
Plains
You and your cells

10. Example
Forests Light enters the system and plants fix energy during photosynthesis.
Topsoil may be removed by wind and rain
Mineral nutrients are leached out of soil and transported in groundwater to streams and rivers.
Water is lost through evaporation and transpiration.

11. To Do: using the model below, draw your own system for a cell phone.
Flows
Flows
Inputs
Outputs
Storage

12. Closed System Exchanges energy but not matter with the environment.
Extremely rare in nature
The Earth as a planet can be thought of as almost closed. Energy is exchanged in the form of visible light and infrared.
Very little matter gets in and out. Can you give examples?

13. Biosphere 2 An attempt at a closed system.
Never produced enough food to sustain human participants
Often ran low on oxygen

14. Isolated System
Exchanges neither matter nor energy with its environment
Do not exist naturally
It’s possible to think as the entire universe as and isolated system.

15. Review System Energy Exchanged Matter Exchanged Open Yes Closed No
Isolated
System
Energy Exchanged
Matter Exchanged
Open
Closed
Isolated
Yes Yes
Yes No
No No

16. Flows Flows Storage Energy and matter both flow through an ecosystem.
At different stages both energy and matter can be stored, the place where they are stored is called a stock.

17. Flows Energy initially enters ecosystems from the sun as light
It is converted and stored as chemical potential energy organic molecules pass through down through chains
Respiration releases this energy
All energy enters an ecosystem and is lost again

18. Flows
Inputs are the things that enter the system, outputs are the things that exit the system

19. Flows Matter cycles through an ecosystem.
Nitrogen is fixed by bacteria
Plants assimilate the nitrogen
Herbivores consume these plants and the nitrogen compounds pass through the food chain.
Eventually the plants or animals will die and decomposer break down organic matter and return it to the soil.

21. Stock
There is a stock of chemical potential energy in the flesh of animals.
This same flesh is composed primarily of proteins.
The amino acids making up these proteins contains a nitrogen stock.

22. Flows and Systems
In systems diagrams, flows are represented by arrows and stores by boxes

23. Energy in Systems
1st Law of Thermodynamics: Energy is neither created nor destroyed.
Energy can change from one form to another (light to heat) but no new energy is created.
Sometimes called conservation of energy.
In a food chain: Light is
changed to chemical energy
through photosynthesis and
transferred again as chemical
energy to an herbivore and
then carnivore.

24. 1st Law Continued
What about sunlight? What happens to all of the light that reaches Earth?
30% reflected back into space
50% converted to heat
19% powers hydrologic cycle
1% used for photosynthesis
That’s 100%

25. 2nd Law of Thermodymics
When energy is transformed into work, some energy is always lost as waste heat.
Energy = work + heat
Can you give an example of this law that you may experience often?
Car engine: Does work but gets very hot. Engineers would love to create an engine that doesn’t lose energy as heat. Think how fast you could go!

26. 2nd Law Continued: Does the lion get as much energy from the plant as the herbivore?

27. Energy Efficiency

28. Equilibrium
Tendency of a system to return to an original state following disturbance.
A rubber band can be stretched but it will always return to its original shape.
Open systems tend to exist in a state of equilibrium.

29. Equilibrium
Stable Equilibrium: System returns to same equilibrium after disturbance
Steady-State Equilibrium: No change over the long term but small changes over the short term.
Unstable Equilibrium: System returns to a NEW equilibrium after disturbance. (Climate?)

30. Ecosystem Equilibrium
Unstable Equilibrium
Stable Equilibrium

31. Tipping Point
The minimum amount of change within a system that will destabilize it, causing it to reach a new equilibrium or stable state.
Can you think of any human impacts on the environment that might lead to a tipping point?

32. Positive and Negative Feedback
Most systems are affected by feedback- the processes, energy, or matter that change the system.
Positive Feedback: Encourages a change
Negative Feedback: Discourages further change

33. Positive Feedback
Negative Feedback
Causes a system to change further.
Example: Climate Change
Causes as system to change in opposite direction it is moving or causes it to slow down.
Ex. Thermostat

34. Positive Feedback
Positive Feedback is a feedback mechanism in which the output enhances the original stimulus and the state of equilibrium is subject to change
The change is always in the same direction
It may push a system into a new state of equilibrium
The change is always away from the steady state

35. Models of systems Models of a system predict changes Limitations:
Physical Models: Wind tunnel, globe, solar system, aquarium
Software Models: Climate change, population dynamics, groundwater flow
Mathematical equations
Data flow diagrams
Limitations:
may lack some complexities of real world
Rely on available data

36. Climate Model Inputs

37. Population Growth Model

38. Groundwater Flow Model

39. To Do:
1.) Daisyworld Modeling: ls/Daisyworld
2.) Climate Modeling: Using Netlogo, open the climate model and follow instructions.
Models of Systems Activity (Handout)