Systems and Models

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

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.

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

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

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

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

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

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.

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

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?

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

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.

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

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.

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

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

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.

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.

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

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.

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%

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!

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

Energy Efficiency

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.

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?)

Ecosystem Equilibrium Unstable Equilibrium Stable Equilibrium

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?

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

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

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

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

Climate Model Inputs

Population Growth Model

Groundwater Flow Model

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