1.3 Energy and Equilibria Significant Ideas The laws of thermodynamics govern the flow of energy in a system and the ability to do work Systems can exist in alternative stable states or as equilibria between which there are tipping points Destabilizing positive feedback mechanisms will drive systems toward these tipping points, whereas stabilizing negative feedback mechanisms will resist such changes Big questions: What strengths and weaknesses of the systems approach and the use of models have been revealed through this topic How are the issues addressed in this topic of relevance to sustainability or sustainable development? The principle of conservation of energy can be modeled by the energy transformations along food chains and energy production systems: what are the strengths and limitations for such models? How do the delays involved in feedback loops make it difficult to predict tipping points and add to the complexity of modelling systems? Do the benefits of the models used to predict tipping points outweigh their limitations? How does sustainability reduce the change that tipping points will be reached?

1.3 Energy and Equilibria – energy in systems 1st Law of Thermodynamics = energy is neither created nor destroyed (but can be transferred & transformed) Energy can change from one form to another (light to heat) but no new energy is created. There has always been, and always will be, exactly the same amount of energy in the universe Sometimes called conservation of energy.

1st Law of Thermodynamics Ex: 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%

1st Law of Thermodynamics In a food chain: Light is changed to chemical energy through photosynthesis and transferred again as chemical energy to an herbivore and then carnivore. The energy at one level must come from the previous level Hence, the 1st Law of Thermodynamics explains why the Energy Pyramids is always bigger on the bottom than on the top

1.3 Energy and Equilibria – energy in systems 2nd Law of Thermodynamics Aka the Law of Entropy (disorder, randomness, chaos) Essentially, as energy is transformed from one state to another, the conversion is never 100% efficient, and therefore energy is always lost to that system Every transformation or transfer results in an increase in the disorder of the universe When energy is transformed into work, some energy is always lost (transformed) as heat waste Energy = work + heat

Energy efficiency

J = Joule Which is a SI Unit of Energy

Summary of energy transfers and transformations in a food chain Sunlight enters ecosystem. Sunlight is transformed into chemical energy (biomass) Chemical energy in producers is passed along the food chain as biomass or given off as heat during respiration Available energy is used to do work (growth, movement, building molecules) All energy leaves the ecosystem as heat. No new energy has been created. It has simply transformed and passed from one form to another. Matter can be recycled, energy cannot be. Once it has been lost from the system as heat, it is not available to that system again.

Equilibrium = the tendency of a system to return to an original state following a disturbance; a state of balance exists among the components of that system Open systems tend to exist this way. The more complex, the more stable. Types: Steady-State Equilibrium: No change over the long term but small changes over the short term. Continuous inputs and outputs of energy/matter, hence, includes most open systems. (ex p. 32) Static Equilibrium: no change occurs over time. No energy/ matter inputs or outputs. Includes most non-living systems. Stable Equilibrium: System returns to same equilibrium after disturbance from input/output Unstable Equilibrium: System returns to a NEW equilibrium after disturbance from input/output. (Climate?)

Identify each of the following Steady State Equilibrium Static Equilibrium

Identify each of the following Unstable Equilibrium Stable Equilibrium

Feedback Systems are continually affected by information from outside and inside the system. Ex: feel cold  turn heat up Natural systems work on feedback mechanisms too: Positive feedback loops Negative feedback loops

Positive Feedback Loops Encourages a change of the system to a new state Includes a sequence of events that responds in the same direction as the disturbance, thereby augmenting the change and moving the system further from the equilibrium point “more leads to more / less leads to less” ++ / - -

Negative Feedback Loops Discourages a change to the system Includes a sequence of events that responds in the opposite direction as the disturbance, thereby stabilizing the system by bringing it back to its equilibrium position “more leads to less, less leads to more” + - / - +

https://www.youtube.com/watch?v=inVZoI1AkC8 Ted lesson feedback loops

What type of feedback loop is this?

What type of feedback loop is this?

What type of feedback loop is this?

What type of feedback loop is this?

What type of feedback loop is this?

What type of feedback loop is this?

What type of feedback loop is this?

What type of feedback loop is this? Albedo is the fraction of solar energy (shortwave radiation) reflected from the Earth back into space. It is a measure of the reflectivity of the earth's surface

What type of feedback loop is this?

Resilience & Tipping Points The resilience of a system measures how it responds to a disturbance. The more resilient a system, the more disturbance it can deal with. What are some factors that affect resilience? (p 38) How do humans affect it?

Resilience and Tipping Points A tipping point is the minimum amount of change within a system that will destabilize it, causing it to reach a new equilibrium or new stable state These are hard to predict, and the changes are long lasting and hard to reverse. They are also notoriously delayed from the pressures driving the change and the appearance of the impacts. Can you think of any human impacts on the environment that might lead to a tipping point? Ex: lake eutrophication Extinction of species Coral reef death Climate change Toxicity Reduce the size of storages by harvesting wood, fish and other natural resuources. Humans can also reduce diversity by species extinction which leads to less resilience.