Topic 1 – systems and models
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A system consists of storages, flows (inputs and outputs), processes (transfer or transformation), and feedback mechanisms to maintain stability. Ecosystems are examples of systems that are generally self-contained communities of living things and their environment. The Earth can be considered a single, closed ecosystem (the biosphere) made up of various biomes defined by similar climates. All systems aim for equilibrium, either static, steady-state, stable, or unstable, with feedback mechanisms regulating inputs to maintain the equilibrium state.
Topic 1 – systems and models
- 1. Topic 1 Systems and Models
- 2. What is a System? • A system consists of: – Storages – Flows (inputs and outputs) (of energy or matter) – Processes (transfer or transformation) – Feedback mechanisms (to maintain stability)
- 3. storage Energy or matter in (INPUT) Energy or matter out (OUTPUT) TRANSFORMATION (Feedback mechanism to control input – and maintain EQUILIBRIUM)
- 4. Try to Produce a System Diagram
- 5. Ecosystems • Most of the systems we will look at are ecosystems (self contained communities of living things and their surrounding environment) • Very large ecosystems which span a fairly stable climate are biomes • Many biologists say the whole planet is a single ecosystem (eg Gaia theory). Some of them call it a CLOSED ecosytem
- 6. Open, Closed and Isolated Ecosytems • Open – matter and energy exchanged to suroundings • Closed – only energy exchanged to surroundings • Isolated – neither matter nor energy is exchanged to surroundings • Is the Earth really a closed ecosystem? • Do isolated ecosystems really exist? • Can closed ecosystems be created artificially? (eg Biosphere 2 Project)
- 7. Biomes and Biospheres • Biome – An open ecosystem in a geographically defined area with similar climatic conditions throughout – eg, desert, grassland (savannah), tropical rainforest • Biosphere – A closed ecosytem – generally made up of a range of biomes (i.e. the entire Earth)
- 8. A Climograph Meanannualtemperature(oC) Rainfall (mm/year) -15 -10 -5 -0 5 10 15 20 25 1000 2000 3000 4000 5000 6000 desert grassland Tropical rainforest
- 9. The Laws of Thermodynamics • First Law – Energy can neither be created nor destroyed, but can only be transformed • Second Law – Energy is always changed from a concentrated (useful) form, to a dispersed (less useful) form – we say that ENTROPY (disorder) always increases (this means an isolated system cannot exist – there must be an input of energy to keep entropy low)
- 10. 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
- 11. Static Equilibrium time State of the system Note: this is not realistic – it could only occur in an isolated system
- 12. Steady State Equilibrium time State of the system
- 13. Stable Equilibrium time State of the system disturbance Weebles wobble but they don’t fall down!
- 14. Unstable Equilibrium time State of the system disturbance He’s going down!
- 15. 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
- 16. Negative Feedback • Your (stable) equilibrium body temperature is 37oC • Sensors in the skin detect your skin temperature is rising (you are in Cancún) • Show what happens in a system diagram
- 17. 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