Systems and models
- 1. 1.2 Systems and models
- 2. • What is a model? Def: A simplified version of reality and can be used to understand how a system works an predict how it will respond to change. • Pros and cons of models Pros Cons + Easier to work with than the real thing - The model may be wrong and therefore, lack accuracy + Can be manipulated without damaging real systems - Accuracy is lost because the model is simplified + Used to predict outcomes, if reliable - Predictions may be inaccurate + Visualise the invisible
- 3. What are systems? Def: A set of inter-related parts working together to make a complex whole. • A system can be living or non-living. • Can be on any scale – small or large (a cell, you, a car, a bicycle, an ocean, a farm…). • Can be simplifications of reality – diagrams which represent energy flow and storage. • Open, closed and isolated systems exist in theory though most living systems are open systems. • Comprised of storages and flows. • Material and energy undergo transfers and transformations.
- 4. Systems terminology All systems have: Represented by: STORAGES or stores of matter or energy A box FLOWS into, through and out of the system arrows INPUTS OUTPUTS BOUNDARIES Lines ----------- PROCESSES which transfer or transform energy or matter from storage to storage E.g. Respiration, precipitation, diffusion
- 5. Types of Systems Open System Exchanges both energy and matter across its boundary. E.g. Ecosystems Close System Only exchanges energy across its boundary. E.g. Geochemical cycles / experimentally Isolated System Is a hypothetical concept in which neither energy nor matter is exchanged across the boundary. Energy exchanged Matter exchanged Open a a Closed a x Isolated x x
- 6. Open systems exchanging matter and energy with their environment. In forest ecosystems: • Plants fix energy from light entering the system during photosynthesis. • Nitrogen from the air is fixed by soil bacteria. • Mineral nutrients are leached out of the soil and transported in groundwater
- 7. Closed systems exchanges energy but not matter with its environment. • Extremely rare in nature. However, on a global scale, the hydrological, carbon and nitrogen cycles are closed – they exchange only energy and no matter. • Most closed systems are artificial, and are constructed for experimental purposes. E.g. Biosphere 2 A prototype space city, was a human attempt to create a habitable closed system on Earth. Built in Arizona – never managed to produce enough food and the levels of oxygen were low. – failed – turned into an open system. E.g. The Earth
- 8. Isolated systems exchanges neither matter nor energy with its environment. • Do not exist naturally though it is possible to think of the entire universe as an isolated system.
- 9. Transfers Transfers: when the flow of material or energy does no involve a change of form. • Water moving from a river to the sea, chemical energy in the form of sugars moving from a herbivore to a carnivore or: - The movement of material through living organisms (carnivores eating other animals) - The movement of material in a non-living process (water being carried by a stream) - The movement of energy (ocean currents transferring heat)
- 10. Transformations Transformations: a flow involving a change of form. • Liquid to gas, light to chemical energy: - Matter to matter (soluble glucose converted to insoluble starch in plants) - Energy to energy (light converted to heat by radiating surfaces) - Matter to energy (burning fossil fuels) - Energy to matter (photosynthesis)
- 11. Transfers and transformations Transfer Transformation The Gulfstream Burning a candle Eating a bacon sandwich (but digestion is a transf.) Photosynthesis Carnivores eating other animals Burning fossil fuels