IB Environmental Systems and Societies SYSTEMS
|Open system|| A system that exchanges energy and matter with its surrounding. |
e.g. A forest ecosystem, in which plants obtain energy from light which enters the system.
|Closed system|| |
A system that exchanges energy but not matter. They are rare in nature.
|Isolated system|| |
A system that exchanges nothing with its surroundings.
|2nd law of thermodynamics|| energy = work + heat (and other wasted energy)|
A law stating that the entropy of an isolated system not in equilibrium will tend to increase over time.
e.g. when a zebra runs from a lion, the stored energy is converted to heat and lost from the food chain.
|Equilibrium||The tendency for a system to return to an original state following a disturbance. When this is reached, it is inferred that a balance exists between all the elements of the system.|
|Steady-state equilibrium|| The most common form of equilibrium in natural open systems. In this equilibrium, there is a constant exchanging of energy and matter, but the system always remains relatively constant. |
e.g. Water tank (filling and emptying at the same rate, but remaining at a constant level)
|Static equilibrium|| An equilibrium showing no change over time; and when it has been disturbed, it establishes a new equilibrium.|
e.g. A pile of books that has been knocked over (it will not return to it's original sstate)
|Stable equilibrium||The equilibrium implying the system will return to the same equilibrium after a disturbance.|
|Unstable equilibrium||The equilibrium implying that the system will find a new equilibrium after a disturbance.|
|Positive feedback|| Feedback that enhances a change in the system and it is destabilized and pushed to a new equilibrium. This feedback may cause the process to speed up until the system collapses, resulting in a "vicious circle". |
e.g. Lost on a high snowy mountain (where enzymes slow down at low temperatures, causing lethargy, making the body colder until death occurs)
e.g. exponential population growth.
|Negative feedback|| Feedback that tends to neutralize or counteract any deviation from equilibrium, returning the system to a stead-state equilibrium.|
e.g. Maintenance of body temperature (sweating to maintain coolness)
e.g. Predator-prey interactions (the increase of prey causes the increase of predators, and the decrease of prey causes the decrease of predators)
|Transfer process|| The movement of material/energy in living organisms and non-living processes. This process requires less energy and is more efficient than transformations.|
e.g. water moved from a river to the sea
e.g. chemical energy in the form of sugars moving from when carnivore eats a herbivore
|Transformation process|| The change of form or state |
e.g. matter to matter (soluble glucose converted to insoluble starch in plants)
e.g. energy to energy (light converted to heat by radiating surfaces)
e.g. matter to energy (burning fossil fuels)
e.g. energy to matter (photosynthesis)
|Flows||The inputs and outputs of energy and matter.|
|Storages||The stock of energy and matter.|
|Model|| A system that can help predict changes in the system by modelling reality, as systems work in predictable ways, following rules. |
e.g. data flow diagrams
e.g. mathematical equations
e.g. a software model of climate change
e.g. a physical model of the solar system
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