Systems and Models Flashcards
System (definition)
A set of inter-related parts working together to make a complex whole
Open system (definition)
Exchanges matter + energy with its surroundings
Both matter + energy move through ecosystems as…
Transfers
Transformations
What are transfers and give 2 examples
Transfers occur when energy or matter change location but not state
e. g. water moving from river to sea
e. g. chemical energy moving from herbivore to carnivore
What are transformations and give 3 examples
Transformations occur when energy or matter changes its state
e. g. matter to energy (burning fossil fuels)
e. g. liquid to gas (evaporation)
e. g. energy to matter (photosynthesis)
What type of system are all ecosystems?
All ecosystems are open systems, exchanging matter and energy with their environment
How are forest ecosystems open systems?
- Plants fix energy from light during photosynthesis
- Nitrogen from air fixed by soil bacteria
- Herbivores enrich soil with faeces
- Nutrients leached out of soil into groundwater, streams + rivers
- Water lost through evaporation + transpiration from plants
What is a closed system?
Exchanges energy but not matter with its environment
On a global scale, which cycles are closed systems?
On a global scale, the hydrological, carbon and nitrogen cycles are closed. They exchange only energy and no matter
Can the planet itself be though of as a closed system?
The planet itself can be though of as an ‘almost’ closed system
Give an example of a man-made closed system
Biosphere 2
What was Biosphere 2?
- A human attempt to create a habitable closed system on Earth
- Arizona, 1980s
- Never managed to produce enough food to sustain participants
- Oxygen levels dropped from 21% to 14%
What is an isolated system?
- Exchanges neither matter nor energy with its environment
- Do not exist naturally
- Universe?
Why do we use models of systems?
We use models to help us understand how a system works and to predict what happens if something changes
What are 4 strengths of models?
- Easier to work with than comprehend reality
- Can be used to predict the effect of a change of input
- Applied to other similar situations
- Used to visualise small things (atoms) and large things (solar system)
