1.2: systems & models Flashcards
system definition:
an assemblage of parts and their relationship forming a functioning entirety or whole.
systems approach:
a way of visualizing a complex set of interactions which may be ecological or societal. these interactions produce the emergent properties of the system
characteristics of a system -
- storage
- flows
- processes
- feedback mechanisms that maintain stability and equilibrium
parts of a system -
input: energy or matter that enters a system
output: something produced at the end of a system
storage: areas where energy or matter are accumulated inside a system
flow – movement of energy/matter through a system
boundaries – outside/ edge of a system
flows:
are processes and may be either transfers (a change in location) or transformations (a change in chemical nature, a change in state or a change in energy)
transfers:
occurs when energy or matter flows & changes its location but not its state
- movement of material through living organisms (carnivore eating other animals)
- movement of material in a non-living process (water being carried by a stream)
- movement of energy (ocean currents transferring heat)
transformations:
occurs when energy or matter flows and changes its state
- matter to matter (soluble glucose converted to insoluble starch in plants)
- energy to energy (light converted to hear by radiating surfaces)
- matter to energy (burning fossil fuels)
- energy to matter (photosynthesis)
types of systems -
- open systems
- closed systems
- isolated systems
open system:
an open system exchanges both energy and matter across its boundary.
most systems are open systems. all ecosystems are open systems exchanging matter and energy with their environment.
eg of an open system:
in forest ecosystems for example;
- plants fix energy from light entering the system during photosynthesis
- nitrogen from the air is fixed by soil bacteria
- herbivores that live within the forest may graze in adjacent ecosystems such as grassland, but when they return, they enrich the soil with feces
- forest fires expose topsoil which may be removed by wind and rain
- mineral nutrients are leached out of the soil and transported in groundwater to streams and rivers
- water is lost through evaporation and transpiration from plants
- heat is exchanged with the surrounding environment across the boundaries of the forest
closed system:
only exchanges energy across its boundary.
eg of a closed system:
they are extremely rare in nature. however, on a global scale the hydrological, carbon, and nitrogen cycles are closed – they exchange only energy and no matter.
the planet itself can be considered an ‘almost’ closed system.
most examples of closed systems are artificial and are constructed for experimental purposes. an aquarium or terrarium may be sealed so that only energy in the form of light and heat, but no matter can be exchanged.
isolated system:
a hypothetical concept in which neither energy nor matter is exchanged across the boundary.
a model:
a simplified version of reality and can be used to understand how a system works and predict how it will respond to change.
a model inevitably involves some approximation and loss of accuracy.
