Envr Systems (2-3) Flashcards
What is a system?
A collection of things that:
1. Have a relationship (linkage) between each other
2. Are contained within an identifiable boundary
What are linkages? Give a example.
Any relationship between the “things” of a system.
- cause and effect, exchanges of material or energy.
- can be unidirectional or reversible.
The direction of arrow indicates the direction of effect or movement of matter or energy.
In the hydrological cycle, precipitation, evaporation, and runoff are linkages between the ocean, land, and atmosphere.
What are boundaries of a system? Give an example.
The limits or end of a system - usually difficult to define for most systems because they may not be entirely closed (can allow for passage of energy or material outside of the boundary).
In the hydrological cycle, a single lake could be a boundary for a local system, or the entire planet is a boundary for the global hydrological cycle.
What are the 3 types of systems?
- Open system: both energy and matter can move across the system boundary (most common).
- Closed system: only energy can move across the system boundary (matter is excluded from crossing, rare).
- Isolated system: both energy and matter are excluded from crossing the system boundary (rare).
What are system dynamics?
Understanding the behaviour of a system in action.
Quantifying the movement of energy and matter within a system, or into and out of a system.
What are the 2 states of a system?
- Transient: the input and output across the boundary are unequal.
- results in change to the size of the reservoir inside the boundary - can increase or decrease. - Steady: the input and output across the boundary are equal.
- reservoir inside the boundary remains unchanged over time.
The state of a system is quantified mathematically using the Continuity Equation.
Are most natural systems in a transient or steady state?
Most natural systems are transient.
The state can vary overtime.
Transient systems can appear to be in a steady state over specific time scales.
What is the reservoir time?
Average length of time a substance remains in a reservoir at a steady state.
What are components of a system?
An individual part of a system. A component may be a reservoir of matter of energy, a system attribute, or a subsystem.
What is coupling (aka linkage)? What are the two types?
The links between any two components of a system.
- Positive coupling: change in component A leads to a change in component B in the same direction.
- represented by a solid arrow - Negative coupling: change in component A leads to a change in component B in the opposite direction.
- represented by an open circle
What is a feedback mechanism?
A sequence of interaction in which the final interaction influences the original one. Feedbacks in loops.
What is a feedback loop? What are the 2 types?
A linkage of two or more system components that forms a round-trip flow of information.
- Negative feedback: interaction that reduces or dampens the response of the system in which it is incorporated. It is self-regulating and diminishes the effect of perturbations.
- Positive feedback: interaction that amplifies the response of the system in which it is incorporated. It is self-enhancing.
What is an equilibrium state? What are the 2 types?
The state in which the system will remain (unless something disturbs it).
- Stable: resistant to a range of perturbations (negative feedback loop). The system returns to its equilibrium state after a modest disturbance.
- Unstable: the slightest disturbance may lead to system adjustments that carry the system further and further from that state (positive feedback loop).
