Lecture 1: Environmental Systems (unifinished)

Jan 8th, 2026

A system

• Def: a collection of things (components) that:

  • 1) have a relationship (linkage) between each other

  • 2) are contained within an identifiable boundary

a system is a collection of things (components) that have a relationship (linkage) between each other and are contained within an identifiable boundary

What is a system?

any matter, energy, even ideas or concepts

what is a system made up of (its components)?

Linkages

• Def: any relationship between the components of a system

  • cause and effect, exchanges of material or energy

  • can be unidirectional or reversible

  • can be quantitative and/or qualitative

  • can be positive or negative

linkages are any relationship between the components of a system (cause and effect, exchanges of material or energy)

what are linkages?

quantitative linkages

• Def: numerical values transferring between components across linkages

quantitative linkages are values transferring between components across linkages

what are quantitative linkages?

qualitative linkages

• Def: descriptions of the processes linking the components of your system

qualitative linkages are the descriptions of the processes linking the components of your system

what are qualitative linkages?

positive linkage

• Def: when the increase in one component results in a net increase in the second, linked component

• shown by an arrow

a positive linkage is when the increase in one component results in a net increase in the second, linked component

what is a positive linkage?

negative linkage

• Def: when the increase in one component results in a net decrease in the second, linked component

• shown by a line with a circle

a negative linkage is when an increase in one component results in a net increase in the second, linked component

what is a negative linkage?

Boundary

• Def: the limits or end of a system

  • may not be entirely closed (can allow for passage of energy or material outside of the boundary)

systems are classified by how much energy and matter is able to pass through the boundary of the system

Remember: systems are classified by how much energy and matter is able to pass through the boundary of the system

open, closed, and isolated system

what are the three diff types of systems?

open system

• Def: when both energy and matter can move across the system boundary

• the most common natural system

• show by a dotted boundary

an open system is when both energy and matter can move across the system boundary

what is an open system?

closed system

• Def: when ONLY ENERGY can move across the system boundary

• matter is excluded from crossing

• rare in natural systems

• shown by a dashed boundary

• ex) our atmosphere (allows energy like light through but not water)

a closed system is when only energy can move across the system boundary

What is a closed system?

Isolated system

• Def: when neither energy or matter can cross the system boundary

• mainly theoretical in natural systems

• shown by a completely solid boundary

an isolated system is when neither energy or matter can cross the system boundary

What is an isolated system?

where you draw a boundary around your system can change the definition of a system

Remember: where you draw a boundary around your system can change the definition of a system

system dynamics

• Def: Understanding the behavior of a system in action such as quantifying the movement of energy and matter within a system, or into and out of a system

System dynamics is the understanding of the behavior of a system in action, such as quantifying the movement of energy and matter within a system, or into and out of a system

What are system dynamics?

State of a system

• Def: what condition a system is in at a specific period of time

• influenced by:

  • open vs closed boundary

  • amount or energy or matter being transferred across the boundary

• two states:

  • Transient

  • Steady

the state of a system is what condition that system is in at a specific period of time

what is the state of a system?

the state of a system is influenced by open vs closed boundary and by what amount or energy or matter is being transferred across the boundary

what influences the state of a system?

transient state

• Def: when the input and output across the boundary are unequal and the results in change to the size of the reservoir inside the boundary can increase or decrease

Steady state

• Def: when the input and output across the boundary are equal and the reservoir inside the boundary remains unchanged over time