Systems & Models — Complete Summary
- Systems approach = study connections and interactions (whole picture, not isolated parts)
- A system has components, connections, a function, and emergent properties
- Emergent properties only appear when parts interact (e.g. predator–prey cycles)
- Systems can be studied at different scales (pond → forest → Earth)
- Storages (stocks) = where matter/energy/info builds up
- Flows = movement into/out of storages
- Inflows increase a storage; outflows decrease it
- Flows can change fast, but storages change slowly
- Big storages act as buffers (slow change + create time delays)
- Inputs/outputs = the things that move (water, CO₂, nutrients)
- Inflows/outflows = the processes that move them (rainfall, evaporation, burning)
- Dynamic equilibrium = inflows = outflows (storage stays constant)
- Exam trap: say "rainfall is an inflow", not an input
- Transfers = movement without changing form (same substance, new location)
- Transformations = change in form/state/chemistry (something new is made)
- Both are types of flows in systems
- System boundary = imaginary line separating system from surroundings
- Too small → miss key influences; too big → too complex
- Good boundaries are useful, not perfect (no single “correct” boundary)
- Open system = matter AND energy enter/leave (pond, forest, human, city)
- Closed system = energy enters/leaves, matter stays and is recycled (Earth)
- Global cycles (carbon/water/nitrogen) are closed at Earth scale
- Models = simplified versions of reality used to explain/predict systems
- Models simplify because real systems are too complex to include everything
- There’s always a trade-off: simpler = easier, but less precise
- Common types: diagram, mathematical, physical, computer, written
IB full-mark checklist: name the boundary, identify storages, describe inflows/outflows, state open/closed, and say whether the system is in dynamic equilibrium or changing.