CGP Natural systems

• Natural systems

  Systems that are found in nature
• Systems are made up of stores, flows, boundaries, inputs and outputs
• Inputs


  When matter or energy (e.g. solar energy) is added to the system
• Outputs


  When matter or energy leaves the system
• Stores


  Where matter or energy builds up
• Flows or transfers


  When matter or energy moves from one store to another
• Boundaries

  The limits of the system
• Drainage basin system

  • Water enters as rain input, stored in soil and vegetation, travels to river and out to sea (output)
• Open systems

  Both energy and matter can enter and leave the system
• Drainage basin


  • An open system - energy from the sun enters and leaves, water enters as precipitation and leaves as river discharge
• Closed systems


  Matter cannot enter or leave, but energy can
• Carbon cycle


  • A closed system - energy enters and leaves (e.g. photosynthesis and respiration) but the amount of carbon on Earth stays the same
• Equilibrium


  When the inputs and outputs of a system are balanced, so the system continues in the same way
• Dynamic equilibrium


  When there are small variations in the inputs and outputs, but they remain about balanced on average
• Positive feedback


  Mechanisms that amplify the change in inputs or outputs, moving the system further from its previous state
• Negative feedback


  Mechanisms that counteract the change in inputs or outputs, keeping the system closer to its previous state
• Subsystems of the Earth

  • Cryosphere
  • Hydrosphere
  • Lithosphere
  • Biosphere
  • Atmosphere
• The Earth can be seen as a closed system - energy is input from the Sun and output to space
• The subsystems of the Earth are all interlinked, with matter and energy moving between them
• Changes in one subsystem can affect the others, as the Earth is a cascading system
• • Q) Outline the differences between open and closed systems (4 marks)


  Both energy and matter can enter and leave an open system [1 mark]. In closed systems, matter can't enter or leave and can only cycle between stores [1 mark]. The amount of matter in an open system can change, whereas in a closed system it always stays the same [1 mark]. Energy can enter and leave a closed system [1 mark].
• Q) Explain how positive feedback can alter a natural system (4 marks)

  Positive feedback mechanisms amplify a change in inputs or outputs [1 mark]. This means that the system responds by increasing the effects of the change [1 mark]. The system moves even further from its previous state [1 mark]. For example, higher temperatures cause more ice to melt, so less solar energy is reflected and more is absorbed, leading to even higher temperatures [1 mark].