Systems

• A system is an assemblage of interrelated parts that work together by way of some driving force. They are a series of stores or components that have flows or connections between them.
• The three main types of systems are open, closed, and isolated.
• An open system has inputs and outputs with energy and matter flowing into and out of the system.
• A closed system does not allow any material to enter or leave it but allows energy to flow through it.
• Isolated systems do not let anything in or out so they cannot change over time.
• An example of an open system is the ocean: it is a component of the hydrosphere and is connected to the atmosphere and the biosphere.
• An example of a closed system is a lake: it is part of the hydrosphere and is only connected to other lakes within the same basin.
• In open systems energy and matter can be transferred to the environment.
• In a closed system there are transfers of energy into and beyond the system boundary but no transfer of matter.
• In an isolated system there are no interactions with anything outside the system boundary; no input or output of energy or matter.
• When there is a balance between the inputs and outputs of a system then it is in a state of dynamic equilibrium.
• Most ecosystems are examples of closed environments.
• A river is an open system because water flows through it from its source to its mouth.
• If one of the elements of a system changes it will lead to feedback within the system
• Positive feedback is where the effects of an action are enhanced/amplified by subsequent knock-on effects.
• Negative feedback is where the effects of an action are nullified by its subsequent knock-on effects.
• Earth is considered to be a closed system.

  It has four major subsystems:

  • the atmosphere (air)
  • the lithosphere (rocks)
  • the hydrosphere (water)
  • the biosphere (living organisms)
• The four major subsystems of the Earth are individually considered to be open systems that form part of a chain; a cascading system.
• The water stores of the Earth include the lithosphere (land), the hydrosphere (liquid water), the cryosphere (frozen water) and the atmosphere (air).
• Closed systems:

  • energy transfer in and out of the boundary (e.g. solar & wind energy)
  • no transfer of matter
  • rare in nature
• Open systems:

  • matter and energy can transfer across the boundary (e.g. energy = sun, wind, matter = plants, animals)
  • e.g. ecosystems
• Isolated systems:

  • don't occur in nature (lab experiments)
  • no interactions outside of the boundary
• 𝙋𝙊𝙎𝙄𝙏𝙄𝙑𝙀 𝙁𝙀𝙀𝘿𝘽𝘼𝘾𝙆:

  • enhances or amplifies a change
  • moves a system away from its equilibrium state (becomes more unstable)
  • creates a 'snowball effect'
• 𝙉𝙀𝙂𝘼𝙏𝙄𝙑𝙀 𝙁𝙀𝙀𝘿𝘽𝘼𝘾𝙆:

  • an opposing force
  • counters and lessens any change
  • holds the system in a stable equilibrium
• Positive Feedback example:

  A) warmer

  B) warmer

  C) CO2 uptake

  D) end

  E) accumulates

  
• Negative Feedback example:

  A) equilibrium

  B) decreased

  C) reset

  D) albedo effect

  E) evaporation

  F) greenhouse

  G) temperatures

  
• 𝙁𝘼𝘾𝙏𝙊𝙍𝙎 𝙏𝙃𝘼𝙏 𝘿𝙍𝙄𝙑𝙀 𝘾𝙃𝘼𝙉𝙂𝙀𝙎 𝙄𝙉 𝙏𝙃𝙀 𝙈𝘼𝙂𝙉𝙄𝙏𝙐𝘿𝙀 𝙊𝙁 𝙒𝘼𝙏𝙀𝙍 𝙎𝙏𝙊𝙍𝙀𝙎:

  • evaporation rates
  • condensation
  • precipitation
  • adiabatic cooling
• 𝗘𝗩𝗔𝗣𝗢𝗥𝗔𝗧𝗜𝗢𝗡 𝗥𝗔𝗧𝗘𝗦:

  DEPEND ON:

  • amount of solar energy
  • availability of water
  • humidity of the air
  • temperature of the air
  • transpiration
• The rate of evaporation at a given place is always dependent on the humidity of that place.

  If the air is already saturated with water vapour, it will not have any place to hold excess vapour.

  Therefore, evaporation will occur at an extremely slow rate.
• Warm air can hold more water than cold air.
• Transpiration refers to evaporation from plants.
• 𝗖𝗢𝗡𝗗𝗘𝗡𝗦𝗔𝗧𝗜𝗢𝗡:

  • excess water in the air is converted to liquid at the dew point temperature
  • the water molecules need something to condense on (condensation nuclei or surfaces)
  • if the surface is below freezing the water sublimates, changing directly from gas to solid to form hoar frost
• The dew point temperature is the temperature to which a body of air must be cooled to become completely saturated with water vapour.
• 𝗣𝗥𝗘𝗖𝗜𝗣𝗜𝗧𝗔𝗧𝗜𝗢𝗡:

  • condensation is the direct cause of all forms of precipitation
  • air temperature is reduced but its volume remains constant (dew and hoar frost, fog, etc)
  • adiabatic cooling; the volume of the air increases under lower pressures but there is no addition of heat (e.g. relief, frontal and convectional rainfall)
• Adiabatic cooling is the process of reducing heat through a change in air pressure caused by volume expansion.
• The pressure and volume of a gas have an inverse relationship. If volume increases, then pressure decreases and vice versa (if the temperature is held constant).
• When an initial change within a system brings about further change in the same direction this is known as positive feedback.
• When a system returns to equilibrium following a change in the system this is known as negative feedback. It is negative feedback that allows systems to adjust to short-term changes.

  For example, storms can remove huge quantities of beach material in a short time. After reverting to normal conditions, sediment is slowly shifted back to the beach by waves, so that equilibrium is restored, and the beach looks much the same as before the storm.
• If any inputs or outputs change either because of environmental or human factors, then the system becomes unbalanced and will change.
• Positive feedback mechanisms include melting ice caps releasing trapped methane, thawing permafrost releasing CO2, wildfires releasing CO2 and methane, and ocean acidification reducing the ability of oceans to absorb CO2.