Water and carbon cycles as natural systems Flashcards
What are the five components of a natural system?
Inputs, outputs, stores, flows and boundaries.
What is an input?
When matter or energy is added to a system.
What is an output?
When matter or energy leaves a system.
What are stores?
Where matter or energy build up.
What are flows?
When matter or energy moves from one store to another.
What are boundaries?
The physical limitations of the stores - their capacity to store matter or energy.
How do these elements work in a drainage basin system?
Water enters the system as an input through rainfall, the watershed is the boundary. Some water is stored in soil and some in vegetation, water travels down the basin through flows such as throughflow and eventually is transferred to another system such as the atmosphere through evapotranspiration or the sea.
What is an open system? Relate to drainage basin.
In an open system, both energy and matter can enter and leave. There are inputs and outputs of both. Eg drainage basin where solar energy and water enter and leave.
What is a closed system? Relate to carbon cycle.
A closed system is where matter cannot enter or leave the system, it can only cycle between stores.
- Energy can enter and leave closed systems as inputs and outputs.
Eg. the carbon cycle is a closed system, energy comes from the sun as photosynthesis and is output by respiration, but the amount of carbon on the earth is constant as there are no inputs or outputs.
When are systems in equilibrium (not dynamic.)
This is when the inputs and outputs in a system are balanced so the system is in equilibrium.
Flows and processes continue to occur, but in the same way at all times, so there are no overall changes to the system.
What is dynamic equilibrium?
In reality, there are lots of small variations in inputs and outputs of a system (e.g. the amount of precipitation entering a drainage basin constantly varies).
These variations are usually marginal, so they inputs and outputs remain largely balanced in a system on average. This balance is known as dynamic equilibrium.
-Large long term changes to the balance of inputs and outputs can cause a system to form a new dynamic equilibrium.
What is positive feedback?
Positive feedback mechanisms amplify the change in the inputs and outputs of a system, causing the system to further deviate from its original equilibrium.
Give an example of a positive feedback loop.
Temperatures rise –> Ice covering cold parts of the earth are exposed to higher temperatures and melt more –> ice cover is reduced so less of the suns energy is reflected –> less reflection means more is absorbed by the earth –> temps increase and so on.
What is negative feedback?
Negative feedback mechanisms counteract changes in inputs and outputs.
- This means that the system responds to change by decreasing the effects of change, keeping the system closer to it’s previous state.
Give an example of a negative feedback loop.
Large amounts of c02 are emitted –> CO2 in atmosphere increases –> Extra CO2 exacerbates plant growth –> plants act as more of a carbon sink and store more co2 from the atmosphere –> Co2 in atmosphere reduces. (Closer to previous state).
