OCR A Level Geography Revision Notes: Earth’s Life
Support Systems
hank you so much for purchasing these notes! I hope they will be of use to you.
T
For some additional context, I created these notes myself using both teacher guidance, the OCR textbook, and with a lot of
additional research. Using these notes alone, I was lucky enough to achieve an A* in the 2026 exams. I therefore hope they will
achieve the same for you.
his set includes notes that follow the OCR specification for the Earth’s Life Support Systems topic, including case study
T
knowledge as well. The case studies in this set are the Amazon Rainforest and Arctic Tundra. These are the only 2 case studies
you will need for this specification.
his set also includes an exemplary essay that achieved 16/16 marks and all of the exam techniques that I used throughout the
T
2 year course, securing 10/10 and 16/16 in every essay that I wrote.
astly, I have also included many AO2 points that can be memorised to achieve marks for “application of knowledge” in your
L
essays. Whilst you can of course think of these spontaneously in the exam, I found it beneficial to memorise these key
limitations and simply regurgitate them into my essays so that there was less pressure under exam conditions.
I have also made several other notes available for other OCR A Level Geography topics, so make sure to check those out if you
found these useful.
Good luck!
, Earth’s Life Support Systems
The Water Cycle
Uses
Water is a fundamental prerequisite for life:
● Physical Significance: The potential for water tostore as liquid (due to existence in the “Goldilocks Zone”) is one of the
primary factors for Earth being one of the few habitable planets in the solar system: were it not for the absorbance and
dissipation of 20% solar infrared radiation by all of water’s found forms, Earth would be 15c cooler and unable to sustain
life. Liquid water also moderates global temperatures in a thermohaline circulation cycle in a system of surface
currents, downwelling, deep ocean currents and upwelling.
● Biological significance: 65-95% of all molecules inall organisms are those of water, utilised as a medium for chemical
reactions such as nutrient circulation, photosynthesis and maintenance of turgor;
● Biological Significance: moderation of global andindividual temperatures: transpiration from leaf surfaces, sweating
and panting to evaporate heated water molecules;
● Economic Significance: water is essential for moderneconomies across all levels of development via electricity
generation, agricultural irrigation, manufacturing, recreational and sewage facilities.
Water Distribution and Cycling
ost water is saline (97.5%) stored in oceans, however freshwater (2.5%) is stored as ice or within aquifers, with less than 1% of this
M
accessible to humans.
ydrosphere(oceans, rivers and lakes) = 97% (moderateresidence)
H
Cryosphere(glaciers and permafrost) = 2% (high residence)
Lithosphere(groundwater) = 0.7%
Atmosphere(vapour) = tiny fraction (low residence)
Biosphere(living organisms) = tiny fraction
Inputs and Outputs Characteristics
n a global scale, the water cycle is a closed system transferring water on, above and below the planet’s surface.
O
At a local scale, adrainage basin(an area from whichall precipitation flows into a single set of streams) can be viewed as being
an open system (inputs being solar energy, ablation and precipitation, outputs being rivers, human extraction,
evapotranspiration and groundwater flow into neighbouring basins).
ater balance =P = E + Q +/- Swherein…
W
P = precipitation inputs
E + Q = evaporation + streamflow outputs
S = storage
positive waterbalance occurs when P>E+Q
A
Anegative waterbalance occurs when P<E+Q
Processes of the Cycle
recipitation
P
Any form of water (snow, rain, ice, hail, sleet, etc.) that falls from the atmosphere to the ground after atmospheric vapour has
reached its dew point temperature.
The character of precipitation is influenced by:
Latitude: areas of high altitude/mountain catchmentsare associated with cryospheric (snow and ice) stores, so remain on
ground for several months, potentially, considerably increasing lag time. This is usually followed by a peak in discharge in the
summer months when melted.
Intensity and Duration: high intensity and prolongedevents (e.g. monsoon season in India) leads to inputs exceeding infiltration
capacity of soils, generating rapid overland flow and low lag time.
I nterception (CATCHMENT HYDROLOGY)
The direct intervention of plants’ leaves, stems, etc. in changing the direction or temporarily storing precipitation as it falls to the
earth’s surface.
Any moisture retained by the surface of the leaf acts as aninterception storeand eventually evaporatesasinterception loss-
losses are highest among crops, followed by grasses, and are lowest in trees - or infiltrates into the ground.
I nfiltration (CATCHMENT HYDROLOGY)
The vertical movement of water soaking into the soil due to gravity, eventually reaching the water table to form storage aquifers
or groundwater flow into nearby streams.
un-Off (CATCHMENT HYDROLOGY)
R
Water fails to infiltrate soils and flows above the land due to one of two theories:
Support Systems
hank you so much for purchasing these notes! I hope they will be of use to you.
T
For some additional context, I created these notes myself using both teacher guidance, the OCR textbook, and with a lot of
additional research. Using these notes alone, I was lucky enough to achieve an A* in the 2026 exams. I therefore hope they will
achieve the same for you.
his set includes notes that follow the OCR specification for the Earth’s Life Support Systems topic, including case study
T
knowledge as well. The case studies in this set are the Amazon Rainforest and Arctic Tundra. These are the only 2 case studies
you will need for this specification.
his set also includes an exemplary essay that achieved 16/16 marks and all of the exam techniques that I used throughout the
T
2 year course, securing 10/10 and 16/16 in every essay that I wrote.
astly, I have also included many AO2 points that can be memorised to achieve marks for “application of knowledge” in your
L
essays. Whilst you can of course think of these spontaneously in the exam, I found it beneficial to memorise these key
limitations and simply regurgitate them into my essays so that there was less pressure under exam conditions.
I have also made several other notes available for other OCR A Level Geography topics, so make sure to check those out if you
found these useful.
Good luck!
, Earth’s Life Support Systems
The Water Cycle
Uses
Water is a fundamental prerequisite for life:
● Physical Significance: The potential for water tostore as liquid (due to existence in the “Goldilocks Zone”) is one of the
primary factors for Earth being one of the few habitable planets in the solar system: were it not for the absorbance and
dissipation of 20% solar infrared radiation by all of water’s found forms, Earth would be 15c cooler and unable to sustain
life. Liquid water also moderates global temperatures in a thermohaline circulation cycle in a system of surface
currents, downwelling, deep ocean currents and upwelling.
● Biological significance: 65-95% of all molecules inall organisms are those of water, utilised as a medium for chemical
reactions such as nutrient circulation, photosynthesis and maintenance of turgor;
● Biological Significance: moderation of global andindividual temperatures: transpiration from leaf surfaces, sweating
and panting to evaporate heated water molecules;
● Economic Significance: water is essential for moderneconomies across all levels of development via electricity
generation, agricultural irrigation, manufacturing, recreational and sewage facilities.
Water Distribution and Cycling
ost water is saline (97.5%) stored in oceans, however freshwater (2.5%) is stored as ice or within aquifers, with less than 1% of this
M
accessible to humans.
ydrosphere(oceans, rivers and lakes) = 97% (moderateresidence)
H
Cryosphere(glaciers and permafrost) = 2% (high residence)
Lithosphere(groundwater) = 0.7%
Atmosphere(vapour) = tiny fraction (low residence)
Biosphere(living organisms) = tiny fraction
Inputs and Outputs Characteristics
n a global scale, the water cycle is a closed system transferring water on, above and below the planet’s surface.
O
At a local scale, adrainage basin(an area from whichall precipitation flows into a single set of streams) can be viewed as being
an open system (inputs being solar energy, ablation and precipitation, outputs being rivers, human extraction,
evapotranspiration and groundwater flow into neighbouring basins).
ater balance =P = E + Q +/- Swherein…
W
P = precipitation inputs
E + Q = evaporation + streamflow outputs
S = storage
positive waterbalance occurs when P>E+Q
A
Anegative waterbalance occurs when P<E+Q
Processes of the Cycle
recipitation
P
Any form of water (snow, rain, ice, hail, sleet, etc.) that falls from the atmosphere to the ground after atmospheric vapour has
reached its dew point temperature.
The character of precipitation is influenced by:
Latitude: areas of high altitude/mountain catchmentsare associated with cryospheric (snow and ice) stores, so remain on
ground for several months, potentially, considerably increasing lag time. This is usually followed by a peak in discharge in the
summer months when melted.
Intensity and Duration: high intensity and prolongedevents (e.g. monsoon season in India) leads to inputs exceeding infiltration
capacity of soils, generating rapid overland flow and low lag time.
I nterception (CATCHMENT HYDROLOGY)
The direct intervention of plants’ leaves, stems, etc. in changing the direction or temporarily storing precipitation as it falls to the
earth’s surface.
Any moisture retained by the surface of the leaf acts as aninterception storeand eventually evaporatesasinterception loss-
losses are highest among crops, followed by grasses, and are lowest in trees - or infiltrates into the ground.
I nfiltration (CATCHMENT HYDROLOGY)
The vertical movement of water soaking into the soil due to gravity, eventually reaching the water table to form storage aquifers
or groundwater flow into nearby streams.
un-Off (CATCHMENT HYDROLOGY)
R
Water fails to infiltrate soils and flows above the land due to one of two theories:
