Earth’s Life Support Systems | OCR A-Level Geography (H481)

Earth’s Life Support Systems

271 questions
17 subtopics
Component 01: Physical systems, one landscape of three plus the compulsory life support systems
Component 01

Earth’s Life Support Systems is examined in Component 01, Physical systems.

It covers water and carbon as the foundations of life on Earth, open and closed systems, and the major global stores of water and carbon, inputs and outputs of the water cycle: precipitation, snowmelt and evapotranspiration, inputs and outputs of the carbon cycle, and the forms of chemical weathering, evaporation, transpiration, condensation and the causes of rainfall, interception, runoff and catchment hydrology, photosynthesis, respiration, decomposition and combustion as carbon flows, natural sequestration in oceans, vegetation, sediments and rock, stores, flows and physical controls in the tropical rainforest, deforestation, farming and forest management in an Amazon drainage basin, stores, flows and seasonal change in the Arctic tundra, oil and gas development in the Arctic tundra, and its management, dynamic equilibrium, land use change and water extraction, fossil fuel combustion, carbon sequestration and feedback loops, change over time in the cycles, and the monitoring that records it, links and interdependence between the water and carbon cycles and global strategies to protect the carbon and water cycles.

Sample questions from Earth’s Life Support Systems

Answer each one closed book first, then open the answer.

Water and carbon as the foundations of life on Earth

Name the three sectors of human water use in order of the volume they withdraw.

Show the answer
Agriculture is much the largest at roughly 70% of withdrawals, then industry at about 20%, then domestic use for drinking, cooking, washing and sanitation at around 10%.
Inputs and outputs of the water cycle: precipitation, snowmelt and evapotranspiration

What does ablation mean when applied to snow and ice?

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Ablation is the total loss of snow and ice by melting, sublimation, evaporation and calving.
Evaporation, transpiration, condensation and the causes of rainfall

What is the dew point?

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The dew point is the temperature at which air becomes saturated, so that any further cooling forces water vapour to condense.
Photosynthesis, respiration, decomposition and combustion as carbon flows

Compare net primary productivity in a tropical rainforest with that of tundra.

Show the answer
Tropical rainforest produces around 2,200 g m⁻² yr⁻¹ of dry matter, more than ten times the roughly 150 g m⁻² yr⁻¹ produced in tundra.
Stores, flows and physical controls in the tropical rainforest

How does a single emergent tree influence the water cycle around it?

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Its canopy intercepts rain and evaporates part of it, its roots draw soil moisture from depth, and it transpires several hundred litres of water back to the atmosphere on a hot day.
Stores, flows and seasonal change in the Arctic tundra

Why is the tundra water cycle described as slow?

Show the answer
For most of the year water is locked up as ground ice and snow so flows almost cease, and only during the brief summer does liquid water move through the system at all.
Dynamic equilibrium, land use change and water extraction

Why does repeated ploughing with heavy machinery increase runoff?

Show the answer
It breaks down the soil's structure and creates a compacted plough pan below the tilled layer, so water cannot percolate and moves laterally or over the surface instead.
Change over time in the cycles, and the monitoring that records it

How does the loss of foliage change the water cycle in a deciduous woodland?

Show the answer
With leaves in summer interception and transpiration are high and runoff is low, but once the leaves fall interception loss drops sharply and much more rain reaches the ground.

The 17 subtopics

One subtopic is one session. Work down the list.

Subtopic	What it covers	Questions
Water and carbon as the foundations of life on Earth	Recall questions on why water and carbon support life: water as a solvent, its thermal properties and role in photosynthesis and transpiration, human water use by sector, wetlands, carbon chemistry and the biosphere, human use of carbon resources, the fast and slow carbon cycles, and carbon dioxide as a resource.	12
Open and closed systems, and the major global stores of water and carbon	Recall questions on open and closed systems, stores and flows, how water and carbon move between ocean, atmosphere and land, the sizes of the ocean, cryosphere, groundwater, lake and atmospheric water stores, a residence time calculation, and the rock, ocean, atmosphere, soil and vegetation carbon stores.	18
Inputs and outputs of the water cycle: precipitation, snowmelt and evapotranspiration	Recall questions on drainage basin inputs and outputs, potential and actual evapotranspiration, ablation and snowmelt regimes, the conditions and vegetation that raise evapotranspiration, the water balance equation with worked runoff and volume calculations, and summer soil moisture deficits.	13
Inputs and outputs of the carbon cycle, and the forms of chemical weathering	Recall questions on how precipitation, photosynthesis, decomposition, plant and soil respiration and combustion move carbon, the photosynthesis equation, carbonation, hydrolysis and oxidation weathering, and the carbon moved each year by weathering and by burning fossil fuels.	14
Evaporation, transpiration, condensation and the causes of rainfall	Recall questions on evaporation and its controls, stomata and transpiration, condensation, dew point and condensation nuclei, the dry and saturated adiabatic lapse rates with a worked calculation, convectional, frontal and orographic rainfall, rain shadows, and how cloud droplets grow into rain.	15
Interception, runoff and catchment hydrology	Recall questions on interception, infiltration and infiltration capacity, infiltration-excess and saturated overland flow, percolation, throughflow and groundwater flow, porosity, permeability and the chalk aquifer, cryospheric processes, a discharge calculation, and fieldwork on infiltration and interception.	18
Photosynthesis, respiration, decomposition and combustion as carbon flows	Recall questions on gross and net primary productivity, productivity in rainforest and tundra, the respiration equation, soil respiration and the decomposition of a leaf, methane from waterlogged ground, wildfire and fossil fuel combustion, and the residence time of atmospheric carbon.	14
Natural sequestration in oceans, vegetation, sediments and rock	Recall questions on carbon sequestration, the solubility, biological and carbonate pumps, the formation of limestone, net carbon uptake by the oceans and land biosphere, soil carbon, carbon in sedimentary rock and silicate weathering, and blue carbon.	13
Stores, flows and physical controls in the tropical rainforest	Recall questions on the rainfall and temperature of the Amazon rainforest, its fast water cycle, interception and recycled rainfall, where its carbon is stored, rapid decomposition and latosols, and how temperature, rock permeability, relief and mineral composition control both cycles.	15
Deforestation, farming and forest management in an Amazon drainage basin	Recall questions on the causes and scale of Amazon deforestation, its effects on runoff, storm hydrographs, rainfall, soils and carbon, afforestation, agroforestry, selective logging and REDD+, the tipping point, the Amazon flood pulse, droughts and El Niño, record levels of the Rio Negro at Manaus, and comparing soil organic matter.	26
Stores, flows and seasonal change in the Arctic tundra	Recall questions on the precipitation and temperatures of the Arctic tundra, permafrost and the active layer, its slow water cycle, the permafrost carbon store and tundra vegetation, the short growing season, spring melt and seasonal carbon exchange, and the effects of bedrock, relief and albedo.	17
Oil and gas development in the Arctic tundra, and its management	Recall questions on the Prudhoe Bay field and the Trans-Alaska Pipeline, how construction thaws permafrost, and the measures used to limit the damage.	15
Dynamic equilibrium, land use change and water extraction	Recall questions on dynamic equilibrium in the cycles, how urban growth, ploughing, commercial forestry and peatland drainage change water and carbon stores, aquifers, confined and unconfined, the Great Artesian Basin, over-abstraction and the Ogallala aquifer, and the effects of surface extraction and reservoirs.	16
Fossil fuel combustion, carbon sequestration and feedback loops	Recall questions on the rise in atmospheric carbon dioxide since the industrial era, how much human carbon stays airborne, carbon capture and storage at Sleipner and its limits, the permafrost carbon, ice-albedo and water vapour feedbacks, negative feedbacks, and why methane matters.	14
Change over time in the cycles, and the monitoring that records it	Recall questions on daily and seasonal change in the cycles, the sawtooth carbon dioxide record, deciduous woodland and monsoon water cycles, long-term change through volcanic outgassing, the carbonate-silicate cycle, the Carboniferous and glacial periods, and monitoring by Mauna Loa, ice cores, flux towers and satellites.	18
Links and interdependence between the water and carbon cycles	Recall questions on how the oceans, cryosphere, atmosphere and a single leaf link the two cycles, ocean acidification, plant water use under higher carbon dioxide, human use of carbon stores, a more intense water cycle as the climate warms, glacier-fed rivers, drought turning forest into a carbon source, and sea-level rise.	15
Global strategies to protect the carbon and water cycles	Recall questions on afforestation and China's Three-North Shelterbelt, peatland restoration, soil carbon farming and agroforestry, carbon trading and the EU Emissions Trading System, the Paris Agreement and the Kyoto Protocol, improved forestry, integrated drainage basin management, water allocation, and shared river basins.	18

Earth’s Life Support Systems is 271 of the 3,740 questions in the guide.Get the guide, £7

How the guide is worked

Answering a question from memory stores it far better than reading the answer again. The guide runs that as a fixed procedure on one subtopic at a time, about twenty minutes a session.

Step 1 · Closed book
Cover the answers. Work through one subtopic and write down what you can. Leave blanks where you have nothing.
Step 2 · Open book
Go back to the top. Read each printed answer and write it out in full, including the ones you had right.
Step 3 · Closed book again
Same questions, same order, from memory. The gap between pass one and pass three is the session result.

Read the full method, the return schedule and the research behind it.