AQA A-level Geography · 3.1.1

Water, carbon, climate and life on Earth

50 exam-style questions with answers for 3.1.1 Water, carbon, climate and life on Earth in AQA A-level Geography (spec 7037). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 3.1.1.4 · Supporting life
Explain the importance of water stores and the water cycle for life on Earth. [3 marks]
Answer:
Water is a solvent and reactant needed for chemical reactions in cells, including photosynthesis (1); it provides habitats in oceans, rivers and lakes (1); the water cycle redistributes fresh water and heat, making land environments habitable (1).
Question 2 · Spec 3.1.1.4 · Supporting life
Explain the importance of carbon for life on Earth. [2 marks]
Answer:
Carbon is the basis of organic molecules such as carbohydrates, proteins and fats (1); the carbon cycle supplies carbon dioxide for photosynthesis and returns it through respiration and decay (1).
Question 3 · Spec 3.1.1.4 · Supporting life
Explain the natural greenhouse effect. [3 marks]
Answer:
Short-wave radiation from the Sun passes through the atmosphere and warms the Earth's surface (1); the surface emits long-wave radiation, which greenhouse gases absorb and re-emit (1); this keeps average temperatures at about 15 °C instead of about −18 °C, making life possible (1).
Question 4 · Spec 3.1.1.4 · Supporting life
Name two greenhouse gases that form part of the water and carbon cycles. [2 marks]
Answer:
Water vapour (1); carbon dioxide (or methane) (1).
Question 5 · Spec 3.1.1.4 · Supporting life
Explain how the water cycle helps to regulate climate. [3 marks]
Answer:
Evaporation absorbs energy as latent heat and condensation releases it (1); this transfers heat from the tropics towards higher latitudes (1); clouds reflect incoming radiation and trap outgoing heat, affecting temperature (1).
Question 6 · Spec 3.1.1.4 · Supporting life
Explain the role of the oceans in regulating climate. [3 marks]
Answer:
Oceans absorb large amounts of heat, moderating temperature change (1); ocean currents transfer heat around the globe (1); oceans absorb carbon dioxide, reducing the amount in the atmosphere (1).
Question 7 · Spec 3.1.1.4 · Supporting life
Explain how photosynthesis links the water and carbon cycles. [2 marks]
Answer:
Plants take in carbon dioxide and water (1); they use sunlight to produce glucose and oxygen, storing carbon in biomass and using water as a reactant (1).
Question 8 · Spec 3.1.1.4 · Supporting life
Explain how stomata link the water and carbon cycles. [2 marks]
Answer:
Carbon dioxide enters the leaf through stomata for photosynthesis (1); water vapour leaves through the same openings by transpiration (1).
Question 9 · Spec 3.1.1.4 · Atmospheric links
Compare the roles of water vapour and carbon dioxide in climate change. [3 marks]
Answer:
Water vapour is the most abundant greenhouse gas, but its concentration is controlled by temperature (1); carbon dioxide stays in the atmosphere for years to centuries and drives the initial warming (1); warming from carbon dioxide increases water vapour, amplifying the effect (1).
Question 10 · Spec 3.1.1.4 · Atmospheric links
Explain the water vapour feedback. [3 marks]
Answer:
Warming increases evaporation, so the atmosphere holds more water vapour (1); water vapour traps more outgoing heat (1); this causes further warming, so it is a positive feedback (1).
Question 11 · Spec 3.1.1.4 · Atmospheric links
Explain the ice-albedo feedback. [3 marks]
Answer:
Warming melts snow and ice, which are highly reflective (1); the darker land or ocean surfaces beneath absorb more solar radiation (1); this causes more warming and more melting, a positive feedback (1).
Question 12 · Spec 3.1.1.4 · Atmospheric links
Explain why the effect of clouds on climate is complex. [3 marks]
Answer:
Low clouds reflect incoming solar radiation, cooling the surface (1); high, thin clouds trap outgoing heat, warming it (1); the net effect of changing cloud cover on warming is uncertain (1).
Question 13 · Spec 3.1.1.4 · Atmospheric links
Explain how precipitation removes carbon dioxide from the atmosphere. [2 marks]
Answer:
Carbon dioxide dissolves in raindrops, forming weak carbonic acid (1); it reaches the ground and oceans, where weathering and ocean uptake store the carbon (1).
Question 14 · Spec 3.1.1.4 · Atmospheric links
Explain how ocean circulation links the water and carbon cycles. [3 marks]
Answer:
Cold, salty surface water absorbs carbon dioxide and sinks in the North Atlantic and around Antarctica (1); deep currents store carbon for hundreds of years (1); upwelling returns carbon-rich water to the surface, where some may be released to the atmosphere (1).
Question 15 · Spec 3.1.1.4 · Feedbacks and climate change
What is a tipping point in the climate system? [1 mark]
Answer:
A threshold beyond which a small change causes a large, often irreversible, shift in a system.
Question 16 · Spec 3.1.1.4 · Feedbacks and climate change
Explain how rainforests recycle water and why this makes them vulnerable to deforestation. [3 marks]
Answer:
Transpiration and evaporation return water to the atmosphere, forming cloud and rain over the forest (1); removing trees reduces this recycling, so rainfall falls and the climate becomes drier (1); dry conditions favour fire and further forest loss, a positive feedback (1).
Question 17 · Spec 3.1.1.4 · Feedbacks and climate change
Explain how forest dieback in the Amazon could affect both the water and carbon cycles. [3 marks]
Answer:
Fewer trees reduce transpiration and rainfall, causing drought (1); dead and burnt trees release stored carbon to the atmosphere (1); less photosynthesis means less carbon uptake, increasing warming (1).
Question 18 · Spec 3.1.1.4 · Feedbacks and climate change
Explain how warming of sediments could cause a positive feedback involving methane hydrates. [3 marks]
Answer:
Methane hydrates are frozen methane stored in ocean sediments and permafrost (1); warming can destabilise them, releasing methane to the atmosphere (1); methane is a powerful greenhouse gas, so it causes more warming and more release (1).
Question 19 · Spec 3.1.1.4 · Feedbacks and climate change
Give two examples of negative feedback in the climate system. [2 marks]
Answer:
More low cloud reflecting sunlight (1); increased plant growth taking up more carbon dioxide (1).
Question 20 · Spec 3.1.1.4 · Feedbacks and climate change
Explain how climate change is altering the water cycle. [3 marks]
Answer:
Warmer air holds more water vapour, so evaporation and the intensity of heavy precipitation increase (1); patterns shift, with many wet regions becoming wetter and dry regions drier (1); glaciers and ice sheets melt, changing river flows and raising sea level (1).
Question 21 · Spec 3.1.1.4 · Feedbacks and climate change
Explain how climate change is altering carbon stores on land and in the ocean. [3 marks]
Answer:
Warming and drought can increase fire, decomposition and thaw, releasing carbon from forests, soils and permafrost (1); longer growing seasons may increase plant uptake in some areas (1); the oceans absorb more carbon dioxide but become more acidic and absorb less as they warm (1).
Question 22 · Spec 3.1.1.4 · Implications for life
Suggest implications of changes in the water and carbon cycles for food production. [3 marks]
Answer:
Droughts and floods damage crops and reduce yields (1); shifting climate zones change where crops can be grown (1); ocean acidification and warming reduce fish stocks and coral reef productivity (1).
Question 23 · Spec 3.1.1.4 · Implications for life
Suggest implications of changes in the water and carbon cycles for ecosystems. [3 marks]
Answer:
Warming and acidification cause coral bleaching and loss of marine biodiversity (1); species must migrate or adapt as climate zones shift (1); drought, fire and permafrost thaw change terrestrial habitats (1).
Question 24 · Spec 3.1.1.4 · Implications for life
Suggest implications of sea level rise for people. [2 marks]
Answer:
Coastal flooding and erosion threaten low-lying settlements, farmland and infrastructure (1); salt water contaminates freshwater supplies and people may be displaced (1).
Question 25 · Spec 3.1.1.4 · Implications for life
Explain how changes in the water and carbon cycles cause sea level to rise. [3 marks]
Answer:
Melting of glaciers and ice sheets adds water to the oceans (1); warmer water expands (thermal expansion) (1); groundwater extraction and runoff add to the ocean store (1).
Question 26 · Spec 3.1.1.4 · Human interventions
Explain how afforestation can mitigate climate change. [2 marks]
Answer:
Growing trees absorb carbon dioxide by photosynthesis and store carbon in biomass (1); forests also help regulate the water cycle by increasing interception and infiltration (1).
Question 27 · Spec 3.1.1.4 · Human interventions
Explain how protecting existing forests helps reduce carbon emissions. [2 marks]
Answer:
Intact forests store large amounts of carbon and continue to absorb carbon dioxide (1); schemes such as REDD+ pay countries not to cut forest, preventing release of stored carbon (1).
Question 28 · Spec 3.1.1.4 · Human interventions
Explain how peatland restoration helps reduce carbon emissions. [2 marks]
Answer:
Re-wetting drained peat stops it drying and oxidising, which releases carbon dioxide (1); waterlogging restores peat formation so the peatland can act as a carbon sink again (1).
Question 29 · Spec 3.1.1.4 · Human interventions
Explain how changing farming practices can increase soil carbon storage. [2 marks]
Answer:
Reduced ploughing (no-till) and cover crops leave more organic matter in soils (1); adding manure or compost and agroforestry increase carbon stored in soils and biomass (1).
Question 30 · Spec 3.1.1.4 · Human interventions
Explain how carbon capture and storage (CCS) works. [3 marks]
Answer:
Carbon dioxide is captured from power stations or industrial plants before it reaches the atmosphere (1); it is transported by pipeline or ship (1); it is stored underground, for example in depleted oil and gas fields or saline aquifers (1).
Question 31 · Spec 3.1.1.4 · Human interventions
Explain how biofuels can reduce net carbon emissions. [2 marks]
Answer:
Plants used for fuel absorb carbon dioxide as they grow (1); burning them releases roughly the same carbon, so net emissions are lower than from fossil fuels, though land use change can reduce this benefit (1).
Question 32 · Spec 3.1.1.4 · Human interventions
Explain how blue carbon ecosystems help to mitigate climate change. [2 marks]
Answer:
Mangroves, seagrass and saltmarshes absorb carbon dioxide by photosynthesis (1); waterlogged sediments store carbon for centuries, so protecting them keeps carbon locked away (1).
Question 33 · Spec 3.1.1.4 · Human interventions
Explain what is meant by ocean iron fertilisation and one risk associated with it. [2 marks]
Answer:
Adding iron to the ocean to stimulate phytoplankton growth so more carbon dioxide is taken up (1); risk: it may harm ecosystems, cause oxygen depletion, and the carbon may not stay stored (1).
Question 34 · Spec 3.1.1.4 · Human interventions
Outline the aims of the 2015 Paris Agreement. [3 marks]
Answer:
To limit global warming to well below 2 °C above pre-industrial levels (1); and pursue efforts to limit it to 1.5 °C (1); countries set their own national emission targets and report progress (1).
Question 35 · Spec 3.1.1.4 · Human interventions
Explain how carbon taxes or emissions trading can reduce carbon emissions. [2 marks]
Answer:
They put a price on carbon dioxide emissions, making fossil fuels more expensive (1); this encourages companies to cut emissions or switch to cleaner energy (1).
Question 36 · Spec 3.1.1.4 · Human interventions
Suggest why international action to reduce carbon emissions is difficult. [3 marks]
Answer:
Economies still rely heavily on fossil fuels (1); countries differ in wealth and responsibility, and some argue that developing countries should be allowed to grow (1); agreements rely on voluntary commitments that are hard to enforce (1).
Question 37 · Spec 3.1.1.4 · Human interventions
Explain how a shift to renewable energy changes carbon transfers. [2 marks]
Answer:
It reduces the burning of fossil fuels, so less carbon is moved from the lithosphere to the atmosphere (1); solar, wind and hydro generate energy without direct carbon dioxide emissions in use (1).
Question 38 · Spec 3.1.1.4 · Rainforest case study
Describe the water cycle in a tropical rainforest. [3 marks]
Answer:
High rainfall (over 2,000 mm a year) (1); dense canopy gives high interception and high transpiration (1); water is recycled rapidly, with a large share of rainfall returned to the atmosphere and cloud forming locally (1).
Question 39 · Spec 3.1.1.4 · Rainforest case study
Describe the carbon cycle in a tropical rainforest. [3 marks]
Answer:
A very large store of carbon in biomass, in trees and other vegetation (1); rapid cycling, as high temperatures and moisture give fast growth and decomposition (1); nutrients and carbon are held mainly in the biomass, and the soil store is relatively thin (1).
Question 40 · Spec 3.1.1.4 · Rainforest case study
Describe the main causes of deforestation in the Amazon rainforest. [3 marks]
Answer:
Any three from: clearing land for cattle ranching (1); soy and other commercial crops (1); logging (1); road building which opens up forest (1); mining and settlement (1).
Question 41 · Spec 3.1.1.4 · Rainforest case study
Explain how deforestation in the Amazon has changed the water cycle. [3 marks]
Answer:
Less interception and transpiration reduce the water returned to the atmosphere (1); more overland flow and soil erosion increase runoff and river sedimentation (1); reduced evaporation lowers regional rainfall and lengthens dry seasons (1).
Question 42 · Spec 3.1.1.4 · Rainforest case study
Explain how deforestation and fire may change parts of the Amazon from a carbon sink to a carbon source. [2 marks]
Answer:
Burning and decay of cleared vegetation release large amounts of carbon dioxide (1); drought and degradation reduce uptake by the remaining forest, so emissions may exceed absorption (1).
Question 43 · Spec 3.1.1.4 · River catchment case study
Explain how field data on rainfall and discharge can be used to assess flood risk in a catchment. [3 marks]
Answer:
Comparing rainfall with river discharge shows lag times and peak flows (1); repeated events show how antecedent conditions and intensity affect the hydrograph (1); the data can identify the rainfall needed to reach bankfull discharge (1).
Question 44 · Spec 3.1.1.4 · River catchment case study
Describe how field data could be used to investigate the effect of land use on drainage basin stores. [3 marks]
Answer:
Measure infiltration rates at sites with different land uses, such as woodland, pasture and compacted ground (1); measure soil moisture and interception at each site (1); compare results to show how land use alters stores and flows (1).
Question 45 · Spec 3.1.1.4 · River catchment case study
Explain how a reservoir can both support and harm sustainable water supply. [3 marks]
Answer:
It stores winter surplus water for use in dry periods, giving a reliable supply (1); it can flood land, alter river flow and trap sediment downstream (1); high evaporation losses and abstraction can reduce river flow and damage habitats (1).
Question 46 · Spec 3.1.1.4 · Quantitative skills
Atmospheric carbon dioxide rose from 280 ppm to 420 ppm. Calculate the percentage increase. [2 marks]
Answer:
(420 − 280) ÷ 280 × 100 (1); = 50% (1).
Question 47 · Spec 3.1.1.4 · Quantitative skills
A carbon flux is 5 GtC per year. Express this in tonnes of carbon per year (1 Gt = 1,000,000,000 tonnes). [1 mark]
Answer:
5,000,000,000 tonnes (5 × 10⁹) per year.
Question 48 · Spec 3.1.1.4 · Quantitative skills
A reservoir holds 120 million m³. In one month, 30 million m³ flows in and 22 million m³ is lost. Calculate the new volume. [2 marks]
Answer:
Net change = 30 − 22 = +8 million m³ (1); new volume = 128 million m³ (1).
Question 49 · Spec 3.1.1.4 · Quantitative skills
Describe how field data on soil organic carbon could be collected. [3 marks]
Answer:
Take soil cores at randomly or systematically chosen sample points (1); dry and weigh the samples, then burn off organic matter (loss on ignition) and reweigh (1); calculate the percentage of organic matter and compare between sites or land uses (1).
Question 50 · Spec 3.1.1.4 · Feedbacks and climate change
Explain how warming oceans could act as a positive feedback for atmospheric carbon dioxide. [2 marks]
Answer:
Warmer water dissolves less carbon dioxide, so the oceans absorb less (1); more carbon dioxide stays in the atmosphere, causing further warming (1).

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Water, carbon, climate and life on Earth

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