2026 Cambridge IGCSE Environmental Management (0680) 模擬試題連答案詳解

Limestone is a sedimentary rock formed from compressed sediments and skeletal fragments of marine organisms. Most sedimentary rocks (including limestone and sandstone) contain interconnected pore spaces that allow water to pass through, making them permeable.

- Basalt is an extrusive igneous rock and is impermeable.
- Marble is a metamorphic rock formed from limestone and is impermeable.
- Sandstone is a sedimentary rock and is permeable.

B [1]

(a) Potable water is water that is safe to drink / suitable for human consumption.
(b) Chlorination is carried out to kill harmful bacteria, pathogens, and microorganisms, sterilising or disinfecting the water supply.
(c) Rural communities are often geographically isolated or sparsely populated, making the capital investment required to lay water supply pipes and build treatment stations economically challenging compared to densely populated urban centres.

(a) M1: water that is safe to drink / suitable for human consumption [1]
(b) M1: to kill pathogens / bacteria / microorganisms / sterilise / disinfect [1] (reject: just 'to clean the water' / 'to filter out dirt')
(c) M1: any valid reason [1], e.g.:
- high cost of laying pipes / infrastructure across long / remote distances;
- lower population density makes piped water networks less cost-effective;
- lack of government investment / funding in remote rural communities.

(a) Two strategies to manage marine harvesting include establishing legal fishing quotas (catch limits) and introducing closed fishing seasons during breeding periods.
(b) Enforcing minimum net mesh sizes allows small, juvenile fish to escape capture and survive until they reach reproductive maturity, replenishing the fish population.

(a) Award 1 mark for each valid strategy up to max [2]:
- fishing quotas / catch limits [1];
- closed seasons / banning fishing during breeding periods [1];
- marine protected areas (MPAs) / marine reserves / no-take zones [1];
- restricting gear / banning destructive methods (e.g. drift nets / benthic trawls) / promoting pole and line [1];
- international fishing agreements / conservation legislation [1].
(b) M1: allows young / juvenile / immature / small fish to escape so they can reach maturity / reproduce [1].

(a) The vector for malaria is the female Anopheles mosquito.
(b) The disease is caused by a protozoan parasite belonging to the genus Plasmodium.
(c) Vector control can be achieved by removing or draining stagnant bodies of water to eliminate breeding sites, spraying indoor residual insecticides to kill adult mosquitoes, or adding fish to water bodies to consume larvae.

(a) M1: female Anopheles (mosquito) [1] (accept: Anopheles mosquito; reject: just 'mosquito')
(b) M1: Plasmodium [1]
(c) M1: one valid vector control method with description [1], e.g.:
- draining / covering standing / stagnant water to remove breeding sites;
- spraying insecticides / indoor residual spraying (IRS) to kill mosquitoes;
- pouring oil / film on water surfaces to prevent larvae from breathing / suffocating larvae;
- introducing biological control / fish that eat mosquito larvae;
- applying larvicides to water bodies.
(reject: personal protection methods such as using bed nets or taking antimalarial medication as these do not constitute vector control).

(a) In order from the Earth's surface upwards: Layer W is the troposphere (0 to 12 km), Layer X is the stratosphere (12 to 50 km), Layer Y is the mesosphere (50 to 85 km), and Layer Z is the thermosphere (85 to 600 km).

(b)(i) The stratospheric ozone layer is located in Layer X (stratosphere), primarily between 15 km and 35 km altitude.
(b)(ii) The dense lowest layer containing the majority of atmospheric gases (78% nitrogen, 21% oxygen) and where weather processes occur is Layer W (troposphere).

(a) 1.5 marks total (0.5 marks for each correct layer):
- Layer W: troposphere [0.5]
- Layer X: stratosphere [0.5]
- Layer Z: thermosphere [0.5]
(Reject: mesosphere for W, X, or Z; accept phonetic spelling)

(b)(i) X [1.0] (allow: stratosphere)
(b)(ii) W [1.0] (allow: troposphere)

(a) Stage A uses screens/bars to remove coarse debris, known as screening. Stage B allows suspended solid particles to settle by gravity, known as sedimentation (or settling). Stage D adds a chemical agent like chlorine gas or hypochlorite to kill pathogens, known as chlorination (or disinfection).

(b)(i) Passing water through beds of sand and gravel to trap smaller insoluble particles is filtration.
(b)(ii) Potable water is water of sufficient quality that is safe and fit for human consumption and drinking without causing illness.

(a) 1.5 marks total (0.5 marks each):
- Stage A: screening [0.5] (allow: coarse filtration / bar screen)
- Stage B: sedimentation [0.5] (allow: settling / clarification)
- Stage D: chlorination [0.5] (allow: disinfection / sterilisation)

(b)(i) filtration [1.0] (allow: sand filtration)
(b)(ii) water that is safe / fit to drink / suitable for human consumption [1.0] (reject: just 'clean water' or 'pure water' without reference to drinking/safe consumption)

1. Dead trees and vegetation fall into waterlogged, oxygen-poor swamps or marshes, which prevents full decomposition by microorganisms.
2. Over time, layers of mud, sand, and other sediments build up above the organic layer.
3. The increasing weight creates high pressure and heat, which expels moisture and gases, compressing the material into solid coal over millions of years.

Award marks for any valid process points (up to 2.5 marks):
- M1: Accumulation of dead plant material / trees in swamps / wetlands / anoxic conditions (preventing decay);
- M2: Burial by successive layers of sediment / silt / sand;
- M3: Compaction under high heat and pressure over millions of years / long periods of time.

[Allow: peat formation as an intermediate stage]
[Reject: reference to marine organisms / plankton / algae converting into coal]

1. Screening: River water is passed through metal grids or screens to trap and remove large floating debris, leaves, and litter.
2. Sedimentation: The water sits in settling tanks so heavy suspended solids and silt sink to the bottom.
3. Filtration: Water passes through layers of sand and gravel to remove smaller suspended particles.
4. Chlorination: A controlled amount of chlorine is added to disinfect the water by killing pathogenic bacteria and microorganisms.

Award marks for describing the correct sequence of water treatment stages (up to 2.5 marks):
- M1: Screening to remove large debris / litter / floating objects;
- M2: Sedimentation / settling tanks to allow suspended solids / soil particles to settle;
- M3: Filtration (through sand / gravel) to remove fine / smaller insoluble particles;
- M4: Chlorination / adding chlorine to kill bacteria / pathogens / disinfect water.

[Note: 3 stages correctly matched with purpose = 2.5 marks; 2 stages = 1.5 marks; 1 stage = 0.5 marks]
[Reject: boiling or distillation as large-scale municipal water treatment steps unless explicitly qualified]

To construct the bar chart correctly:
1. Axes and Labels: Label the horizontal axis ($x$-axis) as 'Energy resource' (and name each resource: Solar, Wind, Hydro-electric, Biomass, Geothermal). Label the vertical axis ($y$-axis) as 'Electricity generated / TWh'.
2. Scale: Choose a sensible linear scale on the vertical axis starting at 0 and going up to at least 70 or 80 TWh (e.g., 10 TWh per major grid division) so the data occupies more than 50% of the available grid height.
3. Plotting: Plot the height of each bar accurately:
- Solar: 42 TWh
- Wind: 68 TWh
- Hydro-electric: 54 TWh
- Biomass: 26 TWh
- Geothermal: 18 TWh
4. Presentation: Draw bars with equal widths and consistent spacing between bars using a ruler.

Award [1] for each of the following points (up to 4 marks total):
- M1 (Axes): Both axes labelled with quantity and correct units on vertical axis ('Electricity generated / TWh' or 'Electricity generated in TWh') and categories/energy resources clearly identified on the horizontal axis [1]
- M2 (Scale): Linear and sensible scale on vertical axis where plotted data occupies more than half the grid height [1]
- M3 (Plotting): All 5 bars accurately plotted to within $\pm$ half a small square [1]
(Allow 1 error in plotting for [0] on M3)
- M4 (Bar presentation): Bars drawn of equal width with equal spacing between bars (or touching consistently) using straight lines [1]

Step 1: Identify and sum the electricity generated from renewable sources (hydro-electric, wind, and solar):
$$\text{Renewable electricity} = 63 + 45 + 27 = 135\text{ TWh}$$

Step 2: Divide by the total electricity generated and multiply by 100:
$$\text{Percentage} = \left(\frac{135}{450}\right) \times 100 = 30\%$$

M1: Correct identification and sum of renewable energy generation (63 + 45 + 27 = 135) OR correct fraction formulation (135 / 450);
A1: 30(%) [allow ECF if single addition error in numerator but method is correct]

Step 1: Determine the decrease in fish catch:
$$\text{Decrease} = 84\,000 - 54\,600 = 29\,400\text{ tonnes}$$

Step 2: Calculate the percentage decrease relative to the original 2013 catch:
$$\text{Percentage decrease} = \left(\frac{29\,400}{84\,000}\right) \times 100 = 35\%$$

M1: Correct subtraction to find change (84 000 - 54 600 = 29 400) OR correct calculation setup ((29 400 / 84 000) * 100);
A1: 35(%)

Step 1: Use the formula for population density:
$$\text{Population density} = \frac{\text{Total population}}{\text{Total land area}}$$

Step 2: Substitute the values:
$$\text{Population density} = \frac{408\,000}{2\,400} = 170\text{ people per km}^2$$

M1: Correct substitution into density formula (408 000 / 2 400);
A1: 170 (people per km²)

Step 1: Set up the trophic efficiency calculation:
$$\text{Transfer percentage} = \left(\frac{\text{Energy in primary consumers}}{\text{Energy in primary producers}}\right) \times 100$$

Step 2: Substitute the data into the equation:
$$\text{Transfer percentage} = \left(\frac{5\,760}{48\,000}\right) \times 100 = 12\%$$

M1: Correct ratio or calculation setup ((5 760 / 48 000) * 100);
A1: 12(%)

Three distinct environmental impacts are: upstream flooding submerges terrestrial vegetation and habitats; the physical dam wall acts as a barrier to migrating aquatic species such as fish; downstream water bodies lose sediment load because silt is trapped behind the dam wall, reducing nutrient replenishment on downstream agricultural floodplains and causing riverbed scouring.

Award 1 mark for each valid point up to a maximum of 3 marks:
• M1: Upstream flooding of terrestrial habitats / displacement of wildlife / loss of biodiversity;
• M2: Disruption of aquatic migration / barrier to fish breeding cycles;
• M3: Trapping of silt / sediment behind the dam, reducing downstream soil fertility / causing riverbed erosion downstream;
• Allow: Greenhouse gas emissions ( ext{CH}_4/ ext{CO}_2) from decomposing submerged vegetation in the reservoir;
• Allow: Alteration of downstream water temperature / dissolved oxygen levels / flow regimes;
• Reject: General economic or social impacts (e.g. displacement of people).

Increasing the minimum mesh size allows juvenile and non-target small fish to pass through the net without being captured. By surviving, these young fish are able to grow to sexual maturity and reproduce, thereby sustaining the fish population and preventing recruitment overfishing.

Award 1 mark for each point up to a maximum of 3 marks:
• M1: Juvenile / young / immature fish are able to escape through the wider gaps;
• M2: Fish survive to reach reproductive maturity / adult breeding age;
• M3: Allows fish to reproduce / spawn / replenish the population stocks / maintain sustainable recruitment;
• Allow: Reduces accidental bycatch of non-target small species;
• Reject: Vague statements such as 'stops all overfishing' without explaining the mechanism of juvenile survival.

Transport policies can target fossil fuel reduction via three main mechanisms: investing in efficient, low-cost electrified public transport reduces single-occupancy petrol/diesel car journeys; establishing dedicated active travel infrastructure (cycle tracks and walkways) promotes zero-emission movement; and applying economic deterrents such as congestion charges or low-emission zones discourages driving inefficient combustion-engine vehicles.

Award 1 mark for each developed point up to a maximum of 3 marks:
• M1: Developing / subsidising electrified public transport (e.g. electric buses / trams / metro) to reduce private vehicle journeys;
• M2: Creating infrastructure for active travel (e.g. dedicated cycle lanes / pedestrianised streets / park-and-ride schemes);
• M3: Introducing economic disincentives (e.g. congestion charging / low-emission zones / higher parking levies for high-emission vehicles);
• Allow: Subsidies or preferential parking / charging infrastructure for electrically propelled vehicles (EVs);
• Reject: Vague statements such as 'tell people to stop driving' without specifying a policy measure.

Manufacturing industries can adopt several sustainable resource strategies: recycling post-consumer and industrial scrap metal decreases demand for newly mined ore; substituting scarce metals with alternative materials (such as engineered bio-plastics or composites) extends finite supplies; and improving manufacturing and smelting efficiency ensures that less raw material is discarded as waste.

Award 1 mark for each distinct strategy up to a maximum of 3 marks:
• M1: Recycling scrap metals / mineral-based waste into new manufacturing cycles;
• M2: Substituting scarce minerals with alternative / renewable materials (e.g. plant-based composites / abundant alternatives);
• M3: Increasing extraction / manufacturing / smelting efficiency to reduce mineral waste during production;
• Allow: Designing modular products that can be easily repaired, reused, or disassembled for component reclamation;
• Allow: Reducing the quantity of raw material required per product unit (lightweighting);
• Reject: Vague 'stop extracting ores' or 'use less electricity'.

Vector control targets the mosquito vector at different life stages: eliminating standing water removes breeding habitats; applying biological control or larvicides destroys aquatic larvae; and applying indoor residual insecticide sprays kills adult female Anopheles mosquitoes, preventing the vector from biting an infected host and transmitting the Plasmodium parasite to uninfected individuals.

Award 1 mark for each point up to a maximum of 3 marks:
• M1: Draining standing / stagnant water / clearing drainage channels removes breeding habitats, preventing mosquito larvae from developing;
• M2: Applying biological control (e.g. fish eating larvae) or chemical larvicides destroys larvae before they become flying adults;
• M3: Indoor residual spraying (IRS) with insecticides kills adult female Anopheles mosquitoes, halting the transfer of the Plasmodium parasite between human hosts;
• Allow: Reference to clearing dense vegetation / brush near dwellings to remove adult mosquito resting sites;
• Reject: Personal protection measures (e.g. bed nets, insect repellent, antimalarial medication) since the question specifically asks for vector control.

Energy transfer between consecutive trophic levels is inefficient, with roughly 10% passed on. The remaining 90% of energy is lost as heat generated during cellular respiration, used in metabolic processes and locomotion, or lost in excretory and egested waste (faeces). Consequently, the total available energy declines rapidly along the food chain until insufficient energy remains to support another viable predator population.

Award 1 mark for each point up to a maximum of 3 marks:
• M1: Inefficiency of energy transfer / only ~10% of energy is transferred from one trophic level to the next;
• M2: Energy is lost as heat / through cellular respiration / movement / excretion / egested faeces / unconsumed biomass;
• M3: After 4 or 5 levels, the remaining energy is too small to support a viable breeding population of higher-level consumers / apex predators;
• Reject: Energy is 'destroyed' or 'disappears'.

Under natural waterlogged conditions, anaerobic conditions slow down organic decay. When wetlands are drained, oxygen enters the soil, enabling aerobic microorganisms to rapidly decompose stored peat and organic matter, releasing carbon dioxide into the air. In addition, the loss of wetland plants eliminates a photosynthetic carbon sink.

Award 1 mark for each valid reason up to a maximum of 2 marks:
• M1: Drainage allows atmospheric oxygen to penetrate soil / creates aerobic conditions, enabling rapid microbial decomposition / respiration of stored organic matter / peat, which releases ext{CO}_2;
• M2: Removal / destruction of wetland vegetation eliminates an active carbon sink / reduces uptake of ext{CO}_2 by photosynthesis;
• Allow: Dried peat becomes susceptible to accidental or intentional burning, which releases stored carbon directly as ext{CO}_2;
• Reject: General 'pollution from tractors' unless linked directly to the wetland conversion process.

Floating booms encircle and trap the floating oil, stopping the surface slick from drifting toward sensitive intertidal mudflats, beaches, and coral reefs. Chemical detergent sprays break up continuous oil slicks into microscopic droplets; this increases the surface area for oil-degrading microbes and prevents the formation of thick surface layers that coat the feathers of seabirds and the fur/skin of marine mammals.

Award 1 mark for the explanation of each technique:
• M1 (Floating booms): Contain / physically trap the floating oil slick on the surface, preventing it from reaching / coating sensitive shorelines / beaches / coral reefs / mangroves;
• M2 (Chemical detergent sprays): Break the oil slick into small droplets / disperse the oil, which increases surface area for microbial biodegradation / prevents surface oil from coating marine mammals / seabirds;
• Reject: Statement that detergents 'destroy' or 'dissolve' oil completely without explaining dispersal into droplets / accelerated breakdown.

To encourage homeowners to reduce domestic energy consumption, local authorities can:
1. Offer financial incentives, such as grants or subsidies, to lower the upfront cost of installing loft insulation, cavity wall insulation, or solar panels.
2. Introduce or tighten local building codes and regulations that require mandatory minimum energy efficiency standards, such as double or triple glazing and heat pump installations.
3. Implement educational initiatives, free energy assessment audits, or subsidised smart meters to help residents monitor and reduce their energy usage.

Award 1 mark for each valid strategy, up to a maximum of 3 marks:
- financial incentives / subsidies / grants / tax reductions for installing insulation (e.g. loft / cavity wall) or energy-efficient devices (e.g. heat pumps / solar panels) [1];
- implementing / enforcing stricter building codes / regulations (e.g. requiring double glazing / efficient heating) [1];
- public education campaigns / workshops promoting energy-saving behaviours [1];
- offering free / subsidised home energy audits or smart meters [1];
- subsidising / promoting energy-efficient lighting (e.g. LED bulbs) / high-efficiency appliances [1].

[Total: 3]

Recycling metals supports sustainability by:
1. Conserving finite reserves of mineral ores because less virgin rock needs to be mined from the ground.
2. Saving substantial amounts of energy; remelting scrap metal uses far less electricity and fossil fuels than the refining and smelting of raw ore.
3. Minimising the environmental degradation associated with open-cast or deep mining, such as land clearance, overburden waste, soil erosion, and water contamination from tailings.

Award 1 mark for each valid explanation, up to a maximum of 3 marks:
- reduces the rate of extraction / prevents rapid depletion of finite / non-renewable mineral reserves [1];
- uses less energy / electricity compared to mining, refining, and smelting primary ores [1];
- lowers greenhouse gas emissions / air pollution associated with fossil fuel combustion during mineral extraction [1];
- reduces environmental impacts of mining (e.g. habitat destruction / deforestation / overburden disposal / toxic tailings) [1];
- reduces the volume of solid waste sent to landfill sites [1].

[Total: 3]

A minimum mesh size ensures that the holes in fishing nets are large enough for immature and undersized fish to swim through and escape. As a result, juvenile fish can survive until they reach reproductive age and spawn, replenishing the population. This prevents overfishing of breeding stocks and reduces unwanted bycatch.

Award 1 mark for each distinct marking point, up to a maximum of 3 marks:
- allows juvenile / young / immature fish to escape through the net [1];
- enables fish to reach sexual maturity / reproductive age [1];
- allows fish to spawn / reproduce and replenish the population / maintain breeding stock [1];
- reduces the capture / bycatch of non-target or undersized marine species [1].

[Total: 3]

Apart from generating hydro-electric power, a multipurpose dam provides multiple advantages:
1. It creates a large reservoir that stores water for irrigating farmland during dry seasons or drought.
2. It secures a dependable supply of fresh water for drinking, domestic needs, and local industries.
3. It controls downstream flooding by retaining peak flow during heavy precipitation and releasing water at a controlled rate.
4. It can also create opportunities for inland aquaculture, tourism, and water-based recreation.

Award 1 mark for each valid suggestion, up to a maximum of 3 marks:
- stores water for irrigation of crops (especially in dry seasons / during drought) [1];
- provides a reliable supply of potable / domestic / industrial fresh water [1];
- controls flooding downstream by regulating river flow / storing excess storm water [1];
- creates a reservoir that can be used for aquaculture / fish farming [1];
- provides opportunities for recreation / water sports / tourism [1];
- creates a transport route / improves navigability on the reservoir [1].

[Note: Reject any mention of hydro-electric power / electricity generation as it is excluded in the question.]

[Total: 3]

Vector control targets the mosquito vector to stop the transmission of the Plasmodium parasite:
1. Removing or draining standing water (such as puddles, ditches, and uncovered containers) eliminates breeding habitats where female Anopheles mosquitoes lay eggs.
2. Treating water bodies with biological control agents (e.g. larva-eating fish) or applying larvicides/insecticides kills mosquito larvae before they develop into flying adults.

Award 1 mark for each valid vector control method, up to a maximum of 2 marks:
- draining / filling in / covering stagnant / standing water to remove breeding sites [1];
- introducing biological control agents (e.g. fish that eat larvae / bacteria such as Bacillus thuringiensis) into water bodies [1];
- applying insecticides / larvicides to breeding pools / water surfaces [1];
- spraying residual insecticides on interior walls where adult mosquitoes rest [1];
- applying a thin film of oil / biodegradable surfactant to standing water to suffocate larvae [1].

[Note: Reject personal protection measures, e.g. mosquito nets, repellent sprays on skin, or antimalarial medication, as the question specifies vector control.]

[Total: 2]

Arguments supporting aquaculture over wild harvesting:
- Reduces pressure on wild fish stocks, helping depleted marine populations recover from overfishing.
- Eliminates bycatch of non-target marine animals and avoids destructive fishing techniques like bottom trawling that damage seabed habitats.
- Delivers a stable, reliable food supply with controlled harvest timings to meet increasing global protein demands.
- Aquaculture facilities can be situated nearer to supply chains, reducing transport logistics.

Arguments opposing aquaculture / in favour of sustainable wild harvesting:
- Many farmed species are carnivorous and require fishmeal made from wild-caught pelagic fish, which continues to stress marine food webs.
- High stocking densities in pens lead to outbreaks of parasites and infectious diseases, which can spread to native wild stocks.
- Uneaten feed and concentrated faecal waste cause nutrient enrichment (eutrophication), reducing dissolved oxygen in surrounding waters.
- Escaped farmed fish can outcompete native species or cause genetic dilution.
- Clearing of vital coastal ecosystems (e.g. mangrove forests for coastal ponds) leads to loss of biodiversity and nursery grounds.
- Wild fisheries can be operated sustainably through effective management tools such as quotas, minimum mesh sizes, no-take zones, and closed seasons.
- Millions of artisanal and subsistence fishers rely directly on wild marine harvesting for nutrition and livelihoods.

Conclusion / Evaluation:
Aquaculture is a valuable supplement to meet global seafood demand and alleviate wild stock depletion, but it cannot completely replace wild fisheries due to ecological impacts, feed dependencies, and socio-economic reliance on artisanal fishing. A combination of well-regulated aquaculture and sustainable wild fishery management is the most viable approach.

Level 3 (5–6 marks):
- A balanced and well-developed evaluation discussing both the advantages of marine aquaculture and its environmental/practical limitations relative to wild fisheries.
- Uses precise environmental terminology accurately (e.g. overfishing, bycatch, eutrophication, disease transmission, fishmeal demand, habitat destruction, quotas).
- Provides a clear, reasoned judgment/conclusion linked to the arguments presented.

Level 2 (3–4 marks):
- A sound discussion offering arguments on both sides or a well-developed argument focused primarily on one perspective.
- Uses appropriate environmental terminology with relevant supporting points.

Level 1 (1–2 marks):
- Basic points, unsupported assertions, or an isolated list of features of aquaculture/fishing.
- Lacks balance and depth of explanation.

0 marks:
- No creditable response.

To calculate the actual distance in kilometres:

$$\text{Actual distance} = \text{Map distance} \times \text{Scale factor}$$
$$\text{Actual distance} = 4.8\text{ cm} \times 2.5\text{ km/cm} = 12\text{ km}$$

12 (\(\text{km}\)) [1]

Allow \(12.0\)

From the table, the mean weed density values are: Sector A = 3.0, Sector B = 6.0, Sector C = 1.5, Sector D = 9.0, Sector E = 4.0. The lowest value is 1.5 weeds per ha, which corresponds to Sector C.

Sector C / C [1]

Allow: Sector C (1.5 weeds per ha)
Reject: 1.5 without identifying Sector C

1. Identify the formula for population density:
\[\text{Population density} = \frac{\text{Total population}}{\text{Land area in }\text{km}^2}\]

2. Substitute the given values:
\[\text{Population density} = \frac{3\,615\,000}{48\,200} = 75\]

3. State the correct unit: \(\text{people per km}^2\) (or \(\text{people/km}^2\)).

M1 for correct calculation: \(\frac{3\,615\,000}{48\,200} = 75\) [1];
M2 for correct unit: people per \(\text{km}^2\) / people/\(\text{km}^2\) / persons per \(\text{km}^2\) [0.75].
(Allow ECF if correct division method shown with transcription error).

1. Calculate the natural increase in population:
\[\text{Natural increase} = \text{Births} - \text{Deaths} = 6\,720 - 2\,160 = 4\,560\]

2. Calculate the percentage rate of natural increase relative to the starting population:
\[\text{Percentage rate} = \left(\frac{4\,560}{240\,000}\right) \times 100 = 1.9\%\]

M1 for correct natural increase determination: \(6\,720 - 2\,160 = 4\,560\) OR for setting up the calculation \(\frac{4\,560}{240\,000} \times 100\) [1];
M2 for correct final answer of \(1.9\) or \(1.9\%\) [0.75].

1. Calculate the absolute increase in population:
\[\text{Increase} = 1\,827\,000 - 1\,450\,000 = 377\,000\]

2. Divide the increase by the original 2015 population and multiply by 100:
\[\text{Percentage increase} = \left(\frac{377\,000}{1\,450\,000}\right) \times 100 = 26\%\]

M1 for calculating the population difference: \(1\,827\,000 - 1\,450\,000 = 377\,000\) OR formula with substituted values \(\frac{377\,000}{1\,450\,000} \times 100\) [1];
M2 for correct final evaluation: \(26\) or \(26\%\) [0.75].

1. Find the total number of dependants:
\[\text{Total dependants} = 22\,100 + 6\,800 = 28\,900\]

2. Subtract total dependants from the total population to find the working population:
\[\text{Working population} = 85\,000 - 28\,900 = 56\,100\]

3. Calculate the percentage of the total population:
\[\text{Percentage working population} = \left(\frac{56\,100}{85\,000}\right) \times 100 = 66\%\]

M1 for finding working population size: \(85\,000 - (22\,100 + 6\,800) = 56\,100\) OR for finding total dependant percentage \(34\%\) [1];
M2 for correct final percentage of economically active population: \(66\) or \(66\%\) [0.75].

(a) Angle for Solar = \(\frac{20}{100} \times 360^\circ = 72^\circ\).
(b) To complete the pie chart:
- Measure and draw a line at \(72^\circ\) from the last drawn sector for Solar (leaving the final sector as \(36^\circ\) for Wind, calculated as \(\frac{10}{100} \times 360^\circ = 36^\circ\)).
- Clearly label each new sector as 'Solar' and 'Wind', or add a labelled key/legend.
(c) Generating electricity from wind and solar replaces fossil fuels (natural gas), which reduces emissions of carbon dioxide (\(\text{CO}_2\)), mitigating the enhanced greenhouse effect and global warming.

(a) [1 mark]
- \(72^\circ\) [1]

(b) [1.5 marks]
- Sector of \(72^\circ\) drawn for Solar AND \(36^\circ\) drawn for Wind (allow \(\pm 1^\circ\)) [1]
- Both sectors clearly labelled ('Solar' and 'Wind') or correctly shaded with an accompanying key [0.5]

(c) [1 mark]
- Any 1 from:
- Reduces emissions of greenhouse gases / carbon dioxide / \(\text{CO}_2\) [1]
- Reduces contribution to global warming / climate change [1]
- Conserves finite fossil fuel reserves / avoids resource depletion [1]
- Reduces emissions of oxides of nitrogen (\(\text{NO}_x\)) / prevents acid rain [1]
(Reject: 'does not cause pollution' unqualified)

To ensure pitfall traps collect valid ecological data while remaining ethical:
1. The trap must be set with its top rim exactly level with the soil surface so crawling invertebrates fall in easily, and a raised cover (such as a flat stone supported by twigs) should be positioned above the trap to shelter it from rainfall (preventing drowning) and birds (preventing predation).
2. Traps must be visited and emptied at regular, frequent intervals (e.g., within 24 hours) so that captured specimens do not starve, dry out, or suffer predation within the cup.

Award [1 mark] for each valid precaution with explanation (max 2 marks / scaled to 1.33):
- M1: Ensure top of trap / rim is flush / level with soil surface OR place a raised cover / roof / stone over the trap (to prevent rain filling trap / prevent predation by birds / mammals); [1]
- M2: Check and empty the traps frequently / at set intervals / within 24 hours (to prevent animals dying / drying out / predating each other); [1]
- Accept: add drainage holes to bottom of cup (if live-sampling during rain) OR add non-toxic preserving fluid / detergent water (if humane lethal sampling is permitted);
- Reject: vague unqualified statements such as 'handle with care' or 'wear gloves'.

(a) Systematic sampling along a transect line.
(b) Because the environmental conditions (e.g. soil moisture, salinity, light levels) change continuously from the water body inland, systematic sampling at regular intervals captures the progressive zonation and environmental gradient. Random sampling might cluster points in one zone and miss transition zones entirely.

(a) M1: Systematic sampling / belt transect / transect sampling; [1]
(b) M2: Identifies / measures / displays changes or trends along an environmental gradient / zonation / with distance from water; [1]
- Accept: ensures all distances / zones are sampled evenly without clustering;
- Reject: 'it is faster / easier' unqualified.

1. The method suffers from deliberate investigator bias because quadrats were placed only where weeds were visible, which grossly overestimates the true population density across the entire field. This can be resolved by using a grid overlay and a random number generator to select unbiased coordinates.
2. The sample area is far too small (4 quadrats \(\times 0.25\text{ m}^2 = 1\text{ m}^2\) out of a \(2500\text{ m}^2\) field, representing just 0.04% of the site), meaning data is not representative or reliable. The researcher should sample at least 20 to 30 quadrats or use larger \(1\text{ m} \times 1\text{ m}\) quadrats.

Award [1 mark] for each limitation paired with a valid corresponding improvement (max 2 marks / scaled to 1.33):
- M1 (Bias): Limitation: biased / subjective / non-random placement AND Improvement: use random sampling / random number generator / grid coordinates; [1]
- M2 (Sample size): Limitation: sample size too small / unrepresentative sample area (only 4 quadrats / 1 m2 out of 2500 m2) AND Improvement: increase number of quadrats / use more repeats / sample a larger percentage of the site; [1]
- Accept for M2: quadrat dimensions too small (0.5 m x 0.5 m) AND use larger quadrats (e.g. 1 m x 1 m);
- Reject: 'repeat the study next year' as an improvement for sample size.

(a) Percentage efficiency = \(\frac{\text{Energy in secondary consumers}}{\text{Energy in primary consumers}} \times 100\)
\[\text{Efficiency} = \frac{350}{3500} \times 100 = 10\%\]

(b) Between any two trophic levels, energy is not 100% transferred because organisms lose energy as heat during cellular respiration, and energy remains locked in unconsumed materials (e.g. roots, bones) or is excreted/egested as metabolic waste and faeces.

(a) M1: Correct calculation showing \(\frac{350}{3500} \times 100 = 10\%\) [1]
(b) M2 & M3: Any two from:
- Released as heat / during (aerobic) respiration [1];
- Lost through excretion / egestion / urine / faeces [1];
- Not all parts of the organism are consumed / bones / shells / roots left behind [1];
- Death without being consumed (passed to decomposers) [1].
Reject: 'energy destroyed' (violates conservation of energy).

A pyramid of numbers simply counts individual organisms regardless of their size. One massive tree is counted as '1', but it contains enough biomass and chemical energy to nourish thousands of smaller primary consumers (caterpillars), creating an inverted or narrow base. Conversely, a pyramid of energy depicts the rate of energy flow or energy content. Because energy is inevitably lost at each transfer (via respiration, metabolic heat, and waste), lower trophic levels must contain more energy than the trophic levels above them, ensuring the pyramid of energy is always wide at the base and strictly upright.

M1: Explanation of pyramid of numbers: One large producer / high biomass tree provides food for many smaller primary consumers / number of individuals is low at base [1];

M2: Explanation of energy pyramid shape: Energy is lost at each trophic level / only ~10% is transferred to the next level [1];

M3: Linking energy: Producer level contains the greatest total chemical energy / energy cannot increase moving up trophic levels, making the energy pyramid always upright [1].

(a) Energy at Trophic Level 1 (Phytoplankton) = \(74\,000\text{ kJ/m}^2/\text{year}\)
Energy at Trophic Level 2 (Zooplankton) = \(74\,000 \times 0.10 = 7\,400\text{ kJ/m}^2/\text{year}\)
Energy at Trophic Level 3 (Mullet fish) = \(7\,400 \times 0.10 = 740\text{ kJ/m}^2/\text{year}\)
Energy at Trophic Level 4 (Osprey) = \(740 \times 0.10 = 74\text{ kJ/m}^2/\text{year}\)

(b) With roughly 90% of energy lost at each trophic step due to metabolic heat, respiration, and unconsumed parts, the total energy remaining after 4 to 5 levels is too small to sustain the metabolic requirements and reproductive population size of a higher-level apex predator.

(a) M1: Correct numerical calculation \(74\) [1] and correct unit \(\text{kJ/m}^2/\text{year}\) [1] (Allow 1 mark for correct method with one arithmetic slip: e.g. 740 divided by 10).

(b) M2: Idea that massive energy loss occurs at each trophic level / only 10% transferred / 90% lost to respiration/heat/excretion [1];

M3: Insufficient energy left at the top to support a viable population / biomass of higher-level carnivores / apex predators [1].

Reverse osmosis produces a highly concentrated brine effluent that is often discharged back into the sea, increasing local salinity and harming benthic/marine organisms. Additionally, the process requires substantial electrical energy, which, if generated from fossil fuels, increases carbon emissions and contributes to global warming.

Award 1 mark for each valid limitation (maximum 2 marks):
- Production / discharge of concentrated brine / hyper-saline water damaging marine organisms / benthic ecosystems;
- High electrical energy / power requirement (leading to enhanced greenhouse gas emissions / high operational carbon footprint);
- Entrapment / entrainment of marine organisms / larvae at water intake pipes;
- Thermal pollution / release of chemical pre-treatment agents into the ocean.

[Reject 'costs a lot of money' without environmental qualification].

Vector control targets the mosquito life cycle. Draining or covering stagnant water eliminates potential breeding habitats where female Anopheles lay eggs. Introducing biological predators (e.g. fish that feed on larvae) or applying bacterial larvicides reduces the emergence of adult vectors.

Award 1 mark for each valid vector control method (maximum 2 marks):
- Draining / covering standing / stagnant water / puddles / empty containers (to remove breeding sites);
- Introducing biological control / stocking ponds with fish (e.g. Gambusia) that feed on larvae;
- Applying larvicides / bacterial sprays (e.g. Bti) to water surfaces;
- Residual indoor spraying of insecticides on walls;
- Clearing tall grass / vegetation near settlements where adult mosquitoes rest.

[Reject personal protection methods such as bed nets, repellents, or antimalarial medication — question specifically asks for vector control].

Regulating net mesh sizes ensures that juvenile fish escape and reach reproductive maturity. Setting closed seasons (seasonal bans during breeding periods) or establishing no-take marine protected areas ensures adult fish can reproduce without disturbance.

Award 1 mark for each valid management policy (maximum 2 marks):
- Setting / enforcing minimum mesh sizes on nets (to allow juvenile / young fish to escape);
- Introducing catch quotas / total allowable catches (TACs);
- Establishing closed seasons / bans during the breeding / spawning periods;
- Creating marine protected areas (MPAs) / no-take zones / marine reserves;
- Banning destructive fishing methods / restricting gear (e.g. banning bottom trawling / mandating pole and line);
- Requiring fishing licences / limiting vessel numbers / limiting days at sea.

Land restoration involves reshaping the steep spoil heaps, re-spreading conserved topsoil over the graded overburden, and incorporating organic matter/fertilisers to rebuild microbial activity and soil structure. Planting hardy native tree species or using bioremediating plants helps stabilise the soil and extract or immobilise residual toxins.

Award 1 mark for each valid technique (maximum 2 marks):
- Re-spreading / replacing saved topsoil / subsoil over regraded overburden;
- Regrading / re-profiling steep spoil heaps / terracing slopes to prevent mass movement / erosion;
- Bioremediation / planting hyperaccumulating plants to extract / immobilise heavy metal toxins;
- Tree planting / reforestation using native species to stabilise soil / restore biodiversity;
- Adding organic matter / manure / compost / lime to neutralise acidity and restore soil nutrients.

Governments can stimulate technology adoption by providing direct financial grants or low-interest loans for replacing fossil-fuel boilers with ground or air source heat pumps. Tax exemptions, reduced registration fees, or home EV-charger grants also accelerate the uptake of electric vehicles.

Award 1 mark for each valid incentive (maximum 2 marks):
- Financial subsidies / grants / vouchers for installing heat pumps (ground or air source) / home insulation;
- Tax reductions / rebates / subsidies for purchasing electrically propelled vehicles (EVs) / EV chargers;
- Feed-in tariffs / incentives for domestic rooftop solar panel and battery storage installations;
- Reduced electricity rates / variable tariffs during off-peak hours for smart appliance usage;
- Free parking / exemptions from congestion charges for low-emission / electric vehicles.

Farmers can minimise nutrient leaching and run-off by timing fertiliser application precisely—avoiding waterlogged soils or rainy forecasts so nutrients are absorbed by crops rather than washed into waterways. Planting permanent grass or forested buffer strips along riparian zones intercepts surface run-off and absorbs excess nitrates and phosphates.

Award 1 mark for each valid practice (maximum 2 marks):
- Planting / maintaining vegetated buffer strips / riparian vegetation along field edges / riverbanks;
- Avoiding fertiliser application during rainy periods / when soil is waterlogged / frozen;
- Using precision farming / applying exact NPK nutrient doses calculated for crop needs;
- Switching to slow-release fertilisers / organic compost instead of highly soluble mineral fertilisers;
- Practising contour ploughing / bunding to slow surface run-off across fields.

Local authorities can use land-use zoning regulations to prevent new development on vulnerable tidal floodplains. Building codes can mandate structural adaptations, such as elevating ground floors on stilts or pilings and placing electrical infrastructure on upper storeys.

Award 1 mark for each valid strategy (maximum 2 marks):
- Enforcing land-use zoning / restricting / banning construction on vulnerable floodplains / low-lying coastal margins;
- Mandating elevated construction / building houses on stilts / pilings / raised foundations;
- Requiring water-resistant building materials on lower floors / fitting non-return drainage valves;
- Requiring critical utilities (electrical wiring / generators / switchboards) to be situated on upper floors / roofs;
- Mandating permeable surfaces / green roofs in new developments to reduce surface run-off.

Wildlife corridors bridge isolated habitat fragments, enabling safe migration, foraging, and gene flow. Deploying modern technologies such as automated camera traps, aerial surveillance drones, and GPS telemetry collars allows real-time tracking of animal movements and early detection of illegal poaching activities.

Award 1 mark for each valid strategy (maximum 2 marks):
- Creating / maintaining wildlife corridors / habitat bridges between isolated reserves;
- Using aerial surveillance drones / automated trail cameras to monitor wildlife and detect poachers;
- Deploying satellite / GPS tracking collars on target animals to track migration / distress;
- Establishing designated core conservation zones with restricted public / tourist access;
- Using artificial intelligence (AI) / acoustic sensors to identify gunfire or chainsaw sounds in real time.

1. Ground source heat pumps do not directly burn fossil fuels on-site, significantly reducing carbon dioxide (\(\text{CO}_2\)) emissions that contribute to the enhanced greenhouse effect.
2. They eliminate emissions of acidic gases (such as \(\text{SO}_2\) and \(\text{NO}_x\)) and particulate matter at the point of use, improving local air quality and removing the risk of fuel oil leaks into soil or groundwater.

Award 1 mark for each valid point (max 2):
- [M1] Reduction in carbon dioxide (\(\text{CO}_2\)) / greenhouse gas emissions / reduced contribution to global warming;
- [M2] Reduction in emissions of sulfur dioxide (\(\text{SO}_2\)) / oxides of nitrogen (\(\text{NO}_x\)) / particulates / soot;
- [M3] Eliminates the risk of fuel spills / soil or groundwater contamination from oil storage;
- [M4] Utilises a renewable / geothermal heat source rather than a finite fossil fuel.

Reject: 'reduces pollution' unqualified.