2023 Cambridge IGCSE Environmental Management (0680) 模擬試題連答案詳解

To find the combined percentage of water in glaciers, ice caps, and groundwater, add the individual percentages: 2.15% + 0.62% = 2.77%.

1 mark for the correct calculation and answer: 2.77% (accept 2.77).

Fossil fuels in this list are coal and natural gas. Total percentage = 35% (coal) + 28% (natural gas) = 63%.

1 mark for the correct total of 63% (accept 63).

Total number of sampled trees = 12 + 8 + 15 + 5 = 40. Percentage of Mahogany = (12 / 40) * 100 = 30%.

1 mark for the correct calculation: 30% (accept 30).

Decrease in catch = Catch in 2015 - Catch in 2019 = 12.4 million tonnes - 8.0 million tonnes = 4.4 million tonnes.

1 mark for the correct subtraction: 4.4 million tonnes (accept 4.4).

Comparing the daily concentrations: 62 ppb is the highest value, which was recorded on Wednesday.

1 mark for identifying Wednesday.

Natural increase rate per 1000 = Crude Birth Rate - Crude Death Rate = 18 - 6 = 12 per 1000. Expressed as a percentage: (12 / 1000) * 100 = 1.2%.

1 mark for the correct percentage calculation: 1.2% (accept 1.2).

Total storage capacity lost = Capacity in 1980 - Capacity in 2020 = 500 million cubic metres - 395 million cubic metres = 105 million cubic metres.

1 mark for 105 million cubic metres (accept 105).

A wind speed of 215 km/h falls within the range of 209 to 251 km/h, which corresponds to Category 4.

1 mark for stating Category 4 (accept 4).

Calculate the difference in TAC: 15,000 tonnes - 12,000 tonnes = 3,000 tonnes. Calculate the percentage decrease relative to Year 1: (3,000 / 15,000) * 100 = 20%.

Award 1 mark for the correct percentage decrease: 20% (also accept '20').

To find how many times greater Region A is compared to Region C, divide Region A's daily average consumption by Region C's: 600 / 150 = 4.

Award 1 mark for the correct value: 4 (also accept '4 times').

Closed seasons prohibit fishing during specific periods of the year. This is usually timed during the breeding/spawning season of key fish species. By banning fishing, adult fish are allowed to mate and release eggs without disruption, and young, juvenile fish are given time to grow and mature without being caught, helping to maintain or recover the fish stocks.

Max 2.5 marks: 1 mark for identifying that closed seasons occur during the breeding/spawning season of fish. 1 mark for explaining that this allows reproduction to occur, increasing population numbers/restocking. 0.5 marks for mentioning that it protects pregnant/spawning adults or juvenile fish from being harvested before they can reproduce.

Double hulls provide a dual-barrier system. The outer hull absorbs the initial impact of a grounding or collision. The space between the hulls (typically 1 to 2 metres) acts as a safety buffer. Because the cargo tanks containing the oil are housed inside the inner hull, they are protected from damage, dramatically reducing the probability of oil spills during low-to-medium-energy accidents.

Max 2.5 marks: 1 mark for describing the design (an inner and outer hull with a gap/space between them). 1 mark for explaining that if the outer hull is ruptured/damaged in a collision, the inner hull remains intact. 0.5 marks for stating this prevents the oil in the inner tanks from leaking into the sea/ocean.

High-temperature combustion in vehicle engines causes nitrogen and oxygen in the air to react, forming nitrogen oxides (\(\text{NO}_x\)). Vehicles also release unburnt hydrocarbons (volatile organic compounds, or VOCs). When these primary pollutants are exposed to sunlight, specifically ultraviolet (UV) radiation, a series of photochemical reactions occur, forming ground-level (tropospheric) ozone (\(\text{O}_3\)).

Max 2.5 marks: 1 mark for identifying nitrogen oxides (\(\text{NO}_x\)) and/or hydrocarbons/VOCs as primary pollutants released by vehicle engines. 1 mark for explaining that these substances react in the presence of sunlight/UV radiation (photochemical reaction). 0.5 marks for stating that ground-level ozone is formed as a secondary pollutant (or a key component of photochemical smog).

Cholera is a water-borne disease transmitted via water contaminated with human faeces containing the bacterium Vibrio cholerae. Improving sanitation (such as proper sewage treatment and secure latrines) prevents human waste from entering drinking water systems, breaking the transmission cycle for the entire population. While antibiotics treat individual symptoms, they do not eliminate the contaminated environmental reservoir, leaving everyone else at risk of reinfection.

Max 2.5 marks: 1 mark for explaining that cholera is water-borne/transmitted through water contaminated with faeces/sewage. 1 mark for explaining that improving sanitation removes/prevents the source of contamination, protecting the whole community (preventative measure). 0.5 marks for explaining that antibiotics only treat already infected individuals but do not stop the ongoing spread/reinfection from the contaminated water source.

Acid rain (pH < 5.6) deposited on forests has both direct and indirect impacts. Indirectly, it lowers soil pH, which leaches vital plant nutrients like magnesium and calcium out of the soil. It also mobilizes toxic aluminium ions (\(\text{Al}^{3+}\)), which damage root hairs and reduce water and nutrient uptake. Directly, acidic water damages the waxy cuticle on needles, reducing photosynthesis and leaving the trees vulnerable to drought, frost, and pests.

Max 2.5 marks: 1 mark for explaining soil effects (leaching of essential nutrients like calcium/magnesium OR mobilization of toxic aluminium ions that damage roots). 1 mark for explaining direct effects on trees (damage to the waxy cuticle of needles/leaves, which reduces photosynthesis). 0.5 marks for mentioning that this weakens the trees and increases their vulnerability to diseases, extreme cold, or pests.

Seismic building codes mandate engineering practices that allow structures to withstand seismic waves. This includes using ductile (flexible) materials like structural steel, incorporating base isolation systems (shock absorbers) to isolate the building from ground movement, and reinforcing concrete with steel rebars. By preventing total building collapse, which is the leading cause of death during earthquakes, occupants are given the time and physical space to evacuate.

Max 2.5 marks: 1 mark for identifying specific earthquake-resistant engineering features (e.g., flexible steel frames, base isolators/shock absorbers, reinforced foundations, cross-bracing). 1 mark for explaining that these features allow the building to sway or absorb kinetic energy without collapsing/pancaking. 0.5 marks for stating that preventing building collapse is the primary way to prevent injuries and allow safe evacuation/reduce loss of life.

Habitat fragmentation splits large ecosystems into smaller, isolated patches, separating wildlife populations. Ecological corridors—strips of natural habitat connecting these fragments—allow wildlife to move freely. This movement facilitates gene flow (mating between different subpopulations), which maintains genetic diversity and reduces the risks of inbreeding depression. It also allows animals to forage across a wider area and recolonize patches where local extinctions may have occurred.

Max 2.5 marks: 1 mark for explaining that corridors provide a safe passage/route for animals to travel between isolated habitat patches. 1 mark for explaining that this facilitates gene flow/prevents inbreeding by linking isolated populations. 0.5 marks for mentioning that it allows species to access larger areas for foraging, mating, or migration in response to environmental changes.

Once open-cast mining is complete, the degraded site can undergo reclamation. The first step involves backfilling the deep pits with the overburden (rock and soil removed during initial excavation) and grading the land to match the natural contours. Stored topsoil, which was set aside before mining, is spread over the surface to provide nutrients. Finally, native grasses, shrubs, or trees are planted to stabilize the soil, prevent erosion, and allow the land to be reused for agriculture, forestry, or recreation.

Max 2.5 marks: 1 mark for explaining physical restoration steps (backfilling the mine pit with overburden/waste rock and leveling/contouring the land). 1 mark for explaining ecological restoration (replacing stored topsoil and replanting native vegetation/re-vegetation to prevent erosion). 0.5 marks for identifying a productive post-restoration land use (e.g., community park, agriculture, forestry, nature reserve).

Burning fossil fuels in power stations releases sulfur dioxide (SO2) and nitrogen oxides (NOx) [1 mark]. These gases react with water vapor and oxygen in the atmosphere to form weak sulfuric and nitric acids, lowering the pH of rainfall [1 mark]. In aquatic ecosystems, acid rain causes aluminum to leach from soils into lakes and streams, which is toxic to fish and clogs their gills, or directly kills sensitive eggs and larvae [0.5 marks].

Award 1.0 mark for identifying SO2 or NOx as the pollutant gases. Award 1.0 mark for describing their reaction with atmospheric water vapor to form sulfuric/nitric acid. Award 0.5 marks for describing a specific aquatic impact, such as aluminum toxicity or death of fish eggs.

A national park provides legal protection for core habitats, banning activities such as logging, mining, and hunting, which prevents habitat fragmentation and species loss [1 mark]. Buffer zones surround this core area and act as transition zones that absorb human-induced disturbances from neighboring agricultural or urban lands [1 mark]. This minimizes edge effects and provides extra space for wide-ranging species [0.5 marks].

Award 1.0 mark for explaining how national parks legally protect core habitats. Award 1.0 mark for explaining the role of buffer zones in absorbing external disturbances. Award 0.5 marks for mentioning reduction of edge effects or allowing wildlife migration.

First, oil coats the plumage of seabirds, ruining their natural insulation and waterproofing. This causes them to die of hypothermia or lose buoyancy and drown [1 mark]. Second, when birds preen their feathers to clean them, they ingest toxic hydrocarbons, leading to internal poisoning and organ failure [1 mark]. A long-term impact on coastal food webs is bioaccumulation/biomagnification of toxic chemicals or loss of food resources resulting in trophic cascades [0.5 marks].

Award 1.0 mark for explaining feather damage leading to hypothermia/drowning. Award 1.0 mark for explaining ingestion of toxic oil during preening leading to organ failure. Award 0.5 marks for identifying a valid long-term food web impact (e.g., biomagnification or loss of critical prey species).

Setting a minimum net mesh size allows juvenile and non-target smaller fish to pass through the gaps unharmed [1 mark]. This ensures these young fish live to reach reproductive maturity, allowing them to spawn and replenish the fish stock [1 mark]. Enforcement is difficult because of the vastness of ocean fishing grounds, high costs of patrol boats, or fishers using illegal inserts (liners) that reduce the mesh size temporarily [0.5 marks].

Award 1.0 mark for explaining that larger mesh sizes let juvenile fish escape. Award 1.0 mark for linking this to reproductive maturity and replenishment of fish stocks. Award 0.5 marks for identifying a valid enforcement challenge (e.g., large patrol areas, illegal liners, or high costs).

Two features of earthquake-resistant design include base isolators (which separate the building from ground movement) and diagonal steel cross-bracing (which provides structural rigidity and prevents wall collapse) [1 mark]. Seismic hazard maps display geographic areas highly vulnerable to ground shaking or liquefaction [1 mark]. Urban planners use this data to enforce strict building codes or completely restrict high-density construction and critical infrastructure in active fault zones [0.5 marks].

Award 1.0 mark for identifying two valid earthquake-resistant design features (0.5 marks each). Award 1.0 mark for explaining how seismic hazard maps show risk zones like liquefaction or fault lines. Award 0.5 marks for describing how planners use this to restrict development or manage land use.

Geothermal power is a baseload energy source that depends on heat from the Earth's crust, which is constant and unaffected by external weather conditions [1 mark]. This makes it far more reliable than wind energy, which is intermittent and variable because it relies on fluctuating wind speeds [1 mark]. A localized disadvantage of geothermal plants is the release of toxic gases (such as hydrogen sulfide) during drilling, or localized land subsidence as fluids are extracted [0.5 marks].

Award 1.0 mark for explaining the continuous, weather-independent nature of geothermal heat. Award 1.0 mark for contrasting it with the variable/intermittent nature of wind. Award 0.5 marks for stating a localized impact (e.g., hydrogen sulfide release, minor seismic risk, or ground subsidence).

Over-extraction of groundwater lowers the freshwater table and reduces the hydrostatic pressure pushing outward toward the sea [1 mark]. This allows saline ocean water to flow inland into the empty spaces of the aquifer, causing saltwater intrusion which contaminates freshwater wells [1 mark]. This can be managed by implementing strict extraction quotas or utilizing managed aquifer recharge to pump treated water back underground [0.5 marks].

Award 1.0 mark for describing how excessive extraction reduces hydrostatic pressure/lowers the water table. Award 1.0 mark for explaining how this drives saltwater intrusion into the freshwater aquifer. Award 0.5 marks for proposing a suitable management strategy (e.g., managed aquifer recharge, physical barriers, or water pricing/quotas).

1. Spreading: Immediately upon spilling, gravity and wind cause the oil to spread over the water surface, forming a thin layer called an oil slick. 2. Evaporation: The lighter, volatile liquid components of the oil quickly evaporate into the atmosphere, reducing the volume of the slick. 3. Emulsification: Turbulent wave action mixes seawater into the oil, creating a highly viscous water-in-oil emulsion often called mousse. 4. Dispersion and Dissolution: Wave action also breaks up the slick into small droplets that disperse into the water column, while some soluble compounds dissolve. 5. Sedimentation: Heavy residue compounds may bind with suspended particulate matter in the water and sink to the sea floor.

Award marks for descriptions of the following physical processes (maximum 4.5 marks): Spreading: Oil expands outward across the sea surface due to gravity/winds/currents (1 mark); Evaporation: Light-fraction hydrocarbons vaporize into the air (1 mark); Emulsification: Wave motion mixes water into the oil, forming thick mousse (1 mark); Dispersion/Dissolution: Splitting of oil into microscopic droplets in the water column or dissolving of soluble parts (1 mark); Sedimentation: Heavy components bind with suspended particles and sink to the ocean floor (0.5 marks).

1. Aeration: Sewage is pumped into aeration tanks where mechanical aerators or diffusers inject oxygen. 2. Aerobic digestion: Aerobic bacteria use the oxygen to break down and digest dissolved organic nutrients and wastes. 3. Flocculation and Settling: The bacteria form clusters (flocs) that settle to the bottom of a secondary sedimentation tank (clarifier) as activated sludge. 4. Sludge recycling: A portion of the activated sludge is pumped back into the aeration tanks to ensure a high concentration of active bacteria is maintained, while the remaining sludge is treated or disposed of.

Award marks for detailed sequence descriptions (maximum 4.5 marks): Aeration: Introduction of oxygen/air into the wastewater to support aerobic respiration (1 mark); Decomposition: Aerobic bacteria digest and break down dissolved organic wastes into stable products like \(CO_2\) and water (1 mark); Sedimentation: Flow slows down in secondary clarifiers, allowing biological flocs to settle as activated sludge (1 mark); Sludge recycling: Returning a portion of the settled active biomass to the aeration basin to sustain the biological process (1 mark); Overall identification: Stating that this is a biological/aerobic treatment stage (0.5 marks).

1. Interception: Leaves and vegetation catch rainfall, delaying or preventing it from reaching the ground. 2. Infiltration: Water soaking into the upper layer of soil from the surface. 3. Throughflow: Water moving downslope laterally through the soil layer towards the river. 4. Percolation and Groundwater flow: Water moving deeper downwards (percolation) into the bedrock and then flowing laterally through rock pores/fractures (groundwater flow). 5. Surface runoff (overland flow): Water flowing directly over the land surface when rainfall intensity exceeds infiltration capacity.

Award marks for identifying and describing the processes (maximum 4.5 marks): Interception: Vegetation catches precipitation, reducing immediate ground input (1 mark); Infiltration: Downward movement of water from the surface into the soil (1 mark); Throughflow OR Surface Runoff: Lateral movement through soil (throughflow) OR flow across the surface due to saturation/high intensity (surface runoff) (1 mark); Percolation/Groundwater flow: Deep vertical movement into bedrock (percolation) followed by slow lateral flow in the saturated zone (1 mark); Sequential coherence: Explaining the logical order from precipitation to entering the river channel (0.5 marks).

1. Construction of steps: A steep natural slope is reshaped into a series of horizontal, flat steps or platforms. 2. Bund creation: Retaining walls made of stones or raised earth ridges (bunds) are constructed along the outer edges of each terrace. 3. Runoff reduction: The flat platform stops water from gaining high velocity down the slope, converting fast sheet runoff into slow, controlled flows. 4. Infiltration enhancement: Because water is held on the flat surfaces, it has more time to infiltrate deep into the soil profile. 5. Silt retention: Any soil particles that are detached by rain are caught on the flat terrace floor below, preventing net loss of soil from the hillside.

Award marks for structural and mechanical descriptions (maximum 4.5 marks): Step construction: Cutting steep slopes into flat horizontal platforms/benches (1 mark); Retaining barriers: Constructing bunds or stone walls at the edge of each flat tier to hold water/soil (1 mark); Velocity reduction: Flat surfaces interrupt slope continuity, slowing down surface runoff velocity (1 mark); Infiltration promotion: Water stays stationary on the terrace, increasing the volume and rate of water infiltration (1 mark); Soil retention: Capturing loose sediments on the next platform down (0.5 marks).

1. Chemical to Thermal: Coal is combusted in a furnace, releasing high-temperature heat energy. 2. Water to Steam: This heat is transferred to water flowing in boiler tubes, vaporizing it into high-pressure steam. 3. Thermal to Kinetic: The high-pressure steam is directed onto the blades of a turbine, causing the turbine shaft to spin rapidly. 4. Kinetic to Electrical: The rotating shaft spins a rotor inside a generator, creating a changing magnetic field that induces an electric current in the surrounding stator windings. 5. Condensation: Used steam is cooled and condensed back to water in a cooling tower/condenser to repeat the cycle.

Award marks for detailed sequence of energy changes and components (maximum 4.5 marks): Combustion: Chemical energy in coal is converted to thermal energy in a boiler (1 mark); Steam generation: Thermal energy turns liquid water into pressurized steam (1 mark); Turbine rotation: High-pressure steam drives turbine blades, converting thermal/pressure energy to mechanical kinetic energy (1 mark); Generator operation: Rotating turbine spins magnets inside generator coils to produce electrical energy by electromagnetic induction (1 mark); Cooling system: Steam is condensed back to liquid water to maintain pressure difference and cycle efficiency (0.5 marks).

1. Setting up the transect line: A tape measure is laid out in a straight line across the environmental gradient (perpendicular to the shore, from pioneer dunes inland). 2. Establishing sample stations: Sampling points are decided at regular systematic intervals along the tape measure (e.g., every 5 meters). 3. Placing the quadrat: A quadrat frame is placed on the ground at each designated interval. 4. Collecting vegetation data: Identify the species present and measure abundance (e.g., percentage cover, frequency, or species density) within the quadrat. 5. Environmental parameters and repetition: Record abiotic data (e.g., sand moisture, wind exposure) at each point, and repeat the transect at several parallel lines along the coast to obtain reliable, representative results.

Award marks for systematic sampling steps (maximum 4.5 marks): Transect orientation: Laying a tape measure straight across the environmental gradient (from sea to inland dunes) (1 mark); Regular intervals: Placing quadrats at predetermined, fixed distances along the tape to ensure systematic sampling (1 mark); Abundance measurement: Identifying species and estimating percentage cover or counting individual plants inside each quadrat (1 mark); Abiotic correlation: Measuring environmental variables (e.g., soil moisture, pH, wind speed) at each quadrat location (1 mark); Replay/Reliability: Replicating the entire transect process in multiple parallel locations (0.5 marks).

An exemplar response achieving Level 3:

I disagree that quotas and marine reserves are useless, although I agree they present major enforcement challenges. A combination of all these strategies is necessary to manage marine species sustainably.

Mesh size regulations and closed seasons are highly effective local tools. Increasing mesh sizes allows juvenile fish to escape and reproduce, while closed seasons protect fish during their spawning periods. These are relatively easy to enforce because fisheries officers can inspect nets and catch at landing ports. However, they do not limit the total volume of fish caught, meaning overfishing can still occur during the open season.

On the other hand, international agreements such as Total Allowable Catches (quotas) are vital to prevent the absolute depletion of transboundary stocks. While they are hard to police on the high seas and can lead to illegal dumping of bycatch (discards), modern tracking technologies like satellite monitoring (VMS) are making enforcement more viable. Similarly, marine reserves provide safe havens where ecosystems can fully recover, replenishing surrounding areas through the 'spillover effect'. Although patrolling large offshore reserves is difficult and costly, they are essential for biodiversity conservation.

In conclusion, while gear and seasonal restrictions are practical and effective at a local level, they cannot solve the global crisis of overfishing alone. International agreements and reserves are not useless; rather, they are indispensable components of global marine management that require stronger international cooperation and technology to enforce.

Level 3 (5–6 marks):
- Demonstrates a thorough and balanced evaluation of both parts of the statement (local regulations vs. international/spatial restrictions).
- Discusses the advantages and limitations of at least three management strategies (e.g., net mesh size, closed seasons, quotas, marine reserves).
- Explicitly addresses the challenges of enforcement/policing for different methods.
- Reaches a clear, reasoned conclusion based on the arguments presented.

Level 2 (3–4 marks):
- Explains at least two management strategies with some attempt to evaluate their effectiveness.
- Explains how some methods are easier or harder to enforce than others.
- Offers a structured response but may be one-sided or lack depth in the final conclusion.

Level 1 (1–2 marks):
- Identifies or briefly describes one or two management methods.
- Outlines general ideas about overfishing with little or no evaluation of the statement.
- No clear conclusion is reached.

0 marks:
- No response or no response worthy of credit.

First, find the natural increase per 1000 people: \(23 - 8 = 15\). To convert this rate per 1000 to a percentage (rate per 100), divide the value by 10: \(15 / 10 = 1.5\%\).

Award 1 mark for showing correct working of the natural increase per 1000 (e.g. \(23 - 8 = 15\)). Award 1 mark for the correct final answer of 1.5% (accept 1.5 without the % symbol if unit is implied).

The efficiency is calculated by dividing the useful electrical energy output by the total thermal energy input, then multiplying by 100: \(\text{Efficiency} = (45 / 250) \times 100 = 0.18 \times 100 = 18\%\).

Award 1 mark for correct working showing the fraction \(45 / 250\) or equivalent decimal ratio (0.18). Award 1 mark for the correct final percentage of 18%.

First, calculate the actual increase in the orchid population: \(1160 - 800 = 360\) individuals. Next, divide this increase by the original population in 2018 and multiply by 100 to find the percentage: \(\text{Percentage Increase} = (360 / 800) \times 100 = 45\%\).

Award 1 mark for calculating the population increase of 360 orchids. Award 1 mark for the correct final answer of 45%.

First, find the mass of target species kept by subtracting the bycatch from the total catch: \(12.5 - 3.5 = 9.0\) tonnes. Next, calculate this mass as a percentage of the total landed catch: \(\text{Percentage Target} = (9.0 / 12.5) \times 100 = 72\%\).

Award 1 mark for calculating the target catch mass as 9.0 tonnes (or calculating the bycatch percentage as 28%). Award 1 mark for the correct final answer of 72%.

First, calculate how many months the water will last: \(2,400,000 / 80,000 = 30\) months. Next, convert this duration into years by dividing the total months by 12: \(30 / 12 = 2.5\) years.

Award 1 mark for calculating the duration in months (30 months) or for showing the division setup: \(2,400,000 / (80,000 \times 12)\). Award 1 mark for the correct final answer of 2.5 years (or 2 years and 6 months).

Step 1: Label the horizontal axis (x-axis) as 'Year'. Step 2: Label the vertical axis (y-axis) as 'Population of breeding pairs'. Step 3: Choose a linear scale for the y-axis, for example, from 0 to 700 with grid intervals of 100. Step 4: Plot the points accurately: (2014, 450), (2015, 320), (2016, 180), (2017, 250), (2018, 380), (2019, 500), (2020, 620). Step 5: Draw neat straight lines with a ruler to connect the consecutive points. Do not extrapolate the line before 2014 or after 2020.

Award marks as follows: 1 mark: both axes labeled correctly with units (x-axis: Year; y-axis: Population of breeding pairs). 1 mark: linear, sensible scales on both axes (data must occupy more than half of the grid). 1 mark: all 7 points plotted correctly within half a small grid square. 1 mark: points connected with neat, straight, ruler-drawn lines (point-to-point, no bar charts, no line of best fit, no extrapolation).

1. Vast size of oceans: International waters cover millions of square kilometers, making physical surveillance by patrol boats or aircraft extremely challenging and expensive. 2. Lack of international jurisdiction: No single country has the legal authority to enforce laws in international waters, and agreements rely heavily on voluntary compliance or flag-state self-regulation.

Award 1 mark for each valid reason, up to a maximum of 2 marks: - Vast area of ocean / difficult and expensive to patrol (1) - Lack of international jurisdiction / no single authority has power in international waters (1) - Flag of convenience issues / vessels registering in countries with lax regulations (1) - High cost of monitoring technology (e.g., satellite tracking) for all vessels (1)

1. Quadrats are only suitable for sessile or very slow-moving organisms. Highly mobile beetles would escape the quadrat frame before or during counting, leading to inaccurate population estimates. 2. A more suitable method is mark-release-recapture. This involves catching beetles using pitfall traps, marking them safely, releasing them, and then resampling later to calculate population size using the Lincoln Index.

Award 1 mark for explaining why quadrats are inappropriate: - Organisms are mobile / will move out of or into the quadrat, leading to inaccurate counts (1) Award 1 mark for suggesting a suitable alternative: - Mark-release-recapture / pitfall trapping (1)

1. It oxidizes harmful carbon monoxide (CO) and unburnt hydrocarbons to form less harmful carbon dioxide (CO2) and water (H2O). 2. It reduces toxic nitrogen oxides (NOx) into harmless nitrogen gas (N2) and oxygen gas (O2) using catalysts like platinum, palladium, or rhodium.

Award 1 mark for each point, up to 2 marks: - Oxidation of carbon monoxide to carbon dioxide / unburnt hydrocarbons to water and carbon dioxide (1) - Reduction of nitrogen oxides to nitrogen gas (1) - Reference to the use of metal catalysts (e.g., platinum, palladium, or rhodium) to facilitate these reactions (1)

1. Financial constraints: The capital cost of building industrial wastewater treatment plants and monitoring infrastructure is very high for developing economies. 2. Economic priorities: Strict enforcement of environmental regulations may increase operating costs for businesses, leading to lower profits, potential job losses, or companies relocating to other countries with laxer regulations.

Award 1 mark for each suggestion, up to 2 marks: - High cost of building or maintaining wastewater treatment facilities (1) - Fear of discouraging foreign investment / negative impact on economic growth and jobs (1) - Lack of trained personnel / monitoring equipment to detect illegal dumping (1) - Corruption or bribery of inspectors (1) - Economic growth prioritized over environmental protection (1)

1. Water treatment: Boiling water before drinking or cooking kills the Vibrio cholerae bacteria. Alternatively, chemical treatment with chlorine tablets disinfects the water. 2. Sanitation: Building emergency latrines away from open water sources prevents human faeces containing the bacteria from washing into the drinking water supply.

Award 1 mark for each valid physical measure, up to 2 marks: - Boiling drinking water (1) - Adding chlorine / water purification tablets / chemical disinfection (1) - Safe disposal of sewage / building latrines far away from water sources (1) - Providing bottled or piped clean water from a secure source (1) - Improving hand hygiene by providing soap and clean water stations (1) Reject: 'Education', 'vaccination', or 'medical treatment' as these are not immediate physical water/sanitation management measures.

1. Energy security and reliability: Coal-fired power stations provide reliable baseload electricity that is available 24/7, unlike wind or solar power which are intermittent. 2. Economic reasons: Coal infrastructure is already built and paid for, and coal may be cheap and locally abundant, making transition to renewable alternatives financially difficult in the short term.

Award 1 mark for explanation of reliability/baseload, and 1 mark for economic/abundance reasons: - Coal provides a reliable / continuous / baseload power supply (unlike intermittent renewables like wind/solar) (1) - Coal is cheap / abundant / locally sourced in that country (1) - High capital cost of replacing existing coal infrastructure with renewable energy systems (1) - Preventing job losses in coal mining and power sector communities (1)

1. High financial cost: Sea walls are very expensive to construct, and they require ongoing, costly maintenance as they are continuously damaged by wave action. 2. Environmental disruption: They can deflect wave energy to adjacent undefended areas of the coastline, causing increased erosion there (terminal groyne effect). They also destroy coastal habitats like salt marshes or beaches.

Award 1 mark for each valid explanation, up to 2 marks: - High economic cost of construction and maintenance (1) - Displaces wave energy / causes increased erosion further along the coast (1) - Can be breached by extreme storms / gives a false sense of security (1) - Destroys natural coastal ecosystems / habitats (e.g., beaches, mangroves) (1) - Sea walls do not address the root cause of sea-level rise / cannot be built high enough indefinitely (1)

1. Use of plants (phytoremediation): Specific plants that are hyperaccumulators can be grown on the contaminated mining site to absorb heavy metals (such as lead, cadmium, or copper) through their roots. The plants are then harvested and safely disposed of. 2. Use of microorganisms: Specialized bacteria or fungi can be introduced to the soil to biochemically break down or immobilize contaminants, rendering them non-toxic.

Award 1 mark for identifying the biological agent and 1 mark for explaining its action: - Use of plants (phytoremediation) to absorb / accumulate toxic heavy metals from the soil (1) - Use of microorganisms / bacteria / fungi to break down or immobilize contaminants (1) - Harvesting and safe disposal of the plants containing the toxins (1) - Restoring soil quality / making soil fertile enough for native species to return (1)

A temperature inversion occurs when a layer of warm air sits on top of cooler air. Under normal conditions, warm air rises and carries pollutants away. During an inversion, the cooler air containing sulfur dioxide is trapped beneath the warm layer, preventing vertical mixing and dispersion. This keeps the sulfur dioxide concentrated at ground level where local residents breathe.

1.2 marks: Explaining that a layer of warm air traps cooler air below it or prevents air from rising. 1.2 marks: Explaining that this prevents the dispersion of sulfur dioxide or keeps the gas concentrated near the ground where people breathe.

A key limitation of the mark-release-recapture method is the potential loss of marks. If the paint or mark rubs off the beetles during the study period, these beetles will be counted as unmarked when recaptured. This artificially reduces the number of recaptured marked individuals, which mathematically leads to an overestimation of the total population size.

1.2 marks: Suggesting a valid limitation (e.g. marks rubbing off, or marks making beetles more visible to predators). 1.2 marks: Explaining the effect on the calculation (e.g. fewer marked beetles recaptured leads to an overestimation of the population).

When oil washes into a mangrove forest, it floats on the water surface and settles on the roots as the tide recedes. It coats the pneumatophores (breathing roots) with a thick, sticky layer. This layer blocks the small pores (lenticels) used for gas exchange. As a result, oxygen cannot reach the submerged root tissues, leading to suffocation and death of the trees.

1.2 marks: Suggesting that oil coats or covers the pneumatophores / breathing roots. 1.2 marks: Explaining that this blocks gas exchange or oxygen intake, leading to suffocation of the roots or trees.

Cod typically reproduce during the spring. By banning fishing during this period (a closed season), breeding adults are protected from being harvested. This allows them to spawn undisturbed, maximizing the number of eggs laid and fertilized. This results in higher recruitment of young fish, helping to replenish the cod population and sustain the fishery.

1.2 marks: Suggesting that spring is the breeding / spawning season for cod. 1.2 marks: Explaining that this allows undisturbed reproduction or increases the survival and recruitment of offspring to replenish stocks.

Base isolators are flexible bearings made of rubber and steel placed between the building's foundation and its superstructure. When an earthquake occurs, these isolators act as shock absorbers, decoupling the building from the shaking ground. This dissipates or absorbs the kinetic energy of the seismic waves, reducing the amount of lateral movement and structural stress transferred to the building.

1.2 marks: Suggesting that base isolators decouple or separate the building from the moving ground or act as shock absorbers. 1.2 marks: Explaining that they absorb or dampen seismic energy, reducing structural movement and stress.

The capacity factor is the ratio of actual energy generated to the maximum possible energy output over a period. Wind is an intermittent and unpredictable resource; wind turbines only generate electricity when the wind speed is within a specific operational range (neither too calm nor too stormy). In contrast, a coal-fired power station is a baseload generator that can burn fuel continuously regardless of weather conditions, resulting in a much higher capacity factor.

1.2 marks: Suggesting that wind is intermittent, weather-dependent, or not always blowing at the correct speed. 1.2 marks: Explaining that turbines cannot generate power continuously, whereas coal-fired plants can operate constantly.

Reverse osmosis desalination produces a waste byproduct called brine, which has an extremely high concentration of salt and may contain treatment chemicals. When discharged back into the sea, this brine is denser than regular seawater, causing it to sink to the ocean floor. This creates localized hypersaline and hypoxic (low oxygen) conditions, which can dehydrate marine organisms due to osmotic shock and damage benthic ecosystems.

1.2 marks: Identifying the waste product as highly concentrated, dense brine or warm saline water. 1.2 marks: Explaining its impact on marine life (e.g., sinking to the seabed, causing osmotic stress or dehydration, or depleting oxygen).

When crops are fertilized, rain can wash excess nitrates and phosphates off the fields as agricultural runoff. A riparian buffer strip of trees and shrubs physically intercepts this runoff. The root systems of these plants absorb the dissolved nutrients (nitrates and phosphates) for their own growth. This significantly reduces the quantity of nutrients entering the lake, preventing the rapid growth of algae (algal blooms) that leads to eutrophication.

1.2 marks: Suggesting that the roots or plants absorb agricultural runoff containing fertilizers / nutrients (nitrates and phosphates). 1.2 marks: Explaining that this prevents excess nutrients from entering the lake, thus preventing algal blooms / eutrophication.

To manage overfishing on a coral reef, the community can use several strategies:
1. Closed seasons: Banning fishing during the spawning/breeding season allows fish to reproduce undisturbed, increasing recruitment rates.
2. Mesh size regulation: Using larger net mesh sizes allows juvenile fish to escape, ensuring they reach sexual maturity and reproduce at least once.
3. Marine Protected Areas (MPAs): Designating a 'no-take zone' protects a portion of the habitat where fish can grow and reproduce freely, leading to a spillover effect into fished areas.
4. Quotas/bag limits: Restricting the quantity or size of fish harvested limits overall exploitation rate.

Award 1 mark for each valid strategy suggested (up to 2 marks) and 1 mark for each corresponding explanation of how it conserves fish (up to 2 marks).

Suggested strategies and explanations:
- Closed season [1] - protects fish during breeding/spawning, allowing reproduction [1]
- Minimum net mesh size [1] - allows immature/juvenile fish to escape and reach breeding age [1]
- Marine protected areas / no-take zones [1] - provides a safe breeding ground / nursery area [1]
- Catch quotas / size limits [1] - limits the total quantity of fish taken / prevents taking of breeding adults [1]

Do NOT accept: 'stop fishing entirely' (unrealistic for a community relying on it).

Eutrophication is caused by nutrient runoff (nitrates and phosphates). To mitigate this, the farmer can:
1. Install a buffer strip (riparian zone) of plants/trees between the fields and the lake. These plants absorb the nutrients from runoff water.
2. Apply fertilizers only during dry weather and avoid applying right before predicted heavy rainfall, reducing the chance of surface wash-off.
3. Use slow-release organic fertilizers instead of synthetic ones, which leach less rapidly.
4. Use soil testing to apply the exact amount of fertilizer required by the crops, preventing excess nutrients from building up in the soil.

Award 1 mark for each valid method suggested (up to 2 marks) and 1 mark for each correct explanation of how it reduces fertilizer runoff (up to 2 marks).

Suggested methods and explanations:
- Riparian buffer strip / planting vegetation along the lake border [1] - plants absorb nutrients from runoff before they reach the lake [1]
- Avoid applying fertilizer before heavy rain / only apply in dry periods [1] - prevents rain from washing fertilizer off the soil surface [1]
- Use slow-release / organic fertilizers (e.g., manure) [1] - releases nutrients slowly, reducing leaching and runoff [1]
- Precision farming / soil testing to apply only the required amount [1] - prevents accumulation of excess unused nutrients in the soil [1]

Sulfur dioxide is released into the atmosphere from burning fossil fuels like coal. In the atmosphere, it reacts with water vapor, oxygen, and other chemicals to form dilute sulfuric acid, which falls as acid rain. When acid rain reaches the forest, it leaches essential nutrients, such as calcium and magnesium, from the soil, making them unavailable to the trees. It also releases toxic aluminum ions into the soil, which damage tree roots and reduce water uptake. Additionally, direct contact with acid rain damages the waxy cuticle of conifer needles, reducing their ability to photosynthesize and making them vulnerable to pests, disease, and extreme cold.

Award 1 mark for each valid point up to a maximum of 4 marks: 1. Sulfur dioxide reacts with water vapor or oxygen in the atmosphere to form sulfuric acid/acid rain. 2. Acid rain lowers the pH of the soil, leaching essential nutrients like calcium or magnesium away from root zones. 3. Acidic conditions release toxic aluminum ions from the soil, which damage root hair cells and limit water absorption. 4. Direct contact with acid rain damages the waxy cuticle of needles, reducing photosynthesis and increasing susceptibility to pests or frost.

The nitrate fertilizer is washed into the lake by surface runoff, causing a rapid increase in nutrient levels. This nutrient enrichment triggers an algal bloom, where algae grow rapidly and cover the water surface, blocking sunlight from reaching submerged plants, which subsequently die. When the algae and plants die, populations of decomposers (bacteria) increase exponentially as they feed on the dead organic matter. These aerobic bacteria consume large amounts of dissolved oxygen during respiration, creating anoxic (oxygen-depleted) conditions. Fish and other aquatic organisms die due to the lack of dissolved oxygen for respiration.

Award 1 mark for each valid point up to a maximum of 4 marks: 1. Runoff of nitrates causes rapid growth of algae / algal bloom on the water surface. 2. Algae block sunlight, causing deeper aquatic plants to die due to lack of photosynthesis. 3. Dead plants and algae are decomposed by aerobic bacteria, which multiply rapidly. 4. Bacteria use up dissolved oxygen in respiration, creating hypoxic/anoxic conditions, leading to the suffocation and death of fish.

The spilled crude oil floats on the water surface and is carried by tides into the mangrove forest. The sticky oil coats the specialized aerial roots (pneumatophores) of the mangrove trees, blocking the lenticels (pores) and preventing gas exchange, which eventually suffocates and kills the trees. The loss of mangroves destroys the critical nursery habitat for many juvenile fish, crabs, and shrimp. Toxic hydrocarbons in the oil also bioaccumulate in the food chain, poisoning filter feeders and predators, and the lack of root structure leads to coastal erosion.

Award 1 mark for each valid point up to a maximum of 4 marks: 1. Floating oil coats the aerial roots (pneumatophores) of mangrove trees. 2. This blocks lenticels/pores, preventing oxygen uptake/gas exchange and suffocating the trees. 3. Toxic chemical components of the oil are absorbed, poisoning the trees or marine organisms. 4. Loss of mangrove structure destroys the nursery grounds/habitats for juvenile fish and shellfish, reducing biodiversity.

The complete prohibition of fishing within the 'no-take' zone eliminates fishing mortality, allowing cod populations to survive to adulthood and reproduce. As the fish grow older and larger, their reproductive capacity increases exponentially because larger fish produce significantly more eggs. Over time, the recovering population leads to overcrowding inside the protected area, causing adult fish and larvae to migrate out of the boundary into adjacent waters. This process, known as the 'spillover effect,' increases the fish density in legally fishable areas, resulting in higher and more sustainable catches for local fishers.

Award 1 mark for each valid point up to a maximum of 4 marks: 1. Eliminating fishing allows fish to reach maturity/reproduce without human intervention. 2. Larger, older fish produce significantly more eggs/offspring, accelerating population recovery. 3. Overpopulation/carrying capacity limits within the MPA cause fish/larvae to migrate outside the boundaries (spillover effect). 4. This increases fish stocks and catch yields in the surrounding areas where fishing is permitted.

The restoration process begins by backfilling the open pit with the overburden (rock and soil removed during initial excavation) and grading the land to match the natural contours of the surrounding landscape to prevent erosion. Next, the original topsoil, which was stored separately during mining, is replaced over the graded area to provide a fertile growing medium. The soil is then treated with fertilizers or lime to correct any nutrient deficiencies or acidity. Finally, the area is replanted with native vegetation or fast-growing cover crops to stabilize the soil, encourage biodiversity, and restore ecosystem functions.

Award 1 mark for each valid point up to a maximum of 4 marks: 1. Backfilling the pit with overburden and grading/shaping the land to restore natural topography. 2. Replacing the stored topsoil over the surface to provide nutrients and structure for plant growth. 3. Treating the soil (adding lime to neutralize acidity / adding fertilizers to restore nutrients). 4. Replanting with native flora / cover crops to prevent soil erosion and encourage ecological succession.

Flooding damages water infrastructure, causing raw sewage from overwhelmed sanitation systems to mix with drinking water sources, contaminating them with Vibrio cholerae bacteria. Because clean tap water is unavailable, people are forced to use or ingest contaminated floodwater, leading to rapid waterborne transmission of cholera. To manage this, authorities must immediately distribute water purification tablets (chlorine) or bottled water to ensure safe drinking supplies. They should also set up temporary sanitation facilities (chemical toilets) to prevent further human waste from contaminating water sources, and establish specialized cholera treatment centers to isolate and treat patients.

Award 1 mark for each valid point up to a maximum of 4 marks: 1. Floodwaters cause sewage systems to overflow, contaminating drinking water sources with Vibrio cholerae. 2. Lack of clean water forces people to drink or wash utensils in contaminated water, transmitting the pathogen. 3. Immediate management measure (max 2 marks): Distributing water purification tablets / boiling drinking water / supplying clean bottled water. 4. Immediate management measure (max 2 marks): Providing portable toilets / temporary sanitation to prevent further fecal contamination, or setting up isolation/treatment centers.