2025 Cambridge IGCSE Environmental Management (0680) Practice Paper with Answers

1. Calculate the total area sampled: \(10 \times 0.25\text{ m}^2 = 2.5\text{ m}^2\). 2. Calculate the density: \(45 \div 2.5\text{ m}^2 = 18\text{ plants/m}^2\).

1 mark for showing a correct method to find the total area sampled (2.5) or dividing 45 by the total area. 0.8 mark for the correct final answer of 18.

1. Recall the relationship for efficiency: \(\text{Electrical energy generated} = \text{Input energy} \times \text{Efficiency}\). 2. Substitute the values: \(1200\text{ kJ/s} \times 0.40 = 480\text{ kJ/s}\) (or \(480\text{ kW}\)).

1 mark for showing the correct multiplication method (e.g., \(1200 \times 0.40\) or \(1200 \times \frac{40}{100}\)). 0.8 mark for the correct final value of 480 (with or without units).

1. Calculate the total catch: \(12\text{ tonnes} + 3\text{ tonnes} = 15\text{ tonnes}\). 2. Calculate the percentage of bycatch: \(\frac{3}{15} \times 100 = 20\%\).

1 mark for calculating the total catch of 15 tonnes. 0.8 mark for calculating the correct percentage of 20%.

1. Calculate the natural increase per 1000 people: \(24 - 9 = 15\) per 1000. 2. Convert to a percentage by dividing by 10: \(\frac{15}{10} = 1.5\%\).

1 mark for calculating the rate of natural increase per 1000 people (15) or showing the correct subtraction formula. 0.8 mark for converting this correctly to 1.5%.

1. Calculate the total reduction in tonnes: \(80,000 - 68,000 = 12,000\) tonnes. 2. Calculate the percentage decrease: \(\frac{12,000}{80,000} \times 100 = 15\%\).

1 mark for calculating the absolute reduction of 12,000 tonnes. 0.8 mark for calculating the correct percentage decrease of 15%.

National parks protect endangered plant species in-situ (in their natural environment). By designating an area as a national park, governments can legally ban activities like logging, agriculture, and development, ensuring the native ecosystem is preserved. Controlling visitor access also prevents direct physical damage such as trampling or over-harvesting.

1 mark for stating that it protects the species' natural habitat or ecosystem from destruction. 0.8 mark for explaining how human activities (such as logging, agriculture, or urban development) are restricted or prohibited within the designated area.

Building a physical barrier (barrage) across an estuary alters the natural tidal flow and restricts water movement. This traps sediments, alters local salinity levels, and blocks the migration routes of fish and other aquatic species moving between the sea and the river.

1 mark for identifying a valid environmental impact (e.g., blocking migration pathways for fish, altering estuarine salinity/siltation, destroying mudflats). 0.8 mark for explaining the consequences of this impact on local wildlife (e.g., loss of feeding grounds for wading birds, decline in fish populations).

A closed season legally bans fishing during certain times of the year, typically during the spawning (breeding) season. This allows adult fish to reproduce successfully and the young to grow without being caught, maintaining the breeding population and ensuring future fish stocks.

1 mark for identifying that fishing is prohibited during the spawning/breeding season of the fish. 0.8 mark for explaining that this ensures fish can reproduce or young fish can grow, maintaining sustainable population levels.

Seed banks preserve plant genetic diversity by drying the seeds to low moisture levels (typically below 5% to 6%) and storing them at sub-zero temperatures (usually -20 degrees Celsius). This slows down their metabolism and prevents germination or decay.

Award 0.9 marks for each correct condition listed up to a maximum of 1.8 marks: - Dry conditions / low humidity / low moisture (0.9 marks); - Cold temperatures / freezing / -20 degrees Celsius (0.9 marks).

Geothermal energy relies on heat from the Earth's crust, which is only easily accessible near tectonic plate boundaries or volcanic hot spots. In other areas, the crust is too thick, making drilling economically unviable due to high initial capital installation costs.

Award 0.9 marks for each valid reason up to a maximum of 1.8 marks: - Only accessible near tectonic plate boundaries / volcanic activity (0.9 marks); - High initial capital / installation costs / deep drilling required in non-tectonic areas (0.9 marks).

Upwelling currents bring cold, nutrient-rich water from the deep ocean to the sunlit surface. These nutrients (like nitrates and phosphates) stimulate the rapid growth of phytoplankton (primary producers). This supports large populations of zooplankton and fish, creating highly productive fishing grounds.

Award 1.8 marks for a complete explanation showing: - Nutrients (nitrates/phosphates) are brought to the surface from deep water (0.9 marks); - This increases phytoplankton/algae growth, which increases the food supply for fish (0.9 marks).

Rate of natural increase = \( \text{Birth Rate} - \text{Death Rate} = 24 - 6 = 18 \text{ per } 1000 \). To convert this to a percentage: \( \frac{18}{1000} \times 100 = 1.8\% \).

Award 0.9 marks for showing correct working: \( (24 - 6) / 10 = 1.8 \) (0.9 marks). Award 0.9 marks for the correct final answer: 1.8% (0.9 marks).

Increasing the mesh size of fishing nets allows smaller, juvenile fish to pass through and escape being caught. This ensures they can grow to maturity and reproduce, maintaining the breeding population for future generations.

Award up to 1.8 marks for a detailed explanation: - Allows juvenile/young/small fish to escape (0.9 marks); - Ensures fish can reach reproductive age/breed before capture (0.9 marks).

Habitat fragmentation isolates species into small populations, which can lead to inbreeding and extinction. Wildlife corridors connect these isolated pockets, enabling animals to migrate, access more food and mates, and maintain genetic diversity.

Award up to 1.8 marks: - Allows movement/migration between isolated habitat fragments (0.9 marks); - Prevents inbreeding / increases genetic exchange and diversity (0.9 marks).

Although wind power is renewable, it has environmental drawbacks, including noise pollution from the rotating turbines and the potential for rotating blades to collide with and kill birds and bats.

Award 0.9 marks for each valid environmental disadvantage up to a maximum of 1.8 marks: - Visual pollution/spoiling natural landscape (0.9 marks); - Noise pollution/sound disturbance (0.9 marks); - Harm/death to birds/bats colliding with blades (0.9 marks); - Large land area required (0.9 marks).

Bycatch refers to fish or other marine species (such as turtles, seabirds, dolphins, or non-target fish) that are caught unintentionally while targeting a specific species. It is a major concern because it leads to high mortality of non-target organisms, disrupting marine food webs and threatening endangered species.

Award 0.9 marks for a clear definition: - Unintentional/accidental capture of non-target species (0.9 marks). Award 0.9 marks for the concern: - Leads to decline/death of non-target/threatened species OR disrupts marine food webs (0.9 marks).

Natural Increase Rate is calculated as: \(\text{Natural Increase Rate} = \frac{\text{Birth Rate} - \text{Death Rate}}{10}\). Substituting the given values: \(\frac{18 - 6}{10} = 1.2\%\).

1 mark for showing correct working: (18 - 6) / 10. 0.8 marks for the correct final answer of 1.2% with unit.

Commercial fishing methods like bottom trawling and drift netting are non-selective. Bottom trawling involves dragging a large, weighted net along the ocean floor, which catches everything in its path including non-target species (bycatch) and damages benthic habitats.

0.8 marks for naming two correct commercial fishing methods (e.g., bottom trawling, drift netting, long-lining). 1 mark for a clear explanation of how the chosen method indiscriminately captures non-target species.

Geothermal energy is harnessed by drilling wells deep into the ground where rocks are hot. Cold water is pumped down, heated by the rocks, and converted into high-pressure steam. This steam rises to the surface and turns a turbine, which spins a generator to produce electricity.

1 mark for explaining that water is heated by hot underground rocks to produce steam. 0.8 marks for stating that the steam drives a turbine and generator to produce electricity.

In situ conservation involves protecting species within their natural environment, such as creating a nature reserve or national park. Ex situ conservation involves protecting species outside their natural habitat, such as in a zoo, botanical garden, or seed bank.

0.9 marks for correctly defining and giving an example of in situ conservation. 0.9 marks for correctly defining and giving an example of ex situ conservation.

By enforcing a minimum mesh size, the spaces in the fishing net are large enough to let juvenile and immature fish swim through and escape. This allows them to reach sexual maturity and reproduce, which replenishes the fish population and ensures sustainable stocks.

0.9 marks for stating that larger mesh allows juvenile/immature fish to escape. 0.9 marks for explaining that this allows them to reach breeding age/reproduce and sustain the population.

The biologist should place the 1 m2 quadrat randomly across the meadow several times (e.g., 10 or more times) to avoid bias. They must count the number of wildflowers in each quadrat and calculate the average (mean) density per square meter. Finally, they multiply this mean density by the total area of the meadow (100 m2) to estimate the total population.

0.9 marks for describing random sampling using multiple quadrats to find a mean density. 0.9 marks for multiplying the mean density by the total area (100 m2) to get the total population estimate.

An environmental advantage of nuclear power is that it does not release greenhouse gases like carbon dioxide or air pollutants like sulfur dioxide during operation, which helps combat global warming and acid rain. An environmental disadvantage is the production of radioactive waste which remains hazardous for thousands of years and is difficult to store safely, or the potential risk of radioactive contamination from accidents.

0.9 marks for a valid environmental advantage (e.g., no CO2/greenhouse gas emissions during generation, no sulfur dioxide emissions). 0.9 marks for a valid environmental disadvantage (e.g., long-term disposal of radioactive waste, risk of nuclear accidents/radiation leaks).

Inside a marine reserve, fishing is completely banned, allowing fish to grow larger, live longer, and produce significantly more offspring. This leads to a population surplus. The adult fish and their larvae then migrate or drift out of the reserve boundaries into adjacent fishing zones, a process known as the 'spillover effect', which replenishes fished populations.

0.9 marks for explaining that fish inside the reserve can breed and increase in size/number without human disturbance. 0.9 marks for describing the spillover effect (migration/drift of fish or larvae into adjacent fished waters).

1. Calculate the actual reduction in mass: \(120\text{ kg} - 18\text{ kg} = 102\text{ kg}\). 2. Calculate the percentage reduction based on the initial mass: \(\frac{102}{120} \times 100 = 85\%\).

1 mark for correct method of calculation: \(\frac{120-18}{120} \times 100\) or equivalent. 0.8 marks for the correct final answer: 85% (accept 85).

1. Calculate the rate of natural increase per 1000 population: \(24 - 9 = 15\) per 1000. 2. Convert this rate to a percentage: \(\frac{15}{1000} \times 100 = 1.5\%\).

1 mark for calculating the natural increase per 1000: \(24 - 9 = 15\), or for the correct conversion method: \(\frac{24 - 9}{10}\). 0.8 marks for the correct final answer: 1.5% (accept 1.5).

1. Use the formula for percentage efficiency: \(\text{Efficiency} = \frac{\text{Useful Energy Output}}{\text{Total Energy Input}} \times 100\). 2. Substitute the values: \(\text{Efficiency} = \frac{280}{800} \times 100 = 35\%\).

1 mark for the correct method: \(\frac{280}{800} \times 100\). 0.8 marks for the correct final answer: 35% (accept 35).

To estimate and compare plant biodiversity using quadrats: 1. Establish a sampling grid in each woodland area using tape measures at right angles. 2. Generate random numbers to serve as coordinates, ensuring that the quadrats are placed without human bias. 3. Place the quadrat at each coordinate, identify the species present, and count either their abundance or percentage cover. 4. Repeat this multiple times (e.g., 10 or more) in both woodland areas to calculate a reliable mean, allowing a valid comparison of species richness and evenness.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Grid setup: Use of tape measures at right angles to establish a coordinate system [1 mark] - Randomisation: Generating random numbers/coordinates to place quadrats to prevent bias [1 mark] - Data collection & repetition: Counting species richness/abundance in each quadrat and repeating multiple times to find an average [1 mark] (Reject: non-random placement or only placing one quadrat per area)

National parks are not just closed areas; they conserve biodiversity through several active strategies: - Active Management: Rangers manage ecosystems by controlling invasive species, restoring degraded habitats, or conducting controlled burns. - Protection and Enforcement: Anti-poaching patrols monitor the park to deter and arrest illegal hunters and loggers. - Zoning and Ecotourism: Zoning allows visitors in designated areas, generating revenue from ecotourism to fund conservation work, while fragile core zones remain completely undisturbed.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Habitat management: Active measures such as controlling invasive species, habitat restoration, or controlled burning [1 mark] - Law enforcement: Anti-poaching patrols, monitoring, or enforcing wildlife protection laws [1 mark] - Zoning / Controlled tourism: Restricting human access to specific zones or using ecotourism revenue to fund conservation [1 mark]

Geothermal electricity generation works as follows: - High-pressure cold water is injected deep into the Earth's crust where volcanic activity makes rocks very hot. - The intense heat converts the water into high-pressure steam. - The steam is channeled back to the surface, where it turns a turbine. - The spinning turbine drives an electrical generator, producing electricity, which is then sent to the grid.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Water injection: Pump water deep underground into hot rock layers [1 mark] - Steam production: Heat from the rocks converts the water into high-pressure steam [1 mark] - Kinetic-to-electrical conversion: Steam turns a turbine, which drives a generator to produce electricity [1 mark]

Biogas digesters process organic waste anaerobically to produce methane gas. This reduces environmental degradation by: - Reducing Deforestation: Having a clean gas source for cooking reduces the need to harvest fuelwood, preserving forests and preventing soil erosion. - Reducing Water Pollution: Collecting animal manure and sewage for the digester prevents these wastes from washing into local rivers, reducing pathogens and organic pollution. - Providing Organic Fertilizer: The leftover digestate is high in nutrients and can be applied to fields, replacing synthetic fertilizers and reducing chemical runoff.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Forest preservation: Reduces dependency on fuelwood, preventing deforestation / habitat loss / soil erosion [1 mark] - Waste management: Collects organic waste/manure, preventing runoff and contamination of local water bodies [1 mark] - Fertilizer byproduct: Produces organic digestate/slurry, reducing the use of synthetic chemical fertilizers and subsequent eutrophication [1 mark]

Under normal conditions, strong trade winds blow westwards, driving the upwelling of cold, nutrient-rich deep water along the Peruvian coast, supporting high primary productivity. During an El Niño event: - The trade winds weaken or reverse direction. - This stops the upwelling of cold, nutrient-rich water, replacing it with warm, nutrient-poor surface water. - Without nutrients, phytoplankton populations collapse, meaning there is no food for small fish like anchovies, causing them to die or migrate elsewhere.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Wind behavior: Trade winds weaken or reverse direction [1 mark] - Suppression of upwelling: Prevents the upwelling of cold, nutrient-rich water to the surface / warm water accumulates [1 mark] - Food web collapse: Lack of nutrients reduces phytoplankton levels, starving fish populations or forcing them to migrate [1 mark]

Improving female education is a highly effective way to reduce birth rates because: - Career and Marriage Delay: Women spend more years in school and university, which delays marriage and the start of childbearing, reducing the total reproductive window. - Family Planning Awareness: Education increases literacy and access to information about contraception, empowering women to make informed decisions about family size. - Economic Independence & Child Survival: Educated women often prioritize career progression, and with better child survival rates due to improved healthcare knowledge, they opt for fewer children.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Age of childbearing: Delaying marriage / childbearing to focus on education or careers [1 mark] - Contraception: Greater knowledge, access, and usage of family planning / contraception [1 mark] - Child survival/Economic focus: Lower infant mortality means less need for replacement children, or prioritizing quality of life over quantity of children [1 mark]

Marine reserves protect fish from being harvested. This benefits external areas through two key mechanisms: - Inside the reserve, fish live longer and grow larger. Larger fish produce significantly more eggs than smaller fish, resulting in a population boom. - Spillover effect: As the reserve becomes crowded, adult and juvenile fish naturally migrate across the boundaries into fished areas. - Larval export: Ocean currents carry the massive abundance of eggs and larvae produced inside the reserve out into open fishing grounds, replenishing those stocks.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Safe breeding/Size: Fish can grow larger and reach breeding maturity without being caught [1 mark] - Spillover effect: Overcrowded adult/juvenile fish migrate out of the reserve into surrounding fishing zones [1 mark] - Larval export: Currents disperse eggs and larvae from the reserve to replenish outside waters [1 mark]

Fishing quotas (Total Allowable Catches) often fail due to several key factors: - Discarding: When fishers catch fish that exceed their quota or are of the wrong species, they often throw them back into the sea (discards). Most of these fish are already dead, so the actual mortality is much higher than recorded. - Enforcement Challenges: It is very difficult and expensive to monitor fishing vessels at sea, allowing illegal, unreported, and unregulated (IUU) fishing to bypass quotas. - Political Pressure: Governments may set quotas higher than recommended by scientists to protect short-term jobs and economic interests of the fishing industry.

Award 1 mark for each of the following points, up to a maximum of 3 marks: - Discards/Bycatch: Throwing back dead fish to avoid exceeding legal landing limits [1 mark] - Monitoring & Enforcement: High cost and difficulty of policing large ocean areas, leading to illegal/unreported fishing [1 mark] - Political/Economic influence: Quotas set above sustainable scientific recommendations due to lobbying or preserving local jobs [1 mark]

To estimate species richness and population size using random quadrat sampling: First, map the area as a grid and use random numbers to select coordinates for placing the quadrats, which avoids bias. Second, place the quadrat at these coordinates and count the number of individuals of each target species, or record the presence of different species to assess richness. Finally, calculate the mean density per quadrat and multiply this by the total area of the ecosystem to estimate the total population.

Award up to 3.1 marks: [1 mark] for explaining how to avoid bias using random coordinates or a grid system; [1 mark] for describing the recording or counting of species within the quadrat; [1 mark] for explaining how to scale up the sample (calculating mean density and multiplying by the total area).

National parks manage biodiversity by establishing legal protections that restrict activities like logging, mining, and urban development, ensuring that native species' habitats remain undisturbed. They also enforce anti-poaching laws. However, conflicts often arise because local or indigenous communities may be restricted from using the land for agricultural grazing, traditional hunting, or resource gathering, which can threaten their livelihoods.

Award up to 3.1 marks: [1 mark] for explaining legal protection of habitats or restriction of human activities; [1 mark] for mentioning active management like anti-poaching patrols or ecological restoration; [1 mark] for identifying a valid conflict (e.g., displacement of indigenous communities, loss of agricultural land, or crop damage by protected animals).

Geothermal energy works by drilling deep wells into the ground to access underground reservoirs of hot water and steam heated by volcanic/magmatic activity. This high-pressure steam is piped to the surface where it drives a turbine. The spinning turbine turns a generator, which produces electricity. One environmental advantage is that geothermal plants release virtually no greenhouse gases (such as carbon dioxide) during electricity generation, reducing their contribution to global warming.

Award up to 3.1 marks: [1 mark] for describing steam/hot water being extracted from underground; [1 mark] for explaining that steam drives a turbine which turns a generator; [1 mark] for stating an environmental advantage (e.g., no greenhouse gas emissions during operation, small land footprint, or reliable baseload with minimal air pollution).

Concentrated solar power (CSP) systems use large arrays of mirrors (heliostats) to reflect and focus sunlight onto a central receiver. This concentrated thermal energy heats a transfer fluid (such as water or molten salt) to very high temperatures. The heated fluid is used to generate steam, which expands through a steam turbine connected to an electrical generator. A primary limitation of CSP is that it requires direct, intense sunlight to heat the fluid effectively, making it unsuitable for cloudy regions, and it requires vast tracts of flat land, unlike PV which can be deployed on domestic rooftops.

Award up to 3.1 marks: [1 mark] for explaining that mirrors/heliostats reflect and focus sunlight onto a receiver to generate thermal energy; [1 mark] for explaining that this heat creates steam to drive a turbine and generator; [1 mark] for identifying a limitation (e.g., requires direct solar radiation/doesn't work well under cloud cover, or high space/water cooling requirement compared to PV).

Fishing down the food web is a process where fisheries, having depleted the large, high-trophic-level predatory fish (such as tuna or cod), shift their targets to progressively smaller, lower-trophic-level species (such as invertebrates and small planktivorous fish). This practice severely disrupts marine ecosystems because removing top predators can cause trophic cascades, leading to population explosions of prey species. Eventually, targeting the lower levels deprives remaining marine mammals and seabirds of their primary food sources, risking food web collapse.

Award up to 3.1 marks: [1 mark] for defining the term (depleting top/large predatory fish and moving to catch smaller/lower-trophic-level species); [1 mark] for explaining the impact of removing top predators (e.g., trophic cascades, predator-prey imbalance); [1 mark] for explaining how targeting lower trophic levels starves other marine predators or risks total food web collapse.

During a normal year, strong trade winds push warm surface water westward, allowing deep, cold, nutrient-rich water to rise (upwelling) along the Peruvian coast, supporting huge blooms of phytoplankton and a massive anchovy population. During an El Niño event, trade winds weaken or reverse, causing warm surface water to flow eastward toward Peru. This warm water suppresses the cold upwelling. Without nutrients, phytoplankton productivity crashes, leading to a lack of food for anchovies, causing them to die or migrate to cooler waters, which decimates the local fishery.

Award up to 3.1 marks: [1 mark] for explaining that El Niño weakens trade winds, preventing the cold upwelling along the Peruvian coast; [1 mark] for stating that this leads to a reduction in nutrients and a subsequent decline in phytoplankton/primary productivity; [1 mark] for concluding that anchovies starve, die, or migrate elsewhere, causing a collapse in the fishery.

In Stage 3 of the Demographic Transition Model, the birth rate falls rapidly due to several socioeconomic changes: First, there is improved access to family planning and contraception, allowing parents to control family size. Second, urbanization occurs, meaning children are no longer needed as free labor on agricultural land; instead, they become an economic liability due to the high cost of education and living. Third, increased opportunities for female education and careers lead women to marry later and have fewer children.

Award up to 3.1 marks: [1 mark] for explaining increased availability/use of contraception/family planning; [1 mark] for explaining urbanization/children changing from economic assets (farm labor) to liabilities (school costs); [1 mark] for explaining social changes, such as increased female education, careers, or a decline in infant mortality reducing the need to have 'replacement' children.

Total Allowable Cathes (TACs) set a scientifically determined maximum limit on the weight of a fish species that can be legally harvested in a season, preventing the population from being overexploited. Individual Transferable Quotas (ITQs) divide this TAC among individual fishers or companies as secure property rights, which can be bought or sold. This reduces the competitive 'race to fish,' promoting safer and more efficient fishing. However, a major disadvantage is 'high-grading,' where fishers discard dead, smaller, or less valuable fish back into the ocean to ensure their quota is only filled with high-value fish, resulting in unrecorded mortality.

Award up to 3.1 marks: [1 mark] for explaining that TACs set a safe biological limit to prevent depletion of fish stocks; [1 mark] for explaining that ITQs allocate shares to fishers, reducing the competitive rush and incentivizing sustainable stewardship; [1 mark] for identifying a disadvantage (e.g., high-grading/discarding, high cost of monitoring and enforcement, or marginalization of small-scale local fishers).

1. Wildlife corridors link isolated patches of habitat that have been separated by human activities like roads. 2. This allows species to safely migrate and access necessary resources such as food, water, and nesting sites. 3. It facilitates gene flow between previously isolated populations, which reduces the risk of inbreeding depression and increases genetic diversity.

Award 1 mark for each valid explanation point, up to a maximum of 3 marks: Connects fragmented habitats or links isolated patches (1 mark); Allows species to migrate or access resources safely (1 mark); Promotes genetic diversity or prevents inbreeding (1 mark); Reduces roadkill or human-wildlife conflict (1 mark).

1. Revenue generated from entry fees and guided tours can be directly reinvested into park management and anti-poaching patrol salaries. 2. It provides alternative employment for local communities (such as tour guides or lodge staff), which reduces their reliance on unsustainable activities like illegal logging and poaching. 3. It raises environmental awareness and educates both visitors and local communities about the ecological value of protecting biodiversity.

Award 1 mark for each distinct, well-explained point up to 3 marks: Funding for park management or conservation efforts from tourist fees (1 mark); Alternative employment reduces local reliance on logging or poaching (1 mark); Education or increased environmental awareness among tourists and locals (1 mark).

1. High-pressure steam or superheated water is pumped up from deep underground geothermal reservoirs. 2. This steam is used to rotate a turbine, which is mechanically connected to a generator that produces electricity. 3. An environmental limitation is that drilling and extraction can release harmful underground gases, such as hydrogen sulfide or small amounts of carbon dioxide, and can occasionally cause minor localized earthquakes.

Award up to 2 marks for explaining the generation process: Underground steam or hot water is pumped to the surface (1 mark); Steam rotates a turbine connected to a generator (1 mark). Award 1 mark for describing an environmental limitation: Release of toxic or greenhouse gases like hydrogen sulfide or carbon dioxide (1 mark); Risk of land subsidence or minor seismic activity (1 mark); Disposing of mineral-rich or toxic wastewater (1 mark).

1. Large-scale farming of biofuel crops often leads to deforestation and the destruction of natural habitats to clear land, causing severe biodiversity loss. 2. Intensive agricultural production requires significant quantities of chemical fertilizers and pesticides, which can wash into nearby water bodies and cause eutrophication. 3. The high demand for irrigation water to grow these crops can deplete local aquifers and deplete scarce freshwater resources.

Award 1 mark for each valid environmental disadvantage explained, up to a maximum of 3 marks: Habitat loss or deforestation for crop cultivation (1 mark); Water pollution or eutrophication from fertilizer and pesticide runoff (1 mark); Depletion of local water resources due to high irrigation demands (1 mark); Carbon emissions from soil disturbance and land clearance (1 mark).

1. During an El Nino event, the easterly trade winds weaken or reverse direction across the Pacific Ocean. 2. This stops the normal upwelling of cold, nutrient-rich deep water along the coast of Peru, replacing it with warm, nutrient-poor water. 3. Without nutrients, the growth of phytoplankton (the primary producers) drops dramatically. This leads to starvation, death, or migration of fish populations that rely on them.

Award 1 mark for each step in the explanation, up to a maximum of 3 marks: Weakening or reversal of trade winds stops upwelling (1 mark); Lack of cold, nutrient-rich water reaching the surface (1 mark); Sharp decline in phytoplankton or primary productivity (1 mark); Starvation, reduced reproduction, or migration of fish (1 mark).

1. The shockwaves from dynamite explosions physically shatter and destroy the underlying coral reef structure, which can take many decades or centuries to recover. 2. This destruction of the reef habitat eliminates crucial breeding grounds, nurseries, and shelters for hundreds of marine species, causing local biodiversity to collapse. 3. The explosions kill all fish and marine life in the surrounding area indiscriminately, including juvenile fish and non-target species, which severely disrupts local marine food webs.

Award 1 mark for each valid ecological consequence explained, up to a maximum of 3 marks: Physical destruction of coral reefs or loss of slow-growing structures (1 mark); Loss of habitat, shelter, and breeding grounds for marine species (1 mark); Indiscriminate mortality of non-target and juvenile species (1 mark); Interruption and collapse of food chains or webs (1 mark).

1. High infant mortality rates: Parents have many children to increase the likelihood that some will survive to support them in old age. 2. Economic need: In agricultural societies, children are seen as economic assets who provide manual labor on family farms. 3. Lack of family planning: There is minimal access to contraception and little education about family planning methods.

Award 1 mark for each distinct, well-explained reason, up to a maximum of 3 marks: High infant mortality or desire for surviving children (1 mark); Need for children as agricultural labor or economic assets (1 mark); Absence of government social security or dependency on children for old-age care (1 mark); Lack of access to or knowledge of contraception or family planning (1 mark); Cultural or religious values that encourage large families (1 mark).

1. Closed seasons involve legally banning fishing during specific times of the year, usually during the key breeding or spawning seasons of the target fish species. 2. This protects adult fish when they are concentrated in spawning grounds, ensuring they are not caught before they can reproduce. 3. By allowing fish to successfully spawn and encouraging larval survival, it ensures a new generation of fish, allowing stocks to replenish and stay sustainable.

Award 1 mark for each valid explanation, up to a maximum of 3 marks: Imposing fishing bans during critical times of the year or spawning periods (1 mark); Protecting mature breeding adult fish from harvest (1 mark); Allowing undisturbed reproduction to increase recruitment or offspring survival (1 mark); Helping to rebuild and maintain sustainable fish stock populations (1 mark).

Firstly, seed banks dry and freeze seeds at sub-zero temperatures, which maintains their viability for many decades. Secondly, they act as an insurance policy or genetic backup to prevent the extinction of threatened and endangered plant species. Thirdly, they provide a source of genetic material for ecological restoration, replanting devastated areas, and breeding crops that are resilient to pests or climate change.

Award 1 mark for each explanation point, up to a maximum of 3 marks: 1. Preserving viability by storing seeds in dry and low-temperature (sub-zero) environments. 2. Protecting genetic diversity / acting as a backup against extinction in the wild. 3. Providing seeds for ecological restoration of degraded habitats or research into pest-resistant crops.

During Stage 2 of the Demographic Transition Model, the death rate decreases rapidly due to three main factors. First, healthcare improves with the introduction of modern medicines, vaccines, and antibiotics which cure or prevent infectious diseases. Second, public infrastructure is upgraded to provide safe drinking water and effective sanitation, which significantly reduces water-borne diseases like cholera. Third, agricultural productivity increases and transportation improves, which ensures a more stable, reliable food supply and reduces deaths from famine.

Award 1 mark for each distinct reason explained, up to a maximum of 3 marks: 1. Improved healthcare and medical facilities (e.g., introduction of vaccinations and antibiotics). 2. Improved sanitation and clean water supply, reducing the transmission of water-borne pathogens. 3. Better food security, nutrition, and agricultural techniques, reducing deaths from starvation.

An effective response must explain at least three to four distinct fisheries management strategies, linking each to how it helps recover and sustain fish stocks. For example: net mesh regulations allow young fish to escape and breed; quotas prevent total stock collapse by limiting annual catches; closed seasons protect fish during vulnerable spawning periods; MPAs protect critical habitats and allow populations to rebuild; and strict monitoring/enforcement ensures these rules are followed in practice.

Award 1 mark for each valid management strategy explained, up to a maximum of 6 marks.
- Net mesh size/selective gear: explaining how larger mesh sizes allow juveniles to escape to reach reproductive age (1 mark).
- Quotas (Total Allowable Catches): explaining how setting limits prevents over-extraction and maintains viable breeding stock levels (1 mark).
- Closed seasons: explaining how banning fishing during spawning seasons protects breeding individuals and increases recruitment (1 mark).
- Marine Protected Areas (MPAs)/No-take zones: explaining how closed areas provide safe havens for population recovery and biodiversity conservation (1 mark).
- Licensing/limiting fishing effort: explaining how restricting vessel numbers or days at sea prevents excessive fishing pressure (1 mark).
- Enforcement and monitoring: explaining how patrols, onboard observers, or satellite tracking (VMS) prevent illegal fishing (1 mark).
- Alternative livelihoods/removing subsidies: explaining how reducing capacity reduces overall fishing pressure (1 mark).

1. Area of one quadrat: \(0.5\text{ m} \times 0.5\text{ m} = 0.25\text{ m}^2\).
2. Total area sampled: \(10 \times 0.25\text{ m}^2 = 2.5\text{ m}^2\).
3. Density: \(\frac{35\text{ plants}}{2.5\text{ m}^2} = 14\text{ plants per m}^2\).

Award 1 mark for correct calculation of total area sampled (\(2.5\text{ m}^2\)) and 0.14 marks for dividing the total count by the total area to give 14.

1. Rate of natural increase per 1000: \(24 - 8 = 16\) per 1000.
2. Convert to percentage: \(\frac{16}{1000} \times 100 = 1.6\%\).

Award 1 mark for obtaining the increase of 16 per 1000 population, and 0.14 marks for dividing by 10 to convert to 1.6%.

Efficiency \(= \frac{\text{Electrical Energy Output}}{\text{Thermal Energy Input}} \times 100 = \frac{135}{450} \times 100 = 30\%\).

Award 1 mark for setting up the ratio \(\frac{135}{450}\), and 0.14 marks for calculating the correct final percentage of 30%.

1. Absolute reduction in catch: \(120,000 - 78,000 = 42,000\) tonnes.
2. Percentage reduction: \(\frac{42,000}{120,000} \times 100 = 35\%\).

Award 1 mark for calculating the correct difference of 42,000 tonnes, and 0.14 marks for calculating the percentage reduction of 35%.

1. Number of underfished stocks: \(150 - (36 + 99) = 150 - 135 = 15\).
2. Percentage underfished: \(\frac{15}{150} \times 100 = 10\%\).

Award 1 mark for identifying that 15 stocks are underfished, and 0.14 marks for finding that this constitutes 10% of the total 150 stocks.

1. Absolute increase: \(5.4 - 4.0 = 1.4\) billion kWh.
2. Percentage increase: \(\frac{1.4}{4.0} \times 100 = 35\%\).

Award 1 mark for finding the increase of 1.4 billion kWh, and 0.14 marks for calculating the correct percentage increase of 35%.

1. Convert mass from kg to grams: \(4.8\text{ kg} = 4,800\text{ g}\).
2. Calculate concentration: \(\frac{4,800\text{ g}}{1,200\text{ m}^3} = 4\text{ g/m}^3\).

Award 1 mark for converting the mass to 4,800 grams, and 0.14 marks for dividing by 1,200 to obtain the concentration of 4.

To plot the line graph: 1. Identify the independent variable (Year) for the x-axis and the dependent variable (Birth Rate per 1000) for the y-axis. 2. Choose a linear scale for the y-axis (e.g., 0 to 30, with increments of 5) that occupies at least half of the grid space. 3. Plot the coordinate points precisely: (2010, 24), (2012, 21), (2014, 18), (2016, 15), (2018, 13), and (2020, 12). 4. Draw straight lines to connect the successive points.

1 mark: Both axes correctly labeled with units (Year on x-axis; Birth rate / per 1000 on y-axis) and linear scales.
1 mark: All 6 points plotted accurately within +/- 1 mm on the grid.
0.33 marks: Points connected with a clean, continuous line and scale occupies at least half the grid height.

To draw the bar chart: 1. Label the horizontal x-axis as 'Year' and the vertical y-axis as 'Annual wild catch / millions of tonnes'. 2. Create a scale on the y-axis from 0 to 5.0 with major intervals of 1.0. 3. Draw five bars of equal width with gaps between them. The heights of the bars must accurately correspond to: 2015 = 4.2, 2016 = 3.8, 2017 = 3.5, 2018 = 2.9, and 2019 = 2.1.

1 mark: Correctly labeled axes with units (Year on x-axis; Annual wild catch / millions of tonnes on y-axis).
1 mark: All 5 bars plotted to the exact correct height.
0.33 marks: Bars drawn with equal widths and consistent gaps between them, using a sensible scale.

To construct the bar chart: 1. Set the x-axis as 'Quadrat Number' and the y-axis as 'Species richness / number of plant species'. 2. Draw a linear scale on the y-axis from 0 to 16 with increments of 2. 3. Draw five individual vertical bars of equal width, ensuring there are clear gaps between the bars. Plot the bar heights: Quadrat 1 = 8, Quadrat 2 = 12, Quadrat 3 = 15, Quadrat 4 = 11, Quadrat 5 = 14.

1 mark: Correct axes labels (Quadrat number on x-axis; Species richness / number of plant species on y-axis).
1 mark: All 5 bars plotted to the correct heights.
0.33 marks: Consistent bar widths and gaps, with a linear scale that utilizes more than half of the grid height.

A closed season bans fishing during the reproductive period of a species. This directly allows mature adults to breed without being harvested, ensuring the recruitment of new offspring. Other measures like increasing mesh size protect young fish, while quotas and licensing control overall fishing pressure but do not specifically target the spawning season.

1 mark for identifying the correct option B. No marks for incorrect options.

A closed season bans fishing during the reproductive period of a species. This directly allows mature adults to breed without being harvested, ensuring the recruitment of new offspring. Other measures like increasing mesh size protect young fish, while quotas and licensing control overall fishing pressure but do not specifically target the spawning season.

1 mark for identifying the correct option B. No marks for incorrect options.

1. Ex situ conservation refers to the preservation of components of biological diversity outside their natural habitats (such as in zoos, botanic gardens, or seed banks).
2. A seed bank is a specific type of gene bank where seeds are dried and stored at very low temperatures to keep them viable for long periods.

Award 1.33 marks for the first blank: 'ex situ' (accept 'ex-situ').
Award 1.34 marks for the second blank: 'seed bank' (accept 'gene bank').
Reject: 'in situ' for the first blank.

In a geothermal power station, water is heated by geothermal energy from deep within the Earth to produce high-pressure steam. This steam is then directed to spin a turbine, which mechanical drives a generator to produce electrical energy.

Award 1.33 marks for the first blank: 'steam' (accept 'water vapor' or 'water vapour').
Award 1.34 marks for the second blank: 'turbine'.
Reject: 'smoke' or 'gas' (unless specified as steam/water vapor).

1. Closed seasons (or seasonal fishing bans) are used to restrict fishing during the breeding season of fish species, protecting them when they are most vulnerable.
2. Increasing the mesh size of nets ensures that only larger, mature fish are captured, while smaller immature fish escape to maintain the breeding population.

Award 1.33 marks for the first blank: 'closed seasons' (accept 'fishing bans' or 'seasonal closures').
Award 1.34 marks for the second blank: 'mesh size' (accept 'net mesh size').