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

A line transect is laid out across the woodland area. Quadrats are placed at pre-determined, regular intervals (for example, every 5 meters) along this line. Within each quadrat, the percentage cover or number of individuals of each plant species is recorded.

Award 1 mark for identifying the use of a transect line / belt transect. Award 1 mark for describing placing quadrats at regular/systematic intervals along the line to count or identify plants.

Underground heat heats water to produce high-pressure steam. This steam is directed to turn the blades of a turbine. The rotating turbine shaft spins a generator, which converts the kinetic energy into electrical energy.

M1: Steam rotates / turns a turbine. M2: The turbine is connected to a generator which produces / generates electricity.

1. Cold, nutrient-rich water is brought from the deep ocean to the sunlit surface layer. 2. These nutrients (like nitrates and phosphates) promote the rapid growth and reproduction of phytoplankton, providing abundant food for primary consumers and fish.

M1: Upwelling brings nutrients / named nutrients (such as nitrates or phosphates) to the surface. M2: This increases phytoplankton / algae growth, providing more food for fish (directly or indirectly).

\(\text{Natural increase per 1000} = \text{birth rate} - \text{death rate} = 24 - 8 = 16\). To convert to a percentage: \(\frac{16}{1000} \times 100 = 1.6\%\).

M1: Correct calculation of natural increase per 1000 (16 per 1000) OR showing the formula (24 - 8) / 10. M2: Correct percentage value: 1.6% (allow 1.6 with or without % sign if already in unit, but must have correct working for full marks).

Increasing the mesh size ensures that smaller, juvenile fish can easily swim through the net and escape. This allows them to reach sexual maturity and reproduce, replenishing the fish population before they are harvested.

M1: Allows small / young / juvenile / immature fish to escape from the net. M2: These fish can grow / reach breeding age / reproduce to replenish stocks.

Ecotourism generates revenue directly through park entry fees, which can be spent on conservation staff and anti-poaching patrols. Additionally, voluntary donations from visitors or eco-lodges provide financial support for local habitat restoration projects.

Any two from: Park entry fees / permit fees can be used to pay for rangers / anti-poaching patrols; Donations from tourists / eco-lodges can fund conservation / restoration projects; Sale of educational materials / merchandise to visitors; Tourism creates local jobs, reducing the need for destructive activities like poaching or illegal logging.

Disadvantages include: 1. Visual impact on pristine natural landscapes (visual pollution). 2. Risks to wildlife, particularly bird and bat collisions with the rotating blades.

Any two from: Collision risk to birds / bats; Habitat destruction / fragmentation during construction of turbines and access roads; Noise pollution affecting local wildlife or residents; Visual pollution / alteration of landscape views.

Farmed fish are often bred for rapid growth and may outcompete wild fish for limited food resources or nesting sites. Furthermore, high densities in cages make farmed fish susceptible to diseases and sea lice, which can be transmitted to wild populations upon escape.

Any two from: Outcompete wild fish for food / habitat / resources; Spread diseases / parasites (such as sea lice) to wild fish; Interbreed with wild fish, weakening the wild gene pool / reducing genetic diversity; Alter local food webs / predator-prey dynamics.

The capture-mark-recapture method can be used. A sample of lizards is captured, marked harmlessly, and released back into the environment. After a period of time, a second sample is captured, and the proportion of marked individuals is used to estimate the total population.

M1: Capturing a sample of animals, marking them safely, and releasing them back into the wild;
M2: Capturing a second sample later and using the proportion of marked to unmarked individuals to calculate the total population size (Lincoln Index).

Geothermal energy is reliable because it is available 24/7, independent of weather conditions or time of day, unlike wind power which depends on wind speeds.

M1: Geothermal energy is continuously available / can operate 24/7 / is not weather-dependent;
M2: It does not experience intermittent drops in generation like wind power does.

When a fishery collapses, there is a loss of employment for fishermen and processing workers. This also leads to a reduction in local business revenue and decline in export earnings.

M1: loss of jobs / unemployment for fishermen or fish processing workers;
M2: reduction in income for local businesses / loss of export revenue for the region.

During stage two, death rates fall due to improvements in medical care (e.g., vaccines) and better sanitation/clean water access, reducing the spread of infectious diseases.

M1: improvements in healthcare / medical technology / vaccines;
M2: better access to clean water / improved sanitation;
M3: more reliable food supply / improved nutrition.

Increasing net mesh size allows young, immature fish to escape through the larger gaps. This ensures they can reach reproductive age and spawn, maintaining future population levels.

M1: allows small / juvenile / immature fish to escape the nets;
M2: ensures fish can reach maturity / reproductive age to spawn and replenish the population.

Seed banks store a wide variety of seeds under cold, dry conditions. This preserves genetic material and rare species, which can be used to replant and restore degraded ecosystems in the future.

M1: preserves genetic material / prevents extinction of rare / threatened plant species;
M2: provides seeds for future habitat restoration / replanting of destroyed areas.

An environmental advantage is that solar panels produce no greenhouse gases during operation, reducing the carbon footprint. An environmental disadvantage is that their manufacturing process uses toxic chemicals and generates hazardous waste.

M1 (Advantage): no greenhouse gas emissions / no air pollution during operation;
M2 (Disadvantage): hazardous waste / toxic chemicals generated during manufacture OR disposal challenges of panels at the end of their life.

Within MPAs, fish populations increase and mature due to the ban on fishing. As the protected area becomes crowded, fish migrate out (the spillover effect) into adjacent unprotected waters, increasing catches for local fisheries.

M1: MPAs allow fish populations inside the zone to recover, grow larger, and reproduce safely;
M2: surplus fish / offspring migrate out of the MPA (spillover effect) into adjacent areas where they can be fished.

To keep seeds viable for long periods in a seed bank, the temperature must be kept very low (often below freezing, around -20 °C) to slow down cellular respiration and prevent germination. Additionally, the humidity must be kept low (dry conditions) to prevent fungal growth and decay.

Award 1 mark for each correct condition up to a maximum of 2 marks:
- low temperature / freezing / cold / refrigeration (1)
- dry conditions / low moisture / low humidity / dehydration (1)

Ecotourism minimizes negative impacts by establishing strict limits on the number of visitors allowed into sensitive areas (carrying capacity) to prevent habitat trampling. It also provides education to tourists about environmental protection and employs local guides to ensure visitors stick to designated paths.

Award 1 mark for each explanation point up to a maximum of 2 marks:
- limits on visitor numbers / capping tourist capacity / zoning (1)
- education of tourists on protecting wildlife / environmental awareness (1)
- hiring local guides to enforce rules / keeping tourists to designated paths to prevent trampling (1)
- reinvesting tour fees directly into habitat restoration / anti-poaching patrols (1)

Although geothermal energy is renewable, drilling into underground reservoirs can release toxic gases such as hydrogen sulfide, sulfur dioxide, and small amounts of carbon dioxide into the atmosphere. Furthermore, the high-pressure injection of water into geothermal wells can sometimes trigger minor earthquakes or ground instability.

Award 1 mark for each distinct disadvantage up to a maximum of 2 marks:
- release of toxic gases / hydrogen sulfide / sulfur dioxide / carbon dioxide (1)
- seismic instability / triggering earthquakes (1)
- land subsidence / sinking of land around the site (1)
- disposal of saline/mineral-rich wastewater which can contaminate freshwater sources (1)

Tidal power is highly predictable because tides are governed by the gravitational pull of the Moon and the Sun, which follow precise, well-known daily cycles. In contrast, wind power is highly intermittent and depends on atmospheric weather conditions, making it much harder to predict and integrate reliably into the national grid.

Award 1 mark for identifying the advantage and 1 mark for the explanation/contrast:
- tidal power is highly predictable / reliable / constant (1)
- because tides follow regular astronomical / lunar cycles, whereas wind is intermittent / unpredictable / weather-dependent (1)

During an El Niño event, the prevailing trade winds weaken, allowing warm water to spread eastward across the Pacific. This warm surface layer prevents the upwelling of deep, cold, nutrient-rich waters along the coast of South America. Without these nutrients, phytoplankton populations collapse, leading to a shortage of food for fish and causing their populations to decline or migrate.

Award 1 mark for each point up to a maximum of 2 marks:
- stops / reduces upwelling of cold, nutrient-rich water (1)
- reduction in nutrients leads to less phytoplankton / primary productivity (1)
- less food available for fish / disruption of the marine food chain (1)
- fish die or migrate to find cooler, more nutrient-rich water (1)

The formula for the rate of natural increase (RNI) is:
$$\text{RNI (per 1000)} = \text{Crude Birth Rate} - \text{Crude Death Rate}$$
$$\text{RNI (per 1000)} = 24 - 9 = 15\text{ per 1000}.$$
To convert this to a percentage:
$$\text{Percentage RNI} = \frac{15}{1000} \times 100 = 1.5\%.$$

Award 1 mark for correct working and 1 mark for the correct final percentage value:
- Correct working: \frac{24 - 9}{10} or 15 per 1000 (1)
- Correct answer: 1.5% (1)
Note: Award 2 marks for a correct final answer of 1.5% with no working shown.

Fish quotas (Total Allowable Catches) restrict the total tonnage of a specific fish species that can be harvested within a set timeframe. By limiting the catch, governments ensure that a sufficient number of mature, breeding adult fish remain in the wild to reproduce and replenish the population for future years.

Award 1 mark for each point up to a maximum of 2 marks:
- limits / caps the total amount / mass of fish caught (1)
- ensures enough mature / adult / breeding fish survive to reproduce (1)
- prevents overexploitation / overfishing / depletion of fish stocks (1)

Closed seasons are timed to coincide with the peak spawning or breeding periods of specific marine species. By banning fishing during these months, adult fish are allowed to mate and lay eggs without being caught or disturbed. This also prevents the accidental destruction of spawning grounds and ensures high survival rates for the young offspring.

Award 1 mark for each explanation point up to a maximum of 2 marks:
- protects fish during their breeding / spawning / reproductive period (1)
- allows fish to lay eggs / produce offspring undisturbed (1)
- prevents the harvesting of pregnant / egg-carrying females (1)
- allows juvenile fish to grow to maturity before being targeted by fisheries (1)

To calculate the birth rate per 1000 people:
$$\text{Birth rate} = \frac{\text{Number of births}}{\text{Total population}} \times 1000$$
$$\text{Birth rate} = \frac{2250}{125000} \times 1000 = 18$$

M1 for correct working showing:
$$\frac{2250}{125000} \times 1000$$ [1]

M2 for the correct calculation:
18 [1]

Closed seasons restrict fishing during specific times of the year, which typically align with fish breeding cycles or periods of vulnerability, reducing overall fishing pressure and allowing populations to maintain sustainable levels.

Award 1 mark for each valid point up to a maximum of 2 marks:
- protects fish during breeding / spawning season [1]
- allows fish to reproduce successfully / increase population [1]
- reduces the overall annual catch / reduces fishing effort [1]
- allows juvenile fish time to grow to maturity [1]

Tidal cycles are governed by gravitational forces of the Moon and Sun, making them highly predictable and constant in frequency. In contrast, wind energy depends on atmospheric pressure changes and weather conditions, which are highly variable and unpredictable.

Award 1 mark for explaining tidal predictability and 1 mark for contrasting with wind variability:
- tides are predictable / regular / guaranteed to happen [1]
- wind is intermittent / variable / dependent on weather conditions / not always blowing [1]

Captive breeding programmes protect endangered species from immediate threats in the wild by keeping them in controlled, predator-free environments to safely increase their population size. Zoos manage breeding records (using studbooks) to ensure genetic diversity is maintained and to prevent inbreeding. Ultimately, the goal is to release individuals back into restored or protected natural habitats to rebuild wild populations.

Award 1 mark for each valid point up to a maximum of 3 marks: 1. Increases the population size of endangered species in a safe, controlled environment. 2. Maintains genetic diversity and prevents inbreeding through managed breeding records or studbooks. 3. Provides individuals for reintroduction back into their natural, wild habitats once threats are managed.

Geothermal energy requires specific geological conditions to be viable, meaning it is typically restricted to regions near active tectonic plate boundaries where hot rocks are close to the Earth's surface. Additionally, the initial capital costs of exploring, drilling deep wells, and building specialized power plants are exceptionally high. Finally, drilling can release hazardous gases, such as hydrogen sulfide, which must be carefully managed to avoid atmospheric pollution.

Award 1 mark for each valid point up to a maximum of 3 marks: 1. It is geographically restricted to active tectonic plate boundaries or volcanic regions where hot rocks are accessible. 2. It has very high initial capital costs for deep-well drilling and plant construction. 3. There is a risk of releasing underground greenhouse or toxic gases (such as hydrogen sulfide) during extraction.

During an El Niño event, warm surface waters move eastward across the Pacific Ocean, which suppresses or stops the normal upwelling of cold, nutrient-rich deep water off the coast of South America. Because there are fewer nutrients available in the surface waters, the growth of phytoplankton declines rapidly. This lack of primary food sources leads to starvation, reduced reproduction, and the migration or death of fish species, such as anchovies, that depend on the phytoplankton food web.

Award 1 mark for each valid point up to a maximum of 3 marks: 1. Warm surface currents stop/suppress the upwelling of cold, nutrient-rich deep ocean water. 2. Reduced nutrient availability leads to a decline in phytoplankton and algae growth at the base of the food chain. 3. Fish populations (such as anchovies) starve, experience high mortality, or migrate to find colder waters.

The death rate has decreased in developing nations due to three main advancements: first, improvements in medical care, hospitals, and child immunization programmes prevent and treat deadly diseases; second, the provision of clean piped water and municipal sewage systems greatly reduces the transmission of waterborne pathogens; and third, better farming techniques and transport networks have improved food security, reducing death from starvation and malnutrition.

Award 1 mark for each valid reason and explanation up to a maximum of 3 marks: 1. Improved healthcare, healthcare facilities, or immunization programs reduce mortality from infectious diseases. 2. Access to clean drinking water and modern sanitation/sewage treatment systems prevents the spread of deadly waterborne diseases like cholera. 3. Increased food security, better agricultural yields, or improved food distribution networks reduce malnutrition and famine.

Increasing the size of the gaps in fishing nets allows smaller, immature (juvenile) fish to pass through and escape capture. This ensures that these young fish survive long enough to reach reproductive age and breed, which replenishes the wild fish stocks. Additionally, it helps reduce the volume of unwanted bycatch of non-target smaller marine species, reducing overall damage to the marine food web.

Award 1 mark for each valid point up to a maximum of 3 marks: 1. It allows juvenile/young/small fish to escape through the larger gaps in the net. 2. It ensures more fish survive to reach sexual maturity and reproduce, maintaining future stock levels. 3. It reduces the capture and waste of non-target smaller marine organisms (bycatch).

Seed banks store a vast and diverse collection of seeds from wild and crop plant species under dry, freezing conditions to preserve their viability for centuries. This acts as an insurance policy against the extinction of species in the wild due to habitat loss, climate change, or natural disasters. Furthermore, these stored seeds provide a source of genetic material for scientific research, selective breeding to improve agricultural resilience, and ecological restoration projects to replant degraded land.

Award 1 mark for each valid point up to a maximum of 3 marks: 1. They store seeds in cold, dry, climate-controlled environments to preserve their viability for long periods. 2. They act as a genetic backup/insurance policy to prevent the complete extinction of plant species in the wild. 3. They provide genetic stock for scientific study, crop breeding, or replanting and restoring destroyed ecosystems.

First, growing biofuel crops on a large scale often requires clearing natural forests or grasslands, causing severe habitat destruction and loss of biodiversity. Second, intensive monoculture farming of these crops relies on large inputs of chemical fertilizers and pesticides, which can wash into nearby watercourses and cause eutrophication and toxic water pollution. Third, these crops consume immense amounts of water for irrigation, which can deplete local aquifers and freshwater resources, worsening regional water stress.

Award 1 mark for each valid environmental disadvantage up to a maximum of 3 marks: 1. Land clearance/deforestation for growing biomass crops leads to habitat destruction and a loss of biodiversity. 2. Heavy application of chemical fertilizers and pesticides leads to agricultural runoff, causing water pollution/eutrophication in nearby water bodies. 3. Large-scale cultivation of biofuel crops requires high amounts of water for irrigation, depleting local freshwater resources/aquifers.

When women have access to higher education and professional career tracks, they often choose to delay marriage and childbirth to focus on their personal and professional development, which naturally shortens their lifetime reproductive window. Additionally, educated women generally have greater access to and knowledge of family planning services, reproductive health, and contraceptive methods. Finally, as women enter the workforce, the economic dynamics change: children are no longer viewed primarily as a source of household labor but instead represent a high cost of upbringing, encouraging families to have fewer, more highly supported children.

Award 1 mark for each valid point up to a maximum of 3 marks: 1. Pursuing education and careers delays the age of marriage and the birth of the first child, shortening the active reproductive period. 2. Education increases awareness, understanding, and consistent usage of modern family planning and contraceptive methods. 3. Working women gain financial independence and may prioritize career progression over raising large families, viewing children as an economic cost rather than a source of family labor.

Wildlife corridors connect isolated habitat patches. This allows species to migrate and find food or mates, increases genetic diversity by enabling interbreeding between populations, and reduces the risk of localized extinction by allowing recolonization.

Award 1 mark for each valid explanation point up to a maximum of 3 marks: [1] allows movement of animals between isolated forest areas to find resources or mates; [1] increases genetic diversity or gene flow, preventing inbreeding; [1] reduces the risk of local extinction by allowing recolonization after catastrophic events.

Geothermal power is a reliable and non-intermittent energy source available 24/7. Wind energy fluctuates depending on wind speeds, making it unreliable for base-load supply without backup or battery storage. Geothermal plants also have a much smaller land footprint.

Award 1 mark for each valid explanation point up to a maximum of 3 marks: [1] geothermal energy is reliable, consistent, and independent of weather conditions; [1] wind energy is intermittent and fluctuates with wind speed; [1] geothermal can meet constant base-load demand without requiring backup generation or battery storage.

Sonar technology allows vessels to locate the exact position and depth of fish schools. This increases fishing efficiency and dramatically reduces search time. Consequently, fish populations have fewer refuges, leading to rapid overexploitation of stocks.

Award 1 mark for each valid explanation point up to a maximum of 3 marks: [1] sonar precisely locates the position and depth of fish schools; [1] increases catch efficiency and reduces search time for fishing vessels; [1] removes natural refuges, allowing vessels to target and deplete remaining stocks, preventing population recovery.

Economic development reduces death rates because of: 1. Improved healthcare, such as access to vaccines and hospitals, which reduces mortality from preventable diseases. 2. Better sanitation and clean water, which prevents the transmission of infectious water-borne diseases like cholera.

Award marks for stating and explaining up to two reasons, up to a maximum of 3 marks overall: [1] stating improved healthcare or access to medical treatment/vaccines; [1] explaining that this reduces deaths from preventable or infectious diseases; [1] stating improved sanitation or access to clean drinking water; [1] explaining that this lowers the spread of water-borne pathogens.

A closed season restricts fishing during critical spawning periods. This allows adult fish to reproduce, increasing the number of offspring. It also protects vulnerable juvenile fish, giving them time to grow and reach sexual maturity before they are caught.

Award 1 mark for each valid explanation point up to a maximum of 3 marks: [1] restricts fishing during critical spawning or breeding periods; [1] allows adult fish to reproduce and replenish the population; [1] protects vulnerable eggs, juveniles, or spawning habitats from physical disturbance and harvesting.

Seed banks have several limitations: 1. Some seeds (recalcitrant seeds) cannot survive the drying and freezing process. 2. Seeds lose viability over time and must be periodically germinated and replaced, which is expensive. 3. Plants stored as seeds do not evolve in response to changing pests, diseases, or climate conditions.

Award 1 mark for each valid limitation point up to a maximum of 3 marks: [1] certain species produce recalcitrant seeds that cannot survive freezing/drying; [1] seeds lose viability over time and require costly, periodic germination and collection; [1] seeds do not evolve or adapt to shifting wild environmental conditions, pests, or diseases.

Coal containing sulfur impurities releases sulfur dioxide (SO2) when burned. High combustion temperatures also cause nitrogen and oxygen in the air to combine into nitrogen oxides (NOx). These acidic gases dissolve in atmospheric water vapor to form sulfuric and nitric acids, which fall as acid rain.

Award 1 mark for each valid explanation point up to a maximum of 3 marks: [1] burning coal releases sulfur dioxide from sulfur impurities in the coal; [1] high combustion temperatures cause nitrogen and oxygen in the air to combine into nitrogen oxides; [1] these gases rise and dissolve in atmospheric water vapor to form sulfuric and nitric acids, lowering the pH of rainfall.

Drift nets impact marine ecosystems in several ways: 1. They cause massive bycatch of non-target species like marine mammals and seabirds because they are non-selective. 2. They can cause rapid depletion of fish stocks across multiple trophic levels. 3. Lost drift nets become ghost nets that continue to entangle and kill organisms.

Award 1 mark for each valid impact point up to a maximum of 3 marks: [1] non-selective catching leads to high bycatch of non-target species such as marine mammals, turtles, or seabirds; [1] can overexploit populations and disrupt marine food webs; [1] lost nets become ghost nets that continue to entangle and kill marine life for a long time.

1. Lay a tape measure or line from the woodland edge into the open grassland. 2. Place quadrats at regular or fixed intervals along the line. 3. Record the species found and their abundance or percentage cover in each quadrat to relate species distribution to distance.

M1: tape measure or line laid out across the environmental gradient [1] M2: quadrats placed at regular/systematic intervals along the tape [1] M3: record species presence/abundance/percentage cover in each quadrat [1]

1. Habitat protection: prevents land clearance, urbanisation, or agricultural expansion, keeping ecosystems intact. 2. Protection of endangered species: reduces the risk of poaching and species extinction. 3. Funding through ecotourism: raises revenue that can be reinvested directly into park management and conservation.

Any three from: protects habitats from destructive human activities (e.g., logging, agriculture) [1]; prevents species extinction / protects endangered species [1]; provides economic revenue from ecotourism which can fund conservation [1]; allows scientific research / public education [1]

1. Hot water or steam is extracted under high pressure from underground reservoirs. 2. This high-pressure steam drives and turns a turbine. 3. The spinning turbine turns a generator, which produces electricity.

M1: steam or hot water extracted from hot underground rocks [1] M2: steam turns/drives a turbine [1] M3: turbine turns a generator to produce electricity [1]

1. Cost and abundance: coal is cheap, readily available, and abundant in many regions. 2. Reliability: provides a continuous baseload of electricity, unlike weather-dependent wind or solar. 3. Existing infrastructure: power plants and transport networks are already established and expensive to replace.

Any three from: coal is cheap / cost-effective / abundant [1]; provides a reliable / continuous / baseload power supply [1]; existing infrastructure / power stations are already built / expensive to decommission [1]; creates jobs in mining and energy sectors [1]

1. Trade winds weaken, stopping the upwelling of cold, nutrient-rich deep water. 2. Lack of nutrients reduces phytoplankton and primary productivity. 3. Less food is available for anchovies, causing starvation, migration, or a collapse in the fish population.

M1: weakening of trade winds prevents upwelling of cold, nutrient-rich water [1] M2: leads to a decrease in nutrients/phytoplankton/primary productivity [1] M3: anchovies starve / migrate / populations collapse due to lack of food [1]

1. Water pollution: excess nutrients from uneaten feed and fish waste lead to local eutrophication. 2. Disease transmission: high density of fish in cages allows parasites like sea lice to multiply and spread to wild fish. 3. Escaped fish: escaped fish can compete with wild fish for resources or breed with them, weakening the wild gene pool.

Any three from: organic waste / uneaten feed causes eutrophication / localized water pollution [1]; rapid spread of diseases / parasites (e.g., sea lice) to wild populations [1]; escaped fish outcompete wild fish / interbreed and weaken wild gene pool [1]; use of wild-caught fish as feed puts pressure on wild stocks [1]; use of antibiotics / chemicals pollutes the surrounding water [1]

Reasons include: 1. Increased career and educational opportunities for women, which leads them to delay marriage and childbirth. 2. High financial cost of raising children, meaning parents choose to have fewer children to maintain their standard of living.

Two marks for two correct reasons, and one mark for an explanation of either. (Max 3 marks) Reasons: access to family planning / contraception [1]; increased career/educational opportunities for women [1]; high economic cost of raising children [1]; lower infant mortality rate [1] Explanation: e.g., for women's careers: leads to delayed childbearing / choice to have smaller families [1]; for cost: parents choose fewer children to maintain standard of living [1]

1. Large mesh sizes allow small, young, or immature fish to swim through the net and escape. 2. These juvenile fish are left in the ocean to grow to adulthood. 3. This allows them to reproduce at least once, replenishing the population and keeping the fishery sustainable.

M1: allows juvenile / immature / small fish to escape through the larger holes [1] M2: juvenile fish remain in the sea to grow to maturity [1] M3: allows fish to reproduce / spawn to replenish the population [1]

1. Larger mesh holes allow juvenile and immature fish to escape from the net.
2. Escaped young fish can grow, reach maturity, and reproduce.
3. This maintains the breeding population and sustains the fish stock over time.

Award up to 3 marks for any three of the following points:
- M1: larger mesh size allows smaller / young / juvenile fish to escape or pass through the net;
- M2: allows escaped fish to reach maturity / breeding age / reproduce;
- M3: replenishes the fish stock / maintains population levels / prevents overfishing;
- M4: reduces bycatch of smaller non-target species;

1. Cold water is injected into hot volcanic rocks underground.
2. The heat from the Earth's crust boils the water, turning it into high-pressure steam.
3. The steam rises and rotates a turbine, which is connected to a generator that produces electricity.

Award up to 3 marks for any three of the following points:
- M1: water is pumped underground into hot rocks / hot geologic zones;
- M2: natural heat from the Earth turns the water into steam;
- M3: high-pressure steam rises to the surface;
- M4: the steam spins / drives a turbine;
- M5: the turbine is connected to a generator to produce electricity / convert kinetic to electrical energy;

A high-scoring essay should evaluate both sides of the statement:

1. Arguments in support of focusing entirely on national parks:
- Protecting habitats preserves the entire ecological community, food webs, and biodiversity, rather than just one targeted species.
- Species can continue to adapt and evolve naturally within their native environment.
- It is generally more cost-effective to protect a large area of habitat than to feed, house, and medically care for animals in captivity.
- National parks can generate sustainable income through regulated ecotourism, which supports local human communities.

2. Arguments in favor of captive breeding programs:
- If a species' habitat is completely destroyed, polluted, or dominated by invasive predators, captive breeding is the only way to prevent absolute extinction.
- It provides a safe, monitored environment to increase the population size of critically endangered species with minimal mortality.
- Zoos and captive breeding centers raise public awareness and generate significant funding that is often directed back into habitat preservation.

Conclusion:
An effective conservation strategy requires a balanced approach. Habitat protection is the ultimate goal, but captive breeding acts as a critical safety net that prepares species for future reintroduction once wild habitats are restored and secured.

Level 3 (5–6 marks):
A coherent response is given that develops and supports the candidate's conclusion using relevant details and examples.
Indicative content and subject-specific vocabulary (e.g., in-situ, ex-situ, gene pool, ecotourism, biodiversity) are generally used precisely and accurately.
Good responses present a balanced evaluation of the statement.

Level 2 (3–4 marks):
Development and support of the conclusion is evident, though the response may lack some coherence and/or detail.
Some irrelevant detail may be present.
Indicative content and subject-specific vocabulary are used but may lack precision and/or accuracy.
Responses contain evaluation of the statement, but this may not be fully balanced.

Level 1 (1–2 marks):
The response may be limited in development and/or support.
Contradictions and/or irrelevant detail may be present.
Indicative content and subject-specific vocabulary are limited or absent.
Responses may lack structure or be in the form of a simple list. Evaluation is limited or absent.

No response or no creditable response (0 marks)

Indicative content:

Agree:
- National parks protect entire ecosystems, not just single species.
- Cost-effective (protecting large land areas vs. high upkeep of zoos).
- Reintroduction from captivity can fail due to loss of survival instincts or disease transmission.
- Tourism in national parks funds local communities, creating positive incentives for conservation.

Disagree:
- Captive breeding is a crucial safeguard if wild habitats are completely unsafe/destroyed.
- Controlled breeding prevents immediate extinction and maintains genetic diversity (avoiding inbreeding depression).
- Zoo programs raise critical public awareness and funding.
- Success stories exist (e.g., Arabian oryx, California condor) where captive breeding rescued species before successful reintroduction.

1. Calculate the remaining percentage of the catch: \( 100\% - 65\% = 35\% \).
2. Calculate the 2022 catch: \( 8.4 \text{ million tonnes} \times 0.35 = 2.94 \text{ million tonnes} \).

1 mark for showing correct working: e.g., \( 8.4 \times 0.35 \) or \( 8.4 - (8.4 \times 0.65) \).
1 mark for the correct answer: 2.94.

1. Calculate net natural change: \( 950 \text{ births} - 320 \text{ deaths} = 630 \).
2. Calculate net migration change: \( 120 \text{ immigrants} - 80 \text{ emigrants} = 40 \).
3. Calculate total net change: \( 630 + 40 = 670 \).

1 mark for correct method showing both natural change and migration calculation: e.g., \( (950 - 320) + (120 - 80) \).
1 mark for the correct answer: 670.

1. Determine the percentage contribution of the diesel generator: \( 100\% - 70\% - 20\% = 10\% \).
2. Calculate the capacity generated by diesel: \( 120 \text{ MW} \times 0.10 = 12 \text{ MW} \).

1 mark for correct working showing the remaining percentage (10%) or \( 120 \times 0.10 \).
1 mark for the correct answer: 12.

Estimated population = Reserve area \( \times \) average density = \( 25,000 \text{ m}^2 \times 0.08 \text{ plants/m}^2 = 2,000 \text{ plants} \).

1 mark for correct working: \( 25,000 \times 0.08 \).
1 mark for the correct answer: 2000.

1. Determine total population: \( 180,000 + 145,000 = 325,000 \text{ people} \).
2. Calculate density: \( 325,000 \text{ people} / 12,500 \text{ km}^2 = 26 \text{ people per km}^2 \).

1 mark for showing correct sum of total population (325,000) or division step \( 325,000 / 12,500 \).
1 mark for the correct answer: 26.

Copper extracted = Total ore \( \times \) grade percentage = \( 15 \text{ million tonnes} \times 0.008 = 0.12 \text{ million tonnes} \).

1 mark for correct working: \( 15 \times 0.008 \) or \( 15 \times (0.8 / 100) \).
1 mark for the correct answer: 0.12.

1. Determine percentage not recycled: \( 100\% - 78\% = 22\% \).
2. Calculate non-recycled volume: \( 450 \text{ m}^3 \times 0.22 = 99 \text{ m}^3 \).

1 mark for correct calculation of 22% or working: \( 450 \times 0.22 \) or \( 450 - (450 \times 0.78) \).
1 mark for the correct answer: 99.

To describe the relationship, we observe the trend in both variables:
- In 2010, when the number of active vessels is lowest (120), the biomass is at its highest (10.2 million tonnes).
- In 2016, when the number of active vessels is highest (240), the biomass is at its lowest (2.3 million tonnes).
- Therefore, there is an inverse relationship (negative correlation) between the two variables.

Award up to 2 marks:
- 1 mark for identifying the inverse relationship / negative correlation (i.e., as active vessels increase, biomass decreases).
- 1 mark for supporting the description with paired data from the table (e.g., 10.2 million tonnes at 120 vessels versus 2.3 million tonnes at 240 vessels).

The rate of natural increase is calculated using the formula:
Rate of Natural Increase = Birth Rate - Death Rate

For the year 2000:
- Birth rate = 31 per 1000
- Death rate = 9 per 1000

Calculation:
31 - 9 = 22 per 1000

Award up to 2 marks:
- 1 mark for extracting the correct birth rate (31) and death rate (9) for the year 2000 from the table.
- 1 mark for calculating the correct rate of natural increase as 22.

To find the year with the greatest difference, calculate the absolute difference between the wind and solar percentages for each recorded year:
- 2015: 5% - 2% = 3%
- 2017: 12% - 6% = 6%
- 2019: 24% - 15% = 9%
- 2021: 38% - 28% = 10%
- 2023: 45% - 42% = 3%

The difference is greatest in the year 2021, and the value of this difference is 10%.

Award up to 2 marks:
- 1 mark for stating the correct year: 2021.
- 1 mark for stating the correct maximum difference: 10% (allow 10).

To calculate the percentage decrease: 1. Find the decrease in biomass: 50000 - 15000 = 35000 tonnes. 2. Divide the decrease by the original biomass in 2018: 35000 / 50000 = 0.70. 3. Multiply by 100 to get the percentage: 0.70 * 100 = 70%.

Award 1 mark for the correct calculation showing 70%.

1. succession
2. indicator
3. keystone

Award 1 mark for each correct term (up to a maximum of 2.67 marks total, approximately 0.89 marks per correct blank):
- Blank 1: succession
- Blank 2: indicator
- Blank 3: keystone

1. chemical
2. turbine
3. photovoltaic

Award 1 mark for each correct term (up to a maximum of 2.67 marks total, approximately 0.89 marks per correct blank):
- Blank 1: chemical
- Blank 2: turbine
- Blank 3: photovoltaic

1. bycatch
2. mesh
3. quotas

Award 1 mark for each correct term (up to a maximum of 2.67 marks total, approximately 0.89 marks per correct blank):
- Blank 1: bycatch
- Blank 2: mesh
- Blank 3: quotas