Mark Scheme

Section A — Structured Questions

Question 1

(a) Calculate the rate of reaction at pH 7.

• Rate = 1 ÷ 90 (1 mark)
• = 0.0111 (s⁻¹) (1 mark)

Accept: 0.01111 or better

(b) Describe the effect of pH on the rate of enzyme action.

• Rate of reaction increases from pH 3 to pH 7 (1 mark)
• Rate of reaction decreases from pH 7 to pH 11 / pH 7 shows the highest/fastest rate (1 mark)

Accept: equivalent descriptions of the pattern Reject: statements about optimum pH without reference to the data pattern

(c) Explain why the rate of reaction decreases at pH 11.

• The pH is too high/alkaline / is not the optimum pH (1 mark)
• The active site changes shape / enzyme denatures (1 mark)
• The substrate no longer fits the active site / enzyme-substrate complexes cannot form (1 mark)

Accept: "active site is damaged/altered" Reject: "enzyme dies" or "enzyme breaks down into smaller pieces"

(d) Suggest why temperature control is important.

• Temperature affects enzyme/reaction rate / is a variable (1 mark)
• To make it a fair test / to ensure pH is the only variable affecting rate (1 mark)

Accept: "to keep it constant" for first mark if linked to fairness

Question 2

(a) State two structures visible in Cell A that are not in Cell B. Two from:

• Cell wall (1 mark)
• Chloroplasts (1 mark)
• (Permanent) vacuole (1 mark)

Accept: large/sap vacuole Reject: "nucleus" or "cytoplasm"

(b) Explain why mitochondria are present in plant cells.

• Chloroplasts only produce glucose/energy during photosynthesis / only in light / only in cells with chloroplasts (1 mark)
• Mitochondria release energy from glucose (by respiration) (1 mark)
• Energy is needed all the time / at night / for active processes / for all cells (1 mark)

Accept: "not all plant cells have chloroplasts" Reject: "to make energy" without reference to respiration

(c) Calculate the length of the cell image.

• Magnification = image size ÷ actual size OR image size = magnification × actual size (1 mark)
• Image size = 400 × 50 = 20,000 μm (1 mark)
• = 20 mm (1 mark)

Accept: correct working shown even if formula not stated explicitly for first mark Accept: 0.02 m or 2 cm if converted correctly

(d) Explain what is meant by resolution.

• Resolution is the ability to distinguish between two (separate) points / the smallest distance between two points that can be seen as separate (1 mark)
• Higher resolution allows more detail/structures to be seen / allows smaller structures/organelles to be seen (1 mark)
• Named example of structure that can be seen with electron microscope but not light microscope, e.g., ribosomes / mitochondrial cristae / endoplasmic reticulum (1 mark)

Accept: "clarity" or "sharpness" only if linked to distinguishing separate points Reject: "magnification" instead of resolution

Question 3

(a) State two differences between cancer cells and stem cells. Two from:

• Cancer cells divide uncontrollably / stem cells divide in a controlled way (1 mark)
• Stem cells can differentiate / cancer cells cannot differentiate (or have lost specialisation) (1 mark)
• Cancer cells can spread to other tissues/metastasise / stem cells remain in specific locations (1 mark)
• Cancer cells are harmful / stem cells are useful for growth and repair (1 mark)

Accept: equivalent statements showing clear contrast

(b) Describe what happens during mitosis.

• DNA/chromosomes replicate / double (1 mark)
• (Chromosomes/DNA) line up along the centre/equator of the cell (1 mark)
• (Chromosomes) are pulled apart / move to opposite ends/poles of the cell (1 mark)
• Two identical (daughter) cells are formed / nucleus divides / cytoplasm divides (1 mark)

Accept: "copied" for replicate Reject: descriptions of meiosis Maximum 3 marks if stages not in logical order

(c) Explain why these treatments cause side effects.

• The treatments affect all rapidly dividing cells / cannot distinguish between cancer cells and normal dividing cells (1 mark)
• Hair follicle cells divide rapidly (1 mark)
• (White) blood cells / cells in bone marrow divide rapidly / immune system cells divide rapidly (1 mark)
• So hair falls out and fewer white blood cells are produced / immune system is weakened (1 mark)

Accept: any two examples of rapidly dividing normal cells with appropriate side effects Maximum 3 marks if no link made between treatment and side effects

Question 4

(a) Name organ D.

• Pancreas (1 mark)

(b) State two other organs that produce lipase. Two from:

• Small intestine (1 mark)
• Stomach (1 mark)

Reject: large intestine, liver, salivary glands

(c) Give two reasons why the stomach produces hydrochloric acid. Two from:

• To kill bacteria/pathogens (in food) (1 mark)
• To provide optimum/acidic pH for protease/pepsin (1 mark)
• To denature enzymes (in food/from pathogens) (1 mark)

Accept: "to digest protein" if linked to enzyme function Reject: "to break down food" alone without reference to specific function

(d) Describe three adaptations of the small intestine. Three from:

• Long (length) / large surface area (1 mark)
• Has villi/microvilli / highly folded (1 mark)
• Good/rich blood supply / network of capillaries (1 mark)
• Thin wall/lining / one cell thick / short diffusion distance (1 mark)

Accept: specific measurements if accurate (e.g., "several metres long") Each mark requires clear statement of adaptation

Question 5

(a) Calculate the percentage change in mass.

• (–0.2 ÷ 2.5) × 100 (1 mark)
• = –8.0 (%) (1 mark)

Accept: –8 or 8% decrease Reject: positive value

(b) Explain why the potato cylinder increased in mass.

• Water potential is higher outside the cell / lower inside the cell / water potential gradient exists (1 mark)
• Water moves into the cell by osmosis (1 mark)
• Through a partially permeable membrane / from high to low water potential (1 mark)

Accept: "more dilute outside" or "more concentrated inside" Reject: "higher concentration outside" without specifying of water Must mention osmosis for second mark

(c) Estimate the concentration and explain.

• 0.4 mol/dm³ (1 mark)
• Because there is no change in mass / water potential inside equals water potential outside (1 mark)

Accept: "no net movement of water" Accept: range 0.35–0.45 mol/dm³

(d) Suggest one other variable to control. One from:

• Volume of solution (1 mark)
• Surface area of potato cylinder / dimensions (1 mark)
• Temperature (1 mark)
• Time left in solution (1 mark)
• Type of potato / source (1 mark)

Accept: any reasonable control variable with correct justification if given

Question 6

(a) Explain what is meant by a double pump.

• One pump sends blood to the lungs (1 mark)
• One pump sends blood to the body/rest of the body/organs (1 mark)

Accept: pulmonary and systemic circulation Reject: "right and left side" without reference to where blood goes

(b) Explain why structure X has a thicker wall.

• (Because) it has to pump blood further / around the whole body / at higher pressure (1 mark)
• So needs more muscle / to generate more force (1 mark)

Accept: "to the body" rather than "around the body" Reject: "to pump more blood" alone

(c) Describe two adaptations and explain how each helps. One mark for each adaptation, one mark for each explanation:

• Biconcave shape / disc shape (1 mark)
  • Increases surface area (for oxygen diffusion/absorption) (1 mark)
• No nucleus (1 mark)
  • More space/room for haemoglobin / more oxygen can be carried (1 mark)
• Contains haemoglobin (1 mark)
  • (Haemoglobin) binds to/carries/combines with oxygen (1 mark)

Accept: "contains lots of haemoglobin" Reject: "small" or "flexible" without further detail Maximum 4 marks total

(d) Evaluate the use of stents and statins. Indicative content:

Stents:

• Keep arteries open / prevent blockages
• Quick/immediate effect / surgical procedure
• Risk of infection / blood clots / surgery risks
• Does not prevent further buildup

Statins:

• Lower cholesterol levels / reduce plaque formation
• Long-term solution / prevent future problems
• Must be taken regularly / for life
• Can have side effects / not suitable for everyone

Award marks for:

• Two or more advantages of stents or statins (1 mark each, max 2)
• Two or more disadvantages or limitations (1 mark each, max 2)
• Must cover both stents AND statins for full marks

Accept: balanced evaluation showing both treatments Reject: purely descriptive answers without evaluation

Section B — Extended Response

Question 7 — Mark scheme (10 marks)

This question assesses AO1 (knowledge), AO2 (application), and AO3 (evaluation).

Level 3 (7–10 marks): A detailed and coherent evaluation that:

• Provides multiple reasoned arguments for and against animal testing
• Shows clear understanding of drug development stages and why animals are used
• Evaluates alternative methods and their limitations
• Reaches a supported conclusion
• Uses scientific terminology accurately throughout
• At top of band: balanced, nuanced discussion with explicit links between points

Level 2 (4–6 marks): A reasonable evaluation that:

• Provides some arguments for and/or against animal testing
• Shows some understanding of why animals are used
• May mention alternatives but evaluation is limited
• May reach a simple conclusion
• Some scientific terminology used correctly

Level 1 (1–3 marks): A limited response that:

• States simple points about animal testing
• Limited scientific understanding shown
• May be one-sided or descriptive
• Little or no evaluation
• Limited use of scientific terminology

0 marks: No relevant content

Indicative content (not prescriptive):

Why animals are used:

• Whole organism testing needed to see effects on organs/systems
• Similar physiology to humans
• Can test for side effects
• Required by law before human trials
• Computer models and cell cultures have limitations

Ethical concerns:

• Causes suffering to animals
• Animals cannot consent
• Moral question about using animals for human benefit
• Should minimize harm (3Rs: replace, reduce, refine)

Alternatives:

• Computer modelling – limited by knowledge gaps
• Cell/tissue culture – doesn't show whole organism effects
• Human volunteers – only after other testing
• Each has limitations that mean cannot fully replace animal testing currently

Evaluation points:

• Balance between human safety and animal welfare
• Legal and regulatory requirements
• Scientific necessity vs ethical concerns
• Progress in alternatives but not yet sufficient

Question 8 — Mark scheme (10 marks)

This question assesses AO1 (knowledge) and AO2 (application of knowledge to compare systems).

Level 3 (7–10 marks): A detailed and coherent comparison that:

• Covers structure and function of both plant and animal transport systems
• Makes explicit comparisons between the two systems
• Explains adaptations in relation to function
• Uses accurate scientific terminology throughout
• Shows integrated understanding of similarities and differences
• At top of band: sophisticated comparisons with detailed explanations

Level 2 (4–6 marks): A reasonable comparison that:

• Describes structure and/or function of both systems
• Makes some comparisons
• May explain some adaptations
• Uses scientific terminology with some accuracy
• May treat systems separately rather than comparing throughout

Level 1 (1–3 marks): A limited response that:

• Describes one or both systems with limited detail
• Few or no comparisons made
• Limited explanation of adaptations
• Limited use of scientific terminology
• May contain errors

0 marks: No relevant content

Indicative content (not prescriptive):

Substances transported:

• Plants: water and mineral ions (xylem), sugars/amino acids (phloem)
• Animals: oxygen, carbon dioxide, glucose, amino acids, urea, hormones, antibodies, etc.
• Both transport nutrients and other essential substances

Structure:

• Plants: xylem (dead cells, lignified walls), phloem (living cells, sieve plates, companion cells)
• Animals: arteries (thick elastic walls, muscle), veins (valves, thinner walls), capillaries (one cell thick)
• Both have specialized vessel types for different functions

Adaptations:

• Xylem: hollow tubes, lignin for strength, allows mass flow under tension
• Phloem: sieve plates for flow, companion cells provide energy for active transport
• Arteries: elastic walls for pulse/pressure, muscle for control
• Veins: valves prevent backflow, large lumen for low-pressure flow
• Capillaries: thin walls for diffusion, permeable, large surface area

Functional comparisons:

• Plants: transpiration stream pulls water up, translocation moves sugars both directions
• Animals: heart provides pressure, arteries carry away from heart, veins return to heart
• Both: pressure gradients drive flow, branching increases surface area
• Difference: plants no pump (transpiration pull), animals have pump (heart)

Question 9

(a) Calculate the percentage efficiency.

• (2 ÷ 8) × 100 (1 mark)
• = 25(%) (1 mark)

Accept: 25.0

(b) Explain why biomass decreases at each stage.

• Not all of the organism is eaten / some parts not digested (1 mark)
• Energy/biomass is used in respiration (1 mark)
• Energy/biomass lost as heat / in movement / maintaining body temperature (1 mark)
• Energy/biomass lost in waste / in urine / in faeces (1 mark)

Accept: "lost in excretion" for waste Maximum 4 marks

(c) Evaluate the use of biological control compared to pesticides. (6 marks)

Level 3 (5–6 marks): A detailed evaluation that:

• Discusses effectiveness of both methods
• Considers environmental impact of both
• Considers economic factors
• Reaches a balanced, supported conclusion
• At top of band: nuanced discussion of contexts where each is more suitable

Level 2 (3–4 marks): A reasonable evaluation that:

• Discusses some aspects of both methods
• Some consideration of different factors
• May reach a simple conclusion
• Some evaluation rather than pure description

Level 1 (1–2 marks): A limited response that:

• States simple points about one or both methods
• Little evaluation
• Largely descriptive

0 marks: No relevant content

Indicative content:

Biological control:

• Advantages: natural, no chemicals, long-term effect once established, no resistance, specific to pest
• Disadvantages: slow to work, may affect non-target species, control organism may become pest, expensive to establish

Pesticides:

• Advantages: fast-acting, kills most/all pests, relatively cheap, predictable results
• Disadvantages: kills beneficial insects, bioaccumulation, resistance develops, repeated application needed, environmental damage

Economic factors:

• Initial cost vs long-term cost
• Crop yield and quality
• Organic premium pricing

Question 10

(a) Describe the relationship between light intensity and rate of photosynthesis.

• As light intensity increases, rate of photosynthesis increases (1 mark)
• (Positive) correlation / directly proportional (at least initially) (1 mark)

Accept: "more bubbles produced at higher light intensity" Accept: reference to specific data

(b) Explain why increasing light intensity increases the rate.

• Light is needed for photosynthesis / provides energy for the reaction (1 mark)
• More light means more energy (available) (1 mark)
• So more glucose produced / more reactions per unit time / faster reaction rate (1 mark)

Accept: "photosynthesis is faster" Reject: "plants need light to see"

(c) Explain why these factors were controlled and how each could become limiting.

• Temperature and CO₂ need to be controlled to make it a fair test / so only light intensity varies (1 mark)

Temperature:

• If temperature is too low, enzymes work slowly / less kinetic energy (1 mark)
• If temperature is too high, enzymes denature (1 mark)

Carbon dioxide:

• CO₂ is a reactant in photosynthesis (1 mark)
• If CO₂ is low, it becomes the limiting factor / not enough substrate for the reaction (1 mark)
• Enriched CO₂ ensures it is not limiting (in this investigation) (1 mark)

Maximum 6 marks total Must address both why controlled AND how each becomes limiting

(d) Evaluate whether increased costs are justified. (7 marks)

Level 3 (6–7 marks): A detailed, coherent evaluation that:

• Explains how lighting and heating affect photosynthesis
• Considers multiple costs (installation, running, maintenance)
• Considers economic benefits (increased yield, out-of-season production, quality)
• Weighs costs against benefits
• Reaches a balanced, supported conclusion considering different contexts
• At top of band: sophisticated discussion of when costs are/aren't justified (crop type, climate, market)

Level 2 (3–5 marks): A reasonable evaluation that:

• Explains some effects on photosynthesis
• Considers some costs and/or benefits
• Shows some evaluation rather than pure description
• May reach a simple conclusion

Level 1 (1–2 marks): A limited response that:

• States simple points about costs or benefits
• Limited explanation of photosynthesis effects
• Largely descriptive with little evaluation

0 marks: No relevant content

Indicative content:

Effects on photosynthesis:

• Artificial lighting increases light intensity (especially winter/night)
• Heating maintains optimum temperature for enzymes
• Both increase rate of photosynthesis
• Allows photosynthesis when natural conditions limiting

Costs:

• High initial installation costs (lights, heating systems, control systems)
• Ongoing electricity/fuel costs
• Maintenance and replacement
• May be unaffordable for small farms

Economic benefits:

• Increased yield per unit area
• Faster growth = more harvests per year
• Year-round production / out-of-season production
• Better quality produce = higher prices
• Can grow in regions/climates otherwise unsuitable
• More predictable/reliable production

Evaluation:

• For high-value crops (tomatoes, lettuce, flowers), costs likely justified
• In cold climates, more justifiable than warm climates
• In areas with high crop prices, more economically viable
• Need to consider crop type, location, market prices, scale of operation
• Environmental considerations (carbon footprint)
• Renewable energy sources may reduce long-term costs

Sample Answers with Examiner Commentary

Question 7 — Sample Answers

Grade 9 (top of Higher) answer

Animal testing plays a crucial role in drug development but raises significant ethical concerns. Animals are used because they provide whole-organism models that can show how a drug affects different organ systems and whether it causes unexpected side effects that cannot be detected in cell cultures. Mammals like mice and rabbits share similar physiology to humans, making them useful for predicting human responses. Computer models are limited by gaps in our knowledge of biological systems, and testing on human cells cannot show how a drug behaves in a complete organism or whether it accumulates in certain organs.

However, animal testing raises serious ethical issues. Animals cannot consent to being used in experiments and may suffer pain or distress. Many people argue that it is morally wrong to use animals for human benefit, regardless of the potential medical advances. Scientists are required to follow the 3Rs principle: replace animal testing where possible, reduce the number of animals used, and refine procedures to minimize suffering. Despite these safeguards, animal welfare remains a major concern.

Alternative methods are being developed but have limitations. Computer modelling has improved significantly but cannot fully simulate the complexity of biological systems. Tissue cultures can test toxicity but don't show effects on whole organs or interactions between systems. Some testing can now be done on human volunteers using microdoses, but this is only possible after extensive safety testing using other methods. Currently, alternatives cannot completely replace animal testing, though they can reduce the number of animals needed.

In conclusion, while animal testing has significant ethical problems, it remains necessary for developing safe medicines under current technology and regulations. The best approach is to continue developing alternatives while minimizing animal use and suffering through strict regulation and the 3Rs. As technology advances, particularly in computer modelling and artificial tissues, we may eventually be able to replace most or all animal testing.

Mark: 10/10

Examiner commentary: This answer achieves full marks by providing a sophisticated, balanced evaluation. The candidate demonstrates detailed understanding of why animals are used, acknowledges ethical concerns with specific reference to the 3Rs principle, and critically evaluates alternatives with clear explanation of their limitations. The answer shows excellent structure with each paragraph addressing a different aspect, uses precise scientific terminology throughout, and reaches a nuanced conclusion that recognizes complexity and future possibilities. This is Level 3 high.

Grade 6 (solid pass) answer

Animal testing is used in drug development because scientists need to test if drugs are safe before giving them to humans. Animals like mice are similar to humans so they can show if a drug will have side effects. They test on cells first but this doesn't show everything. Computer models can be used but they aren't as good as real animals because they can't show everything that happens in a body.

Some people think animal testing is wrong because it hurts animals and they can't agree to it. Animals might feel pain in the experiments. The 3Rs means scientists should try to use fewer animals and cause less suffering.

There are alternatives like computer programmes and testing on cells in a lab. These don't hurt animals which is better. But they can't completely replace animal testing yet because they don't show all the effects. Human volunteers can be used but only after other testing because it wouldn't be safe.

In conclusion, animal testing is needed to make sure drugs are safe but scientists should try to use alternatives when they can to reduce animal suffering. It's important for developing medicines but we should keep trying to find better methods.

Mark: 6/10

Examiner commentary: This answer achieves a mid-Level 2 mark. The candidate demonstrates sound understanding of the main points: why animals are used, ethical concerns, and limitations of alternatives. The answer shows reasonable structure and reaches a conclusion. However, the explanation lacks depth and scientific detail compared to the top answer. The discussion of alternatives is superficial, and the evaluation is limited – points are stated but not fully developed. To reach Level 3, the candidate needed to provide more detailed explanation of mechanisms, more sophisticated evaluation weighing up different factors, and more precise scientific terminology.

Grade 3 (near miss) answer

Animal testing is when scientists test drugs on animals to see if they work. They use animals because they can't test on humans straight away as it might be dangerous. Mice and rabbits are used because they are small and easy to keep.

Some people don't like animal testing because it's cruel to animals. Animals have feelings and it's not fair to hurt them. We should use computers instead because then no animals get hurt. Computers can show what drugs do without needing animals.

Animals are also expensive to look after and you need special buildings for them. It would be cheaper to just use computers. Animal testing should be banned because it's cruel and there are other ways to test drugs now.

Mark: 3/10

Examiner commentary: This answer achieves Level 1. The candidate shows basic awareness that animal testing is used for safety and that there are ethical concerns, but understanding is superficial. A key misconception is that computer models can fully replace animal testing – the candidate hasn't recognized the limitations of alternatives. The answer lacks scientific detail and evaluation; statements are made but not justified or explained. The conclusion is one-sided without balanced consideration. There's also a misconception that cost is primarily about animal housing rather than broader economic factors. To improve, the candidate needs to: explain why animals are similar to humans (physiology/biology); recognize that alternatives have limitations; provide balanced arguments; and use scientific terminology rather than everyday language like "see if they work."

Question 10(d) — Sample Answers

Grade 9 (top of Higher) answer

The justification for using artificial lighting and heating depends on several economic and practical factors.

Artificial lighting and heating directly increase photosynthesis rate. Light provides the energy for photosynthesis, and in winter or at night, natural light intensity is often limiting. Artificial lights overcome this, allowing photosynthesis to occur at higher rates for longer periods. Heating maintains temperature at the optimum for photosynthetic enzymes (around 25-30°C), preventing temperature from becoming the limiting factor, especially in cooler climates or seasons.

The costs are substantial. Initial installation of lighting systems, heaters, and automated controls requires significant capital investment. Running costs are also high – electricity for lighting and fuel for heating are expensive, particularly for large commercial operations. Maintenance and eventual replacement of equipment add further costs. These expenses are ongoing throughout the growing season.

However, the economic benefits can outweigh these costs. Increased photosynthesis rates lead to faster plant growth and higher yields per unit area, meaning more product to sell from the same greenhouse. The greenhouse can operate year-round rather than only in summer, allowing multiple harvest cycles annually. Out-of-season production commands premium prices – tomatoes in winter sell for significantly more than summer tomatoes. Produce quality is also more consistent and reliable because growing conditions are controlled, which can access premium markets.

Whether costs are justified depends on context. For high-value crops like tomatoes, peppers, or cut flowers with strong market demand and high prices, the investment is typically worthwhile. In warmer climates, heating costs are lower, making it more economically viable. For low-value crops like potatoes, the costs would likely exceed additional revenue. Scale matters too – large commercial operations can spread fixed costs across more production. Additionally, environmental considerations like carbon footprint from energy use may affect long-term viability, though renewable energy sources could mitigate this.

In conclusion, the costs can be justified for appropriate crops, climates, and scales of operation, but the decision requires careful economic analysis balancing investment and running costs against potential revenue from increased and higher-quality production.

Mark: 7/7

Examiner commentary: This answer achieves full marks with a sophisticated, well-structured evaluation. The candidate demonstrates excellent understanding of the biological principles (how light and temperature affect photosynthesis and limiting factors), comprehensively covers multiple types of costs, and provides detailed economic benefits with specific examples (out-of-season pricing, multiple harvests). Most importantly, the evaluation is nuanced, recognizing that justification depends on crop type, climate, scale, and environmental factors. The conclusion is balanced and addresses the question directly. This is high Level 3 – the candidate has shown the critical thinking and analytical skills expected at Grade 9.

Grade 6 (solid pass) answer

Artificial lighting and heating both increase the rate of photosynthesis, which helps plants grow faster and produce more crop.

Light is needed for photosynthesis because it provides energy for the reaction. In winter there is less natural light so artificial lights increase light intensity and allow photosynthesis to happen faster. Heating keeps the temperature at the right level for enzymes. If it's too cold, photosynthesis slows down, so heaters keep it at the optimum temperature.

The costs include buying and installing the lights and heaters, which is expensive. Running them also costs money because they use electricity and gas. These costs happen every month so they add up to a lot over the year.

The benefits are that more crops are produced because the plants grow faster. This means farmers can sell more crops and make more money. They can also grow crops all year round instead of just in summer. Some crops are worth more when they're grown out of season.

Overall, I think the costs are justified because even though lighting and heating are expensive, the farmer makes more money from selling extra crops. For expensive crops like tomatoes it would definitely be worth it. However, for cheaper crops it might not be worth the cost.

Mark: 4/7

Examiner commentary: This answer achieves Level 2. The candidate demonstrates sound understanding of how light and temperature affect photosynthesis and mentions both costs and benefits. There's a reasonable attempt at evaluation and a conclusion that considers crop type. However, the answer lacks the depth and sophistication of Level 3. The discussion of costs is generic without detail about different cost types or scale. Economic benefits are mentioned but not fully developed (e.g., no mention of quality, premium markets, yield per area). The evaluation is present but simplistic. To reach Level 3, the candidate needed more detailed economic analysis, consideration of multiple contexts, and more sophisticated weighing of factors.

Grade 3 (near miss) answer

Artificial lighting and heating help plants grow better. Lights give the plants light to photosynthesise and heaters keep them warm. This means the plants can grow faster.

It costs money to buy lights and heaters and run them. Electricity is expensive so this would cost a lot. But the farmers get more crops to sell so they make more money. The crops are better quality too.

I think it is justified because the farmers make profit from the extra crops. Even though it costs money for the equipment, they get it back from selling more vegetables. Greenhouses are good because you can control the conditions and grow crops all year.

Mark: 2/7

Examiner commentary: This answer achieves low Level 1. The candidate shows basic awareness that light and heat help plants grow and that there are costs and benefits, but understanding is superficial. A key weakness is the lack of scientific explanation – photosynthesis is mentioned but not explained in relation to limiting factors or rate. The answer doesn't demonstrate understanding of why or how these factors affect photosynthesis. The evaluation is extremely limited, essentially stating "costs money but makes profit" without any analysis. There's a misconception that farmers automatically make profit without considering whether revenue exceeds costs. To improve, the candidate needs to: explain the biology of limiting factors properly; provide specific details about costs and benefits; evaluate by weighing factors rather than making unsupported assertions; and recognize that economic viability varies with context.