AQA GCSE Biology Biology Paper 1 (Higher), June 2023: Question 1

✅ Mark Scheme Answer

Any one of the following:

• A group of similar cells (or the same cells).
• A group of cells with a similar or specific function.

❌ Common Errors

• Writing just "a group of cells" unqualified receives 0 marks. You must state that they are similar or work together for a specific job.
• Giving an example of what root tissues do rather than defining the term.

✅ Mark Scheme Answer

Meristem (tissue)

💡 Key Knowledge

Meristem tissue is located in growing tips of roots and shoots. Unlike animal stem cells, plant meristem cells can differentiate into any type of plant cell throughout the entire life of the plant.

❌ Common Errors

• Confusing meristem with xylem, phloem, or root hair cells (which are already specialised cells).

✅ Mark Scheme Answer

Willow (or willow tree / willow bark)

💡 Drug Origins to Remember for GCSE

• Aspirin (painkiller) → Willow
• Digitalis (heart condition drug) → Foxgloves
• Penicillin (antibiotic) → Penicillium mould (discovered by Alexander Fleming)

✅ Mark Scheme Answer

Any one acceptable point:

• Berries are easier to access / pick.
• It is easier to extract chemical A from berries.
• Taking berries will not harm / kill the plant (roots or leaves are needed for survival and future yield).
• Lower concentration in berries makes handling safer / less toxic.

🧠 Exam Technique

Even though Table 1 shows berries have the lowest concentration (0.7 g per 100 g vs 1.3 g in roots), practical harvesting considerations matter! Pulling up roots kills the plant permanently, preventing future harvesting.

❌ Examiner Guidance

Do not simply write "berries are not underground". You must explain the practical benefit: easier picking or not damaging root systems.

📐 Step-by-Step Calculation

Data provided:

• Healthy leaves contain 1.2 g per 100 g plant tissue.
• Chlorosis leaves have 60% of this concentration.
• Sample size: 200 g of leaves.
• Target unit: mg.

1. Calculate chemical in 100 g of chlorotic leaves:
   0.60 × 1.2 g = 0.72 g  [Mark 1]
2. Scale up for 200 g of leaves:
   0.72 g × 2 = 1.44 g  [Mark 2]
   (Alternative route: 200 g healthy = 2.4 g → 2.4 × 0.60 = 1.44 g)
3. Convert grams to milligrams (×1000):
   1.44 × 1000  [Mark 3]
4. Final Answer:
   1440 mg  [Mark 4]

❌ Common Traps to Avoid

• Forgetting to double: Table 1 provides values per 100 g, but the question asks for 200 g.
• Incorrect unit conversion: There are 1000 mg in 1 g. Multiplying by 100 or dividing by 1000 loses the final answer mark.
• Using the wrong row in Table 1: Be careful to read the row for leaves (1.2 g), not roots (1.3 g) or berries (0.7 g).

✅ Mark Scheme Answer

Any one of:

• Lack of chlorophyll
• Lack of magnesium ions (needed to synthesise chlorophyll)
• Lack of mineral ions / named ion (e.g. iron, nitrate, potassium)
• Lack of light / incorrect soil pH / viral or fungal infection

💡 Why Magnesium?

Magnesium is the central mineral ion inside a chlorophyll molecule. Without magnesium absorbed from the soil, plant cells cannot make green chlorophyll, resulting in yellow leaves (chlorosis) and reduced photosynthesis.

❌ Ignored Answers

The mark scheme explicitly says: ignore "lack of nutrients" or "lack of nitrogen" without qualification.

✅ Mark Scheme Answer

Any two from:

• To check toxicity (safety / side effects / ensure it is not harmful or poisonous).
• To check dosage (find the optimum / correct amount needed).
• To check efficacy (whether the drug actually works and is effective).

🧠 Top Tip: The "Big Three" of Drug Testing

Always memorise these three words together for GCSE clinical trial questions:

1. Toxicity (Is it safe?)
2. Efficacy (Does it work?)
3. Dose (How much is needed?)

✅ Mark Scheme Answer

Any one of:

• The writers / companies may get a financial gain (make money / sell products).
• A competitor company may suffer a financial loss / competitor wants to discredit it.

❌ Common Errors

• Writing "it has not been peer reviewed" or "they did not use a double-blind trial". These explain why evidence is not valid, not why the authors are biased!
• Bias implies a conflict of interest, typically commercial or personal profit.

✅ Correct Answer

Tick box 3:

☑ Have the claims peer reviewed.

💡 What is Peer Review?

Before scientific findings are published, other independent scientists in the same field check the methodology, data analysis, and conclusions to prevent false claims, poor design, or bias.

❌ Why Other Options Are Wrong

• Social media and newspapers can easily publish unverified or sensationalised claims.
• Commercial manufacturing companies produce drugs for profit, which does not independently guarantee validity.