AQA GCSE Biology Biology Paper 2 (Foundation), November 2021: Question 6

✅ Correct Answer

Place the quadrat using random coordinates.

💡 Key Knowledge

• Sampling must always be random to prevent sampling bias.
• Random coordinates are typically generated using a random number generator along two tape measures set out at right angles (X and Y axes).

❌ Common Errors

• "Place where there are many buttercups": This introduces deliberate bias and drastically overestimates population size.
• "Use the same person to place all quadrats": Does not prevent human bias in choosing where to drop or throw a quadrat.

📐 Step-by-Step Calculation

Values from Table 1: 40, 52, 88, 80, 40

1. Sum the percentage values:
   40 + 52 + 88 + 80 + 40 = 300 [1 mark]
2. Divide by the number of quadrats (5):
   300 ÷ 5 = 60% [1 mark]

X = 60 %

🧠 Exam Technique

• Always show your working: writing 300 / 5 scores a method mark even if you make a silly mental arithmetic mistake at the end.
• Double-check that you added all 5 values and divided by 5, not the number of squares (25).

✅ Correct Answer

The area of buttercup plants in quadrat 5 is much larger.

💡 Examiner Insight

In both quadrats, buttercups touched 10 squares (giving an estimated 40% cover for each). However, in Quadrat 1, small leaves just touched the edges of 10 squares, whereas in Quadrat 5, a huge dense clump filled almost the entire 10 squares.

Counting any square with a plant as "1 whole square" creates an inaccurate estimate.

✅ Any Two Valid Improvements [2 marks]

• Place (many) more quadrats / repeat and calculate a mean / combine results with other students.
• Divide quadrats into more / smaller squares (e.g. 100 squares instead of 25).
• Estimate actual percentage cover inside the quadrat (rather than simply counting squares touched).
• Only count squares that have at least 50% cover by buttercups.
• Use a point quadrat (pin frame).

❌ Common Misconceptions & What to Avoid

• Do NOT write: "Place quadrats randomly" — the mark scheme explicitly states ignore random placement here because that was already addressed in 06.1.
• Do NOT write: Vague answers like "be more careful", "use a bigger quadrat", or "count better".

✅ Acceptable Factors (Give any THREE) [3 marks]

• Light (intensity)
• Water / moisture / rainfall
• Mineral ions / salts (e.g. nitrates, phosphates, or fertilizer)
• Soil pH
• Temperature
• Herbivores (grazing by cows/sheep)
• Trampling (by humans or animals) / cultivation
• Pathogens / plant diseases
• Use of weedkiller / herbicides
• Wind speed
• Soil aeration / oxygen in soil

❌ Rejected Answers (Examiner Traps)

• "Weather": Too vague! Name specific abiotic factors like temperature or rainfall.
• "Carbon dioxide": Specifically ignored on the mark scheme because open field atmospheric CO₂ levels are relatively uniform and rarely limit buttercup distribution across a single field.