AQA GCSE Biology Biology Paper 2 (Higher), June 2025: Question 2
10 marks · Standard Demand difficulty · Short Answer
Analyse an investigation into the distribution of daisy plants and soil water content at varying distances from a tree along a transect line.
Practise this questionQuestion
Question text
02 Students investigated how many daisy plants were growing in a field at different
distances from a tree.
This is the method used.
1. Place a 20-metre tape measure on the ground, with the tree at 0 metres.
2. Place a 1 m2 quadrat on the ground every 4 metres along the tape measure.
3. Count the number of daisy plants in each quadrat.
4. Take a soil sample from each quadrat to find the percentage of water in the soil.
Figure 2 shows the tree and the tape measure.
Figure 2
This is the method used for finding the percentage of water in each soil sample
(step 4):
5. Weigh an empty container.
6. Place the soil sample in the container and weigh again.
7. Heat the container of soil in an oven at 100 °C for several hours.
8. Allow the container of soil to cool and weigh again.
9. Repeat steps 7 and 8 until there is no further change in mass.
02.1 Suggest why the students repeated steps 7 and 8 until there was no further change
in mass.
*04* [1 mark]
Table 2 shows the results.
Table 2
Distance from the tree in metres
48 12 16 20
Mass of fresh soil in grams 250 266 260 248 252
Mass of dried soil in grams 225 234 209 184 181
Mass of water lost from soil in grams 25 32 51 64 71
Percentage of water in soil 10 12 20 26 X
Number of daisies per m2 0 7 15 28 32
02.2 Calculate percentage X in Table 2.
Give your answer to the nearest whole number.
[3 marks]
Percentage X (nearest whole number) = %
02.3 Describe the effect of distance from the tree on the percentage of water in the soil
between 4 metres and 16 metres.
Use Table 2.
*05* [1 mark]
02.4 A student concluded:
*06* ‘As the water content of the soil increases, so does the number of daisy plants.’
Describe two changes to the investigation that would increase the validity of the
student’s conclusion.
[2 marks]
02.5 The percentage of water in the soil is an abiotic factor.
Suggest three other abiotic factors that might have caused more daisy plants to grow
further away from the tree.
Do not refer to water in your answer.
[3 marks]
Mark scheme
Show the mark scheme
Question 2
AO /
Question Answers Extra information Mark
Spec. Ref.
02.1 to remove all / the water allow to make sure there is no 1 AO3
water left 4.7.1.2
allow to make sure the soil is 4.7.2.1
(completely) dry
ignore to remove water
unqualified
AO /
Spec. Ref.
02.2 71 1 AO2
× 100 4.7.1.2
1 4.7.2.1
28.1(746…)
28 (%) allow student’s incorrectly 1
calculated percentage using
mass data for 20 metres,
rounded to nearest whole
number
AO /
Spec. Ref.
02.3 as distance increases the allow positive correlation 1 AO3
percentage of water increases allow as one increases the other 4.7.1.2
increases 4.7.2.1
allow as one decreases the RPA9
other decreases
ignore directly proportional
AO /
Spec. Ref.
02.4 any two from: 2 AO3
4.7.1.2
• repeat (at each distance) and allow repeat (at each distance) 4.7.2.1
calculate a mean and remove / identify anomalies RPA9
• test at intermediate / further
distances
• test around more / different allow test more areas
trees
• test at different angles around
the (same) tree
AO /
Spec. Ref.
02.5 any three from: 3 AO2
4.7.1.1
• light (intensity) if neither awarded allow 4.7.1.2
• temperature shade for 1 mark 4.7.2.1
RPA9
ignore sun
• type of soil
• pH (of soil) allow acidity / alkalinity (of soil)
• minerals / ions (in soil) allow salts or named examples
of ions, such as nitrate
allow fertiliser
ignore nitrogen / nutrients
• wind (intensity / direction)
• oxygen in soil
ignore (availability of) space
ignore carbon dioxide
Total Question 2 10
How to answer it
Investigating Plant Distribution & Abiotic Factors
This question assesses practical ecology skills from Required Practical 9 (sampling techniques using transects and quadrats). It evaluates your ability to understand experimental controls (heating to constant mass), calculate percentages from experimental data, describe trends from tabular data, evaluate experimental validity, and recall abiotic factors that influence communities.
Question 02.1: Heating to Constant Mass
Suggest why the students repeated steps 7 and 8 until there was no further change in mass. [1 mark]
✅ Mark Scheme Answer
- To remove all the water (or to make sure there is no water left / the soil is completely dry).
🧠 Exam Technique: Be Specific
Simply writing "to remove water" scores 0 marks. Water starts evaporating immediately, but heating repeatedly until constant mass ensures that all water has evaporated.
❌ Common Errors
- Writing "to remove water" without stating "all".
- Stating "to burn away organic matter" (organic matter burns at much higher temperatures than 100 °C).
Question 02.2: Calculating Water Percentage
Calculate percentage X in Table 2. Give your answer to the nearest whole number. [3 marks]
📐 Step-by-Step Calculation
- Identify data at 20 m:
Mass of water lost = 71 g
Mass of fresh soil = 252 g - Apply the percentage formula:
(Mass of water lost ÷ Fresh soil mass) × 100
= (71 ÷ 252) × 100 [1 mark] - Calculate raw answer:
= 28.1746...% [1 mark] - Round to nearest whole number:
= 28% [1 mark]
❌ Calculation Traps
- Dividing by dried mass: Dividing 71 by 181 gives 39.2% — this is incorrect because the original percentage must be based on the initial fresh mass.
- Ignoring rounding instructions: Writing 28.2% or 28.17% loses the 3rd mark. Always re-read the required precision!
Question 02.3: Describing the Trend
Describe the effect of distance from the tree on the percentage of water in the soil between 4 metres and 16 metres. [1 mark]
✅ Accepted Answers
- As distance increases, the percentage of water increases.
- Positive correlation (or as one increases, the other increases).
🧠 Exam Technique: Use Clear Comparative Language
State both variables clearly: "As [variable X] increases, [variable Y] increases."
Question 02.4: Improving Validity
Describe two changes to the investigation that would increase the validity of the student's conclusion. [2 marks]
✅ Any TWO from:
- Repeat at each distance and calculate a mean (or identify/remove anomalies).
- Sample at intermediate distances (e.g. every 1 m or 2 m) or further distances.
- Repeat the investigation around more trees / different trees.
- Sample along transects at different angles / compass directions around the same tree.
💡 Key Concept: What is Validity?
An investigation is valid if it properly tests the hypothesis and provides reliable, generalisable conclusions.
Single transects only show what happens in one specific direction from one tree. Trees have asymmetric canopies, root systems, and shade patterns, so testing multiple directions and trees ensures findings are valid.
Question 02.5: Abiotic Factors
Suggest three other abiotic factors that might have caused more daisy plants to grow further away from the tree. Do not refer to water. [3 marks]
✅ Any THREE from:
- Light intensity (more sunlight further from the canopy)
- Temperature (warmer away from tree shade)
- Soil pH (or acidity/alkalinity)
- Mineral ions / nutrients in soil (e.g. nitrates, salts)
- Soil type
- Wind intensity / direction
- Oxygen concentration in soil
❌ Common Rejections by Examiners
- Water: Specifically forbidden by the question rubric!
- "Sun" or "Sunlight": Too vague. Must specify light intensity or temperature.
- Space: Space / room is not considered an abiotic factor in AQA mark schemes.
- Carbon dioxide: Atmospheric CO₂ concentration is uniform across an open field, so it is ignored.
- Biotic factors: Do not name animals, competition, trampling, or herbivores!
Topics
Biology · Required Practicals · B7: Ecology · Required Practicals
Question and mark scheme from the AQA GCSE Biology examination, Biology Paper 2 (Higher), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.