AQA GCSE Combined Science: Trilogy Biology Paper 1 (Foundation), June 2025: Question 2
13 marks · Low Demand difficulty · Short Answer
Investigate the rate of photosynthesis in pondweed with changing distance and temperature, identify leaf tissue structures, and explain the effects of fungal infection on plant growth.
Practise this questionQuestion
Question text
02 Photosynthesis is important for plant growth.
A student used pondweed to investigate photosynthesis.
Figure 3 shows the apparatus used.
Figure 3
This is the method used.
1. Set up the apparatus as shown in Figure 3.
2. Switch on the lamp.
3. After 1 hour, record the volume of oxygen collected in the measuring cylinder.
4. Repeat steps 1 to 3 a further four times, placing the lamp at different distances from
the pondweed.
02.1 What are two control variables the student should use in the investigation?
[2 marks]
Tick ( ) two boxes.
The distance of the lamp from the pondweed.
The length of the pondweed.
The size of the beaker.
The temperature of the water.
The volume of oxygen collected.
Table 2 shows the results.
Table 2
Distance of the lamp from 3
Volume of oxygen in cm
the pondweed in cm
20 1.0
30 0.4
40 0.2
50 0.0
02.2 Describe the trend shown in Table 2.
[1 mark]
02.3 Figure 4 shows the volume of oxygen when the lamp was 10 cm from the pondweed.
Figure 4
What volume of oxygen is shown in Figure 4?
[1 mark]
11 3
Volume = cm
02.4 The student repeated the investigation using a measuring cylinder with smaller
intervals of 0.1 cm3.
What did using smaller intervals improve?
[1 mark]
Tick ( ) one box.
Accuracy
Repeatability
Reproducibility
02.5 The student did the investigation at 10 °C.
The student repeated the investigation at 20 °C.
Complete the sentence.
*10Choose the answer from the box.*
[2 marks]
smaller the same greater
Compared to the results at 10 °C, the volumes of oxygen collected
in one hour at 20 °C would be .
Give a reason for your answer.
Photosynthesis is important for apple trees.
Figure 5 shows a section through the leaf of an apple tree.
Figure 5
02.6 What is tissue A?
[1 mark]
Tick ( ) one box.
Epidermis
Palisade mesophyll
Spongy mesophyll
02.7 The cells in tissue A contain chloroplasts.
What is the name of the green chemical in chloroplasts?
[1 mark]
Apple scab is a disease of apple trees.
Apple scab is caused by a fungus.
*12Figure 6* shows a leaf from an apple tree infected with apple scab fungus.
Figure 6
02.8 How could the fungal infection be removed from the tree?
[1 mark]
Tick ( ) one box.
Destroy the affected leaves.
Spray the affected leaves with antibiotics.
Use an antitoxin on the affected leaves.14
02.9 Infection with apple scab fungus decreases the number of chloroplasts in the leaves.
Explain why apple trees with apple scab fungus produce smaller apples than apple
trees that are not infected.
[3 marks]
Mark scheme
Show the mark scheme
AO /
Question Answers Extra information Mark
Spec. Ref.
02.1 the length of the pondweed 1 AO1
4.4.1.2
the temperature of the water 1 RPA5
AO /
Spec. Ref.
02.2 as the distance increases the allow as the light intensity 1 AO2
volume / oxygen decreases decreases the volume / oxygen 4.4.1.2
decreases RPA5
ignore use of figures
AO /
Spec. Ref.
02.3 3.6 (cm3) 1 AO2
4.4.1.2
RPA 5
AO /
Spec. Ref.
02.4 accuracy 1 AO2
4.4.1.2
RPA5
AO /
Spec. Ref.
no marks if incorrect word
02.5 chosen AO2
greater 1 4.4.1.2
(because) the rate of allow (because) photosynthesis 1
photosynthesis is higher would be faster / quicker
allow (because) there is more
photosynthesis
allow (because) photosynthesis
is controlled by enzymes
allow (because) enzymes work
faster
allow (because) particles have
more energy
allow (because) the rate of
reaction is faster / quicker
AO / 9
Spec. Ref.
02.6 palisade mesophyll 1 AO1
4.2.3.1
AO /
Spec. Ref.
02.7 chlorophyll 1 AO1
4.1.1.2
4.4.1.2
AO /
Spec. Ref.
02.8 destroy the affected leaves 1 AO2
4.3.1.4
AO /
Spec. Ref.
02.9 less / no light absorbed 1 AO2
4.3.1.4
(so) less / no photosynthesis allow (because) chloroplasts / 1 4.4.1.2
chlorophyll is needed for
photosynthesis
(so) less / no glucose / sugar (is allow (so) less / no protein / fat / 1
made / produced) starch / cellulose (is made /
produced)
Total Question 2 13
Question 3
How to answer it
Photosynthesis Practical, Leaf Tissues & Plant Disease
Core Practical & Specification Links: AQA Combined Science Biology Paper 1 (Topics B4.1 Photosynthesis, B4.2 Plant Tissues & B3.1 Plant Disease).
- Required Practical 5 (Photosynthesis): Identifying control variables, reading inverted apparatus scales, and interpreting trends.
- Scientific Working: Understanding vocabulary such as accuracy when choosing measuring equipment with finer graduations.
- Enzyme & Rate Concepts: Predicting how temperature shifts affect rate of oxygen production.
- Plant Biology: Identifying leaf cross-section tissues (palisade mesophyll) and pigments (chlorophyll).
- Disease & Growth Linking: Linking fungal infections to reduced chlorophyll, reduced photosynthesis, and stunted yield (small apples).
Investigating Light Distance and Oxygen Production
✅ 02.1 Correct Answers (2 Marks)
Tick two control variables:
- The length of the pondweed [1 mark]
- The temperature of the water [1 mark]
❌ Common Error: 02.1 Variable Confusion
Many students confuse the independent variable (distance of lamp) and the dependent variable (volume of oxygen collected) with control variables (factors kept constant to make it a fair test).
✅ 02.2 Correct Answer (1 Mark)
"As the distance increases, the volume of oxygen decreases."
Also accepted: "As light intensity decreases, the volume of oxygen decreases."
🧠 Exam Technique: Describing Trends
Use the standard trend formula: "As [X] increases, [Y] [increases/decreases]." Do not explain why it happens when the command word is just "Describe".
Measuring Gas Volume and Measurement Accuracy
📐 02.3 Reading the Scale (1 Mark)
Reading from Figure 4:
- Major markings run from 3 downwards to 4.
- There are 5 subdivisions between 3 and 4, meaning each tick = 0.2 cm³.
- The water/gas meniscus sits exactly 3 intervals below 3:
3 + (3 × 0.2) = 3.6 cm³.
Answer: 3.6 cm³
❌ Common Trap: Inverted Scales
Because the measuring cylinder is inverted, gas fills from the closed top downwards. Students often mistakenly count backwards from 4 or miscalculate subdivisions as 0.1 rather than 0.2.
✅ 02.4 Correct Answer (1 Mark)
What did using smaller intervals (0.1 cm³) improve?
Accuracy [1 mark]
💡 Key Terminology: Scientific Vocabulary
- Accuracy: How close a measurement is to the true value (smaller scale divisions reduce reading error).
- Repeatability: When the same investigator repeats the test using the same method and gets similar results.
- Reproducibility: When a different investigator repeats the test and gets the same results.
Effect of Increasing Temperature to 20 °C
✅ Correct Answer (2 Marks)
Sentence: "Compared to the results at 10 °C, the volumes of oxygen collected in one hour at 20 °C would be greater." [1 mark]
Reason: "(because) the rate of photosynthesis is higher" [1 mark]
🧠 Exam Tip: Linked Marking
The mark scheme notes: "no marks if incorrect word chosen". You cannot earn the reason mark if you selected 'smaller' or 'the same'. Make sure your prediction matches biological theory first!
Leaf Anatomy & Photosynthetic Pigments
✅ 02.6 & 02.7 Correct Answers
02.6 Tissue A: Palisade mesophyll [1 mark]
02.7 Green chemical: Chlorophyll [1 mark]
💡 Leaf Structure Recall
- Upper Epidermis: Transparent top single layer of cells that lets light pass through.
- Palisade Mesophyll: Column-shaped, tightly packed cells near the leaf top crammed with chloroplasts for maximum light absorption.
- Spongy Mesophyll: Loosely packed cells with air gaps for gas exchange (CO₂ and O₂).
- Chlorophyll: The green pigment inside chloroplasts that absorbs light energy.
Apple Scab (Fungus) & Crop Stunting
✅ 02.8 Controlling Fungal Infection (1 Mark)
How could the infection be removed from the tree?
Destroy the affected leaves [1 mark]
❌ Misconception: Antibiotics on Plants
Antibiotics only kill bacteria! They have zero effect on fungal infections like apple scab or rose black spot. Antitoxins counteract bacterial poisons in animals, not fungi on leaves.
✅ 02.9 Structured Explanation (3 Marks)
Explain why infected apple trees produce smaller apples:
- Less light is absorbed (because there are fewer chloroplasts/less chlorophyll) [1 mark]
- (So) less photosynthesis occurs [1 mark]
- (So) less glucose/sugar is made (needed to produce fruit biomass/starch/cellulose) [1 mark]
🧠 Examiner Insight: The Cause-and-Effect Chain
Top students structure plant stunting questions with an unbroken 3-step chain:
Fewer Chloroplasts → Less Light Absorbed → Less Photosynthesis → Less Glucose for Growth
Students who only wrote "the tree gets sick so the apples don't grow" score 0 marks because they omit the biochemical pathway.
Topics
Biology · B2: Organisation · B3: Infection and Response · B4: Bioenergetics
Question and mark scheme from the AQA GCSE Combined Science: Trilogy examination, Biology Paper 1 (Foundation), June 2025. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.