AQA A-Level Biology Paper 1, June 2024: Question 8

8 marks · Medium difficulty · Practical Techniques & Data Analysis

Relate the structural features of the aorta to its function, analyze data on aorta diameter and aneurysm risk, and calculate the percentage change in stroke volume between a diseased and healthy heart.

Practise this question

Question

Question text

08.1 Give two structural features of an aorta wall and explain how they are related to the

function of an aorta.

[2 marks]

08.2 Small tears may occur in the layers of tissue in an aorta wall. These tears weaken the

wall without bursting the aorta.

Scientists:

• measured the aorta diameter (d) in a large population of people over 60 years of

age

• calculated the risk of an aorta wall developing a tear.

Table 4 shows their results.

Table 4

Number of people in Risk of an aorta wall

Aorta diameter d / cm

the population developing a tear

d ≤ 3.5 2765 0.06

3.5 < d ≤ 4.0 630 0.33

4.0 < d ≤ 4.5 98 4.64

d > 4.5 7 380.00

Blood may push through the tears in the aorta wall. This produces a balloon-like

swelling called an aneurysm and increases the aorta diameter. Aneurysms can cause

the aorta to burst.

Using all the information, what can you conclude about aorta diameter and the risk of

developing an aneurysm?

[3 marks]

08.3 A scientist investigated changes in a diseased heart and changes in a healthy heart

during cardiac cycles.

For each heart, the scientist obtained a value for:

*22* • the mean blood volume in a full ventricle just before the ventricle contracts (BVB)

• the mean ejection fraction (EF).

The EF is the proportion of blood pumped out of a full ventricle in one heartbeat.

The EF is calculated using this formula:

Blood volume pumped out of a full ventricle in one heartbeat (stroke volume)

EF =

BVB

Table 5 shows the scientist’s results.

Table 5

Diseased heart Healthy heart

Mean BVB / cm3 100 120

Mean EF 0.45 0.58

Using Table 5, a student calculated that the percentage change in the stroke volume

of the diseased heart compared with the stroke volume of a healthy heart is –30%.

The student’s answer is wrong because the final step of the calculation was

performed incorrectly.

Using the equation and Table 5, calculate the correct percentage change in the stroke

volume of the diseased heart compared with the stroke volume of the healthy heart.

Identify the mathematical error in the final step of the student’s calculation.

[3 marks]

Correct answer %

Mathematical error

Mark scheme

Show the mark scheme

Question Marking Guidance Mark Comments

1. (Smooth) muscle absorbs/resists/withstands high 1. Ignore contraction

(blood) pressure; 1. Ignore maintains

pressure

2. Elastic (tissue/layer) stretches and recoils

maintains/smooths blood pressure; 2. Reject contracts/

2 max relaxes for recoils

3. (Smooth) endothelium reduces friction;

08.1 (2 x

2. Accept dilate OR

4. Protein (coat) prevents (artery) wall splitting AO1)

expand for stretch

4. Accept fibrous OR

Protein (coat) absorbs/resists/withstands high collagen for protein

(blood) pressure;

1. Small diameters are low risk of tears so unlikely 1. Accept the

to/do not have aneurysms converse

OR 1. Accept ≤ 4.5 for

As diameter increases, risk of tears increases small

and (risk of developing) aneurysms increase; 2. Accept the

3 max converse, eg most

2. Few people have/at high risk of tear people at low risk of

08.2 (3 x

OR AO3) tear/aneurysm

Few people have/at high risk of aneurysms; 2. Accept 7/98/105 for

few

3. Diameters > / above 4.5 (cm) at high risk (of

tears) so may have aneurysms; 3. Accept ‘increases

significantly’

4. (High risk of) tear does not mean aneurysm

will/has occurred;

1. and 2. Correct answer of 35 / 35.1 / 35.3 / 35.7 / Accept positive or

36 / 40(%) = 2 marks;; negative values

Accept for 1 mark, incorrect answer but shows:

Evidence of 45 (correct stroke volume for diseased

08.3 (3 x

heart)

AO3)

Evidence of 69.6 OR 70 (correct stroke volume for

healthy heart)

– A-LEVEL BIOLOGY – –

Evidence of 24.6 OR 25 (correct difference 17

between stroke volumes)

Evidence of 48.6 to 50 (correct calculated volume

change, not percentage change)

3. (Mathematical error) incorrect rounding;

How to answer it

Cardiovascular System & Data Analysis Study Guide

What this question tests

This sequence of questions tests your knowledge of vessel adaptations (AO1), your ability to process and interpret epidemiological data tables (AO3), and your competence in applying biological formulas to multi-step calculations involving stroke volume and percentage change (AO3).

Question 08.1 (2 marks)

Aorta Structure and Function

✅ Correct Answers (Any two pairs)

Feature 1: Smooth endothelium → Reduces friction for blood flow.
Feature 2: Elastic tissue (layer) → Stretches and recoils to maintain and smooth out blood pressure surges.
Feature 3: Muscle tissue → Absorbs/withstands high blood pressure.
Feature 4: Protein coat / collagen → Prevents artery wall splitting or withstands high pressure.

❌ Common Student Errors

Saying muscle "contracts/relaxes" to pump blood (the aorta relies on elastic recoil from the left ventricle, not peristalsis).
Vague answers like "it is thick" without explaining *why* or linking it specifically to withstanding high pressure.

Mark scheme guidance: 2 marks max (2 × AO1). Must link a specific structural feature directly to its functional consequence in the aorta.

Question 08.2 (3 marks)

Aorta Diameter and Aneurysm Risk Analysis

✅ Acceptable Conclusions

Small aorta diameters (≤ 3.5 cm) have a very low risk of tears and are unlikely to form aneurysms.
As aorta diameter increases, the risk of developing a tear and subsequent aneurysm increases (exponentially).
Diameters above 4.5 cm show extremely high risk for tears/aneurysms.
Note: A high risk of a tear does not automatically guarantee an aneurysm has or will occur.

🧠 Exam Technique (AO3)

When dealing with large data tables:

Look for trends across rows (e.g., as diameter category increases, risk value escalates from 0.06 to 380.00).
Use exact figures from the table to back up comparative statements for top marks.

Mark scheme guidance: 3 max (3 × AO3). Awarded for identifying the positive correlation between diameter and risk, citing low-risk small sizes, and high-risk large sizes (> 4.5 cm).

Question 08.3 (3 marks)

Stroke Volume Calculations & Percentage Change

📐 Step-by-Step Calculation

Find Stroke Volume (SV) for Healthy Heart:
SV = BVB × EF = 120 cm³ × 0.58 = 69.6 cm³ (or 70 cm³)
Find Stroke Volume (SV) for Diseased Heart:
SV = BVB × EF = 100 cm³ × 0.45 = 45 cm³
Calculate Percentage Change:
Change = ((Diseased - Healthy) / Healthy) × 100
= ((45 - 69.6) / 69.6) × 100 = -35.3% (Accept 35% to 40%)

❌ Mathematical Error Identification

Correct answer: -35.3% (or accept -35 to -40%)

Mathematical error: Incorrect rounding (or failure to calculate the percentage change correctly from the intermediate stroke volume values).

💡 Key Formula Reminder

Stroke volume = Blood volume pumped out in one heartbeat = BVB × EF . Always check whether your intermediate values for stroke volume (45 cm³ and 69.6 cm³) are correct before attempting the final percentage change formula!

Mark scheme guidance: 3 marks total. 2 marks for final correct percentage (35 / 35.1 / 35.3 / 35.7 / 36 / 40%), with 1 mark awarded if an incorrect final answer shows correct intermediate evidence of stroke volumes (45 and 69.6). 1 mark for identifying rounding/mathematical errors.

Topics

Biology · 3.3 Organisms exchange substances with their environment

Question and mark scheme from the AQA A-Level Biology examination, Paper 1, June 2024. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.