AQA AS Level Biology Paper 2, November 2020: Question 3

9 marks · Medium difficulty · Practical Techniques & Data Analysis

Explain arteriole blood flow reduction, deduce cardiac activity and blood movement from heart valve diagrams, identify blood pressure in vessels, and calculate post-exercise heart rate.

Practise this question

Question

A series of biology exam questions on the mammalian cardiovascular system. Question 3.1 asks to explain how an arteriole reduces blood flow into capillaries (2 marks). Figure 1 shows heart valves during one stage of the cardiac cycle, showing valves between ventricles and arteries, and valves between atria and ventricles. Question 3.2 has two parts asking what can be concluded from Figure 1 about heart muscle activity and blood movement between ventricles and arteries (2 marks), and between atria and ventricles (2 marks). Question 3.3 asks to tick one box for the blood vessel carrying blood at the lowest blood pressure among capillary, pulmonary vein, renal vein, and vena cava (1 mark). Question 3.4 provides a table with pre-exercise heart rate, stroke volume, and cardiac output, and asks to calculate the post-exercise heart rate given a 30 percent increase in stroke volume and new cardiac output, to 2 significant figures (2 marks).
Question text

03.1 Explain how an arteriole can reduce the blood flow into capillaries.

[2 marks]

Figure 1 shows heart valves during one stage of a cardiac cycle.

Ventricles are visible through the open valves.

Figure 1

03.2 What can you conclude from the appearance of valves in Figure 1 about

heart muscle activity and blood movement between:

1. ventricles and arteries?

[2 marks]

2. atria and ventricles?

[2 marks]

03.3 Tick ( ) one box next to the blood vessel carrying blood at the lowest blood pressure.

[1 mark]

Capillary

Pulmonary vein

Renal vein

Vena cava

03.4 A scientist measured the heart rate and the volume of blood pumped in a single heart

beat (stroke volume) of an athlete before exercise and calculated the cardiac output.

Cardiac output is calculated using this equation.

cardiac output = heart rate × stroke volume

*07* Her results are shown in Table 1.

Table 1

Heart rate / Stroke volume Cardiac output

beats minute−1 / cm3 / cm3 minute−1

62 80 4960

After exercise, the athlete’s stroke volume increased by 30% and the cardiac output

was 13 832 cm3 minute –1

Calculate the athlete’s heart rate after exercise.

Give the answer to 2 significant figures. Show your working.

[2 marks]

Heart rate beats minute –1

Mark scheme

Show the mark scheme A table showing the mark scheme for questions 3.1 through 3.4. Question 3.1 awards 2 marks for muscle contraction and narrowing the arteriole lumen. Question 3.2 awards 4 marks total, with marking points for ventricle muscle relaxation/artery recoil, no blood backflow, atrial contraction, and blood movement from atria to ventricles. Question 3.3 awards 1 mark for vena cava. Question 3.4 awards 2 marks for the correct final answer of 130 beats per minute, with 1 mark awarded for correctly calculating the intermediate stroke volume value of 104.

Question Marking Guidance Mark Comments

03.1 2 2. Accept decreases

for constricts/narrows

1. Muscle contracts;

2. Accept

2. Constricts/narrows arteriole/lumen;

vasoconstriction for 1

mark

03.2 4 Accept references to

(Ventricles and arteries) ventricle, artery or

1. Ventricle (muscles) relaxed atrium (singular)

OR 1. Accept no muscle

activity

Arteries recoiled;

OR

2. No (blood) backflow (into ventricles)

Diastole

OR

OR

No blood movement to/in/from arteries;

Arteries smoothing

(Atria and ventricles) blood flow

3. Atria (muscle) contracted; 2. and 4. Accept

4. Blood movement from atria (into ventricles); flow/pumped for

movement

03.3 Vena cava; 1

03.4 2 marks for correct answer = 130 (beats min−1);; 2

1 mark for correct stroke volume = 104

TOTAL 9

How to answer it

The Cardiovascular System & Cardiac Cycle

What this question tests

This question assesses your knowledge of blood vessel structure-function relationships, cardiac cycle mechanics interpreted via anatomical diagrams, blood pressure gradients across the circulatory system, and multi-step cardiac output calculations incorporating percentage changes and significant figures.

Question 03.1

Reducing Blood Flow via Arterioles

✅ Correct Answer

1. Muscle contracts;
2. Constricts / narrows arteriole / lumen.

2 marks available (1 mark per marking point)

💡 Key Knowledge

  • Arterioles possess a thick layer of circular smooth muscle in their walls.
  • Contraction of this smooth muscle narrows the lumen (vasoconstriction), increasing resistance and reducing blood flow downstream into capillaries.

🧠 Exam Technique

Be precise with biological terminology. Examiners accept decreases for constricts/narrows, and vasoconstriction directly earns mark 1.

❌ Common Errors

Students frequently attribute the contraction to "elastic tissue" instead of smooth muscle, or incorrectly state that the capillary itself contracts.

Question 03.2

Interpreting Cardiac Cycle Diagrams

✅ Correct Answer

1. Ventricles and arteries:
Ventricle (muscles) relaxed OR Arteries recoiled;
AND
No (blood) backflow (into ventricles) OR No blood movement to/in/from arteries.

2. Atria and ventricles:
Atria (muscle) contracted;
AND
Blood movement from atria (into ventricles).

4 marks total (2 marks per section)

💡 Key Knowledge

Valve positions reflect pressure gradients and chamber activity. Open semilunar (ventricle-artery) or atrioventricular valves indicate the direction of blood flow and whether the surrounding chambers are actively contracting (systole) or relaxing (diastole).

🧠 Exam Technique

Structure your answers clearly by addressing both parts of the question: state the state of the muscle/vessel first, followed by the consequence on blood movement.

❌ Common Errors

Confusing ventricular diastole with ventricular systole, or failing to link valve appearance directly to the direction of blood flow.

Question 03.3

Blood Pressure Gradients

✅ Correct Answer

Vena cava [Tick ticked]

1 mark

💡 Key Knowledge

Blood pressure drops continuously as blood travels away from the heart due to friction and increasing total cross-sectional area: Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Vena cava (lowest pressure just before entering the right atrium).

🧠 Exam Technique

Ensure only one box is ticked. Marking multiple boxes will invalidate your answer, even if the correct one is included.

Question 03.4

Cardiac Output Calculation

✅ Correct Answer

Heart rate = 130 beats min⁻¹ (2 marks)

2 marks total (1 mark for correct intermediate stroke volume = 104 cm³)

📐 Step-by-Step Calculation

  1. Find the new stroke volume after a 30% increase:
    80 × 1.30 = 104 cm³ (awards 1 mark if final answer is wrong)
  2. Rearrange the cardiac output equation:
    Heart Rate = Cardiac Output ÷ Stroke Volume
  3. Substitute the values:
    13 832 ÷ 104 = 133 beats minute⁻¹
  4. Apply significant figures:
    Round to 2 significant figures = 130 beats minute⁻¹

❌ Common Errors

Tragic traps: Forgetting to round to 2 significant figures (leaving 133), or incorrectly calculating 30% increase by adding 30 instead of multiplying by 1.30.

Topics

Biology · 3.3 Organisms exchange substances with their environment

Question and mark scheme from the AQA AS Level Biology examination, Paper 2, November 2020. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.