DP Biology (first assessment 2025)
Question 20N.2.HL.TZ0.22c
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.2.HL.TZ0.22c |
| Level | HL | Paper | 2 | Time zone | TZ0 |
| Command term | Describe | Question number | c | Adapted from | N/A |
c.
[Maximum mark: 2]
20N.2.HL.TZ0.22c
(c)
Describe the mechanism by which the heartbeat is initiated.
[2]
Markscheme
a. sinoatrial node/SAN initiates contraction of atria;
b. SAN sends messages to the atrioventricular/AV node;
c. AV node initiates ventricular contraction;
d. through conducting fibres;
Examiners report
Most candidates did well in this question, strongest candidates distinguishing themselves by complete and very detailed answers.
