DP Biology (first assessment 2025)

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Question 19N.1B.HL.TZ0.21c

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Date November 2019 Marks available [Maximum mark: 3] Reference code 19N.1B.HL.TZ0.21c
Level HL Paper 1B Time zone TZ0
Command term Explain Question number c Adapted from N/A
c.
[Maximum mark: 3]
19N.1B.HL.TZ0.21c
(c)

Explain the heart sounds.

[3]

Markscheme

a. «heart sounds» produced by the closing of the valves ✔

b. first sound «lub» is due to «closure of» the atrioventricular valves ✔ Accept bicuspid/mitral and tricuspid.

c. second sound «dub» is due to «closure of» the semilunar valves ✔ Accept pulmonary/aortic valves.

d. sequence of sounds from a healthy heart is lub dub «pause lub dub pause» ✔ OWTTE

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