Page 220 - SUBSEC October 2017_Neat

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02207020/CAPE/SPEC/KMS 2017
BIOLOGY
UNIT 1 – PAPER 02
KEY AND MARK SCHEME

Question 2 cont’d

(b) Drawing of the heart

https://userscontent2.emaze.com/images/688d237b-f946-4ac5-9217-eafa0d068781/82295c69-0bd1-
4aae-82bb-c82dad81f489.gif

 Appropriate diagram – 1 mark
 All chambers correctly labelled – 2 marks
(1-2 errors or omissions – 1 mark)
 All valves correctly labelled – 2 marks
(1-2 errors or omissions – 1 mark)
[5 marks]

(c) Circulation

Heart adaptations

1. Heart is a muscular pump that forces blood through the system;
cardiac muscle is resistant to fatigue (cells have large numbers of
mitochondria)
2. Double circulatory system (pulmonary and systemic); ensures that
oxygenated blood is delivered to the systemic system at high
pressure/lower pressure is needed in the pulmonary system
3. Presence of valves: atrio-ventricular and semi-lunar valves – allow
one way circulation
4. Stimulus to contract comes from within heart (myogenic) –SAN, AVN,
Purkyne fibres – ensures that the ventricles contract after the
atria and from base upwards

Any 3 points well discussed – 2 marks each = 6 marks
(incomplete discussion – 1 mark each)