Biology · May / June 2022 · Paper 41 · Question 2
0610
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Mammals have a double circulation. Fig. 2.1 is a diagram of a section through the heart of a mammal. The arrows show the direction of blood flow through the heart and blood vessels. C A B C septum D X Fig. 2.1
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2(a)(i)[1]
left ventricle ;
2(a)(ii)[3]
total of three from:
vena cava ;
max. two from:
has valves ;
wide, lumen / AW ;
thin wall ;
(wall) lined by single layer of cells ;
(wall) contains muscle (fibres) ;
(wall) contains elastic (fibres) ;
2(a)(iii)[2]
semilunar valve ;
prevents backflow of blood (correctly described) / ensures that blood flows in one direction ;
2(b)(i)[1]
shading in any part of the pulmonary vein only ;
2(b)(ii)[2]
any two from:
heart has, two / left and right, sides / AW ;
blood must flow through the heart twice in one (complete) circuit / AW (of the body) ;
pulmonary and systemic circuits / circuits from heart to lungs and from heart to rest of body ;
2(b)(iii)[4]
any four from:
1
oxygenated and deoxygenated blood, are kept separate / do not mix / separated by septum ;
2
ensures efficient supply of oxygen (to, body / AW) ;
3
ensures efficient supply of (named) nutrients (to, body / AW) ; 4
low(er) pressure in, pulmonary, artery / circuit / AW ;
5
to prevents damage to (capillaries in the) lungs ;
6
allows more time for gas exchange ;
7
allows high(er) pressure (in body) ;
8
to ensure efficient, blood supply to (rest of) body ;
9
to allow filtration in kidneys (for excretion) ;
10 to allow / maintain, a high, metabolic rate / rate of respiration ; 11 AVP ;
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