7 Gas Exchange in Human II
2nd Term WS 03
1
(a) She
would suck up the lime water if she breathed through tube X. 1m
She
should breathe through tube Y. 1m
(b) The lime
water in flask P remained clear 1m
while
that in flask Q turned milky. 1m
(c) Exhaled
air contains more carbon dioxide than the inhaled air. 1m
(d) Red
hydrogencarbonate indicator 1m
2
(a) The intercostal muscles relax. The rib cage
moves downwards and inwards. 1m
The diaphragm muscles relax. The
diaphragm moves upwards. 1m
The volume of the thoracic cavity
decreases, 1m
causing the volume of the lungs to
decrease. 1m
(b) Breathing rate = 60
/ 5 1m
= 12 breaths per minute 1m
(c) The rib cage / lungs cannot be completely
compressed. 1m
Also, the
bronchi are held open by cartilage. 1m
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