7 Gas Exchange in Human II
2nd Term WS 03
(a) She would suck up the lime water if she breathed through tube X.
She should breathe through tube Y.
(b) The lime water in flask P remained clear
while that in flask Q turned milky.
(c) Exhaled air contains more carbon dioxide than the inhaled air.
(d) Red hydrogencarbonate indicator
(a) The intercostal muscles relax. The rib cage moves downwards and inwards.
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