1.	(a)	(i)	Falls (diving), remains low (submerged), increases (resurfacing);
Any reference to fluctuations / slight rise in pressure after submergence.	2
(ii)	Muscle (in wall);
Contraction / narrowing of arteriole reduces (blood flow) / relaxation /
dilation
increases (blood flow).	2
 
(b)	(i)	46%;	1
(ii)	Respiration Produces carbon dioxide
Increase in carbon dioxide causes decrease in pH;	2
(iii)	(Haemoglobin) yields more oxygen;for respiration.	2
 
(c)	Acts as a store of oxygen / obtains oxygen from haemoglobin;
Oxygen released at very low partial pressures of oxygen;
Allows (aerobic) respiration to continue / delays anaerobic respiration.	2
[11]

2.	(a)	Molecules will have more (kinetic) energy;
Move faster;
Reject references to vibrating in this context	2
 
(b)	(i)	Oxygen diffuses faster/has a higher rate of diffusion
in air than in water;	1
(ii)	Alveolar epithelium/surface is permeable to small molecules;
Water is a small molecule;
Higher concentration of water in cell/blood than outside;
Water diffuses from blood/cells into alveoli;	max 2
 
(c)	Large number gives large (total) surface area;
For diffusion;
Short distance between tracheoles gives short pathway;
Movement/diffusion through muscle is slow;
Reject references to muscle simply being close to tracheoles. Must convey
idea of short pathway to gain credit for third point.	3
[8]

3.	(a)	One cell thick/thin (not thin membrane)/flattened cells for faster
diffusion/shorter diffusion pathway;(Reject greater/more)
Large surface area for faster diffusion;(Reject greater/more)
Ventilation to maintain a diffusion/concentration gradient;	2 max
NB TWO correct features = 1 mark maximum

(b)	(i)	Decreases first from zero;
Then increases to zero;
‘U’ shape (not starting at zero) = 1 mark maximum 	2
 
(ii)	;	1
[5]

4.	(a)	intercostal muscle; (internal/external neutral)	1
(b)	(i)	contracts;
pulling ribs upwards / outwards; (ribcage expands neutral)
(accept answers in terms of antagonistic role of internal intercostals);
lung / chest / thorax volume increased, or lung / chest / thorax
pressure decreased;	3 max
(ii)	maintain / greater diffusion / concentration gradient;
continuous diffusion / faster diffusion;	2
[6]

5.	(a)	contraction of (diaphragm) muscles flattens diaphragm;
contraction of intercostal muscles raises ribcage;
increase in volume decreases pressure;	3
 
(b)	(i)	tidal volume increases steeply, then increase slows down after 10
to 15 kmh-1;	1
(ii)	breathing rate increases slowly then steeply after 10 to 15 kmh-1;	1
(max 1 if no reference to speed where change occurs in either (i) or (ii))
 
(c)	20 × 2.75 = 55 dm2;	2
(award 1 mark for correct method i.e. tidal volume. × rate);
[7]

6.	(a)	droplets/ref. coughing/sneezing;
which are breathed in/taken in through gas exchange system/nose/lungs;
OR
milk;
drunk/taken into digestive system;	2

(b)	2500 × 20.066;
= 50165;	2
allow 1 mark if correct working shown
[4]