(a(i))[1]
State the name of the heart chamber that has the thickest wall.
(a(ii))[3]
State the name of this vein and outline its structure.
(a(iii))[2]
Identify the structure labelled X in Fig. 2.1 and state its role in the heart.
(b(i))[1]
Shade the blood vessel in Fig. 2.2 that carries blood with the highest oxygen concentration.
(b(ii))[2]
Describe the evidence shown in Fig. 2.2 that the mammal has a double circulatory system.
(b(iii))[4]
Explain the advantages of a double circulation.