Four mark question Can use drawn example to show the comparison of a three chambered heart to that of a four chambered heart.(2)Name the different parts of the heart. Mammalian is two atria, two ventricles whilst the amphibian heart consists of a single ventricle. (1) The blood pumping to the outflow tract from the ventricle is split by a septum which splits the blood flow between the body and the lungs. whilst is mammals there are two separate outflow tracts from the ventricles. (1)