Question

Why crocodile have four chambered heart ?

Answer 1

simply why all other animals are different from their own class or order. Adaptation. The crocodiles body is much larger then any other reptile, and along to adjust with the climate it lives in, circulation may have to have been modified so that organism could flourish in that environment. All crocodiles have a fully-divided 4 chambered heart, and in fact are the only animals known to have active control over heart valves (cog-wheel valve leading to the pulmonary artery, and foramen of Panizza joining the two main aortas from the ventricles).  This enables them to alter circulation through the heart during diving, basically diverting the pulmonary flow into the systemic one to concentrate blood into the essential areas when it isn't being renewed.  Crocodiles also have haemoglobin with very high affinity for oxygen (so much so that Hb Scuba has been engineered from crocodile haemoglobin as a potential solution to supplying additional oxygen to heart transplant patients during surgery).More circulation for more body perhaps, but most likely evolution of the organism to adapt

Answer 2

It has a four-chambered heart and two ventricles, an unusual trait among extant reptiles, and both a left and right aorta which are connected by a hole called the Foramen of Panizza. Like birds and mammals, crocodilians have heart valves that direct blood flow in a single direction through the heart chambers.