Question

Which reptile is characterised by the presence of a four-chambered heart?

Answer 1

Hint: Reptiles are four limbed animals belonging to the clade Reptilia. They are said to have originated 310-320 million years ago mostly during the late Carboniferous period.

Complete answer:
Reptiles are vertebrates that have four limbs or have originated from four limbed ancestors and do not possess an aquatic larval stage. Reptiles exhibit cold-bloodedness with respect to body temperature in contrast to mammals and birds which are warm blooded. The optimum body temperature of reptiles ranges from 24 to 35 degree Celsius.

Reptiles can thus modulate their body temperature according to the surroundings, this has an advantage as this helps them to save energy. The food requirement of reptiles is also less compared to birds and mammals as a result they can occupy regions where the previous two species cannot survive. Most of the reptiles are known to possess a three chambered heart comprising of two aorta and one ventricle.

The heart is known to comprise of all the following structures apart from the aorta and ventricle-the sinus venosus, the atrioventricular valve, the cavum pulmonale, the cavum venosum, the cavum arteriosum, the ventricular ridge, the muscular ridge and pulmonary veins. But crocodiles are reptiles which has four-chambered heart consisting of two aorta and two ventricles like birds and mammals.

Note: Generally in reptiles the oxygenated and deoxygenated blood are mixed up together but in case of crocodiles it is different. In case of crocodiles the two types of blood do not mix up, instead the deoxygenated blood is sent to the blood after which it is received by the right ventricle and is further transferred to the left ventricle and pumped to the entire body.