Which one of the following animals has a four- chambered heart?

In the animal kingdom, heart structure varies significantly across different classes. Most reptiles, including the King cobra, Turtle, and Chameleon, possess a three-chambered heart consisting of two atria and one partially divided ventricle [1]. This structure allows for some mixing of oxygenated and deoxygenated blood [1]. However, crocodilians are a notable exception within the reptile class. Crocodiles possess a more advanced four-chambered heart with two atria and two completely separate ventricles [1]. This complete separation prevents the mixing of blood streams, facilitating a highly efficient oxygen supply similar to that found in birds and mammals [1]. This evolutionary adaptation supports the high energy needs and complex behaviors of crocodiles [1]. Therefore, among the given options, only the crocodile has a four-chambered heart [1].

Sources

1. [1] Science , class X (NCERT 2025 ed.) > Chapter 5: Life Processes > Oxygen enters the blood in the lungs > p. 92