Frog - Morphology And Circulation

Vertebrate hearts differ in the degree to which oxygenated and deoxygenated blood are kept apart, and NCERT details the amphibian condition. The frog's heart is three-chambered, consisting of two atria and a single undivided ventricle; because the ventricle is not partitioned, oxygenated and deoxygenated blood mix to some extent, giving an incomplete double circulation suited to its semi-aquatic life. A two-chambered heart with one atrium and one ventricle is characteristic of fishes that pump only deoxygenated blood to the gills, not of frogs. A four-chambered heart with complete separation occurs in birds and mammals, allowing fully oxygenated blood to reach tissues, which is more advanced than the amphibian plan. A single-chambered heart does not occur in vertebrates of this group. As stated in NCERT Class 11, Chapter 7 (Structural Organisation in Animals), the frog possesses a three-chambered heart. A structural sanity check confirms that two atria plus one ventricle total exactly three chambers, matching the amphibian circulatory design.