In which one of the following animals, is skin a respiratory organ?

In amphibians like frogs, the skin serves as a vital respiratory organ through a process known as cutaneous respiration [1][t2]. Frogs possess thin, moist skin that is richly supplied with blood capillaries, allowing oxygen to diffuse directly into the bloodstream and carbon dioxide to exit [t2][t3]. While adult frogs use lungs for breathing on land, they rely heavily on their skin for gas exchange when submerged in water or during hibernation [c1][t3]. In contrast, cockroaches utilize a tracheal system with spiracles for respiration [t6][t7]. Sharks are elasmobranch fish that primarily respire using gills [t1][t7]. Whales are mammals that breathe air through lungs via a nasal opening or blowhole [t7]. Therefore, among the given options, only the frog uses its skin as a functional respiratory organ to supplement or replace lung activity depending on its environment [c1][t3].

Sources

1. [1] Science-Class VII . NCERT(Revised ed 2025) > Chapter 9: Life Processes in Animals > 9.2.2 Do other animals breathe the same way as humans do? > p. 133