Differentiate the nature of skin in four classes of tetrapoda.

The nature of skin in four classes of tetrapoda are-
(i) ClassAmphibia-Thin, moist, glandular and respiratory skin,
(ii) Class Reptilia - Dry and non-glandular skin with scales
(iii) Class Aves - Dry and non-glandular skin with feathers
(iv) Class Mammalia - Glandular skin with hairs.