Describe the external morphology of a frog.

(N/A) $\rightarrow$ Skin of frog: The skin of a frog is smooth and slippery due to the presence of mucus. The skin lacks an exoskeleton and is always maintained in a moist condition.
$\rightarrow$ The colour of the dorsal side of the body is generally olive green with dark irregular spots. On the ventral side, the skin is uniformly pale yellow.
$\rightarrow$ A frog does not drink water but absorbs it through the skin.
$\rightarrow$ The body of a frog is divisible into head and trunk. A neck and tail are absent.
$\rightarrow$ Above the mouth, a pair of nostrils is present.
$\rightarrow$ Eyes are bulged and covered by a nictitating membrane that protects them while in water.
$\rightarrow$ On either side of the eyes, a membranous tympanum (ear) receives sound signals.
$\rightarrow$ The forelimbs and hind limbs help in swimming, walking, leaping, and burrowing.
$\rightarrow$ Feet have webbed digits that help in swimming.
$\rightarrow$ Sexual dimorphism in frogs: Frogs exhibit sexual dimorphism. Male frogs can be distinguished by the presence of sound-producing vocal sacs and a copulatory pad on the first digit of the forelimbs, which are absent in female frogs.
$\rightarrow$ During the mating period, the skin colour of the male frog becomes dark yellow. No such colour change occurs in females.
$\rightarrow$ In male frogs, the abdomen region is narrow and flat, while during the reproductive season, the abdomen of the female becomes broad and inflated due to the development of numerous egg cells in the ovary.