Describe external Morphology of frog.

Explanation

Skin of frog : The skin of frog is smooth and slippery due to the presence of mucus. The skin is without exoskeleton. The skin is always maintained in a moist condition. The colour of dorsal side of body of frog is generally olive green with dark irregular spots. On the ventral side the skin is uniformly pale yellow. frog never drinks water but absorb it by skin.The body of a frog is divisible into head and trunk. A neck and tail are absent. Above the mouth, a pair of nostrils is present. Eyes are bulged and covered by a nictitating membrane that protects them while in water. On either side of eyes a membranous tympanum (ear) receives sound signals. The forelimbs and hind limbs help in swimming, walking, leaping and burrowing. Feet have webbed digits that help in swimming. Sexual dimorphism in frog : Frogs exhibit sexual dimorphism. Male frogs can be distinguished by the presence of sound producing vocal sacs and also a copulatory pad on the first digit of the fore limbs which are absent in female frogs. During mating period the colour of skin of male frog because dark yellow. No change of colour occurs in females In male frog, abdomen region is narrow and flat while during reproduction season, the abdomen of female becomes broad and inflatted due to development of numerous egg cells in ovary.