Essay On Amphibians

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The first major groups of amphibians emerged in the Devonian Period about 360 millions years ago from fishes where the fins had evolved into legs. At that time amphibians were much larger than what we know of amphibians in our contemporary world. The amphibians are the first group among the chordates that live outside water. But the amphibian is still chained to water, in water it is born, to water it must periodically return for respiration. Frog is an amphibian, living both on land and in water. They are cold-blooded vertebrates having two pairs of limbs- tetrapods. Frog is cosmopolitan in distribution. Frogs were the first land animals with vocal cord. They have smooth and moist skin. Rana tigrina is the common Indian bull frog. Rana…show more content…
*It lives in and at the shore of rivers, ponds, ditches and drainage etc. *When in water, it keeps the tip of the snout above the water surface. (Fig.14.1). *Frogs characteristically have squat bodies, smooth skin, strong hind legs for leaping and webbed feet. Most reproduce in water, laying eggs that develop into larvae (tadpoles). It shows following habits: a) Resting: Frogs rest on land in a squatting posture. They keep their short fore limbs upright and the long hind limbs fold inside the body. On any disturbance they suddenly jump in water by extending their hind limbs to escape from enemies. b) Feeding: Frog is a carnivorous animal. It feeds on earthworms, insects, spiders, snails and tadpoles. However, tadpoles feed on aquatic plants, i.e. they are herbivores. The frog is a cold-blooded or poikilothermic animal which means its body temperature fluctuates with that of the environment. Therefore it cannot bear very cold or very hot temperature. The frog needs hibernation (winter-sleep) and aestivation (summer sleep) to tide over the unfavourable

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