External Features of Frog

Introduction to the Experiment

Amphibians are a group of cold-blooded animals that can live both on land and in water. They are members of the phylum Chordata and the kingdom Animalia. These animals, which number over 3,000 species, are distinguished by having smooth skin devoid of scales and possessing glands that keep them moist. They have two pairs of limbs for locomotion and breathe through their skin and lungs. The sexes are different, and fertilisation is usually external. The experiment “External Features of Frog” deals with the study of the external features of an amphibian known as Rana tigrina, commonly known as the Indian bullfrog.

Experiment Procedure

The details of the experiment are as follows:

The preserved specimen of Rana tigrina was examined with the naked eye, and the following features were studied:

Rana tigrina, a short-bodied and tailless amphibian, is commonly found in freshwater wetlands and near aquatic habitats like ponds, pools, and ditches. They have a large, bulky, stout body with a distinct head, trunk, and limbs without a neck or tail. The mouth is terminal, with a bifid tongue and jaws meant for obtaining food. The external nares, or nostrils, help with respiration.

The eyes of this frog are large, spherical, protruding, and covered with a translucent nictitating membrane that serves to protect and lubricate the eyes when swimming underwater.

The tympanic membrane, or eardrum, is a flat, conspicuous, and pigmented circular patch present behind the eyes that allows the frog to hear both on land and in water.

Frogs use their bifid tongue to catch prey. When the frog’s sticky tongue comes into contact with prey, it grasps it and brings it into the frog’s mouth.

The forelimbs are smaller than the hindlimbs and have four clawless digits, providing body support and holding the female during mating. The hindlimbs are larger than the forelimbs and have five clawless digits each. The frog has webbed feet, visible as an interdigital web-like membrane in the hindlimbs, used for swimming.

Male frogs are smaller than females, with the thick, pad-like base of the first digit of the forelimb forming a nuptial pad for holding females during mating. Vocal sacs are present in males for making nuptial calls during breeding season, while females are larger and do not have vocal sacs or nuptial pads.

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