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| Salient Features of Vertebrate Representatives |
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| Two familiar examples of vertebrates frog and rat are chosen here to study the salient features. |
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| Frog a Typical Vertebrate: |
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| Kingdom : Metazoa |
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| Subkingdom : Eumetazoa |
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| Division : Bilateria |
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| Grade : Eucoelomata |
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| Phylum : Chordata |
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| Subphylum : Vertbrate |
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| Class : Amphibia |
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| Order : Anura |
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| Family : Ranidae |
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| Genus : Rana |
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| Species : hexadactyla |
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| The frog is generally considered as a typical vertebrate animal. It is an amphibious animal capable of living both in water and on land. However, it spends most of the time in its aquatic habitat such as ponds, pools and ditches. |
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| Frog has a body which can be distinguished into a head and a trunk. The body is covered by a moist, slimy skin which is loosely attached. The skin has a dark blackish green colour on the dorsal surface and pale white on the ventral surface. It helps in respiration. |
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| The head is roughly triangular in shape. Anteriorly it has a cavernous mouth that can ingest large animals, since the gape of the mouth is large. A pair of nostrils are situated at the anterior tip, dorsally. Two large, retractible eyes are present. Each eye has an upper eyelid, a lower eyelid which is immovable, and a transparent movable third eye lid, called nictitating membrane. A pair of large, flattened tympanic membranes are present posteriorly one on each side, representing the ear drums. |
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| External Features of a Frog |
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| The trunk merges with the head since a distinct neck is absent. It is streamlined for a smooth passage in water. The trunk bears a pair of forelimbs and a pair of hindlimbs. The limbs are set at an awkward angle on the body and can not support the body weight during walking. Hence, frogs propel themselves by leaping or hopping on land. The forelimbs have four digits each and hindlimbs have five digits each. They are much shorter than the hindlimbs and are used only for support while sitting. While leaping, forelimbs are used and also for grasping the female at the time of mating. The hind limbs are longer and have five digits each. The digits are joined by a fold of the skin to form a web. The powerful hind limbs are used for swimming in water. |
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| At the posterior end of the trunk, is an opening called cloaca which serves as a common opening for digestive, excretory and reproductive systems. |
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| The general body cavity which is called coelom gets partitioned into numerous cavities. Following cavities (not necessary coelomic) can be recognised in the body. |
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 A cranial cavity which houses the brain |
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 A pair of orbital cavities that enclose the eyes |
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 A pair of nasal cavities which open into the mouth |
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 A buccal cavity which encloses tongue and teeth |
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 A spinal cavity that encloses the spinal cord |
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 A thoracic cavity that provides shelter for heart and lungs |
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 An abdominal cavity that encloses most of the visceral organs. |
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