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Chapter: BIOLOGY (ZOOLOGY) Standard XI first year 11th text book Assignment topics question and answer Explanation Definition

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Pigeon : The wings

Pigeon : The wings
The forelimbs as modified wings are located in the anterior region of the trunk. The limbs are of the pentadactyl type. The wing has three typical divisions as - the upper arm, forearm and hand.

Pigeon - The wings

 

Pigeon

 

Sub phylum - Vertebrata

Class - Aves

Order - Columbiformes

Type - Columba livia

 

Birds are easily recongnised group of vertebrates. In birds every part of the body is modified to suit their aerial mode of life. Birds possess feathers, beak and feet modified in relation to their aerial life.

 

The Pigeons are flying birds(carinate). They are known both as wild and domesticated forms. The Pigeons are seen both in tropical and temperate zones. About 10 species of Pigeons are found in India. The pigeons fly in flocks and roost together. The domestic pigeons have many varieties, namely panter, fantail and tumblers. They differ in size, colouration and feather ar-rangement. All of them are, however, descendants of the rock pigeon-columba livia.

 

The wings :-

 

The forelimbs as modified wings are located in the anterior region of the trunk. The limbs are of the pentadactyl type. The wing has three typical divisions as - the upper armforearm and hand. The hand has three imper-fectly marked digits. While the pigeon is at rest the three divisions of the wing are bent upon one another in the form of the letter 'Z'. During flight the wings are straightened and extended. A fold of skin the alar membrane orprepatagium , stretches between the upper and forearm along the anterior border of the limb. A smaller fold known as postpatagium is present between the trunk and upperarm.

 

While the pigeon is not flying the whole weight of the body has to be supported by the hind limbs, In order to balance the heavy trunk the hindlimbs are attached for forwards. Each hindlimb or leg has three typical divisions, the thigh, shank and foot. The thigh without being free is enclosed within theboundaries of the trunk. Each hindlimb has four digits. The first toe is directed backward. The feet are naked and covered with horny epidermal scales. Each digit is provided with a horny claw. The tail is small and concealed by the feathers of the trunk. It bears the tail feathers or rectrices.


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