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Detailed Study of Earthworm – Download Notes Biology Class 11

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Mating EarthwormsBiology | Zoology
Detailed Study of Earthworm (Pheritima posthuma)
For: Science Class 11

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Earthworm (Pheritima posthuma)
It is found in soil, which is rich n humus. It is found abundantly in rainy season. Other days it is found in soil. The earthworm is usually active at night and so called nocturnal. They feed on soil; digest organic matters and undigested matter are excreted out called castings. The earthworm plough soil, makes soil fertile, and so called farmers friend.

Body is long elongated and cylindrical. Anterior and posterior ends are blunted. Body is bilaterally symmetrical. A mature worm is 150 mm long and 4-5 mm width. Body is segmented. There are about 100-120 segments. All the segments are similar and so called metamericlly segmented.

The first segment is called peristomium and the last is called anal segment. In front of peristomium there is a lobe like sensitive structure called prostomium. The 14th 15th and 16th segments are thick and united to form clitellum. The region before clitellum is called pre-cliteller and the region after clitellum is called post-clitellar region. At ventral surface on 14th segment there is a mid pore called female genital pore. On ventral surface, at 18th segment there is pair of pore called male genital pores. There are two pairs of outgrowths on 17th and 19th segments called genital papillae. It helps in reproduction.

At each 5-6, 6-7, 7-8, 8-9th segment there is a pair of opening called spermathecal pore. Below each spermathecal pore, small sac like structure is resent called spermathecae. Except one and two segments, minute pores are scattered throughout the body called nephridiopores, which are excretory organs. On the dorsal surface after 12th segment, small pore is present at each segment called dorsal pore, which communicates body cavity to the environment. The locomotion is carried out by setae. The setae are S shaped structure, which penetrate the body wall and embedded into saetal sac. The setae are made up of chitin, which is complex polysaccharide. At the mid portion of setae there is round structure called nodule.

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Posted By : Hari Prasad Chaudhary | Comment RSS | Category : Class XI, Downloads, HSEB Notes
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  1. Posted December 2, 2015 at 3:55 pm


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