body segmentation

Cleavage (Segmentation) - Cleavage is an unique embryological process which transforms the single fertilised egg cell into a sphere of closely aggregated multitude of cells. Immediately after fertilisation the fertilised ovum (egg cell) undergoes a series of cell divisions. These division..

Features of Annelida..

Phylum Annelida (Segmented Worms) - Earthworm Occur in moist soil, fresh water and sea. Body is soft and segemented, triploblastic with bilateral symmetry. First animal with the coelom (body cavity). Body is covered by a non-chintinous cuticle which may have ..

Earthworm Occur in moist soil, fresh water and sea. Body is soft and segemented, triploblastic with bilateral symmetry. First animal with the coelom (body cavity). Body is covered by a non-chintinous cuticle which may have chitinous setae, or parapodia. ..

These lie attached to the inner side of the body wall in all segments except the first t..

Body is bilaterally symmetrical and segmented. It is divided into head, thorax and abdome..

Free-living, terrestrial or aquatic form (freshwater or marine). Body is long, cylindrical and metamerically segmented..

Excretion is carried out by segmentally arranged coiled ducts called nephridia. Based on their location, these nephridia can be distinguished into three types- i. Pharyngeal nephridia which occur as paired tufts on either side of the pharynx and oesophagus in the fourth, fifth and sixth h..

Pheretima posthuma is a common species of earthworm found living in burrows made in moist soil. It is nocturnal in habit. It has an elongated, cylindrical body which is metamerically segmented. Anteriorly the first segment is called peristomium. It encloses a mouth. Ov..

Excretion and Osmoregulation in Earthworm - The earth worm belongs to the phylum Annelida. This group of higher invertebrates possess a number of highly developed organs and organ-systems for performing various vital functions. Earthworm One such elaborate system is the excretory system which consi..