Phylum Annelida: General Characteristics and Classification

Hermaphitodite-both male & Femal Cutaneous reespiration fapt preesent im ane body Respiration Phylum Annelida through body. classification Surface General Characteristics & classification →Aronelida include earth worems, beaches blistere worms etc They arce Hiploblastic & bilaterally symmetrical. → They exhibit metamoric, segmentation & true colom. 7 Theire coelom is acts as hydrostatic skeleton & helps in locomotion. → They have distinct head, tentacles & eyes etc. + They have numerous metamercison & berly is divided into a sercies of similare Segments. → In amelida body is divided into 3 regions such as preastomein. trunk & pygidun →Body call consist of Cuticle, epidermis & dermis Layers. →Alimentary canal is straight and muscular type... → Exchange of rees pircatory gases occurs by diffusion, through the body wall & gills. → Rhod vascular system is closed type. →Exercetorry organ is nephoridia opening of nephreidia is called- nephrostome & to exteriore by nephritisperce. → Nervous system is well developed. Classification of Phylum Annelida Therce arce 8700 species described in this phylum. This phylum annelida is divided into y main Elasses on the basis of presence se absence of parcapedia, Setae & othere morephological Charactere. Annelida Polychaeta Oligochaeta Hirridinea Arcchi amelida. Phylum Annelida origin & significance of metantrism Introduction Metamerism is the condition wh bilatteral animal bevelves Longitu Serties of similare Section the general Segmentation of I division of the badly into lineart 7 •Metamerism is also known as metamentic segmendation. 7 Each section is called metamerce ord somite on segment Each of these Segments has repeat in some ore all units of oregans. Metamerism is a Greek word me mere means "paret. meaning meta means flere & → Metamerism in arumal Kingdom include for the 1st time in annelids. + Apart forom these it is also found in phylum Arethico poda & vertebrata One group of mollusca że monoplaco pharta also exhibit metamercicon. Tape worems show prendemelamerism which is not treve motameric Segmentation. Types of melamerism There are mainly three types of metamenism arce observed such as external & internal metamerism 7 Dr. mass of amelids, metanercism is visible both exteretrally & internally. Phercetima & posthuma are the annelids which shers bom exterceral & internal metamertism + In acarpods metamerism is chairly external, human & otherc vertionate show internal metamerises of blood, nerve etc. → Moreover even the coelom, is segmentally dividest sita coatpactmenst by interesegmental transverse mecanteries called sapta Complete and incomplete melamerice → Complete type of metamernism practically affects ad the body Systems. → In this type the metameries are homonomous and each metamere has segmental blood vessels, nerves, coelomoducts and nephrudis → Thus this condition is also called homonamous metamercism. → Metamentism in Arethrcopods ound othere highere omimals orce incomplete, because of division of laboure. Consequently metamere of different regions of body varry considerable. 7 Such a condition is called heteronomous metamerism. →The larval cand embryonic stages of anthropods and othere vertebrates shouw complete, metamentism with uniforem metamerces. True and Pseudometamerism True Segments in Amelids arce dev developed during the embryonic Stages where as the pseudo segments presend in tape worems artes Supereficial which arce foremed as a result of Strobilization.. Theories of origin and exclution of metamerrism (1) Pseudometamereism theorcy:- This theory coas prieposed by Hum Hymen and Goodrich in 1951 7 This theory explains pseudometamerism that occures in cestorles Such as tapeworms. →According to this theorey, metamerism initially developed Secondarity as a result vessels, coelom, nerves exc to reepetition of body parets like blood (2) Fission Theary This theory was proposed by perrerciere, in 1882. It postulates that pseudemetamerism evolved in flat worms by strobilation of body. →Stitabitation & mainly ained to increase the rate of reproduction. Dr Cyclomerism Theory:- This thearty is proposed by Sedgwick in 1884. According to this theory, metamerciem in chordates evolved fore bettere attrcangement of organs in coelom. (4) Locomotorcy Theory:- 7 This thearty is proposed by Clarck in 1964. This theerly postulates that meta adaptation to Locomotion of different kinds. evolved as an Significance of metamercism:- ix It has provided effective locomotorcy mechanism. in Fluid Filled coelomic compartiments provide hydro static Skeletons fore burrowing cont iii Different segments can be specialized fore differcent functions leading to the development of high grade of organization. It is not clearly marked in amelids but well developed in anthropods.