Saturday, 16 January 2016

CHORDATA PHYLUM

*presence of eal gilnotochord, dorsal hollow nerve cord and paired pharyngeal gill slit are the characterised feature of chotdata.
*habitat- found everywhere
*symmetry- bilateral
*body form- triploblastic
*body cavity- coetomate
*level of organisation-organ system level
*circulatory system- closed type
* phylum chordata is divided into three subphylua-

  1. Urochordata /Tunicata
  2. Cephalochordata
  3. Vertebrata 
*Urochordata and Cephalochordata are comes under protochordates.
*protochordates are exclusively  marine.
*in urochordata the notochord is present only in larval tail.
*in cephalochordata , notochord  extends from head to tail region, throughout life
*e.g.-Urochordata-Ascidia, Salpa,Doliolum
         Cephalochordata-Branchiostoma
*in vertibrata the notochord is replaced by a cartilaginous or bony vertebral column. thus all vertibrates are chordates but all chordates are not vertebrates.


ASCIDIA



BRANCHIOSTOMA 


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