Class 11 Biology Animal Kingdom Phylum Chordata

Phylum Chordata

  • Animals belonging to phylum Chordata are fundamentally characterized by the presence of a notochord, a dorsalhollow nerve cord and paired pharyngeal gill slits.
  • These are bilaterally symmetrical, triploblastic, and coelomate with organ-system level of organization.
  • They possess a post anal tail and a closed circulatory system.
  • Phylum Chordata is divided into three subphyla, which are Urochordata or Tunicata, Cephalochordata and Vertebrata.
  • Subphyla Urochordata and Cephalochordata are often referred to as protochordates.
  • In Urochordata, notochord is present only in larval tail, while in Cephalochordata, it extends from head to tail region and is persistent throughout their life.

Examples- Urochordata – Ascidia

Fig. Ascidia

 Class_11_Biology_AnimalKingdom_Ascidia

 Cephalochordata – Branchiostoma

Class_11_Biology_AnimalKingdom_Cephalochordata

Fig. Branchiostoma

  • The members of Vertebrata possess notochord during the embryonic period, which is replaced by a cartilaginous or bony vertebral column in the adult and hence all vertebrates are chordates but all chordates are not vertebrates.

Comparison of chordates and non-chordates

  1. Notochord is present in chordates, on the other hand, absent in non-chordates.
  2. Central nervous system is dorsal, hollow and single in chordates, whereas ventral, solid, and double in non-chordates.
  3. In chordates, pharynx perforated by gill slits, whereas gill slits are absent in non-chordates.
  4. Heart is ventral in chordates, whereas heart is dorsal in non-chordates.
  5. A post-anal part (tail) is present in chordates but Post-anal tail is absent in non-chordates.

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