4. Kingdom Animalia - part 07 - Phylum : Annelida

 


4. Kingdom Animalia - part 07 - Phylum : Annelida


Phylum : Annelida (Annulus : Ring) :

  • e.g. Nereis, Pheretima (Earthworm), Hirudinaria (Leech).
  • They are commonly called ring worms or segmented worms. 
  • Animals may be aquatic and few may be ectoparasitic or free living or burrowing in moist soil. 
  • They show bilateral symmetry with metameric segmentation.
  • A special region of the body called - clitellum is present. 
  • Locomotion is with the help of longitudinal and circular muscles.
  • Locomotory structures like setae (earthworm), parapodia (Nereis) or suckers (leech) are present. 
  • Alimentary canal is complete.
  • Exchange of gases takes place through body wall. 
  • Circulatory system is of closed type. 
  • Excretion and osmoregulation is carried out with the help of nephridia. 
  • Nervous system consists of nerve ring and ventral nerve cord.
  • Nerve cord is ventral, solid and ganglionated. 
  • Mostly hermaphrodites and few are dioecious (Nereis).

always remember :

  • All animals from Annelida onwards are triploblastic, coelmate with organ system level of organization.

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