All Jharkhand Competitive Exam JSSC, JPSC, Current Affairs, SSC CGL, K-12, NEET-Medical (Botany+Zoology), CSIR-NET(Life Science)

Wednesday, September 30, 2020

Phylum Annelida - NEET-Biology

 Phylum Annelida

Fig: Leech (Hirudinaria)


  • Triploblastic, coelomate, bilaterally symmetrical & metamorphically segmented animals.
  • During muscular contraction, the body wall pushes against each compartment wall. This allows separate regions to contract independently & elongate during locomotion.
  • The body is elongated, cylindrical, or flattened.
  • The segmented worms are triploblastic, i.e. they develop from the three germ layers.
  • The body-cavity is a true coelom, as it is lined by a mesodermal epithelium.
  • It is divided by vertical septa into compartments.
  • A closed circulatory system present.
  • Segmented nephridia for excretion & osmoregulation.
  • Typically, there is a trochophore larva during development.
  • Example: Nereis, Pheretima (Earthworm), & Hirudinaria (Bloodsucking leech).
Fig: Earthworm (Pheretima)



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