Class 11 Biology Animal Kingdom Phylum Annelida

Phylum Annelida

  • The body surface of Annnelids is distinctly marked out into segments or metamere and, hence, the phylum name Annelida.
  • They exhibit organ-system level of body organization, bilateral symmetry,they are triploblastic, metamerically segmented and coelomate animals.
  • Aquatic annelids possess lateral appendages called asparapodia. For example- Nereis
  • Nephridia help in osmoregulation and excretion.
  • Neural system consists of paired ganglia connected by lateral nerves to a double ventral nerve cord.
  • Reproduction is sexual.
  • Nereis, an aquatic form, is dioecious, but earthworms and leeches are monoecious.

Examples - Nereis, Pheretima (Earthworm)


Fig. Earthworm

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