Class 11 Biology Excretory Products Elimination Excretion in different animals

Excretion in different animals

Excretion happens in different ways in different animals.

  • Platyhelminthes
  • Nematoda
  • Annelida
  • Arthropoda
  • Mollusca
  • Echinodermata
  • Chordata




Excretion in Platyhelminthes


  • Specialized cells, Flame cells are present
  • Branched system of ciliated tubules are present throughout the body
  • Flame cells are connected to a duct system of pores to expel wastes
  • Maintain osmoregulation


Excretion in Nematoda

  • Excretory pores are present
  • Nitrogenous wastes are excreted in the form of ammonia
  • ‘Renette glands’ are present in some marine nematodes to excrete salts


Excretion in Annelida


  • Specialized excretory organs, Nephridia are present
  • A pair of nephridia exists in each segment
  • Nephridia are segmentally arranged coiled tubules
  • Types of nephridia:
  • Septal nephridia
    • Present on segment 15 to the last that open into intestine
    • Discharge waste products into alimentary canal
  • Integumentary nephridia
    • Present on lining of the body wall of segment 3 to the last that open on the body surface
    • Discharge waste products to the exterior
  • Pharyngeal nephridia
    • Three paired tufts in the 4th, 5th and 6th segments
    • Discharge waste products into alimentary canal


Excretion in Arthropoda

  • Malpighian tubules are present for Excretion
  • Malpighian tubules are branching tubules connected to hemolymph
  • They collect wastes from blood & put into the intestine
  • Wastes discharged through anus


Excretion in Mollusca

Nephridia are the primary excretory organs in many of them

  • Discharge wastes in the form of ammonia/ uric acid
  • Maintain water balance


Excretion in Echinodermata

  • Specialized organs are absent
  • Excretion occurs by diffusion through respiratory surfaces

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