Class 11 Biology Excretory Products Elimination Introduction


Excretion is the process of removal of harmful metabolic wastes from an organism’s body. Excretion is useful in the following ways:

  • Maintain correct ionic balance in the body
  • Maintain correct amount of water in the body
  • Toxic level rises in body leading to diseases
  • Immunity is adversely affected


Major nitrogenous wastes in the body are:

  • Ammonia
    • Most toxic form of nitrogenous wastes
    • Aquatic animals are Ammonotelic
    • Excretion through body/ gill surfaces
  • Urea
    • Lesser toxic than Ammonia
    • Terrestrial animals are Ureotelic
    • Excretion through Kidneys
  • Uric acid
    • Least toxic form
    • Birds, insects & reptiles are Uricotelic


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