question_answer

   (a) Name the  waste   products   of metabolism and for each waste product, state which organ removes it from the blood. (b) Why is the removal of faeces from the alimentary canal not considered to be excretion?

Answer:

                  (a) The waste products of metabolism and their excretory organs are tabulated below                

Metabolic Waste Products	Excretory Organs
Carbon dioxide and water	Lungs
Urea and nitrogenous substances water	Kidneys
Urea and nitrogenous substances	Liver
Urea and water	Skin

(b) Excretion is the removal of metabolic waste products which are formed in chemical reactions in the cells. Removal of faeces (defaecation) is the removal of undigested or indigestible substances from the alimentary canal through the anus. Since, faecal matter is not produced by metabolism, removal of faeces cannot be considered as excretion.