I) Excretion is the biological process by which an organism eliminates metabolic waste products and other non-useful substances from its body.

a)

i) Excretion is the biological process by which an organism eliminates metabolic waste products and other non-useful substances from its body.

ii) Two excretory products for each organ:

• ($\alpha$) Lungs: Carbon dioxide, Water vapor
• ($\beta$) Kidney: Urea, Excess water (or mineral salts)
• ($\gamma$) Skin: Water, Mineral salts (or urea)