Name the excretory organs in 

i amoeba 

ii insects 

iii earthworm

i) Amoeba — Contractile vacuole

• Function: Expels excess water and metabolic wastes by rhythmic filling and contraction.
• Process: Water enters by osmosis → vacuole swells → moves to the surface → contracts → releases fluid outside.
• Role: Excretion + osmoregulation in a freshwater habitat.

ii) Insects — Malpighian tubules

• Structure: Fine blind-ended tubules opening into the gut between midgut and hindgut.
• Process: Tubules secrete uric acid, ions, and water into the lumen → mixture passes to hindgut → water and salts reabsorbed → semi-solid uric acid paste excreted with faeces.
• Advantage: Minimal water loss, ideal for terrestrial life.

iii) Earthworm — Nephridia

• Types: Integumentary and septal nephridia in most segments.
• Process: Coelomic fluid filtered → useful solutes reabsorbed → nitrogenous wastes (mainly ammonia/urea) expelled through nephridiopores.
• Role: Excretion + ionic and water balance.