• Different organisms have different digestive systems because:
  • Their food differs.
  • Their method of obtaining food differs.
• In simple unicellular organisms, food is taken in through the entire body surface.
• As organisms become more complex, different body parts become specialised for digestion.

Amoeba

• Amoeba uses temporary finger-like projections called pseudopodia to capture food.
• The pseudopodia surround the food particle and form a food vacuole.
• Inside the food vacuole:
  • Complex food substances are broken into simpler substances.
  • Digested food diffuses into the cytoplasm.
• Undigested food is moved to the cell surface and expelled outside.

Paramoecium

• Paramecium has a fixed body shape.
• Food enters through a specific spot in the body.
• Tiny hair-like structures called cilia help in feeding.
• Movement of cilia pushes food towards the food intake region.