Amoeba

• All protista are eukaryotic.
• Most protista are single-celled organisms.

Amoeba Characteristics

• Single-celled organisms.
• Habitat: freshwater rivers, streams, lakes, ponds, seas, and oceans.
• Reproduce asexually through mitosis.
• They are heterotrophic**.** They feed on other protists (e.g. algae), bacteria and single-celled fungi.
• Reproduce asexually through mitosis.

Structure of Amoeba

• Nucleus: controls all cell activities.
• The cytoplasm is made up of two layers:
  • Ectoplasm: thin outer layer.
  • Endoplasm: fluid inner layer.
• Amoeba do not have a definite shape as the cytoplasm is constantly flowing.
• The cytoplasm can push out at any point on its surface to form pseudopodia ('false feet').
• Pseudopodia
  • Used for movement and feeding.
  • Feeding: The prey is surrounded by pseudopodia and pulled into the cytoplasm.
• The cell membrane allows for diffusion of oxygen into the cell and diffusion of carbon dioxide out of the cell.
• Fat droplets store fat as an energy reserve.
• Food vacuole secretes acid and digestive enzymes to kill and digest prey.
• The contractile vacuole allows for osmoregulation.
  • The contractile vacuole collects excess water, expands, moves to the cell surface and squeezes out the water.
• Amoeba reproduce asexually by mitosis.