Flatworms, earthworms and amoeba

• What type of organism is an amoeba?

  Single-celled organism
• What is the significance of the large SA:V ratio in amoeba?

  It facilitates gas exchange by diffusion
• How does gas exchange occur in amoeba?

  By simple diffusion across the cell membrane
• What environment is necessary for gas exchange in amoeba?

  Immersed in water
• Why must the surface of the flatworm remain moist?

  To allow gases to diffuse across the skin
• What shape does a flatworm have to increase its SA:V ratio?

  Flattened body
• Does a flatworm have a circulatory system?

  No circulatory system
• What is the shape of an earthworm?

  Cylindrical shape
• How does the SA:V ratio of earthworms compare to flatworms?

  Lower SA:V ratio than flatworms
• How does gas exchange occur in earthworms?

  Through the moist skin
• What role do blood vessels play in earthworms regarding gas exchange?

  They transport oxygen to tissues
• How is gas exchange in earthworms more efficient than in flatworms?

  Blood vessels transport oxygen, enhancing efficiency