Amoeba, flatworms + earthworms

• What type of organisms are amoeba, flatworm, and earthworm?

  They are examples of different organisms.
• How do small unicellular organisms exchange gases?

  Across the cell surface due to large surface area.
• Why is diffusion rapid in small unicellular organisms?

  Distances within the cell are small.
• What is the surface area to volume ratio in larger multicellular organisms?

  It is smaller compared to unicellular organisms.
• What is the gas exchange method for amoeba?

  Diffusion across the cell surface.
• Why is gaseous exchange rapid in amoeba?

  The cell membrane is thin and diffusion distances are short.
• What is the shape of flatworms and how does it aid in gas exchange?

  Flatworms are flat, increasing surface area.
• How does the shape of flatworms help overcome size increase in gas exchange?

  It ensures no part is far from the surface.
• What type of organism is the earthworm?

  It is a terrestrial organism.
• What is the shape of the earthworm and how does it affect gas exchange?

  It is cylindrical, leading to a smaller surface area to volume ratio.
• What is the respiratory surface of the earthworm?

  The skin, which is kept moist by mucus.
• Why does the earthworm have a low oxygen requirement?

  Because it is slow moving and has a low metabolic rate.
• How does oxygen diffuse in the earthworm?

  It diffuses across the skin into blood capillaries.
• What role does haemoglobin play in the earthworm's gas exchange?

  It carries oxygen around the body in blood vessels.
• How does the earthworm maintain a steep concentration gradient for gas exchange?

  By having haemoglobin in the blood.
• How does carbon dioxide diffuse in the earthworm?

  It diffuses out across the skin down a concentration gradient.
• What is metabolic rate?

  • The rate of energy expenditure by the body.
• What is a terrestrial organism?

  • An organism that lives on land.
• What is the process of oxygen diffusion in earthworms?

  • Oxygen dissolves in moisture on the surface.
  • It then diffuses into capillaries beneath the skin.