Surface Area To volume ratio

Question 1

As organisms get larger what happens to the surface area to volume ratio?

Answer 1

• Falls sharply

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Question 2

Why is this a problem for multicellular organisms?

(Organisms with more than one cell).

Answer 2

• Their surface area is not large enough for their volume.
• Cells on the surface can get enough oxygen by diffusion
  BUT
• not enough energy can diffuse into the cells centre of the organism.
• They are too far away from the surface.

Question 3

Fish Example:

Answer 3

• Oxygen rich water passes into the mouth.
• Flows over gills, where the oxygen is transported into the blood stream.

Features:

• Very Large number of fine filaments:
• Where gasses pass in and out of the blood.
• Filaments give the gills a masive surface area.
• thin membrane: provide a short diffusion pathway.
• Efficient blood supply: Take the oxygenated blood away = ensures the concentration gradient is always high.

Question 4

Oxygen in fills:

Answer 4

• Deoxygenated blood passes into the filament.
• Oxygen diffuses from the water into the blood.
• ## Oxygenated blood returns to the body.