Question 1
Which statement explains why a unicellular organism can rely on diffusion to move substances in and out of the cell?
- It has a large surface area compared with its volume, so diffusion distances are short
- It has a transport system to carry substances
- It has a small surface area compared with its volume
- It uses active transport for all substances
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Answer: A (1)
Question 2
Explain why a large multicellular organism needs a transport system.
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- it has a small surface area : volume ratio (1)
- many cells are deep inside the body / far from the surface, so the diffusion distance is long (1)
- diffusion alone would be too slow to supply oxygen and food / remove waste (1)
Question 3
State what is transported by (a) the xylem and (b) the phloem in a flowering plant.
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- (a) water (1)
- mineral ions (1)
- (b) sucrose (1)
- amino acids (1)