In a small unicellular organism, diffusion is sufficient for transport because
A. the surface area to volume ratio is small
B. they have lungs for diffusion
C. materials have to move over long distance
D. the surface area to volume ratio is large
Transport of water and materials in cellular organisms occurs through diffusion as they do not exist at advanced level of organization where specialized tissues or organs could be used.
Now for the right answer to the above question:
- Option A is incorrect; the surface area might be small, but becomes quite large when expressed as a ratio with its volume.
- Option B is incorrect; unicellular organisms are not advanced enough to have lungs.
- C is also incorrect; movement of materials over long distance has nothing to do with cellular diffusion.
- D is the answer; the surface area, when compared with the volume of these cells, is quite large.
You may please note that:
- Surface area to volume ratio simply mean surface area of each cell divided by its volume. This number is found to be large enough to favour diffusion.
Use the questions and answers session to raise further questions and deal more on this topic…
/ culled from 2016 JAMB-UTME biology past question 35 /