Question Detail
Question
Why is circulation not necessary for organisms less than a few millimetres in size, according to the slides?
Correct Answer
Option B is the correct answer.
Detailed Explanation
Circulation is not necessary for organisms less than a few millimeters in size because diffusion alone is adequate for mass transport at that scale. Small size ensures that oxygen, nutrients, and wastes can move efficiently by diffusion across short distances.
Hint
At very small scales, passive diffusion is sufficient to meet metabolic needs.