The most efficient respiratory structure used by free living protozoan is?

A. body surface
B. gills
C. buccal cavity
D. spiracle

Correct Answer:

Option A – body surface

Explanation

Protozoa do not have any organelle for the process of respiration. The limiting permeable membrane (body surface) acts as a respiratory surface.

The free molecular oxy¬gen from the surrounding media enters into the body by diffusion. Presence of a cyto¬chrome system has been demonstrated in protozoa.