Question

How do most of the unicellular organisms absorb oxygen

Answer 1

Because they are so small, they do not have the organs, pores and entryways to breathe like multicellular organisms. Unicellular organisms breathe through direct diffusion via the cell membrane. ... oxygen diffuses in and carbondioxide diffuse out.

Answer 2

Cellular respiration takes place in each and every living cell. The mechanism of 'breathing' in unicellular organisms is different from multi-cellular organisms. Single celled organisms like Amoeba, Paramoecium etc. respire within their cell. Instead of the actual process of breathing, oxygen simply enters in their bodies by simple diffusion. They don't have any breathing system.

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