Question

Why is diffusion insufficient to meet the oxygen requirements of multicellularorganisms?

Answer 1

Diffusion is insufficient to meet the oxygen requirements of multicellular organisms because they are not in direct contact with the environment

Answer 2

Diffusion is very slow process and Multicellular organisms have large body size compared to the unicellular organisms and the cells of multicellular organisms are not in direct contact of air. So, to meet the o2 requirements multicellular organs have specialized organs unlike unicellular organisms.