Ventilation systems are needed in a <span>multicellular organism to actually obtain oxygen and give out carbon dioxide. Without this ventilation system, it would be very difficult for multicellular organisms to survive. It has been also observed that surface diffusion is not enough for a multicellular organism to breath.</span>
Molecule, organelle, cell, tissue, organ, organ system, organism, community, population, ecosystem, biosphere
D all of these create a magnetic field. let me know if you want me to explain.
