Why do multicellular organisms require specialised organs and systems?
1. For a single cellular organism nutrients can move cell wall in or from different organelles around the cell. The cells of a multicellular organism have trouble with this. Imagine how a cell inside your brain would get access to oxygen unless blood was pumped through your brain. 2. Gaseous exchange allows for oxygen to be absorbed into the blood stream and carbon dioxide to be expelled. Blood that goes through the body slowly accumulates carbon dioxide being expelled from cells, and provides them with oxygen. In the lungs this blood comes into close contact with air. Air has a higher concentration of oxygen than the blood does, which causes oxygen to enter the blood. At the same time air has a lower concentration of carbon dioxide than blood does, so carbon dioxide leave the blood and enters the air.
