eduqas a level
| Front | Why do multicellular organisms require a specialised gas exchange surface? |
| Back | Diffusion across body surface is insufficient to provide enough oxygen for organism to surviveAs the size of an organism increases, its surface area: volume ratio decreasesMany animals have a toughened body surface so have internal gas exchange surfaces, e.g lungsLarger organisms are more metabolically active- higher oxygen demandDiffusion pathway across body surface is too large and rate of diffusion too slowSo larger multicellular organisms need a specialised gas exchange surface between the organism and its external environmentProvide a large number of gas exchange surfaces to increase surface area for diffusionThey also need a method of circulation to distribute the gases around the bodyMany animals have a toughened body surface so have internal gas exchange surfaces, e.g lungsAs the size of an organism increases, its surface area: volume ratio decreases |
| Front | Ends of tracheoles are fluid... |
| Back | fluid-filled and are close to muscle fibres. This fluid is the interface where gas exchange occurs. |
| Front | Gas exchange |
| Back | Process by which oxygen reaches cells and carbon dioxide is removed from them |