Quote from Spurious monkey Yes, giraffes are better at eating whole leaves than bacteria (unless the leaves are dead). Bacteria would eat millions more leaves than giraffes. i'm not answering the surviving part because it is not about surviving Surviving long enough to reproduce is precisely what the Darwinian paradigm is about. Quote from WellCookedFetus I can think of many advantages that multi-celled organisms have over single-celled. For one multi-celled organisms can eat the smaller single-celled by simple mechanical and chemical digestion. Godzilla can eat people, people can eat Godzilla. If multi cell organisms eat single cell organisms and single cell organisms eat multi cell organisms (which they do) then I do not see how this answers my question. Does this demonstrate some ability that metazoans have that bacteria do not have? You made the following statement/question-: Why is it so difficult to believe then if bacteria can occupy different niches that metazoans can occupy niches that can't be occupied by bacteria? I want you to tell me where it is that multi cell organisms can survive that bacteria can not.