I think he means it sounds like homework. And belongs up there.
Plus, while there is nothing wrong with the question - it is akin to asking 'what is life?'
Basically, without respiration (aerobic or anaerobic) nothing would live on Earth as we know life. Second, without fuel provided ultimately by either photosynthesis or chemosynthesis ('hot vents in ocean floor' ecosystem), there could be no respiration. Hence no life - again.