Why is the cycling of matter important to life on earth?

because of the law of conservation of mass. we only have a set amount of every atom and there will never be any more so if once matter came out on an organism it was no longer any good or we consumed the atoms instead of just rearranging them then life could only be sustained for a finite amount of time until we ran out of matter. as it is currently the matter that is in you right now was probably at one time in a prehistoric plant and the last sip of water you had was at one time in a dinosaur's bladder.