Some people say that love makes the world ___1_ (go) round.Others of a less romantic and more practical turn of mind say that it isn’t love; it’s money.But the truth is that it is energy that makes the world ___2_ (go) round.Energy is the currency of the ecological system and life ___3_ (become) possible only when food ___4_ (convert) into energy,which in turn is used ___5_ (seek) more food ___6_ (grow),to reproduce and to survive.On this cycle,all life depends.It is fairly well known that wild animals survive from year to year by eating as much as they can during times of plenty,the summer and fall,storing the excess,usually in the form of fat,and then ___7_ (use) these reserves of fat to survive during the hard times in winter when food ___8_ (be) scarce.But,it is probably less well known that even with their ___9_ (store) fat,wild animals spend less energy to live in winter than in summer.… Life -- and death,too -- is a cycle that goes round and round,and when animals die their bodies become food for other life forms to use by ___10_ (convert) them into energy.