The source of energy contained in the pyruvate molecules produced through glycolysis is The Sun
they need energy because growth is not the only life process that requires energy.Apart from growth, when organism reaches adulthood they need energy to aid in other processes such as locomotion,reproduction. More also, important functions such as cell replacement requires energy.
Habitat corridors allow species that require a wide range to move around safe passage from one Habitat to another without the risk of encountering Human populations where they can be endangered.