Carrying capacity is the maximum amount of organisms a certain ecosystem can sustain with the resources available in a given ecosystem.
Factors that could either increase or decrease the K, carry capacity, would be: drastic weather causing depletion of resources, decreases in competition, etc.
ATP, also called adenosine triphosphate or the body's energy currency, is a compound that is synthesized when we have a compound called adenosine diphosphate (ADP). When this compound gets another phosphate group (P) attached, we get the more known ATP. This is also why the name changes from diphosphate to triphosphate (di - two, tri - three).