Although penguins don't grow from year to year, they increase and decrease in size as they repeatedly form and use energy stores,a significant amount of energy might be stored in fat during part of the year but be missing from the pie chart because it is used later in the year
Allocation of limited endogenous resources causes trade-offs between competing traits, such as reproduction, somatic growth and maintenance
During food deprivation, animals cannot maximize all of their life-history traits and must exhibit adaptive behavioral, physiological and biochemical responses to reduce metabolism and/or the cost of current activities in order to maintain biological value
