By growth, in size and complexity (i.e., changing from more probable to less probable states), plants and animals appear to defy the second law of thermodynamics. The usual explanation describes the input of nutrient and sunlight energy into open thermodynamic systems. However, energy input alone does not address the ability to organize and create complex structures or explain life cycles — in particular, growth, regulation and dying in the presence of adequate nutrients. Understanding the roles of macromolecules such as DNA, with their apparent information-processing capability, affords opportunity to understand biological order.