The energy for life ultimately derives from the sun. In addition, the bonds between the atoms can be used as sources of energy for life processes. Each transformation results in the storage and dissipation of energy into the environment as heat. Matter and energy are conserved in each transformation. The Nervous System and the Behavior of Organisms Like other aspects of an organism's biology, behaviors have evolved through natural selection.
Behaviors often have an adaptive logic when viewed in terms of evolutionary principles.
Organisms have behavioral responses to internal changes and to external stimuli. Responses to external stimuli can result from interactions with the organisms own species and others, as well as environmental changes. These responses can be either innate or learned. The broad patterns of behavior exhibited by animals have evolved to ensure reproductive success. Animals often live in unpredictable environments, and so their behavior must be flexible enough to deal with uncertainty and change.