Paul Andersen reviews the major concepts within the fourth unit of the new AP Biology framework. He begins by differentiating between negative and positive feedback loops. He explains how a stable internal environment is maintained through behavior and physiology. He details thermoregulation, osmoregulation and blood glucose regulation. He also describes how natural selection has shaped behavior. Intro Music Atribution Title: I4dsong_loop_main.wav Artist: CosmicD Link to sound: http://www.freesound.org/people/CosmicD/sounds/72556/ Creative Commons Atribution License