(German) an environmental cue, such as light, that helps to regulate the biological clock in an organism [n -S]
A cue given by the environment, such as a change in light or temperature, to reset the internal body clock
an environmental cue, as the length of daylight, that helps to regulate the cycles of an organism's biological clock.
refers to an environmental agent or event such as the occurrence of light or dark that provides the stimulus which sets or resets an organisms biological clock.
