taxis
n. (pl.
taxes) active movement of motile organisms in response to a stimulus. Taxis can be a negative response, marked by movement away from the stimulus, or positive, in which case the organism moves toward the stimulus. Taxis differs from tropism, which refers to a simple orientation to or from a natural force (e.g., light or gravity) without changing place, as in plants. Kinds of taxes include phototaxis, in which movement is toward or away from a light source; geotaxis, marked by a movement toward the earth; and chemotaxis, in which the movement is in response to chemicals in the environment. Tropotaxis indicates a direct path toward a source, such as a food smell; klinotaxis is a movement interrupted by pauses to evaluate the sources of stimuli. Also called taxic behavior. Compare kinesis. —taxic or tactic
adj.