noun, plural: kineses
Kinesis pertains to the movement of a cell or an organism in response to an external stimulus. It is different from taxis, which is also the movement of a cell or an organism in response to a stimulus but the direction of movement is affected by the stimulant. Kinesis is directionally not oriented, i.e. the movement can be in any direction or may be at random. Taxis is directionally oriented and the movement may be positive or negative. A positive movement is one in which the movement is towards the direction of the source of stimulation (attraction). A negative movement is when the cell or organism moves away from the direction of the source of stimulation (repulsion). Despite the difference between kinesis and taxis, both of them pertain to the movement in response to a stimulus. An example of kinesis is the movement of a cell or an organism as a result of its exposure to certain stimuli such as light, temperature, and chemical.
The two main types of kineses are orthokinesis and klinokinesis. Orthokinesis is a form of kinesis in which the speed of movement of the individual depends upon the intensity of the stimulus. An increase in the speed of movement is a positive orthokinesis whereas a decrease in the speed is referred to as negative orthokinesis. Klinokinesis is another form of kinesis wherein the frequency or rate of turning is proportional to the intensity of the stimulus.
Word origin: Ancient Greek kínēsis (“motion, movement”)