Kinesis
Kinesis is the change in activity rate in response to a stimulus. Such stimuli could be due to altered physical conditions, such as changes in light intensity, ambient temperature or gas compositions within an environment.
Kinesis can be classified into two sub-tyres: orthokinesis and klinokinesis.
Orthokinesis refers to the change in speed of an organism in response to the intensity of a stimulus.
Woodlice in certain parts of the world are found, in cool, damp conditions. The species Porcellio scaber, as shown in Figure 6.3 (a), shows an increased speedof movement or orthokinesis in dry conditions. It also shows shower rates of movement in more humid conditions.
Klinokinesis is the influence of the frequence or rate of turning in an animal in proportion to strength stimulus.
An example of klinokinesis is the effect of light intensity on the flatworm, Dendrocoelum lacteum, as shown in figure 6.3(b). These flatworms increase their rate of turming as light intensity increases and as a result, tend to spend less time in bright places but aggregate in dark places instead.