taxis:
- locomotion of an organism
- in a particular direction
- in response to an external stimulus
- examples:
- Planaria moves towards food = positive chemotaxis
- Euglena moves towards light = positive phototaxis
kinesis:
- the movement (as opposed to growth) of an organism or a cell
- in response to a stimulus
- such that rate depends on intensity, but not direction, of the stimulus
- example:
- woodlice move about less in optimum, humid, conditions, and more in unfavorable, dry conditions
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