Taxis
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- The word taxis can also be plural of taxi.
A taxis (plural taxes, pronounced "takseez") is an innate behavioural response by an organism (or cell) to a directional stimulus (a stimulus from a particular direction) whereby an organism moves (orientation movement) either towards (positive taxis) or away from (negative taxis) the stimulus. A taxis differs from a turning response or tropism in that the organism has motility and demonstrates guided movement to or away from the stimulus (Kendeigh, 1961). For example, flagellate protozoans of the Genus Euglena move towards a light source. Here the directional stimulus is light, and the orientation movement is towards the light. This reaction or behaviour is a positive one to light and specifically termed a positive phototaxis. Phototaxis, then, is a response to a light stimulus. Many other types of taxes that have been identified, and named using one of the following prefixes to specify the stimulus eliciting a response:
- baro- – pressure
- chemo- – chemical, See chemotaxis
- galvano- – current (electricity)
- geo- – gravity. See geotaxis
- hydro- – moisture
- photo- – light. See phototaxis
- rheo- – current (flow). See rheotaxis
- thermo- – temperature. See thermotaxis
- thigmo- – contact (touch)
Depending on the type of sensory organs present, taxes can be classified as klinotaxes, where an organism continuously samples the environment to determine the direction of a stimulus, tropotaxes, where bilateral sense organs are utilized to determine the stimulus direction, and telotaxes, similar to tropotaxes but a single organ suffices to establish the orientation movement.
- See also: haptotaxis, durotaxis.
Kinesis
A kinesis, like a taxis, is a movement or activity of a cell or an organism in response to a stimulus. However, the movement can be in any direction or even random. Its rate—that is, the frequency of turning or reorientation, or of activity—depends on the intensity of the stimulation.
The same prefixes used with taxes can be applied to kineses.
Reference
- Kendeigh, S. Charles. 1961. Animal Ecology. Prentice-Hall, Inc., Englewood Cliffs, N.J., 468 p.de:taxis