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Taxis vs. Kinesis


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Taxis vs. Kinesis

Postby Zissou » Fri Sep 07, 2007 12:45 pm

I'm a little confused as to the difference between the two. On one hand, I hear that kinesis is demonstrated in random movement in all directions as a result of some external stimulus, while taxis is a directional response to the stimulus. On the other hand, I hear that the difference depends on whether the stimulus itself is directional; for example, movement away from directional pressure, a light source, or a current would be taxis while movement away from ambient light or temperature would be kinesis. Can anyone help me to understand this, please?

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Re: Taxis vs. Kinesis

Postby Ozues » Sun May 30, 2010 4:30 pm

From my understanding taxis is the movement of an organism in accordance to the direction of stimulus. So if an organism (or part of an organism) moves towards a stimulus, it is positive taxis, and vice versa if it moves away from a stimulus it is negative taxis.
For example algae moves towards the directional stimulus of light in positive phototaxis as it needs light to photosynthesis.

I find kinesis a bit tricky myself, but from what I understand it's when the stimulus causes a response in the organism, but unlike with taxis the response isn't directional. So when an organism experiences unpleasant stimulus, they increase random movement in order to find an area of more pleasant stimulus.
For example when woodlice are in light, dry conditions (which are unpleasant to them), they increase random movement so that the chance of them finding dark, moist conditions, where they decrease random movement so they stay in the pleasant conditions for longer.

I don't think ambient light would have any taxis affect, as incase of a plant, it will grow the the direction of light so if light is coming from all areas another factor would determine direction of growth.
And with kinesis the direction of the stimulus would have no affect. Whether or not the stimulus is directional, the organism will move randomly and is not affected by the direction of the stimulus at all.

I hope that helps a little.
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