Taxis and Tropism : Response of organism towards stimuli
What is taxis?
Taxis or taxic response is a directional movement of the whole organism in response to an external directional stimulus.
What is kinesis?
Kinesis or kinetic response is a non-directional movement in which the rate of movement is related to intensity of stimulus and not to the direction of stimulation, e.g. the movement of tentacles of Hydra.
What is tropism?
Tropism is the turning movement in plants and sessile animals in response to stimulus.Here are some taxis and related stimulus with their positive and negative responding organisms.
Types of taxis | Movement due to | Examples (+ve) | Examples (-ve) |
---|---|---|---|
Phototaxis | light | Euglena, fruit flies, fire flies | Cockroach, Earthworm |
Hydrotaxis | Water | Fish | Land animals |
Aerotaxis | Air (oxygen) | Motile aerobic bacteria | Anaerobic bacteria |
Chemotaxis | Chemicals | Euglena exposed to glucose or weak acid solution | Euglena exposed to salt/strong acid solution |
Geotaxis | Gravity | Amoeba falls on the bottom of container having water/ Planula larva moves towards sea bed | Ephyra larva of Jelly fish, swims away from sea bed. |
Rheotaxis | Air/water current | Birds moves along the air current | Planaria moves against water current |
Hygrotaxis | Moisture | Earthworm moves towards the moist place | Desert animals moves away from the moist place |
Galvanotaxis | Electric current | Paramecium moves towards cathode where weak electric current is supplied. | Man moves away from the electric current |
Sociotaxis | Colony or group | Colonial animals | Solitary animals |
Thigmotaxis | Touch | Dogs come closer if touched with human hands | Paramecium moves away if touch by some solid objects |
Thermotaxis | Temperature | Planaria shows movement in response to temperature | Migration of birds to escape the extreme temperature |
Some important taxis
Klinotaxis is movement in which animals try to orient their body by comparing intensities of stimulation on two sides of the body. Eg. Euglena, Planaria, earthworm,etc. It is generally shown by organisms that bears sensory receptors but no sense organs.
Tropotaxis is behavioral response of bilaterally symmetrical animals due to stimulus leading to orientation of the body straight towards the stimulus. Eg. Grayling butterflies, Argulus (fish louse), etc.
Telotaxis is the orientation of a bilaterally symmetrical animal at any one of the stimuli but not intermediate or both when two sources of stimuli of same intensity operate at the same time. Honeybee shows this type of taxis.
Menotaxis is the orientation of the body in response to stimulus at a constant angle. It is also known as light compass response.
Mnemotaxis is the orientation of animals depending on some complex stimuli like direction, landmarks, etc. Eg. Hunting wasps. HINT TO LEARN: pronunciation of mnemotaxis is complex= so learn it as complex stimulus.
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Best wishes
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