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