HOME

TheInfoList



OR:

A taxis (; ) is the movement of an
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...
in response to a stimulus such as light or the presence of food. Taxes are innate behavioural responses. A taxis differs from a tropism (turning response, often growth towards or away from a stimulus) in that in the case of taxis, the organism has
motility Motility is the ability of an organism to move independently, using metabolic energy. Definitions Motility, the ability of an organism to move independently, using metabolic energy, can be contrasted with sessility, the state of organisms th ...
and demonstrates guided movement towards or away from the stimulus source. It is sometimes distinguished from a kinesis, a non-directional change in activity in response to a stimulus.


Classification

Taxes are classified based on the type of stimulus, and on whether the organism's response is to move towards or away from the stimulus. If the organism moves towards the stimulus the taxis are positive, while if it moves away the taxis are negative. For example, flagellate protozoans of the genus '' Euglena'' move towards a light source. This reaction or behavior is called ''positive phototaxis'' since phototaxis refers to a response to light and the organism is moving towards the stimulus. Many types of taxis have been identified, including: * '' Aerotaxis'' (stimulation by
oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...
) * ''Anemotaxis'' (by wind) * ''Barotaxis'' (by
pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...
) * '' Chemotaxis'' (by chemicals) * ''
Durotaxis Durotaxis is a form of cell migration in which cells are guided by rigidity gradients, which arise from differential structural properties of the extracellular matrix (ECM). Most normal cells migrate up rigidity gradients (in the direction of gre ...
'' (by
stiffness Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a ...
) * ''
Electrotaxis Electrotaxis, also known as galvanotaxis, is the directed motion of biological cells or organisms guided by an electric field or current. The directed motion of electrotaxis can take many forms, such as; growth, development, active swimming, and p ...
'' or ''galvanotaxis'' (by electric current) * ''
Gravitaxis Gravitaxis (or ''geotaxis'') is a form of taxis characterized by the directional movement of an organism in response to gravity. Gravitaxis is one of the many forms of taxis. It is characterized by the movement of an organism in response to gravita ...
'' or ''geotaxis'' (by
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
) * ''Hydrotaxis'' (by moisture) * '' Magnetotaxis'' (by magnetic field) * '' Phototaxis'' (by
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
) * ''
Rheotaxis (Positive) Rheotaxis is a form of taxis seen in many aquatic organisms, e.g., fish, whereby they will (generally) turn to face into an oncoming current. In a flowing stream, this behavior leads them to hold their position rather than being swept do ...
'' (by fluid flow) * ''
Thermotaxis Thermotaxis is a behavior in which an organism directs its locomotion up or down a gradient of temperature. Lab research has determined that some slime molds and small nematodes (namely Meloidogyne incognita ''Meloidogyne incognita'' (root-kn ...
'' (by changes in
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
) * ''Thigmotaxis'' (by
physical contact In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), and pain. It is ...
) Depending on the type of sensory organs present, a taxis can be classified as a ''klinotaxis'', where an organism continuously samples the environment to determine the direction of a stimulus; a ''tropotaxis'', where bilateral sense organs are used to determine the stimulus direction; and a ''telotaxis'', where a single organ suffices to establish the orientation of the stimulus.


Examples

* Aerotaxis is the response of an organism to variation in oxygen concentration, and is mainly found in aerobic bacteria. * Anemotaxis is the response of an organism to wind. Many insects show a positive anemotactic response (turning/flying into the wind) upon exposure to an airborne stimulus cue from a food source. Cross-wind anemotactic search is exhibited by some olfactory animals in the absence of a target odor including moths, albatrosses, and polar bears. * Chemotaxis is a response elicited by chemicals: that is, a response to a chemical concentration gradient. For example, chemotaxis in response to a sugar gradient has been observed in motile bacteria such as ''E. coli''. Chemotaxis also occurs in the antherozoids of liverworts, ferns, and mosses in response to chemicals secreted by the archegonia. Unicellular (e.g. protozoa) or multicellular (e.g. worms) organisms are targets of chemotactic substances. A concentration gradient of chemicals developed in a fluid phase guides the vectorial movement of responder cells or organisms. Inducers of locomotion towards increasing steps of concentrations are considered as
chemoattractant Chemotaxis (from '' chemo-'' + ''taxis'') is the movement of an organism or entity in response to a chemical stimulus. Somatic cells, bacteria, and other single-cell or multicellular organisms direct their movements according to certain chemica ...
s, while chemorepellents result moving off the chemical. Chemotaxis is described in prokaryotic and
eukaryotic Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...
cells, but signalling mechanisms (receptors, intracellular signaling) and effectors are significantly different. *
Durotaxis Durotaxis is a form of cell migration in which cells are guided by rigidity gradients, which arise from differential structural properties of the extracellular matrix (ECM). Most normal cells migrate up rigidity gradients (in the direction of gre ...
is the directional movement of a cell along a stiffness gradient. *
Electrotaxis Electrotaxis, also known as galvanotaxis, is the directed motion of biological cells or organisms guided by an electric field or current. The directed motion of electrotaxis can take many forms, such as; growth, development, active swimming, and p ...
(or galvanotaxis) is the directional movement of motile cells along the vector of an electric field. It has been suggested that by detecting and orienting themselves toward the electric fields, cells can move towards damages or wounds to repair them. It also is suggested that such a movement may contribute to directional growth of cells and tissues during development and regeneration. This notion is based on the existence of measurable electric fields that naturally occur during wound healing, development and regeneration; and cells in cultures respond to applied electric fields by directional cell migration – electrotaxis / galvanotaxis. * Energy taxis is the orientation of bacteria towards conditions of optimal metabolic activity by sensing the internal energetic conditions of cell. Therefore, in contrast to chemotaxis (taxis towards or away from a specific extracellular compound), energy taxis responds on an intracellular stimulus (e.g. proton motive force, activity of NDH- 1) and requires metabolic activity. *
Gravitaxis Gravitaxis (or ''geotaxis'') is a form of taxis characterized by the directional movement of an organism in response to gravity. Gravitaxis is one of the many forms of taxis. It is characterized by the movement of an organism in response to gravita ...
(known historically as geotaxis) is the directional movement (along the vector of
gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the stro ...
) to the
center of gravity In physics, the center of mass of a distribution of mass in space (sometimes referred to as the balance point) is the unique point where the weighted relative position of the distributed mass sums to zero. This is the point to which a force ma ...
. The planktonic larvae of a king crab, '' Lithodes aequispinus'', combine positive phototaxis (movement towards the light) and negative gravitaxis (upward movement). Also the larvae of a polychaete, '' Platynereis dumerilii'', combine positive phototaxis (movement to the light coming from the water surface) and UV-induced positive gravitaxis (downward movement) to form a ratio-chromatic depth-gauge. Both positive and negative gravitaxes are found in a variety of protozoans (''e.g.'', '' Loxodes'', '' Remanella'' and '' Paramecium''). * Magnetotaxis is, strictly speaking, the ability to sense a magnetic field and coordinate movement in response. However, the term is commonly applied to bacteria that contain magnets and are physically rotated by the force of
Earth's magnetic field Earth's magnetic field, also known as the geomagnetic field, is the magnetic field that extends from Earth's interior out into space, where it interacts with the solar wind, a stream of charged particles emanating from the Sun. The magneti ...
. In this case, the "behaviour" has nothing to do with sensation and the bacteria are more accurately described as "magnetic bacteria". * Pharotaxis is the movement to a specific location in response to learned or conditioned stimuli, or navigation by means of landmarks. * Phonotaxis is the movement of an organism in response to
sound In physics, sound is a vibration that propagates as an acoustic wave, through a transmission medium such as a gas, liquid or solid. In human physiology and psychology, sound is the ''reception'' of such waves and their ''perception'' by ...
. * Phototaxis is the movement of an organism in response to
light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 t ...
: that is, the response to variation in light intensity and direction. Negative phototaxis, or movement away from a light source, is demonstrated in some insects, such as cockroaches. Positive phototaxis, or movement towards a light source, is advantageous for phototrophic organisms as they can orient themselves most efficiently to receive light for photosynthesis. Many phytoflagellates, e.g. '' Euglena'', and the chloroplasts of higher plants positively phototactic, moving towards a light source. Two types of positive phototaxis are observed in prokaryotes: scotophobotaxis is observable as the movement of a bacterium out of the area illuminated by a microscope, when entering darkness signals the cell to reverse direction and reenter the light; a second type of positive phototaxis is true phototaxis, which is a directed movement up a gradient to an increasing amount of light. There is a different classification to orientation towards dark areas called scototaxis. *
Rheotaxis (Positive) Rheotaxis is a form of taxis seen in many aquatic organisms, e.g., fish, whereby they will (generally) turn to face into an oncoming current. In a flowing stream, this behavior leads them to hold their position rather than being swept do ...
is a response to a current in a fluid. Positive rheotaxis is shown by fish turning to face against the current. In a flowing stream, this behaviour leads them to hold their position in a stream rather than being swept downstream. Some fish will exhibit negative rheotaxis where they will avoid currents. *
Thermotaxis Thermotaxis is a behavior in which an organism directs its locomotion up or down a gradient of temperature. Lab research has determined that some slime molds and small nematodes (namely Meloidogyne incognita ''Meloidogyne incognita'' (root-kn ...
is a migration along a gradient of temperature. Some slime molds and small nematodes can migrate along amazingly small temperature gradients of less than 0.1 °C/cm. They apparently use this behaviour to move to an optimal level in soil. * Thigmotaxis is the response of an organism to physical contact or to the proximity of a physical discontinuity in the environment (e.g. rats preferring to swim near the edge of a water maze).
Codling moth The codling moth (''Cydia pomonella'') is a member of the Lepidopteran family Tortricidae. They are major pests to agricultural crops, mainly fruits such as apples and pears. Because the larvae are not able to feed on leaves, they are highly ...
larvae are believed to used thigmotactic sense to locate fruits to feed on. Mice and rats, when inhabiting human-made structures, tend to stick close to vertical surfaces; this primarily manifests as running along the floor/wall juncture. Whiskers ( vibrissae) are often used to detect the presence of a wall or surface in the absence of sufficient light in rodents and felines to aid in thigmotaxis.


Terminology derived from taxis direction

There are five types of taxes based on the movement of organisms. * ''Klinotaxis'' occurs in organisms with receptor cells but no paired receptor organs. The cells for reception are located all over the body, particularly towards the anterior side. The organisms detect the stimuli by turning their head sideways and compare the intensity. When the intensity of stimuli is balanced equally from all sides then the organisms move in a straight line. The movement of blowfly and butterfly larvae clearly demonstrates klinotaxis. * ''Tropotaxis'' is displayed by
organism In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells ( cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and fu ...
s with paired receptor cells. When the stimuli coming from a source are balanced equally the organisms show movement. Because of this, animals are able to move sideways, unlike klinotaxis where the organisms can move only in a straight line. The movement of grayling butterflies and
fish lice The family Argulidae, whose members are commonly known as carp lice or fish lice, are parasitic crustaceans in the class Ichthyostraca. It is the only family in the monotypic subclass Branchiura and the order Arguloida, although a second family, ...
clearly demonstrates tropotaxis. * ''Telotaxis'' requires paired receptors. The movement occurs along the direction where the intensity of the stimuli is stronger. Telotaxis is clearly seen in the movement of
bee Bees are winged insects closely related to wasps and ants, known for their roles in pollination and, in the case of the best-known bee species, the western honey bee, for producing honey. Bees are a monophyletic lineage within the superfami ...
s when they leave their
hive A hive may refer to a beehive, an enclosed structure in which some honey bee species live and raise their young. Hive or hives may also refer to: Arts * ''Hive'' (game), an abstract-strategy board game published in 2001 * "Hive" (song), a 201 ...
to look for food. They balance the stimuli from the sun as well as from
flower A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants (plants of the division Angiospermae). The biological function of a flower is to facilitate reproduction, usually by providing a mechanis ...
s but land on the flower whose stimulus is most intense for them. * ''Menotaxis'' describes organisms' maintenance of a constant angular orientation. A clear demonstration is shown by bees returning to their hive at night and the movement of ants with respect to the sun. * ''Mnemotaxis'' is the use of
memory Memory is the faculty of the mind by which data or information is encoded, stored, and retrieved when needed. It is the retention of information over time for the purpose of influencing future action. If past events could not be remember ...
to follow trails that organisms have left when travelling to or from their home.


See also

* Animal locomotion * Haptotaxis *
Mechanotaxis Mechanotaxis refers to the directed movement of cell motility via mechanical cues (e.g., fluidic shear stress, substrate stiffness gradients, etc.). In response to fluidic shear stress, for example, cells have been shown to migrate in the direction ...
* Optomotor response * Tropism


References


External links


Host-plant finding by insects: orientation, sensory input and search patterns
{{Authority control Cell biology