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 that do not possess a means of self-locomotion and are normally immobile.
Motility differs from mobility, the ability of an object to be moved.
The term vagility encompasses both motility and mobility; sessile organisms including plants and fungi often have vagile parts such as fruits, seeds, or spores which may be dispersed by other agents such as wind, water, or other organisms.
Motility is
genetically determined
Biological determinism, also known as genetic determinism, is the belief that human behaviour is directly controlled by an individual's genes or some component of their physiology, generally at the expense of the role of the environment, whether ...
, but may be affected by environmental factors such as toxins. The
nervous system and musculoskeletal system provide the majority of mammalian motility.
In addition to
animal locomotion, most
animals are motile, though some are vagile, described as having
passive locomotion. Many
bacteria and other
microorganisms, and
multicellular organism
A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism.
All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- ...
s are motile; some mechanisms of
fluid flow
In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including ''aerodynamics'' (the study of air and other gases in motion) an ...
in multicellular organs and tissue are also considered instances of motility, as with
gastrointestinal motility. Motile
marine animals are commonly called free-swimming, and motile non-
parasitic organisms are called free-living.
Motility includes an organism's ability to move food through its
digestive tract. There are two types of intestinal motility –
peristalsis and
segmentation. This motility is brought about by the contraction of smooth muscles in the gastrointestinal tract which mix the luminal contents with various secretions (segmentation) and move contents through the digestive tract from the mouth to the anus (peristalsis).
Cellular level
At the cellular level, different modes of movement exist:
*
amoeboid movement, a crawling-like movement, which also makes swimming possible
*
filopodia, enabling movement of the
axonal
growth cone
*
flagellar motility, a swimming-like motion (observed for example in
spermatozoa, propelled by the regular beat of their
flagellum, or the ''
E. coli
''Escherichia coli'' (),Wells, J. C. (2000) Longman Pronunciation Dictionary. Harlow ngland Pearson Education Ltd. also known as ''E. coli'' (), is a Gram-negative, facultative anaerobic, rod-shaped, coliform bacterium of the genus ''Escher ...
'' bacterium, which swims by rotating a helical prokaryotic flagellum)
*
gliding motility
*
swarming motility
Swarming motility is a rapid (2–10 μm/s) and coordinated translocation of a bacterial population across solid or semi-solid surfaces, and is an example of bacterial multicellularity and swarm behaviour. Swarming motility was first reported b ...
*
twitching motility, a form of motility used by bacteria to crawl over surfaces using grappling hook-like filaments called
type IV pili.
Many cells are not motile, for example ''
Klebsiella pneumoniae'' and ''
Shigella'', or under specific circumstances such as ''
Yersinia pestis'' at 37 °C.
Movements
Events perceived as movements can be directed:
* along a chemical gradient (see
chemotaxis
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 ...
)
* along a temperature gradient (see
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) can migrate along amazingly shallow t ...
)
* along a light gradient (see
phototaxis)
* along a magnetic field line (see
magnetotaxis)
* along an electric field (see
galvanotaxis)
* along the direction of the gravitational force (see
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 ...
)
* along a rigidity gradient (see
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 great ...
)
* along a gradient of cell adhesion sites (see
haptotaxis Haptotaxis (from Greek ἅπτω (hapto, "touch, fasten") and τάξις (taxis, "arrangement, order")) is the directional motility or outgrowth of cells, e.g. in the case of axonal outgrowth, usually up a gradient of cellular adhesion sites or sub ...
)
* along other cells or
biopolymer
Biopolymers are natural polymers produced by the cells of living organisms. Like other polymers, biopolymers consist of monomeric units that are covalently bonded in chains to form larger molecules. There are three main classes of biopolymers, cl ...
s
File:Muscular system.svg, Muscles give the ability for voluntary movement, and involuntary movement as in muscle spasms and reflex
In biology, a reflex, or reflex action, is an involuntary, unplanned sequence or action and nearly instantaneous response to a stimulus.
Reflexes are found with varying levels of complexity in organisms with a nervous system. A reflex occurs ...
es). At the level of the muscular system, motility is a synonym for locomotion.sperm
Sperm is the male reproductive cell, or gamete, in anisogamous forms of sexual reproduction (forms in which there is a larger, female reproductive cell and a smaller, male one). Animals produce motile sperm with a tail known as a flagellum, whi ...
have a single flagellum to help them swim. The cervical
In anatomy, cervical is an adjective that has two meanings:
# of or pertaining to any neck.
# of or pertaining to the female cervix: i.e., the ''neck'' of the uterus.
*Commonly used medical phrases involving the neck are
**cervical collar
**cervic ...
, uterine, and fallopian linings of the female reproductive system play a more important role in transporting sperm to ova.
File:Cheetah chase.jpg, The record speeds cheetahs hold are owed in large to their muscle motility.
File:Phototropism.jpg, The shoots of plants move by growing towards light. This is known as positive phototropism. The roots grow away from light. This is known as negative phototropism.
File:FAGOCITOSI BY RAFF.gif, Monocytes and macrophages of the immune system engulf Bacteria by extending their pseudopodia. Note that this cartoon is not an accurate representation of phagocytosis.
File:Protein translation.gif, Motility at the sub-cellular level. This depicts translation (biology), translation - a motile Nanoscopic scale, nanoscale molecular process using protein dynamics.
See also
* Cell migration
References
{{Authority control
Physiology
Cell movement
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