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Motility is the ability of an
organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life. It is a synonym for "Outline of life forms, life form". Organ ...
to move independently, using metabolic energy.


Definitions

Motility, the ability of an
organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties of life. It is a synonym for "Outline of life forms, life form". Organ ...
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, but may be affected by environmental factors such as toxins. The
nervous system In Biology, biology, the nervous system is a Complex system, highly complex part of an animal that coordinates its Behavior, actions and Sense, sensory information by transmitting action potential, signals to and from different parts of its bo ...
and musculoskeletal system provide the majority of mammalian motility. In addition to animal locomotion, most
animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, ...
s are motile, though some are vagile, described as having passive locomotion. Many
bacteria Bacteria (; common noun bacteria, singular bacterium) are a type of Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a Bacte ...
and other
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology, an organism (from Ancient Greek, Greek: ὀργανισμός, ''organismos'') is any individual contiguous system that embodies the Life#Biology, properties ...
s, and multicellular organisms are motile; some mechanisms of
fluid flow In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), motion and behavior through ...
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
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: * flagellar motility, a swimming-like motion (observed for example in
spermatozoa
spermatozoa
, propelled by the regular beat of their flagellum, or the ''E. coli'' bacterium, which swims by rotating a helical prokaryotic flagellum) * amoeboid movement, a crawling-like movement, which also makes swimming possible * gliding motility * swarming motility * twitching motility, a form of motility used by bacteria to crawl over surfaces using grappling hook-like filaments called Pilus#Type IV pili, type IV pili. * filopodia, enabling movement of the axonal growth cone 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) * along a temperature gradient (see thermotaxis) * 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) * along a rigidity gradient (see durotaxis) * along a gradient of cell adhesion sites (see haptotaxis) * along other cells or biopolymers File:Muscular system.svg , Muscles give the ability for voluntary movement, and involuntary movement as in muscle spasms and reflexes). At the level of the muscular system, motility is a synonym for Animal locomotion, locomotion. Sperm-20051108.jpg , Most sperm have a single flagellum to help them swim. The cervix, cervical, uterus, uterine, and fallopian tubes, fallopian linings of the female reproductive system play a more important role in transporting sperm to Ovum, ova. Cheetah chase.jpg , The record speeds Cheetahs hold are owed in large to their muscle motility. Phototropism.jpg , The shoots of plants move by growing towards light. This is known as phototropism, positive phototropism. The roots grow away from light. This is known as negative phototropism. 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. 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 Articles containing video clips