Terrestrial locomotion has evolved as animals adapted from aquatic to terrestrial environments. Locomotion on land raises different problems than that in water, with reduced friction being replaced by the effects of gravity. There are three basic forms of locomotion found among terrestrial animals Legged – Moving by using appendages Limbless locomotion – moving without legs using the body itself as a propulsive structure. Rolling – rotating the body over the substrate Movement on appendages is the most common form of terrestrial locomotion, it is the basic form of locomotion of two major groups with many terrestrial members, the vertebrates and the arthropods. Important aspects of legged locomotion are posture, the number of legs, the functional structure of the leg and foot. There are many gaits, ways of moving the legs to locomote, such as walking, running, or jumping. Appendages can be used for movement in a lot of ways: the posture, the way the body is supported by the legs, is an important aspect.
There are three main ways in which vertebrates support themselves with their legs – sprawling, semi-erect, erect. Some animals may use different postures in different circumstances, depending on the posture's mechanical advantages. There is no detectable difference in energetic cost between stances; the "sprawling" posture is the most primitive, is the original limb posture from which the others evolved. The upper limbs are held horizontally, while the lower limbs are vertical, though upper limb angle may be increased in large animals; the body may drag along the ground, as in salamanders, or may be elevated, as in monitor lizards. This posture is associated with trotting gaits, the body flexes from side-to-side during movement to increase step length. All limbed reptiles and salamanders use this posture, as does the platypus and several species of frogs that walk. Unusual examples can be found among amphibious fish, such as the mudskipper, which drag themselves across land on their sturdy fins.
Among the invertebrates, most arthropods – which includes the most diverse group of animals, the insects – have a stance best described as sprawling. There is anecdotal evidence that some octopus species can drag themselves across land a short distance by hauling their body along by their tentacles – there may be video evidence of this; the semi-erect posture is more interpreted as an elevated sprawling posture. This mode of locomotion is found in large lizards such as monitor lizards and tegus. Mammals and birds have a erect posture, though each evolved it independently. In these groups the legs are placed beneath the body; this is linked with the evolution of endothermy, as it avoids Carrier's constraint and thus allows prolonged periods of activity. The erect stance is not the "most-evolved" stance. For example, the mesozoic prehistoric crocodilian Erpetosuchus is believed to have had a erect stance and been terrestrial; the number of locomotory appendages varies much between animals, sometimes the same animal may use different numbers of its legs in different circumstances.
The best contender for unipedal movement is the springtail, which while hexapedal, hurls itself away from danger using its furcula, a tail-like forked rod that can be unfurled from the underside of its body. A number of species stand on two legs, that is, they are bipedal; the group, bipedal is the birds, which have either an alternating or a hopping gait. There are a number of bipedal mammals. Most of these move by hopping – including the macropods such as kangaroos and various jumping rodents. Only a few mammals such as humans and the ground pangolin show an alternating bipedal gait. Cockroaches and some lizards may run on their two hind legs. With the exception of the birds, terrestrial vertebrate groups with legs are quadrupedal – the mammals and the amphibians move on four legs. There are many quadrupedal gaits; the most diverse group of animals on earth, the insects, are included in a larger taxon known as hexapods, most of which are hexapedal and standing on six legs. Exceptions among the insects include praying mantises and water scorpions, which are quadrupeds with their front two legs modified for grasping, some butterflies such as the Lycaenidae which use only four legs, some kinds of insect larvae that may have no legs, or additional prolegs.
Spiders and many of their relatives move on eight legs – they are octopedal. However, some creatures move on many more legs. Terrestrial crustaceans may have a fair number – woodlice having fourteen legs; as mentioned, some insect larvae such as caterpillars and sawfly larvae have up to five or nine additional fleshy prolegs in addition to the six legs normal for insects. Some species of invertebrate have more legs, the unusual velvet worm having stubby legs under the length of its body, with around several dozen pairs of legs. Centipedes have one pair of legs per body segment, with around 50 legs, but some species have over 200; the terrestrial animals with the most legs are the millipedes. They have two pairs of legs per body segment, with common species having between 80 and 400 legs overall – with the rare species Illacme plenipe
Running is a method of terrestrial locomotion allowing humans and other animals to move on foot. Running is a type of gait characterized by an aerial phase; this is in contrast to walking, where one foot is always in contact with the ground, the legs are kept straight and the center of gravity vaults over the stance leg or legs in an inverted pendulum fashion. A characteristic feature of a running body from the viewpoint of spring-mass mechanics is that changes in kinetic and potential energy within a stride occur with energy storage accomplished by springy tendons and passive muscle elasticity; the term running can refer to any of a variety of speeds ranging from jogging to sprinting. It is assumed that the ancestors of humankind developed the ability to run for long distances about 2.6 million years ago in order to hunt animals. Competitive running grew out of religious festivals in various areas. Records of competitive racing date back to the Tailteann Games in Ireland between 632 BCE and 1171 BCE, while the first recorded Olympic Games took place in 776 BCE.
Running has been described as the world's most accessible sport. It is thought that human running evolved at least four and a half million years ago out of the ability of the ape-like Australopithecus, an early ancestor of humans, to walk upright on two legs; the theory proposed considered to be the most evolution of running is of early humans' developing as endurance runners from the practice of persistence hunting of animals, the activity of following and chasing until a prey is too exhausted to flee, succumbing to "chase myopathy", that human features such as the nuchal ligament, abundant sweat glands, the Achilles tendons, big knee joints and muscular glutei maximi, were changes caused by this type of activity. The theory as first proposed used comparative physiological evidence and the natural habits of animals when running, indicating the likelihood of this activity as a successful hunting method. Further evidence from observation of modern-day hunting practice indicated this likelihood.
According to Sears scientific investigation of the Nariokotome Skeleton provided further evidence for the Carrier theory. Competitive running grew out of religious festivals in various areas such as Greece, Egypt and the East African Rift in Africa; the Tailteann Games, an Irish sporting festival in honor of the goddess Tailtiu, dates back to 1829 BCE, is one of the earliest records of competitive running. The origins of the Olympics and Marathon running are shrouded by myth and legend, though the first recorded games took place in 776 BCE. Running in Ancient Greece can be traced back to these games of 776 BCE.... I suspect that the sun, earth and heaven, which are still the gods of many barbarians, were the only gods known to the aboriginal Hellenes. Seeing that they were always moving and running, from their running nature they were called gods or runners... Running gait can be divided into two phases in regard to the lower extremity: stance and swing; these can be further divided into absorption, initial swing and terminal swing.
Due to the continuous nature of running gait, no certain point is assumed to be the beginning. However, for simplicity, it will be assumed that absorption and footstrike mark the beginning of the running cycle in a body in motion. Footstrike occurs. Common footstrike types include forefoot and heel strike types; these are characterized by initial contact of the ball of the foot and heel of the foot and heel of the foot respectively. During this time the hip joint is undergoing extension from being in maximal flexion from the previous swing phase. For proper force absorption, the knee joint should be flexed upon footstrike and the ankle should be in front of the body. Footstrike begins the absorption phase as forces from initial contact are attenuated throughout the lower extremity. Absorption of forces continues as the body moves from footstrike to midstance due to vertical propulsion from the toe-off during a previous gait cycle. Midstance is defined as the time at which the lower extremity limb of focus is in knee flexion directly underneath the trunk and hips.
It is at this point that propulsion begins to occur as the hips undergo hip extension, the knee joint undergoes extension and the ankle undergoes plantar flexion. Propulsion continues until the leg is extended behind the body and toe off occurs; this involves maximal hip extension, knee extension and plantar flexion for the subject, resulting in the body being pushed forward from this motion and the ankle/foot leaves the ground as initial swing begins. Most recent research regarding the footstrike debate, has focused on the absorption phases for injury identification and prevention purposes; the propulsion phase of running involves the movement beginning at midstance until toe off. From a full stride length model however, components of the terminal swing and footstrike can aid in propulsion. Set up for propulsion begins at the end of terminal swing as the hip joint flexes, creating the maximal range of motion for the hip extensors to accelerate through and produce force; as the hip extensors change from reciporatory inhibitors to primary muscle movers, the lower extremity is brought back toward the ground, although aided by the stretch reflex and gravity.
Footstrike and absorption phases occur next with two types of outcomes. This phase can be only a continuation of momentum from the stretch reflex reaction to
Fish locomotion is the variety of types of animal locomotion used by fish, principally by swimming. This however is achieved in different groups of fish by a variety of mechanisms of propulsion in water, most by wavelike movements of the fish's body and tail, in various specialised fish by movements of the fins; the major forms of locomotion in fish are anguilliform, in which a wave passes evenly along a long slender body. More specialised fish include movement by pectoral fins with a stiff body, as in the sunfish. In addition, some fish can variously "walk", i.e. move over land, burrow in mud, glide through the air. Fish swim by exerting force against the surrounding water. There are exceptions, but this is achieved by the fish contracting muscles on either side of its body in order to generate waves of flexion that travel the length of the body from nose to tail getting larger as they go along; the vector forces exerted on the water by such motion cancel out laterally, but generate a net force backwards which in turn pushes the fish forward through the water.
Most fishes generate thrust using lateral movements of their body and caudal fin, but many other species move using their median and paired fins. The latter group swim but can turn as is needed when living in coral reefs for example, but they can't swim as fast as fish using caudal fins. There are five groups that differ in the fraction of their body, displaced laterally: In the anguilliform group, containing some long, slender fish such as eels, there is little increase in the amplitude of the flexion wave as it passes along the body; the sub-carangiform group has a more marked increase in wave amplitude along the body with the vast majority of the work being done by the rear half of the fish. In general, the fish body is stiffer. Trout use sub-carangiform locomotion; the carangiform group, named for the Carangidae, are stiffer and faster-moving than the previous groups. The vast majority of movement is concentrated in the rear of the body and tail. Carangiform swimmers have oscillating tails.
The thunniform group contains high-speed long-distance swimmers, is characteristic of tunas and is found in several lamnid sharks. Here all the sideways movement is in the tail and the region connecting the main body to the tail; the tail itself tends to be large and crescent shaped. The ostraciiform group have no appreciable body wave. Only the tail fin; this group includes Ostraciidae. Not all fish fit comfortably in the above groups. Ocean sunfish, for example, have a different system, the tetraodontiform mode, many small fish use their pectoral fins for swimming as well as for steering and dynamic lift. Fish with electric organs, such as those in the knifefish, swim by undulating their long fins while keeping the body still so as not to disturb the electric field that they generate. Many fish swim using combined behavior of their two pectoral fins or both their anal and dorsal fins. Different types of Median paired fin propulsion can be achieved by preferentially using one fin pair over the other, include rajiform, amiiform and balistiform modes.
Rajiform locomotion is characteristic of rays and mantas when thrust is produced by vertical undulations along large, well developed pectoral fins. Diodontiform locomotion propels the fish propagating undulations along large pectoral fins, as seen in the porcupinefish. Amiiform locomotion consists of undulations of a long dorsal fin while the body axis is held straight and stable, as seen in the bowfin. Gymnotiform locomotion consists of undulations of a long anal fin upside down amiiform, seen in the knifefish. In balistiform locomotion, both anal and dorsal fins undulate, it is characteristic of the family Balistidae. It may be seen in the Zeidae. Oscillation is best known as mobuliform locomotion; the motion can be described as the production of less than half a wave on the fin, similar to a bird wing flapping. Pelagic stingrays, such as the manta, cownose and bat rays use oscillatory locomotion. In tetraodontiform locomotion, the dorsal and anal fins are flapped as a unit, either in phase or opposing one another, as seen in the Tetraodontiformes.
The ocean sunfish displays an extreme example of this mode. In labriform locomotion, seen in the wrasses, oscillatory movements of pectoral fins are either drag based or lift based. Propulsion is generated either as a reaction to drag produced by dragging the fins through the water in a rowing motion, or via lift mechanisms. Bone and muscle tissues of fish are denser than water. To maintain depth fish such as sharks, but some bony fish, increase buoyancy by means of a gas bladder or by storing oils or lipids. Fish without these features use dynamic lift instead, it is done using their pectoral fins in a manner similar to the use of wings by birds. As these fish swim, their pectoral fins are positioned to create lift which allows the fish to maintain a certai
The Ipnopidae are a family of fishes in the order Aulopiformes. They are slender fishes, with maximum length ranging from about 10 to 40 cm, they are found in temperate and tropical deep waters of the Atlantic and Pacific Oceans. A number of species in the genus Bathypterois, have elongated pectoral and pelvic fins. In the case of the tripodfish, Bathypterois grallator, these fins are three times as long as the body — up to a meter in length — and are used for standing on the sea floor. Ipnopids either have tiny eyes, or large eyes that lack any lens. Froese and Daniel Pauly, eds.. "Ipnopidae" in FishBase. April 2012 version
A triskelion or triskele is a motif consisting of a triple spiral exhibiting rotational symmetry. The spiral design can be based on interlocking Archimedean spirals, or represent three bent human legs. Both terms are from Greek "τρισκέλιον" or "τρισκελής", "three-legged", from prefix "τρι-", "three times" + "σκέλος", "leg". A triskelion is a traditional symbol of Sicily. Ingushetia has a triskelion in its flag; the triskelion symbol appears in many early cultures, the first in Malta and in the astronomical calendar at the famous megalithic tomb of Newgrange in Ireland built around 3200 BCE, Mycenaean vessels, on coinage in Lycia, on staters of Pamphylia and Pisidia. It appears; the triskelion is an ancient symbol of Sicily, with the head of the Gorgon, with snakes as hair, from which radiate three legs bent at the knee. The symbol dates back to when Sicily was part of Magna Graecia, the colonial extension of Greece beyond the Aegean. Pliny the Elder attributes the origin of the triskelion of Sicily to the triangular form of the island, the ancient Trinacria (from the Greek tri- and ἄκρα akra, which consists of three large capes equidistant from each other, pointing in their respective directions, the names of which were Pelorus and Lilybæum.
The Celtic symbol of three conjoined spirals may have had triple significance similar to the imagery that lies behind the triskelion. The triple spiral motif is a Neolithic symbol in Western Europe. Though popularly considered a "Celtic" symbol, it is in fact a pre-Celtic symbol, it is carved into the rock of a stone lozenge near the main entrance of the prehistoric Newgrange monument in County Meath, Ireland. Newgrange, built around 3200 BCE, predates the Celtic arrival in Ireland, but has long since been incorporated into Celtic culture; the symbol is found carved in rock in Castro Culture settlement in modern-day Galicia and Northern Portugal. In Ireland before the 5th century, in Celtic Christianity the triskele took on new meaning, as a symbol of the Trinity, therefore a symbol of eternity, its popularity continues today as a decorative symbol of faith for Christians of Celtic descent around the world. Traditional Asian versions of the triskelion include the Japanese Mitsudomoe, the Tibetan Buddhist Gankyil, the Korean Sam Taegeuk.
A triskelion is featured on the seal of the United States Department of Transportation. A triskelion shape is the basis for the roundel of the Irish Air Corps, the logo for the Trisquel Linux distribution. A triskelion shape was used in the design of RCA's "Spider" 45 rpm adapter, a popular plastic adapter for vinyl records, which allows larger center-holed 45 rpm records to spin on players designed for smaller center-holed 33-1/3 rpm records; the design was practical, the three curved arms providing equal spring and thus keeping the hole centred. The iconic design of the Spider has led to its adoption as a popular symbol for record and music enthusiasts. One of the most used symbols of the BDSM community is a derivation of a triskelion shape within a circle; the South African neo-Nazi White supremacist White nationalist organization and political party Afrikaner Weerstandsbeweging uses a Triskele composed of three sevens as its symbol in place of the Nazi Swastika. The Flag of the Isle of Man bears 3 legs based on the Triskele.
The crest of the Breton football club En Avant de Guingamp combines the Flag of Brittany, the team colours and the triple spiral triskelion. "The Gamesters of Triskelion" is a second-season episode of the American science fiction television series Star Trek. In the Marvel Universe, the intelligence agency S. H. I. E. L. D. Uses the Triskelion as its headquarters; the Triskele is used as a prominent symbol in MTV's "Teen Wolf" which draws from Celtic mythology. A Triskele was used by some younger betas to keep from shifting & maintain calm; this happens by the beta repeating "Alpha, Omega" or "The Sun, The Moon, The Truth" over and over again until the beta is calm. In Merlin it was used as symbol of druids; the triskele consisting of spirals, but the "horned triskelion", is used by some polytheistic reconstructionist and neopagan groups. As a Celtic symbol, it is used by groups with a Celtic cultural orientation and, less can be found in use by various eclectic or syncretic traditions such as Neopaganism.
The spiral triskele is one of the primary symbols of Celtic Reconstructionist Paganism. Celtic Reconstructionists use the symbol to represent a variety of triplicities in their cosmology and theology; the endocytic protein, clathrin, is triskelion-shaped. The Ediacaran fossil Tribrachidium is triskelion shaped
Fins are the most distinctive anatomical features of a fish. They are composed of bony spines or rays protruding from the body with skin covering them and joining them together, either in a webbed fashion, as seen in most bony fish, or similar to a flipper, as seen in sharks. Apart from the tail or caudal fin, fish fins have no direct connection with the spine and are supported only by muscles, their principal function is to help. Fins located in different places on the fish serve different purposes such as moving forward, keeping an upright position or stopping. Most fish use fins when swimming, flying fish use pectoral fins for gliding, frogfish use them for crawling. Fins can be used for other purposes. For every type of fin, there are a number of fish species in which this particular fin has been lost during evolution. Bony fishes form, they have skeletons made of bone, can be contrasted with cartilaginous fishes which have skeletons made of cartilage. Bony fishes are divided into lobe-finned fish.
Most fish are ray-finned, an diverse and abundant group consisting of over 30,000 species. It is the largest class of vertebrates in existence today. In the distant past, lobe-finned fish were abundant. Nowadays they are extinct, with only eight living species. Bony fish have fin rays called lepidotrichia, they have swim bladders, which allows the fish to create a neutral balance between sinking and floating without having to use its fins. However, swim bladders are absent in many fish, most notably in Lungfishes, which are the only fish to have retained the primitive lung present in the common ancestor of bony fish from which swim bladders evolved. Bony fishes have an operculum, which helps them breathe without having to use fins to swim. Lobe-finned fishes are a class of bony fishes called Sarcopterygii, they have fleshy, paired fins, which are joined to the body by a single bone. The fins of lobe-finned fish differ from those of all other fish in that each is borne on a fleshy, scaly stalk extending from the body.
Pectoral and pelvic fins have articulations resembling those of tetrapod limbs. These fins evolved into legs of the first tetrapod land vertebrates, amphibians, they possess two dorsal fins with separate bases, as opposed to the single dorsal fin of ray-finned fish. The coelacanth is a lobe-finned fish, still extant, it is thought to have evolved into its current form about 408 million years ago, during the early Devonian. Locomotion of the coelacanths is unique to their kind. To move around, coelacanths most take advantage of up or downwellings of the current and drift, they use their paired fins to stabilize their movement through the water. While on the ocean floor their paired fins are not used for any kind of movement. Coelacanths can create thrust for quick starts by using their caudal fins. Due to the high number of fins they possess, coelacanths have high maneuverability and can orient their bodies in any direction in the water, they have been seen swimming belly up. It is thought that their rostral organ helps give the coelacanth electroperception, which aids in their movement around obstacles.
Ray-finned fishes are a class of bony fishes called Actinopterygii. Their fins contain rays. A fin may contain only soft rays, or a combination of both. If both are present, the spiny rays are always anterior. Spines are stiff and sharp. Rays are soft, flexible and may be branched; this segmentation of rays is the main difference. Spines have a variety of uses. In catfish, they are used as a form of defense. Triggerfish use spines to lock themselves in crevices to prevent them being pulled out. Lepidotrichia are bony, bilaterally paired, segmented fin rays found in bony fishes, they develop around actinotrichia as part of the dermal exoskeleton. Lepidotrichia are composed of bone, but in early osteichthyans such as Cheirolepis, there was dentine and enamel, they appear as a series of disks stacked one on top of another. The genetic basis for the formation of the fin rays is thought to be genes coded for the production of certain proteins, it has been suggested that the evolution of the tetrapod limb from lobe-finned fishes is related to the loss of these proteins.
Cartilaginous fishes are a class of fishes called Chondrichthyes. They have skeletons made of cartilage rather than bone; the class includes sharks and chimaeras. Shark fin skeletons are elongated and supported with soft and unsegmented rays named ceratotrichia, filaments of elastic protein resembling the horny keratin in hair and feathers; the pectoral and pelvic girdles, which do not contain any dermal elements, did not connect. In forms, each pair of fins became ventrally connected in the middle when scapulocoracoid and pubioischiadic bars evolved. In rays, the pectoral fins have connected to the head and are flexible. One of the primary characteristics present in most sharks is the heterocercal tail, which aids in locomotion. Most sharks have eight fins. Sharks can only drift away from objects directly in front of them because