document_title: Snake

question_text: where does a snake get its energy from

question_tokens: where does a snake get its energy from

text: Snake

text: Etymology

text: The English word snake comes from Old English snaca, itself from Proto-Germanic *snak-an- (cf. Germanic Schnake "ring snake", Swedish snok "grass snake"), from Proto-Indo-European root *(s)nēg-o- "to crawl", "to creep", which also gave sneak as well as Sanskrit nāgá "snake".[11] The word ousted adder, as adder went on to narrow in meaning, though in Old English næddre was the general word for snake.[12] The other term, serpent, is from French, ultimately from Indo-European *serp- (to creep),[13] which also gave Ancient Greek hérpō (ἕρπω) "I crawl".

text: Evolution

text:
A phylogenetic overview of the extant groups

Modern snakes

Scolecophidia

Leptotyphlopidae

Anomalepididae

Typhlopidae

Alethinophidia

Amerophidia

Anilius

Tropidophiidae

Afrophidia

Uropeltoidea

Uropeltidae

Anomochilus

Cylindrophis

Macrostomata

Pythonoidea

Pythonidae

Xenopeltis

Loxocemus

Caenophidia

Acrochordidae

Xenodermidae

Pareidae

Viperidae

Homalopsidae

Lamprophiidae

Elapidae

Colubridae

Booidea

Boidae

Erycinae

Calabaria

Ungaliophiinae

Sanzinia

Candoia

Note: the tree only indicates relationships, not evolutionary branching times.[14]

text: The fossil record of snakes is relatively poor because snake skeletons are typically small and fragile making fossilization uncommon. Fossils readily identifiable as snakes (though often retaining hind limbs) first appear in the fossil record during the Cretaceous period.[15] The earliest known true snake fossils (members of the crown group Serpentes) come from the marine simoliophiids, the oldest of which is the Late Cretaceous (Cenomanian age) Haasiophis terrasanctus,[1] dated to between 112 and 94 million years old.[16]

text: Based on comparative anatomy, there is consensus that snakes descended from lizards.[17]:11[18] Pythons and boas—primitive groups among modern snakes—have vestigial hind limbs: tiny, clawed digits known as anal spurs, which are used to grasp during mating.[17]:11[19] The families Leptotyphlopidae and Typhlopidae also possess remnants of the pelvic girdle, appearing as horny projections when visible.

text: Front limbs are nonexistent in all known snakes. This is caused by the evolution of their Hox genes, controlling limb morphogenesis. The axial skeleton of the snakes’ common ancestor, like most other tetrapods, had regional specializations consisting of cervical (neck), thoracic (chest), lumbar (lower back), sacral (pelvic), and caudal (tail) vertebrae. Early in snake evolution, the Hox gene expression in the axial skeleton responsible for the development of the thorax became dominant. As a result, the vertebrae anterior to the hindlimb buds (when present) all have the same thoracic-like identity (except from the atlas, axis, and 1–3 neck vertebrae). In other words, most of a snake's skeleton is an extremely extended thorax. Ribs are found exclusively on the thoracic vertebrae. Neck, lumbar and pelvic vertebrae are very reduced in number (only 2–10 lumbar and pelvic vertebrae are present), while only a short tail remains of the caudal vertebrae. However, the tail is still long enough to be of important use in many species, and is modified in some aquatic and tree-dwelling species.

text: Many modern snake groups originated during the Paleocene, alongside the adaptive radiation of mammals following the extinction of (non-avian) dinosaurs. The expansion of grasslands in North America also led to an explosive radiation among snakes.[20] Previously, snakes were a minor component of the North American fauna, but during the Miocene, the number of species and their prevalence increased dramatically with the first appearances of vipers and elapids in North America and the significant diversification of Colubridae (including the origin of many modern genera such as Nerodia, Lampropeltis, Pituophis, and Pantherophis).[20]

text: Origins

text: There is fossil evidence to suggest that snakes may have evolved from burrowing lizards, such as the varanids (or a similar group) during the Cretaceous Period.[21] An early fossil snake relative, Najash rionegrina, was a two-legged burrowing animal with a sacrum, and was fully terrestrial.[22] One extant analog of these putative ancestors is the earless monitor Lanthanotus of Borneo (though it also is semiaquatic).[23] Subterranean species evolved bodies streamlined for burrowing, and eventually lost their limbs.[23] According to this hypothesis, features such as the transparent, fused eyelids (brille) and loss of external ears evolved to cope with fossorial difficulties, such as scratched corneas and dirt in the ears.[21][23] Some primitive snakes are known to have possessed hindlimbs, but their pelvic bones lacked a direct connection to the vertebrae. These include fossil species like Haasiophis, Pachyrhachis and Eupodophis, which are slightly older than Najash.[19]

text: This hypothesis was strengthened in 2015 by the discovery of a 113m year-old fossil of a four-legged snake in Brazil that has been named Tetrapodophis amplectus. It has many snake-like features, is adapted for burrowing and its stomach indicates that it was preying on other animals.[24] It is currently uncertain if Tetrapodophis is a snake or another species, in the squamate order, as a snake-like body has independently evolved at least 26 times. Tetrapodophis does not have distinctive snake features in its spine and skull.[25][26]

text: An alternative hypothesis, based on morphology, suggests the ancestors of snakes were related to mosasaurs—extinct aquatic reptiles from the Cretaceous—which in turn are thought to have derived from varanid lizards.[18] According to this hypothesis, the fused, transparent eyelids of snakes are thought to have evolved to combat marine conditions (corneal water loss through osmosis), and the external ears were lost through disuse in an aquatic environment. This ultimately led to an animal similar to today's sea snakes. In the Late Cretaceous, snakes recolonized land, and continued to diversify into today's snakes. Fossilized snake remains are known from early Late Cretaceous marine sediments, which is consistent with this hypothesis; particularly so, as they are older than the terrestrial Najash rionegrina. Similar skull structure, reduced or absent limbs, and other anatomical features found in both mosasaurs and snakes lead to a positive cladistical correlation, although some of these features are shared with varanids.[citation needed]

text: Genetic studies in recent years have indicated snakes are not as closely related to monitor lizards as was once believed—and therefore not to mosasaurs, the proposed ancestor in the aquatic scenario of their evolution. However, more evidence links mosasaurs to snakes than to varanids. Fragmented remains found from the Jurassic and Early Cretaceous indicate deeper fossil records for these groups, which may potentially refute either hypothesis.[citation needed]

text: In 2016 two studies reported that limb loss in snakes is associated with DNA mutations in the Zone of Polarizing Activity Regulatory Sequence (ZRS), a regulatory region of the sonic hedgehog gene which is critically required for limb development. More advanced snakes have no remnants of limbs, but basal snakes such as pythons and boas do have traces of highly reduced, vestigial hind limbs. Python embryos even have fully developed hind limb buds, but their later development is stopped by the DNA mutations in the ZRS.[27][28][29][30]

text: Distribution

text: There are over 2,900 species of snakes ranging as far northward as the Arctic Circle in Scandinavia and southward through Australia.[18] Snakes can be found on every continent except Antarctica, in the sea, and as high as 16,000 feet (4,900 m) in the Himalayan Mountains of Asia.[18][31]:143 There are numerous islands from which snakes are absent, such as Ireland, Iceland, and New Zealand[4][31] (although New Zealand's waters are infrequently visited by the yellow-bellied sea snake and the banded sea krait).[32]

text: Taxonomy

text: All modern snakes are grouped within the suborder Serpentes in Linnean taxonomy, part of the order Squamata, though their precise placement within squamates remains controversial.[5]

text: The two infraorders of Serpentes are: Alethinophidia and Scolecophidia.[5] This separation is based on morphological characteristics and mitochondrial DNA sequence similarity. Alethinophidia is sometimes split into Henophidia and Caenophidia, with the latter consisting of "colubroid" snakes (colubrids, vipers, elapids, hydrophiids, and atractaspids) and acrochordids, while the other alethinophidian families comprise Henophidia.[33] While not extant today, the Madtsoiidae, a family of giant, primitive, python-like snakes, was around until 50,000 years ago in Australia, represented by genera such as Wonambi.

text: There are numerous debates in the systematics within the group. For instance, many sources classify Boidae and Pythonidae as one family, while some keep the Elapidae and Hydrophiidae (sea snakes) separate for practical reasons despite their extremely close relation.

text: Recent molecular studies support the monophyly of the clades of modern snakes, scolecophidians, typhlopids + anomalepidids, alethinophidians, core alethinophidians, uropeltids (Cylindrophis, Anomochilus, uropeltines), macrostomatans, booids, boids, pythonids and caenophidians.[14]

text: Families

text:
Infraorder Alethinophidia 19 families

Family[6]
Taxon author[6]
Genera[6]
Species[6]
Common name
Geographic range[34]

Acrochordidae
Bonaparte, 1831
1
3
Wart snakes
Western India and Sri Lanka through tropical Southeast Asia to the Philippines, south through the Indonesian/Malaysian island group to Timor, east through New Guinea to the northern coast of Australia to Mussau Island, the Bismarck Archipelago and Guadalcanal Island in the Solomon Islands.

Aniliidae
Stejneger, 1907
1
1
False coral snake
Tropical South America.

Anomochilidae
Cundall, Wallach, 1993
1
3
Dwarf pipe snakes
West Malaysia and on the Indonesian island of Sumatra.

Boidae
Gray, 1825
14
61
Boas
Northern, Central and South America, the Caribbean, southeastern Europe and Asia Minor, Northern, Central and East Africa, Madagascar and Reunion Island, the Arabian Peninsula, Central and southwestern Asia, India and Sri Lanka, the Moluccas and New Guinea through to Melanesia and Samoa.

Bolyeriidae
Hoffstetter, 1946
2
2
Splitjaw snakes
Mauritius.

Colubridae
Oppel, 1811
258[6]
1866[6]
Typical snakes
Widespread on all continents, except Antarctica.[35]

Cylindrophiidae
Fitzinger, 1843
1
14
Asian pipe snakes
Sri Lanka east through Myanmar, Thailand, Cambodia, Vietnam and the Malay Archipelago to as far east as Aru Islands off the southwestern coast of New Guinea. Also found in southern China (Fujian, Hong Kong and on Hainan Island) and in Laos.

Elapidae
Boie, 1827
55
359
Elapids
On land, worldwide in tropical and subtropical regions, except in Europe. Sea snakes occur in the Indian Ocean and the Pacific.[36]

Homalopsidae
Bonaparte, 1845
28
53
Homalopsids
Southeastern Asia and northern Australia.

Lamprophiidae
Fitzinger, 1843
60
314
Lamprophiids (includes former Atractaspididae as well as 6 other subfamilies formerly considered colubrids)
Africa, southern Europe, and western-central Asia; two species into southeastern Asia.

Loxocemidae
Cope, 1861
1
1
Mexican burrowing snake
Along the Pacific versant from Mexico south to Costa Rica.

Pareidae
Romer, 1956
3
20
Snail-eating snakes
Southeast Asia and islands on the Sunda Shelf (Sumatra, Borneo, Java, and their surrounding smaller islands).

Pythonidae
Fitzinger, 1826
8
40
Pythons
Subsaharan Africa, India, Myanmar, southern China, Southeast Asia and from the Philippines southeast through Indonesia to New Guinea and Australia.

Tropidophiidae
Brongersma, 1951
2
34
Dwarf boas
West Indies; also Panama and northwestern South America, as well as in northwestern and southeastern Brazil.

Uropeltidae
Müller, 1832
8
55
Shield-tailed snakes
Southern India and Sri Lanka.

Viperidae
Oppel, 1811
35
341
Vipers
The Americas, Africa, and Eurasia east to Wallace's Line.

Xenodermidae
Cope, 1900
6
18
Dragon & odd-scaled snakes
Southern and southeastern Asia, and islands on the Sunda Shelf (Sumatra, Borneo, Java, and their surrounding smaller islands).

Xenopeltidae
Bonaparte, 1845
1
2
Sunbeam snakes
Southeast Asia from the Andaman and Nicobar Islands, east through Myanmar to southern China, Thailand, Laos, Cambodia, Vietnam, the Malay Peninsula and the East Indies to Sulawesi, as well as the Philippines.

Xenophidiidae
Wallach & Günther, 1998
1
2
Spine-jawed snakes
Borneo & peninsular Malaysia.

text:
Infraorder Scolecophidia 5 families

Family[6]
Taxon author[6]
Genera[6]
Species[6]
Common name
Geographic range[34]

Anomalepidae
Taylor, 1939
4
18
Primitive blind snakes
From southern Central America to northwestern South America. Disjunct populations in northeastern and southeastern South America.

Gerrhopilidae
Vidal, Wynn, Donnellan and Hedges 2010
3
18
Indo-Malayan blindsnakes
Southern & southeastern Asia, including Sri Lanka, the Philippines, and New Guinea.

Leptotyphlopidae
Stejneger, 1892
13
139
Slender blind snakes
Africa, western Asia from Turkey to northwestern India, on Socotra Island, from the southwestern United States south through Mexico and Central to South America, though not in the high Andes. In Pacific South America they occur as far south as southern coastal Peru, and on the Atlantic side as far as Uruguay and Argentina. In the Caribbean they are found on the Bahamas, Hispaniola and the Lesser Antilles.

Typhlopidae
Merrem, 1820
21
266
Typical blind snakes
Most tropical and many subtropical regions around the world, particularly in Africa, Madagascar, Asia, islands in the Pacific, tropical America and in southeastern Europe.

Xenotyphlopidae
Vidal, Vences, Branch and Hedges 2010
1
1
Round-nosed blindsnake
Northern Madagascar.

text: Legless lizards

text: While snakes are limbless reptiles, which evolved from (and are grouped with) lizards, there are many other species of lizards which have lost their limbs independently and superficially look similar to snakes. These include the slowworm and glass snake.

text: Biology

text: Size

text: The now extinct Titanoboa cerrejonensis snakes found were 12.8 m (42 ft) in length.[9] By comparison, the largest extant snakes are the reticulated python, which measures about 6.95 m (22.8 ft) long,[8] and the anaconda, which measures about 5.21 m (17.1 ft) long and is considered the heaviest snake on Earth at 97.5 kg (215 lb).[37]

text: At the other end of the scale, the smallest extant snake is Leptotyphlops carlae, with a length of about 10.4 cm (4.1 in).[7] Most snakes are fairly small animals, approximately 1 m (3.3 ft) in length.[38]

text: Perception

text: Pit vipers, pythons, and some boas have infrared-sensitive receptors in deep grooves on the snout, which allow them to "see" the radiated heat of warm-blooded prey. In pit vipers, the grooves are located between the nostril and the eye in a large "pit" on each side of the head. Other infrared-sensitive snakes have multiple, smaller labial pits lining the upper lip, just below the nostrils.[39]

text: Snakes use smell to track their prey. They smell by using their forked tongues to collect airborne particles, then passing them to the vomeronasal organ or Jacobson's organ in the mouth for examination.[39] The fork in the tongue gives snakes a sort of directional sense of smell and taste simultaneously.[39] They keep their tongues constantly in motion, sampling particles from the air, ground, and water, analyzing the chemicals found, and determining the presence of prey or predators in the local environment. In water-dwelling snakes, such as the anaconda, the tongue functions efficiently underwater.[39]

text: The underside is very sensitive to vibration. This allows snakes to be able to sense approaching animals by detecting faint vibrations in the ground.[39]

text: Snake vision varies greatly, from only being able to distinguish light from dark to keen eyesight, but the main trend is that their vision is adequate although not sharp, and allows them to track movements.[40] Generally, vision is best in arboreal snakes and weakest in burrowing snakes. Some snakes, such as the Asian vine snake (genus Ahaetulla), have binocular vision, with both eyes capable of focusing on the same point. Most snakes focus by moving the lens back and forth in relation to the retina, while in the other amniote groups, the lens is stretched. Many nocturnal snakes have slit pupils while diurnal snakes have round pupils.

text: Skin

text: The skin of a snake is covered in scales. Contrary to the popular notion of snakes being slimy because of possible confusion of snakes with worms, snakeskin has a smooth, dry texture. Most snakes use specialized belly scales to travel, gripping surfaces. The body scales may be smooth, keeled, or granular. The eyelids of a snake are transparent "spectacle" scales, which remain permanently closed, also known as brille.

text: The shedding of scales is called ecdysis (or in normal usage, molting or sloughing). In the case of snakes, the complete outer layer of skin is shed in one layer.[41] Snake scales are not discrete, but extensions of the epidermis—hence they are not shed separately but as a complete outer layer during each molt, akin to a sock being turned inside out.[42]

text: The shape and number of scales on the head, back, and belly are often characteristic and used for taxonomic purposes. Scales are named mainly according to their positions on the body. In "advanced" (Caenophidian) snakes, the broad belly scales and rows of dorsal scales correspond to the vertebrae, allowing scientists to count the vertebrae without dissection.

text: Molting

text: Molting, or ecdysis, serves a number of functions. Firstly, the old and worn skin is replaced; secondly, it helps get rid of parasites such as mites and ticks. Renewal of the skin by moulting is supposed to allow growth in some animals such as insects; however, this has been disputed in the case of snakes.[42][43]

text: Molting occurs periodically throughout the snake's life. Before a molt, the snake stops eating and often hides or moves to a safe place. Just before shedding, the skin becomes dull and dry looking and the eyes become cloudy or blue-colored. The inner surface of the old skin liquefies. This causes the old skin to separate from the new skin beneath it. After a few days, the eyes clear and the snake "crawls" out of its old skin. The old skin breaks near the mouth and the snake wriggles out, aided by rubbing against rough surfaces. In many cases, the cast skin peels backward over the body from head to tail in one piece, like pulling a sock off inside-out. A new, larger, brighter layer of skin has formed underneath.[42][44]

text: An older snake may shed its skin only once or twice a year. But a younger snake, still growing, may shed up to four times a year.[44] The discarded skin gives a perfect imprint of the scale pattern, and it is usually possible to identify the snake if the discarded skin is reasonably intact.[42] This periodic renewal has led to the snake being a symbol of healing and medicine, as pictured in the Rod of Asclepius.[45]

text: Scale counts can sometimes be used to tell the sex of a snake when the species is not distinctly sexually dimorphic. A probe is inserted into the cloaca until it can go no further. The probe is marked at the point where it stops, removed, and compared to the subcaudal depth by laying it alongside the scales.[46] The scalation count determines whether the snake is a male or female as hemipenes of a male will probe to a different depth (usually longer) than the cloaca of a female.[46][clarification needed]

text: Skeleton

text: The skeleton of most snakes consists solely of the skull, hyoid, vertebral column, and ribs, though henophidian snakes retain vestiges of the pelvis and rear limbs.

text: The skull of the snake consists of a solid and complete neurocranium, to which many of the other bones are only loosely attached, particularly the highly mobile jaw bones, which facilitate manipulation and ingestion of large prey items. The left and right sides of the lower jaw are joined only by a flexible ligament at the anterior tips, allowing them to separate widely, while the posterior end of the lower jaw bones articulate with a quadrate bone, allowing further mobility. The bones of the mandible and quadrate bones can also pick up ground borne vibrations.[47] Because the sides of the jaw can move independently of one another, snakes resting their jaws on a surface have sensitive stereo hearing which can detect the position of prey. The jaw-quadrate-stapes pathway is capable of detecting vibrations on the angstrom scale, despite the absence of an outer ear and the ossicle mechanism of impedance matching used in other vertebrates to receive vibrations from the air.[48][49]

text: The hyoid is a small bone located posterior and ventral to the skull, in the 'neck' region, which serves as an attachment for muscles of the snake's tongue, as it does in all other tetrapods.

text: The vertebral column consists of anywhere between 200 and 400 (or more) vertebrae. Tail vertebrae are comparatively few in number (often less than 20% of the total) and lack ribs, while body vertebrae each have two ribs articulating with them. The vertebrae have projections that allow for strong muscle attachment enabling locomotion without limbs.

text: Autotomy of the tail, a feature found in some lizards is absent in most snakes.[50] Caudal autotomy in snakes is rare and is intervertebral, unlike that in lizards, which is intravertebral—that is, the break happens along a predefined fracture plane present on a vertebra.[51][52]

text: In some snakes, most notably boas and pythons, there are vestiges of the hindlimbs in the form of a pair of pelvic spurs. These small, claw-like protrusions on each side of the cloaca are the external portion of the vestigial hindlimb skeleton, which includes the remains of an ilium and femur.

text: Snakes are polyphyodonts with teeth that are continuously replaced.[53]

text: Internal organs

text:
esophagus
trachea
tracheal lungs
rudimentary left lung
right lung
heart
liver
stomach
air sac
gallbladder
pancreas
spleen
intestine
testicles
kidneys

text: The snake's heart is encased in a sac, called the pericardium, located at the bifurcation of the bronchi. The heart is able to move around, however, owing to the lack of a diaphragm. This adjustment protects the heart from potential damage when large ingested prey is passed through the esophagus. The spleen is attached to the gall bladder and pancreas and filters the blood. The thymus is located in fatty tissue above the heart and is responsible for the generation of immune cells in the blood. The cardiovascular system of snakes is also unique for the presence of a renal portal system in which the blood from the snake's tail passes through the kidneys before returning to the heart.[54]

text: The vestigial left lung is often small or sometimes even absent, as snakes' tubular bodies require all of their organs to be long and thin.[54] In the majority of species, only one lung is functional. This lung contains a vascularized anterior portion and a posterior portion that does not function in gas exchange.[54] This 'saccular lung' is used for hydrostatic purposes to adjust buoyancy in some aquatic snakes and its function remains unknown in terrestrial species.[54] Many organs that are paired, such as kidneys or reproductive organs, are staggered within the body, with one located ahead of the other.[54]

text: Snakes have no lymph nodes.[54]

text: Venom

text: Cobras, vipers, and closely related species use venom to immobilize or kill their prey. The venom is modified saliva, delivered through fangs.[17]:243 The fangs of 'advanced' venomous snakes like viperids and elapids are hollow to inject venom more effectively, while the fangs of rear-fanged snakes such as the boomslang merely have a groove on the posterior edge to channel venom into the wound. Snake venoms are often prey specific—their role in self-defense is secondary.[17]:243

text: Venom, like all salivary secretions, is a predigestant that initiates the breakdown of food into soluble compounds, facilitating proper digestion. Even nonvenomous snake bites (like any animal bite) will cause tissue damage.[17]:209

text: Certain birds, mammals, and other snakes (such as kingsnakes) that prey on venomous snakes have developed resistance and even immunity to certain venoms.[17]:243 Venomous snakes include three families of snakes, and do not constitute a formal classification group used in taxonomy.

text: The colloquial term "poisonous snake" is generally an incorrect label for snakes. A poison is inhaled or ingested, whereas venom produced by snakes is injected into its victim via fangs.[55] There are, however, two exceptions: Rhabdophis sequesters toxins from the toads it eats, then secretes them from nuchal glands to ward off predators, and a small unusual population of garter snakes in the U.S. state of Oregon retains enough toxins in their livers from the newts they eat to be effectively poisonous to small local predators (such as crows and foxes).[56]

text: Snake venoms are complex mixtures of proteins, and are stored in venom glands at the back of the head.[56] In all venomous snakes, these glands open through ducts into grooved or hollow teeth in the upper jaw.[17]:243[55] These proteins can potentially be a mix of neurotoxins (which attack the nervous system), hemotoxins (which attack the circulatory system), cytotoxins, bungarotoxins and many other toxins that affect the body in different ways.[55] Almost all snake venom contains hyaluronidase, an enzyme that ensures rapid diffusion of the venom.[17]:243

text: Venomous snakes that use hemotoxins usually have fangs in the front of their mouths, making it easier for them to inject the venom into their victims.[55] Some snakes that use neurotoxins (such as the mangrove snake) have fangs in the back of their mouths, with the fangs curled backwards.[57] This makes it difficult both for the snake to use its venom and for scientists to milk them.[55] Elapids, however, such as cobras and kraits are proteroglyphous—they possess hollow fangs that cannot be erected toward the front of their mouths, and cannot "stab" like a viper. They must actually bite the victim.[17]:242

text: It has recently been suggested that all snakes may be venomous to a certain degree, with harmless snakes having weak venom and no fangs.[58] Most snakes currently labelled "nonvenomous" would still be considered harmless according to this theory, as they either lack a venom delivery method or are incapable of delivering enough to endanger a human. This theory postulates that snakes may have evolved from a common lizard ancestor that was venomous—and that venomous lizards like the gila monster, beaded lizard, monitor lizards, and the now-extinct mosasaurs may also have derived from it. They share this venom clade with various other saurian species.

text: Venomous snakes are classified in two taxonomic families:

text:
Elapids – cobras including king cobras, kraits, mambas, Australian copperheads, sea snakes, and coral snakes.[57]
Viperids – vipers, rattlesnakes, copperheads/cottonmouths, and bushmasters.[57]

tag: ul

text: There is a third family containing the opistoglyphous (rear-fanged) snakes (as well as the majority of other snake species):

text: Colubrids – boomslangs, tree snakes, vine snakes, mangrove snakes, although not all colubrids are venomous.[17]:209[57]

text: Reproduction

text: Although a wide range of reproductive modes are used by snakes, all snakes employ internal fertilization. This is accomplished by means of paired, forked hemipenes, which are stored, inverted, in the male's tail.[59] The hemipenes are often grooved, hooked, or spined in order to grip the walls of the female's cloaca.[59]

text: Most species of snakes lay eggs which they abandon shortly after laying. However, a few species (such as the king cobra) actually construct nests and stay in the vicinity of the hatchlings after incubation.[59] Most pythons coil around their egg-clutches and remain with them until they hatch.[60] A female python will not leave the eggs, except to occasionally bask in the sun or drink water. She will even "shiver" to generate heat to incubate the eggs.[60]

text: Some species of snake are ovoviviparous and retain the eggs within their bodies until they are almost ready to hatch.[61][62] Recently, it has been confirmed that several species of snake are fully viviparous, such as the boa constrictor and green anaconda, nourishing their young through a placenta as well as a yolk sac, which is highly unusual among reptiles, or anything else outside of requiem sharks or placental mammals.[61][62] Retention of eggs and live birth are most often associated with colder environments.[59][62]

text: Sexual selection in snakes is demonstrated by the three thousand species that each use different tactics in acquiring mates.[63] Ritual combat between males for the females they want to mate with includes topping, a behavior exhibited by most viperids in which one male will twist around the vertically elevated fore body of its opponent and forcing it downward. It is common for neck biting to occur while the snakes are entwined.[64]

text: Facultative parthenogenesis

text: Parthenogenesis is a natural form of reproduction in which growth and development of embryos occur without fertilization. Agkistrodon contortrix (copperhead) and Agkistrodon piscivorus (cotton mouth) can reproduce by facultative parthenogenesis. That is, they are capable of switching from a sexual mode of reproduction to an asexual mode.[65] The type of parthenogenesis that likely occurs is automixis with terminal fusion, a process in which two terminal products from the same meiosis fuse to form a diploid zygote. This process leads to genome wide homozygosity, expression of deleterious recessive alleles and often to developmental abnormalities. Both captive-born and wild-born A. contortrix and A. piscivorus appear to be capable of this form of parthenogenesis.[65]

text: Reproduction in squamate reptiles is almost exclusively sexual. Males ordinarily have a ZZ pair of sex determining chromosomes, and females a ZW pair. However, the Colombian Rainbow boa, Epicrates maurus can also reproduce by facultative parthenogenesis resulting in production of WW female progeny.[66] The WW females are likely produced by terminal automixis.

text: Behavior

text: Winter dormancy

text: In regions where winters are colder than snakes can tolerate while remaining active, local species will brumate. Unlike hibernation, in which mammals are actually asleep, brumating reptiles are awake but inactive. Individual snakes may brumate in burrows, under rock piles, or inside fallen trees, or snakes may aggregate in large numbers at hibernacula.

text: Feeding and diet

text: All snakes are strictly carnivorous, eating small animals including lizards, frogs, other snakes, small mammals, birds, eggs, fish, snails or insects.[17][3][18][67] Because snakes cannot bite or tear their food to pieces, they must swallow prey whole. The body size of a snake has a major influence on its eating habits. Smaller snakes eat smaller prey. Juvenile pythons might start out feeding on lizards or mice and graduate to small deer or antelope as an adult, for example.

text: The snake's jaw is a complex structure. Contrary to the popular belief that snakes can dislocate their jaws, snakes have a very flexible lower jaw, the two halves of which are not rigidly attached, and numerous other joints in their skull (see snake skull), allowing them to open their mouths wide enough to swallow their prey whole, even if it is larger in diameter than the snake itself.[67] For example, the African egg-eating snake has flexible jaws adapted for eating eggs much larger than the diameter of its head.[17]:81 This snake has no teeth, but does have bony protrusions on the inside edge of its spine, which it uses to break shells when it eats eggs.[17]:81

text: While the majority of snakes eat a variety of prey animals, there is some specialization by some species. King cobras and the Australian bandy-bandy consume other snakes. Snakes of the family Pareidae have more teeth on the right side of their mouths than on the left, as the shells of their prey usually spiral clockwise.[17]:184[68][69]

text: Some snakes have a venomous bite, which they use to kill their prey before eating it.[67][70] Other snakes kill their prey by constriction.[67] Still others swallow their prey whole and alive.[17]:81[67]

text: After eating, snakes become dormant while the process of digestion takes place.[46] Digestion is an intense activity, especially after consumption of large prey. In species that feed only sporadically, the entire intestine enters a reduced state between meals to conserve energy. The digestive system is then 'up-regulated' to full capacity within 48 hours of prey consumption. Being ectothermic ("cold-blooded"), the surrounding temperature plays a large role in snake digestion. The ideal temperature for snakes to digest is 30 °C (86 °F). So much metabolic energy is involved in a snake's digestion that in the Mexican rattlesnake (Crotalus durissus), surface body temperature increases by as much as 1.2 °C (2.2 °F) during the digestive process.[71] Because of this, a snake disturbed after having eaten recently will often regurgitate its prey to be able to escape the perceived threat. When undisturbed, the digestive process is highly efficient, with the snake's digestive enzymes dissolving and absorbing everything but the prey's hair (or feathers) and claws, which are excreted along with waste.

text: Locomotion

text: The lack of limbs does not impede the movement of snakes. They have developed several different modes of locomotion to deal with particular environments. Unlike the gaits of limbed animals, which form a continuum, each mode of snake locomotion is discrete and distinct from the others; transitions between modes are abrupt.[72][73]

text: Lateral undulation

text: Lateral undulation is the sole mode of aquatic locomotion, and the most common mode of terrestrial locomotion.[73] In this mode, the body of the snake alternately flexes to the left and right, resulting in a series of rearward-moving "waves".[72] While this movement appears rapid, snakes have rarely been documented moving faster than two body-lengths per second, often much less.[74] This mode of movement has the same net cost of transport (calories burned per meter moved) as running in lizards of the same mass.[75]

text: Terrestrial lateral undulation is the most common mode of terrestrial locomotion for most snake species.[72] In this mode, the posteriorly moving waves push against contact points in the environment, such as rocks, twigs, irregularities in the soil, etc.[72] Each of these environmental objects, in turn, generates a reaction force directed forward and towards the midline of the snake, resulting in forward thrust while the lateral components cancel out.[76] The speed of this movement depends upon the density of push-points in the environment, with a medium density of about 8[clarification needed] along the snake's length being ideal.[74] The wave speed is precisely the same as the snake speed, and as a result, every point on the snake's body follows the path of the point ahead of it, allowing snakes to move through very dense vegetation and small openings.[76]

text: When swimming, the waves become larger as they move down the snake's body, and the wave travels backwards faster than the snake moves forwards.[77] Thrust is generated by pushing their body against the water, resulting in the observed slip. In spite of overall similarities, studies show that the pattern of muscle activation is different in aquatic versus terrestrial lateral undulation, which justifies calling them separate modes.[78] All snakes can laterally undulate forward (with backward-moving waves), but only sea snakes have been observed reversing the motion (moving backwards with forward-moving waves).[72]

text: Sidewinding

text: Most often employed by colubroid snakes (colubrids, elapids, and vipers) when the snake must move in an environment that lacks irregularities to push against (rendering lateral undulation impossible), such as a slick mud flat, or a sand dune, sidewinding is a modified form of lateral undulation in which all of the body segments oriented in one direction remain in contact with the ground, while the other segments are lifted up, resulting in a peculiar "rolling" motion.[79][80] This mode of locomotion overcomes the slippery nature of sand or mud by pushing off with only static portions on the body, thereby minimizing slipping.[79] The static nature of the contact points can be shown from the tracks of a sidewinding snake, which show each belly scale imprint, without any smearing. This mode of locomotion has very low caloric cost, less than ⅓ of the cost for a lizard to move the same distance.[75] Contrary to popular belief, there is no evidence that sidewinding is associated with the sand being hot.[79]

text: Concertina

text: When push-points are absent, but there is not enough space to use sidewinding because of lateral constraints, such as in tunnels, snakes rely on concertina locomotion.[72][80] In this mode, the snake braces the posterior portion of its body against the tunnel wall while the front of the snake extends and straightens.[79] The front portion then flexes and forms an anchor point, and the posterior is straightened and pulled forwards. This mode of locomotion is slow and very demanding, up to seven times the cost of laterally undulating over the same distance.[75] This high cost is due to the repeated stops and starts of portions of the body as well as the necessity of using active muscular effort to brace against the tunnel walls.

text: Arboreal

text: The movement of snakes in arboreal habitats has only recently been studied.[81] While on tree branches, snakes use several modes of locomotion depending on species and bark texture.[81] In general, snakes will use a modified form of concertina locomotion on smooth branches, but will laterally undulate if contact points are available.[81] Snakes move faster on small branches and when contact points are present, in contrast to limbed animals, which do better on large branches with little 'clutter'.[81]

text: Gliding snakes (Chrysopelea) of Southeast Asia launch themselves from branch tips, spreading their ribs and laterally undulating as they glide between trees.[79][82][83] These snakes can perform a controlled glide for hundreds of feet depending upon launch altitude and can even turn in midair.[79][82]

text: Rectilinear

text: The slowest mode of snake locomotion is rectilinear locomotion, which is also the only one where the snake does not need to bend its body laterally, though it may do so when turning.[84] In this mode, the belly scales are lifted and pulled forward before being placed down and the body pulled over them. Waves of movement and stasis pass posteriorly, resulting in a series of ripples in the skin.[84] The ribs of the snake do not move in this mode of locomotion and this method is most often used by large pythons, boas, and vipers when stalking prey across open ground as the snake's movements are subtle and harder to detect by their prey in this manner.[79]

text: Interactions with humans

text: Bite

text: Snakes do not ordinarily prey on humans. Unless startled or injured, most snakes prefer to avoid contact and will not attack humans. With the exception of large constrictors, nonvenomous snakes are not a threat to humans. The bite of a nonvenomous snake is usually harmless; their teeth are not designed for tearing or inflicting a deep puncture wound, but rather grabbing and holding. Although the possibility of infection and tissue damage is present in the bite of a nonvenomous snake, venomous snakes present far greater hazard to humans.[17]:209 The World Health Organisation (WHO) lists snakebite under the "other neglected conditions" category.[87]

text: Documented deaths resulting from snake bites are uncommon. Nonfatal bites from venomous snakes may result in the need for amputation of a limb or part thereof. Of the roughly 725 species of venomous snakes worldwide, only 250 are able to kill a human with one bite. Australia averages only one fatal snake bite per year. In India, 250,000 snakebites are recorded in a single year, with as many as 50,000 recorded initial deaths.[88] The WHO estimates that on the order of 100 000 people die each year as a result of snake bites, and around three times as many amputations and other permanent disabilities are caused by snakebites annually.[89]

text: The treatment for a snakebite is as variable as the bite itself. The most common and effective method is through antivenom (or antivenin), a serum made from the venom of the snake. Some antivenom is species-specific (monovalent) while some is made for use with multiple species in mind (polyvalent). In the United States for example, all species of venomous snakes are pit vipers, with the exception of the coral snake. To produce antivenom, a mixture of the venoms of the different species of rattlesnakes, copperheads, and cottonmouths is injected into the body of a horse in ever-increasing dosages until the horse is immunized. Blood is then extracted from the immunized horse. The serum is separated and further purified and freeze-dried. It is reconstituted with sterile water and becomes antivenom. For this reason, people who are allergic to horses are more likely to suffer an allergic reaction to antivenom.[90] Antivenom for the more dangerous species (such as mambas, taipans, and cobras) is made in a similar manner in India, South Africa, and Australia, although these antivenoms are species-specific.

text: Snake charmers

text: In some parts of the world, especially in India, snake charming is a roadside show performed by a charmer. In such a show, the snake charmer carries a basket that contains a snake that he seemingly charms by playing tunes from his flutelike musical instrument, to which the snake responds.[91] Snakes lack external ears, though they do have internal ears, and respond to the movement of the flute, not the actual noise.[91][92]

text: The Wildlife Protection Act of 1972 in India technically proscribes snake charming on grounds of reducing animal cruelty. Other snake charmers also have a snake and mongoose show, where both the animals have a mock fight; however, this is not very common, as the snakes, as well as the mongooses, may be seriously injured or killed. Snake charming as a profession is dying out in India because of competition from modern forms of entertainment and environment laws proscribing the practice.[91]

text: Trapping

text: The Irulas tribe of Andhra Pradesh and Tamil Nadu in India have been hunter-gatherers in the hot, dry plains forests, and have practiced the art of snake catching for generations. They have a vast knowledge of snakes in the field. They generally catch the snakes with the help of a simple stick. Earlier, the Irulas caught thousands of snakes for the snake-skin industry. After the complete ban of the snake-skin industry in India and protection of all snakes under the Indian Wildlife (Protection) Act 1972, they formed the Irula Snake Catcher's Cooperative and switched to catching snakes for removal of venom, releasing them in the wild after four extractions. The venom so collected is used for producing life-saving antivenom, biomedical research and for other medicinal products.[93] The Irulas are also known to eat some of the snakes they catch and are very useful in rat extermination in the villages.

text: Despite the existence of snake charmers, there have also been professional snake catchers or wranglers. Modern-day snake trapping involves a herpetologist using a long stick with a V- shaped end. Some television show hosts, like Bill Haast, Austin Stevens, Steve Irwin, and Jeff Corwin, prefer to catch them using bare hands.

text: Consumption

text: While not commonly thought of as food in most cultures, in some cultures, the consumption of snakes is acceptable, or even considered a delicacy, prized for its alleged pharmaceutical effect of warming the heart. Snake soup of Cantonese cuisine is consumed by local people in autumn, to warm up their body. Western cultures document the consumption of snakes under extreme circumstances of hunger.[94] Cooked rattlesnake meat is an exception, which is commonly consumed in parts of the Midwestern United States. In Asian countries such as China, Taiwan, Thailand, Indonesia, Vietnam and Cambodia, drinking the blood of snakes—particularly the cobra—is believed to increase sexual virility.[95] The blood is drained while the cobra is still alive when possible, and is usually mixed with some form of liquor to improve the taste.[95]

text: In some Asian countries, the use of snakes in alcohol is also accepted. In such cases, the body of a snake or several snakes is left to steep in a jar or container of liquor. It is claimed that this makes the liquor stronger (as well as more expensive). One example of this is the Habu snake sometimes placed in the Okinawan liquor Awamori also known as "Habu Sake".[96]

text: Snake wine (蛇酒) is an alcoholic beverage produced by infusing whole snakes in rice wine or grain alcohol. The drink was first recorded to have been consumed in China during the Western Zhou dynasty and considered an important curative and believed to reinvigorate a person according to Traditional Chinese medicine.[97]

text: Pets

text: In the Western world, some snakes (especially docile species such as the ball python and corn snake) are kept as pets. To meet this demand a captive breeding industry has developed. Snakes bred in captivity tend to make better pets and are considered preferable to wild caught specimens.[98] Snakes can be very low maintenance pets, especially compared to more traditional species. They require minimal space, as most common species do not exceed 5 feet (1.5 m) in length. Pet snakes can be fed relatively infrequently, usually once every 5 to 14 days. Certain snakes have a lifespan of more than 40 years if given proper care.

text: Symbolism

text: In Egyptian history, the snake occupies a primary role with the Nile cobra adorning the crown of the pharaoh in ancient times. It was worshipped as one of the gods and was also used for sinister purposes: murder of an adversary and ritual suicide (Cleopatra).

text: In Greek mythology snakes are often associated with deadly and dangerous antagonists, but this is not to say that snakes are symbolic of evil; in fact, snakes are a chthonic symbol, roughly translated as 'earthbound'. The nine-headed Lernaean Hydra that Hercules defeated and the three Gorgon sisters are children of Gaia, the earth.[99] Medusa was one of the three Gorgon sisters who Perseus defeated.[99] Medusa is described as a hideous mortal, with snakes instead of hair and the power to turn men to stone with her gaze.[99] After killing her, Perseus gave her head to Athena who fixed it to her shield called the Aegis.[99] The Titans are also depicted in art with snakes instead of legs and feet for the same reason—they are children of Gaia and Uranus, so they are bound to the earth.[citation needed]

text: The legendary account of the foundation of Thebes mentioned a monster snake guarding the spring from which the new settlement was to draw its water. In fighting and killing the snake, the companions of the founder Cadmus all perished – leading to the term "Cadmean victory" (i.e. a victory involving one's own ruin).[citation needed]

text: Three medical symbols involving snakes that are still used today are Bowl of Hygieia, symbolizing pharmacy, and the Caduceus and Rod of Asclepius, which are symbols denoting medicine in general.[45]

text: India is often called the land of snakes and is steeped in tradition regarding snakes.[100] Snakes are worshipped as gods even today with many women pouring milk on snake pits (despite snakes' aversion for milk).[100] The cobra is seen on the neck of Shiva and Vishnu is depicted often as sleeping on a seven-headed snake or within the coils of a serpent.[101] There are also several temples in India solely for cobras sometimes called Nagraj (King of Snakes) and it is believed that snakes are symbols of fertility. There is a Hindu festival called Nag Panchami each year on which day snakes are venerated and prayed to. See also Nāga.[citation needed]

text: In India there is another mythology about snakes. Commonly known in Hindi as "Ichchhadhari" snakes. Such snakes can take the form of any living creature, but prefer human form. These mythical snakes possess a valuable gem called "Mani", which is more brilliant than diamond. There are many stories in India about greedy people trying to possess this gem and ending up getting killed.[citation needed]

text: The ouroboros is a symbol associated with many different religions and customs, and is claimed to be related to alchemy. The ouroboros or uroboros is a snake eating its own tail in a clock-wise direction (from the head to the tail) in the shape of a circle, representing the cycle of life, death and rebirth, leading to immortality.[citation needed]

text: The snake is one of the 12 celestial animals of Chinese Zodiac, in the Chinese calendar.[102]

text: Many ancient Peruvian cultures worshipped nature.[103] They emphasized animals and often depicted snakes in their art.[104]

text: Religion

text: This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (April 2017) (Learn how and when to remove this template message)

text: Snakes are a part of Hindu worship. A festival, Nag Panchami, in which participants worship either images of or live Nāgas (cobras) is celebrated every year. Most images of Lord Shiva depict snake around his neck. Puranas have various stories associated with snakes. In the Puranas, Shesha is said to hold all the planets of the Universe on his hoods and to constantly sing the glories of Vishnu from all his mouths. He is sometimes referred to as "Ananta-Shesha", which means "Endless Shesha". Other notable snakes in Hinduism are Ananta, Vasuki, Taxak, Karkotaka and Pingala. The term Nāga is used to refer to entities that take the form of large snakes in Hinduism and Buddhism.

text: Snakes have also been widely revered, such as in ancient Greece, where the serpent was seen as a healer. Asclepius carried a serpent wound around his wand, a symbol seen today on many ambulances.

text: In religious terms, the snake and jaguar are arguably the most important animals in ancient Mesoamerica. "In states of ecstasy, lords dance a serpent dance; great descending snakes adorn and support buildings from Chichen Itza to Tenochtitlan, and the Nahuatl word coatl meaning serpent or twin, forms part of primary deities such as Mixcoatl, Quetzalcoatl, and Coatlicue."[105] In both Maya and Aztec calendars, the fifth day of the week was known as Snake Day.

text: In Judaism, the snake of brass is also a symbol of healing, of one's life being saved from imminent death.[106]

text: In some parts of Christianity, Christ's redemptive work is compared to saving one's life through beholding the Nehushtan (serpent of brass).[107] Snake handlers use snakes as an integral part of church worship in order to exhibit their faith in divine protection. However, more commonly in Christianity, the serpent has been seen as a representative of evil and sly plotting, which can be seen in the description in Genesis chapter 3 of a snake in the Garden of Eden tempting Eve.[108] Saint Patrick is reputed to have expelled all snakes from Ireland while converting the country to Christianity in the 5th century, thus explaining the absence of snakes there.

text: In Christianity and Judaism, the snake makes its infamous appearance in the first book of the Bible when a serpent appears before the first couple Adam and Eve and tempts them with the forbidden fruit from the Tree of Knowledge.[108] The snake returns in Exodus when Moses, as a sign of God's power, turns his staff into a snake and when Moses made the Nehushtan, a bronze snake on a pole that when looked at cured the people of bites from the snakes that plagued them in the desert. The serpent makes its final appearance symbolizing Satan in the Book of Revelation: "And he laid hold on the dragon the old serpent, which is the devil and Satan, and bound him for a thousand years."[109]

text: In Neo-Paganism and Wicca, the snake is seen as a symbol of wisdom and knowledge.

text: Medicine

text: The cytotoxic effect of snake venom is being researched as a potential treatment for cancers.[111]


document_title: Valley

question_text: most common type of valley in the world

question_tokens: most common type of valley in the world

root

text: Valley

text: Valley terminology[edit]

text: A valley in its broadest geographic sense is also known as a dale. Other terms used for valleys are:

tag: p

text:
Vale: A valley through which a river runs.
Dell: A small, secluded and often wooded valley.
Glen: A long valley bounded by gently sloped concave sides.
Strath: A wide, flat valley through which a river runs.
Mountain cove: A small valley, closed at one or both ends, in the central or southern Appalachian Mountains which sometimes results from the erosion of a geologic window.
Hollow: A term used sometimes for a small valley surrounded by mountains or ridges .
cwm (also spelled combe or coombe): A deep, narrow valley.
A steephead valley is a deep, narrow, flat bottomed valley with an abrupt ending.
Erosional valley: A valley formed by erosion.
Structural valley: A valley formed by geologic events such as drop faults or the rise of highlands.[2]
Dry valley: A valley not created by sustained surface water flow.
Longitudinal valley: An elongated valley found between two almost parallel mountain chains.

text: Similar geological structures, such as canyons, ravines, gorges, gullies, chines and kloofs, are not usually referred to as valleys.

text: River valleys [edit]

text: A valley formed by flowing water, or river valley, is usually V-shaped. The exact shape will depend on the characteristics of the stream flowing through it. Rivers with steep gradients, as in mountain ranges, produce steep walls and a bottom. Shallower slopes may produce broader and gentler valleys. However, in the lowest stretch of a river, where it approaches its base level, it begins to deposit sediment and the valley bottom becomes a floodplain.

text: Some broad V examples are:

text:
North America: Black Canyon of the Gunnison National Park, and others in Grand Canyon NP
Europe:

Austria: narrow passages of upper Inn valley (Inntal), affluents of Enns
Switzerland: Napf region, Zurich Oberland, Engadin
Germany: affluents to the middle reaches of Rhine and Mosel

text: Some of the first human complex societies originated in river valleys, such as that of the Nile, Tigris-Euphrates, Indus, Ganges, Yangtze, Yellow River, Mississippi, and arguably Amazon. In prehistory, the rivers were used as a source of fresh water and food (fish and game), as well as a place to wash and a sewer. The proximity of water moderated temperature extremes and provided a source for irrigation, stimulating the development of agriculture. Most of the first civilizations developed from these river valley communities.

text: Vales [edit]

text: This section does not cite any sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (May 2013) (Learn how and when to remove this template message)

tag: table

text: In geography, a vale is a wide river valley, usually with a particularly wide flood plain or flat valley bottom.

text: In Southern England, vales commonly occur between the escarpment slopes of pairs of chalk formations, where the chalk dome has been eroded, exposing less resistant underlying rock, usually claystone.

text: Rift valleys[edit]

text: Rift valleys, such as the Albertine Rift, are formed by the expansion of the Earth's crust due to tectonic activity beneath the Earth's surface.

text: Glacial valleys[edit]

text: There are various forms of valley associated with glaciation that may be referred to as glacial valleys.

text: U-shaped or trough valley[edit]

text: A valley carved by glaciers is normally U-shaped and resembles a trough. This trough valley becomes visible upon the recession of the glacier that forms it. When the ice recedes or thaws, the valley remains, often littered with small boulders that were transported within the ice. Floor gradient does not affect the valley's shape, it is the glacier's size that does. Continuously flowing glaciers – especially in the ice age – and large-sized glaciers carve wide, deep incised valleys, sometimes with valley steps that reflect differing erosion rates.

text: Examples of U-shaped valleys are found in every mountainous region that has experienced glaciation, usually during the Pleistocene ice ages. Most present U-shaped valleys started as V-shaped before glaciation. The glaciers carved it out wider and deeper, simultaneously changing the shape. This proceeds through the glacial erosion processes of glaciation and abrasion, which results in large rocky material (glacial till) being carried in the glacier. A material called boulder clay is deposited on the floor of the valley. As the ice melts and retreats, the valley is left with very steep sides and a wide, flat floor. A river or stream may remain in the valley. This replaces the original stream or river and is known as a misfit stream because it is smaller than one would expect given the size of its valley.

text: Other interesting glacially carved valleys include:

text:
Yosemite Valley (United States)
Side valleys of the Austrian river Salzach for their parallel directions and hanging mouths.
Some Scottish glens full with bushes and flowers.
That of the St. Mary River in Glacier National Park in Montana, USA.

text: Tunnel valley[edit]

text: A tunnel valley is a large, long, U-shaped valley originally cut under the glacial ice near the margin of continental ice sheets such as that now covering Antarctica and formerly covering portions of all continents during past glacial ages.[3]

text: A tunnel valley can be up to 100 km (62 mi), 4 km (2.5 mi) wide, and 400 m (1,300 ft) deep (its depth may vary along its length).

text: Tunnel valleys were formed by subglacial erosion by water. They served as subglacial drainage pathways carrying large volumes of melt water. Their cross-sections exhibit steep-sided flanks similar to fjord walls, and their flat bottoms are typical of subglacial glacial erosion.

text: Meltwater valley[edit]

text: In northern Central Europe, the Scandinavian ice sheet during the various ice ages advanced slightly uphill against the lie of the land. As a result, its meltwaters flowed parallel to the ice margin to reach the North Sea basin, forming huge, flat valleys known as Urstromtäler. Unlike the other forms of glacial valley, these were formed by glacial meltwaters.

text: Transition forms and valley shoulders[edit]

text: Depending on the topography, the rock types and the climate, a lot of transitional forms between V-, U- and plain valleys exist. Their bottoms can be broad or narrow, but characteristic is also the type of valley shoulder. The broader a mountain valley, the lower its shoulders are located in most cases. An important exception are canyons where the shoulder almost is near the top of the valley's slope. In the Alps – e.g. the Tyrolean Inn valley – the shoulders are quite low (100–200 meters above the bottom). Many villages are located here (esp. at the sunny side) because the climate is very mild: even in winter when the valley's floor is completely filled with fog, these villages are in sunshine.

text: In some stress-tectonic regions of the Rockies or the Alps (e.g. Salzburg) the side valleys are parallel to each other, and additionally they are hanging. The brooks flow into the river in form of deep canyons or waterfalls. Usually this fact is the result of a violent erosion of the former valley shoulders, a special genesis found also at arêtes and glacial cirques, at every Scottish glen, or in a northern fjord.

text: Hanging valleys[edit]

text: A hanging valley is a tributary valley that is higher than the main valley. They are most commonly associated with U-shaped valleys when a tributary glacier flows into a glacier of larger volume. The main glacier erodes a deep U-shaped valley with nearly vertical sides while the tributary glacier, with a smaller volume of ice, makes a shallower U-shaped valley. Since the surfaces of the glaciers were originally at the same elevation, the shallower valley appears to be 'hanging' above the main valley. Often, waterfalls form at or near the outlet of the upper valley.[4]

text: Hanging valleys also occur in fjord systems under water. The branches of Sognefjord are for instance much shallower than the main fjord. The mouth of Fjærlandsfjord is about 400 meters deep while the main fjord is 1200 meters nearby. The mouth of Ikjefjord is only 50 meters deep while the main fjord is around 1300 meters at the same point.[5]

text: Glaciated terrain is not the only site of hanging streams and valleys. Hanging valleys are also simply the product of varying rates of erosion of the main valley and the tributary valleys. The varying rates of erosion are associated with the composition of the adjacent rocks in the different valley locations. The tributary valleys are eroded and deepened by glaciers or erosion at a slower rate than that of the main valley floor, thus the difference in the two valleys' depth increases over time. The tributary valley composed of more resistant rock then hangs over the main valley.[6]

text: Trough-shaped valleys[edit]

text: Trough-shaped valleys also form in regions of heavy denudation. By contrast, with glacial U-shaped valleys, there is less downward and sideways erosion. The severe slope denudation results in gently sloping valley sides and their transition to the actual valley bottom is unclear. Trough-shaped valleys occur mainly in periglacial regions and in tropical regions of variable wetness. Both climates are dominated by heavy denudation.

text: Box valleys[edit]

text: Box valleys have wide, relatively level floors and steep sides. They are common in periglacial areas and occur in mid-latitudes, but also occur in tropical and arid regions.[7]

text: Valley floors[edit]

text: Usually the bottom of a main valley is broad – independent of the U or V shape. It typically ranges from about one to ten kilometers in width and is commonly filled with mountain sediments. The shape of the floor can be rather horizontal, similar to a flat cylinder, or terraced.

text: Side valleys are rather V than U-shaped; near the mouth waterfalls are possible if it is a hanging valley. The location of the villages depends on the across-valley profile, on climate and local traditions, and on the danger of avalanches or landslides. Predominant are places on terraces or alluvial fans if they exist.

text: Historic siting of villages within the mainstem valleys, however, have chiefly considered the potential of flooding.

text: Hollows[edit]

text: A hollow is a small valley or dry stream bed. This term is commonly used in New England, Appalachia, and the Ozarks of Arkansas and Missouri to describe such geographic features. In rural areas in America, it may be pronounced as "holler". Many Appalacian story tellers will say that a holler is an area where you have to holler to communicate with your nearest neighbor, meaning how deep in the country you are.

text: Notable examples[edit]

text: Africa[edit]

text:
Great Rift Valley
Nile Valley (Egypt/Sudan/Ethiopia/Uganda)
Valley of the Kings (Egypt)
"Valley of Oueme" (Benin)

text: Asia[edit]

text:
Bagrot Valley (Gilgit-Baltistan, Pakistan)
Barak (India)
Barot (India)
Betaab (India)
Hunza Valley (Pakistan)
Ihlara, Turkey
Dang Valley (Western Nepal)
Indus Valley (Pakistan)
Jordan Valley
Jordan Rift Valley (Jordan - Israel)
Kaghan Valley (Pakistan)
Kangra (India)
Karsog (India)
Kashmir (India)
Kathmandu (Nepal)
Kullu (India)
Lidder Valley (India)
Neelum Valley (Pakistan)
Neora (India)
Nubra (India)
Pangi (India)
Panjshir Valley (Afghanistan)
Parvati Valley (India)
Pin Valley (India)
Sangla (India)
Spiti (India)
Suru (India)
Swat Valley (Pakistan)
Valley of flowers (India)
Yumthang (India)

text: Australia and New Zealand[edit]

text:
Barossa Valley (Australia)
Hunter Region (Australia)
Macarthur, New South Wales (Australia)
Hutt Valley (New Zealand)
Strath Taieri (New Zealand)

text: Europe[edit]

text:
Dalen, Telemark (Telemark, Norway)
Danube Valley (Eastern Europe)
Glen Coe (Scotland, United Kingdom)
Great Glen (Scotland, United Kingdom)
Gudbrandsdalen (Oppland, Norway)
Hallingdalen (Buskerud, Norway)
Heddal (Telemark, Norway)
Iron Gate (Romania/Serbia)
Lauterbrunnen Valley (Bern, Switzerland)
Loire Valley with its famous castles (France)
Midt-Telemark (Telemark, Norway)
Nant Ffrancon (Wales, United Kingdom)
Numedalen (Buskerud, Norway)
Østerdalen (Hedmark, Norway)
Rhone Valley from the Matterhorn to Grenoble and Lyon (France)
Romsdalen (Møre Og Romsdal, Norway)
Setesdal (Agder, Norway)
South Wales Valleys (Wales, United Kingdom)
Upper Rhine Valley or Upper Rhine Plain, an old graben system. (France and Germany)
Vestfjorddalen (Norway)

text: North America[edit]

text:
Central Valley (California)
Death Valley (California)
Fraser Canyon (British Columbia)
Fraser Valley (British Columbia)
Grand Canyon (Arizona, United States)
Hell's Gate (British Columbia)
Hudson Valley (New York)
Las Vegas Valley (Nevada)
Monument Valley (Arizona, Utah)
Napa Valley (California)
Okanagan Valley (British Columbia)
Ottawa Valley (Ontario/Quebec)
Palo Duro Canyon (Texas)
Rio Grande Valley (Texas)
Saint Lawrence Valley (Ontario/Quebec/New York)
San Fernando Valley (California)
Shenandoah Valley (Virginia/West Virginia)
Sonoma Valley, (California)
Toluca Valley (Mexico)
Valley of the Gods (Utah)
Valley of Mexico (Mexico)
Willamette Valley (Oregon)

text: South America[edit]

text:
Aburra Valley (Colombia)
Cauca Valley (Colombia)
Ischigualasto Valley of the Moon (Argentina)


document_title: Bride Wars

question_text: who plays kate hudson brother in bride wars

text: Bride Wars

text: Plot[edit]

text: Emma Allen and Olive 'Liv' Lerner are best friends who have planned every detail of their weddings, since first witnessing a wedding 20 years ago at the Plaza Hotel. They both have made it a priority to be married in the same location in June.

text: The two get engaged at 26, and are expected to be each other's maid of honor. They schedule their weddings with New York's most famous wedding planner, Marion St. Claire, but due to a clerical error they are scheduled to have a wedding on the same day, June 6 (three and a half months later). A week of passive aggressive hostility passes before the two women make it clear that neither will compromise, especially after the headstrong Liv hopes that Emma's passive nature would end their wait of who will surrender their date while Emma rejects the suggestion of a double wedding as she wants a day that is all about herself rather than sharing everything with Liv. Emma's fiancé, Fletcher, begins to show signs of being controlling. The two women declare war after a slight misunderstanding that Liv already set her wedding date, outraging Emma who sets her date as well, which Liv becomes aware of at their shared shower party. The two exchange threats and insults in front of their friends who decide not to take sides.

text: Both women attempt to sabotage each other's wedding, including Liv changing Emma's dance instructor, Emma secretly sending Liv candy to make her too fat to fit into her dress, Liv making Emma's tan turn bright orange, Emma tampering with Liv's hair dye to turn Liv's hair a shocking blue-white color, Liv registering Emma on Babies-R-Us as pregnant, and Emma showing up to Liv's bachelorette party to out-dance her. Emma and Fletcher get into an argument regarding Emma's maniac behavior of sabotaging Liv's wedding and their friendship, including how Emma has changed since they first met. Emma and Fletcher are shown to undergo strains in their relationship because of Emma's new found opinionated and confident trait, a depart from her usual people-pleasing characteristics. Liv has learned to be more sensitive and expressive, which gives her a sense of relief to finally have the luxury of being able to let go and be less controlling. However, due to her stress about the wedding and strained friendship with Emma, she ends up demoted.

text: Both brides-to-be are shown to be in the Plaza very shortly before they are due to be wed, separately. Right before Liv leaves to begin her march to the altar, she encounters Emma's father and receives his blessing; immediately she regrets setting up a wild spring break DVD to play at Emma's wedding. She sends her assistant Kevin to replace the DVD with the right one, filled with childhood memories. Thinking that the DVD is for a prank, he does not do so. Before the brides enter their respective venues, they share a moment of reconciliation as they both smile at each other.

text: Emma begins her walk down the aisle but stops when the footage of her spring break is shown. She loses her temper and tackles Liv after sprinting to the other section of the Plaza. The two brides wrestle in their dresses on the floor while the people closest to the brides having decided to let the brides resolve the problem. After tussling, Emma and Liv lie on the ground panting, and then make up. Emma stands up and walks over to Fletcher who is upset at Emma's behavior. Emma tells him that she is not the same person he fell in love with ten years ago and that she has now changed, as it has been apparent that she learned to be more assertive. With that, the two tearfully call off their wedding. Liv's wedding resumes with Emma participating and dancing with Nate, Liv's brother and a well known magazine journalist.

text: The movie picks up a year later when Liv and Emma meet up for drinks, where it's revealed that Emma married Nate. Emma and Liv also reveal to each other that they are pregnant and that their due dates are the same, March 3, and both friends get excited.

text: Cast[edit]

text:
Kate Hudson as Olive "Liv" Lerner, a successful attorney at Ropes & Gray who is used to getting her way, and won't settle for anything else. She attempts to be perfect instead of taking things lightly, ever since her parents died when she was a child. It was shown that she is protective and extremely caring of Emma.

Zoe O'Grady as Young Liv

Anne Hathaway as Emma Allen, a middle school teacher who takes care of everyone, but forgets about having some time for herself due to her sweet but slightly meek nature. Liv remarked that she is the one who always "gives in" when they both have conflicts with each other.

Shannon Ferber as Young Emma

Chris Pratt as Fletcher Flemson, Emma's fiance. Fletcher is an accountant and the two of them met ten years prior to the film's events. Throughout the film, he is shown to be very controlling, becoming aggravated by Emma's assertive behavior, and begins to have a lot of differences with her.
Bryan Greenberg as Nathan "Nate" Lerner, Liv's younger brother who is in love with Emma.
Steve Howey as Daniel Williams, Liv's fiance and a hedge fund manager. Unlike Fletcher and Emma, he became closer with Liv during the wedding planning process and embraced his fiance's changes in her attitude particularly her newly discovered vulnerability.
Candice Bergen as Marion St. Claire, New York's most sought-after wedding planner, to whom both girls turn when planning their wedding. She also serves as the narrator of the story.
Kristen Johnston as Deb: An obnoxious, lazy woman who is one of Emma's colleagues. She continually unloads her entire workload on Emma. She eventually becomes Emma's maid of honor. She is the one who suggested to Emma that she should fatten Liv with expensive chocolates.
Michael Arden as Kevin, Liv's assistant at work, whom she recruits to be her "Mister of Honor." He gave Liv the suggestion that she should mess up with Emma's dance lessons by replacing her instructor with an eccentric one. He is seen getting romantically involved with Amie near the end of the film.
June Diane Raphael as Amanda, a friend of Emma and Liv's who gets married at the start of the film. She is shown to be frank and expresses her regret in getting married in comical ways, ending with her and her husband getting divorced at the end of the film.
Casey Wilson as Stacy Kindred, another bride and one of Marion St. Claire's clients. Liv and Emma tried to persuade her to give up her date, which end up in a fiasco in a store.
Paul Scheer as Ricky Coo, dance choreographer who calls himself "The Doctor of Dance"
John Pankow as John Allen, Emma's dad.
Hettienne Park as Marissa, one of Emma and Liv's closest friends.
Lauren Bittner as Amie, one of Emma and Liv's closest friends. She is seen getting romantically involved with Kevin near the end of the film.
Dennis Parlato as Dance Instructor
Billy Unger as Additional voices
Colin Ford as Additional voices

text: Production[edit]

text: Raphael and Wilson completed the shooting script of Bride Wars, from an original script by Greg DePaul,[4] before the 2007–2008 Writers Guild of America strike began.[5] Karen McCullah Lutz and Kirsten Smith also contributed to the screenplay.[2][5]

text: Some principal photography took place at the Peabody Essex Museum in Salem, Massachusetts.[6] Most filming occurred in Boston, New York City, and in Salem, Massachusetts.[citation needed]

text: Music[edit]

text: The score to Bride Wars was composed by Edward Shearmur, who recorded his score with a 77-piece ensemble of the Hollywood Studio Symphony at the Newman Scoring Stage at 20th Century Fox.[7]

text: In the beginning of the film, the song "Somethin' Special" by Colbie Caillat was played, however this version had different lyrics than the Beijing Olympic Mix, suggesting that it was the original mix. As the film did not have a soundtrack, the original version remained unreleased until Caillat's album Breakthrough was released, where the song appears as a bonus track on the Rhapsody edition.[8] There is also the song "Dream" by Priscilla Ahn. And "Scared" by Duffy.

text: Reception[edit]

text: Critical reception[edit]

text: Bride Wars has been almost universally panned by critics. The film has received a 10% approval rating on Rotten Tomatoes based on 141 collected reviews.[9] Time named it one of the top 10 worst chick flicks.[10]

text: Manohla Dargis of The New York Times called the film "dopey if largely painless". She said that Hathaway's presence meant "that there’s a little acting in it, along with a few human emotions" and wondered what the film might have been if the writers had explored a potential lesbian subtext suggested by the opening scenes.[11] Carrie Rickey of the Philadelphia Inquirer wrote, "How bad can a movie be, with Goldilocks Hudson and Cinderella Hathaway? So excruciating that Hudson's sunshine can't warm it and Hathaway's rose redolence can't mask its stink."[12] Ty Burr of the Boston Globe was disturbed by the film, claiming that it was "...a chick flick that makes its chick characters — and by extension its chick audience — look like hateful, backward toddlers, and there is something wrong with that."[13]

text: Longtime BBC Radio 5 Live critic Mark Kermode was notably harsh toward the film on his Kermode and Mayo's Film Review show, going so far as to say that he would quit film criticism if Bride Wars did not end up in his list of 10 worst films of 2009.[14] By the end of the year, even when Kermode included Terminator Salvation and Couples Retreat on his list by popular demand, Bride Wars still finished eighth, allowing him to keep his job.[15]

text: In one of the few positive reviews of the film, Time critic Mary Pols wrote, "At least, and this is something to be grateful for, Bride Wars deviates from the usual wedding-flick routine of maids of honor who should be the bride (or groom). And even though the catfighting goes over the top, the notion that a passionate female friendship can turn ugly in a heartbeat is, sadly, realistic."[16]

text: Apart from negative reviews, the film was nominated for 2 awards at the 2009 MTV Movie Awards: Best Fight (Anne Hathaway vs. Kate Hudson)[17] and Anne Hathaway for Best Female Performance.[18] It also had several Teen Choice Award nominations.[citation needed] Candice Bergen was nominated for a Razzie Award as Worst Supporting Actress for her performance in the film.

text: Box office performance[edit]

text: In its opening weekend, the film grossed $21,058,173 ranking #2 at the box office.[1] As of May 26, 2009, it has made $58,715,510 in the United States and Canada, $55,982,521 in foreign countries and a total of $115,049,554 worldwide — a financial success despite its largely negative reviews.[1]

text: Awards[edit]

text: Won[edit]

text: 2009 - Teen Choice Awards for Choice Comedy Movie Actress (Anne Hathaway)

text: Nominated[edit]

text:
2009 - Teen Choice Awards for Choice Comedy Movie Actress (Kate Hudson)
2009 - Teen Choice Awards for Choice Movie Hissy Fit (Kate Hudson)
2009 - Teen Choice Awards for Choice Movie Rockstar Moment (Anne Hathaway)
2009 - Teen Choice Awards for Choice Movie Rumble (Anne Hathaway) & (Kate Hudson)
2009 - MTV Movie Awards for Best Female Performance (Anne Hathaway)
2009 - MTV Movie Awards for Best Fight (Anne Hathaway) & (Kate Hudson)
2010 - Razzie Awards for Worst Supporting Actress (Candice Bergen)
2010 - People's Choice Awards for Favourite Comedy Movie


document_title: Money Heist

question_text: who plays tokyo in la casa de papel

question_tokens: who plays tokyo in la casa de papel

text: Money Heist

text: Premise[edit]

text: A mysterious man, who goes by the name of El Profesor ("The Professor"), is planning the biggest heist in history. In order to carry out the ambitious plan, he recruits a team of eight people with certain abilities who have nothing to lose. The goal is to enter the Royal Mint of Spain and print €2.4 billion. In order to do this, they need 11 days of seclusion, during which they will have to deal with elite police forces and 67 hostages.

text: Production[edit]

text: Location[edit]

text: Although the storyline is set at the Royal Mint of Spain, the series was filmed at the Spanish National Research Council (CSIC) headquarters, which bears a passing resemblance to the mint in Madrid.[4]

text: Music[edit]

text: The Italian anti-fascist song "Bella ciao" is sung multiple times throughout the series.[5] The character Tokyo recounts in one of her narrations, "The life of the Professor revolved around a single idea: Resistance. His grandfather, who had fought against the fascists in Italy, taught him the song and he taught us."[5] The song is also played in other emblematic moments, such as when the thieves succeed in their escape out of the Mint—a metaphor for freedom.[5]

text: Because of the popularity of the series, "Bella ciao", a song interpreted by El Profesor and Berlin (two main characters from the series) charted in France debuting at number 5 in May 2018 on SNEP, the official French Singles Chart.[6] A remixed version of the same song "Bella ciao (Hugel Remix)" featuring El Profesor had peaked in April 2018 at number 16 on SNEP as well as reaching number 2 on the German Singles Chart.[7] Other charting versions of the song include those by The Bear reaching number 45 in France,[8] Sound of Legend version reaching number 34,[9] and Manu Pilas version reaching number 27.[10] The rapper Rémy sampled on the song adding French rapping verses. This version reached number 66 on the French chart.[11] On 18 May 2018, a completely revamped French version with new French-language lyrics keeping a few lines in Italian was released by Maître Gims, Vitaa, Dadju, Slimane and Naestro.[12][13]

text: Cast and characters[edit]

text: Main[edit]

text:
Úrsula Corberó as Tokyo, real name Silene Oliveira
Itziar Ituño as Raquel Murillo
Álvaro Morte as The Professor, real name Sergio Marquina
Paco Tous as Moscow, real name Agustín Ramos
Pedro Alonso as Berlin, real name Andrés de Fonollosa
Alba Flores as Nairobi, real name Ágata Jiménez
Miguel Herrán as Rio, real name Aníbal Cortés
Jaime Lorente as Denver, real name Daniel Ramos[14]
Esther Acebo as Mónica Gaztambide
Enrique Arce as Arturo Román
María Pedraza as Alison Parker
Darko Peric as Helsinki, real name Yashin Dasáyev
Kiti Mánver as Mariví, Raquel's mother

text: Recurring[edit]

text:
Roberto Garcia Ruiz as Oslo, real name Dimitri Mostovói
Anna Gras as Mercedes
Fran Morcillo as Pablo
Clara Alvarado as Ariadna
Fernando Soto as Ángel
Juan Fernández as Coronel Prieto
Mario de la Rosa as Suárez

text: Episodes[edit]

text:
No.TitleDirected byOriginal air dateSpain viewers(millions) [15]1"Episode 1"Jesús Colmenar2 May 2017 (2017-05-02)4.09
2"Episode 2"Miguel Ángel Vivas9 May 2017 (2017-05-09)3.04
3"Episode 3"Francisco Fernandes16 May 2017 (2017-05-16)2.64
4"Episode 4"Alejandro Bazzano23 May 2017 (2017-05-23)2.65
5"Episode 5"Jesús Colmenar30 May 2017 (2017-05-30)2.36
6"Episode 6"Miguel Ángel Vivas6 June 2017 (2017-06-06)2.47
7"Episode 7"Álex Rodrigo13 June 2017 (2017-06-13)2.42
8"Episode 8"Alejandro Bazzano20 June 2017 (2017-06-20)2.07
9"Episode 9"Jesús Colmenar27 June 2017 (2017-06-27)2.19
10"Episode 10"Álex Rodrigo16 October 2017 (2017-10-16)1.99
11"Episode 11"Alejandro Bazzano23 October 2017 (2017-10-23)1.73
12"Episode 12"Javier Quintas2 November 2017 (2017-11-02)1.57
13"Episode 13"Jesús Colmenar & Alex Rodrigo9 November 2017 (2017-11-09)1.53
14"Episode 14"Alejandro Bazzano16 November 2017 (2017-11-16)1.48
15"Episode 15"Jesús Colmenar & Alex Rodrigo23 November 2017 (2017-11-23)1.80[16]

text: Ratings[edit]

text:
Season

Episodes

First aired

Last aired
Avg. viewers(millions)

Date

Viewers(millions)

Date

Viewers(millions)

1

15

2 May 2017 (2017-05-02)

4.09[15]

23 November 2017 (2017-11-23)

1.80[16]
2.28

text: Netflix acquisition[edit]

text: Netflix acquired the rights to stream the series and distributed the first two parts on their streaming service on 25 December 2017 worldwide.[2] However, instead of retaining the original number of nine episodes and the 70 minute runtime of each episode in the season, it was cut into 13 different untitled episodes. Each of the episodes has been limited to 40–50 minutes in length.

text: Netflix released the second season on 6 April 2018 worldwide. The episodes of the second part were re-edited from six to nine episodes with a runtime of 40–50 minutes. Once again, the episodes are untitled.[2]

text: On 18 April 2018, Netflix renewed the series for a third part, which is expected to be released in 2019. The third part will be a Netflix exclusive and released worldwide.[3][17][18] The Latin American Netflix YouTube channel uploaded a video on 18 April 2018 titled "Este es un mensaje para resistencia."[19] In the video, a few cast members appear, talking about how they knew the audience was waiting for more and stating that "the biggest robbery is not over yet."[18]

text: Reception[edit]

text: Netflix announced in its Quarter 1 2018 letter to shareholders that the series was the most watched non-English language series on Netflix ever.[20]

text: Home media[edit]

text: Part one and two of the series were released for purchase on the Spanish Amazon website on 8 January 2018.[21]