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87-495: The oilbird ( Steatornis caripensis ), locally known as the guácharo , is a bird species found in the northern areas of South America including the Caribbean island of Trinidad . It is the only species in the genus Steatornis , the family Steatornithidae , and the order Steatornithiformes . Nesting in colonies in caves, oilbirds are nocturnal feeders on the fruits of the oil palm and tropical laurels . They are

174-837: A considerably smaller portion in the Northern Hemisphere . It can also be described as the southern subregion of the Americas . South America is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean ; North America and the Caribbean Sea lie to the northwest. The continent includes twelve sovereign states : Argentina , Bolivia , Brazil , Chile , Colombia , Ecuador , Guyana , Paraguay , Peru , Suriname , Uruguay , and Venezuela ; two dependent territories :

261-502: A flattened, powerfully hooked, beak surrounded by deep chestnut rictal bristles up to 5 centimetres (2.0 in) long. The adult weighs 350–475 g (12.3–16.8 oz) but the chicks can weigh considerably more, at up to 600 grams (21 oz), when their parents feed them a good deal of fruit before they fly. The feathers of the oilbird are soft like those of many nightbirds, but not as soft as those of owls or nightjars, as they do not need to be silent like predatory species. The oilbird

348-698: A fleet to reach Peru by sea, and sought the military support of various rebels from the Viceroyalty of Peru. In 1822 the two men met at the Guayaquil Conference in Ecuador, where they failed to agree on governance strategies for the liberated nations. Two years later Bolívar's forces beat the Spanish at the Battle of Ayacucho , securing the independence of Peru and the rest of South America. In

435-459: A long history of colonialism , the overwhelming majority of South Americans speak Spanish or Portuguese , and societies and states are rich in Western traditions . Relative to Africa, Asia, and Europe, post-1900 South America has been a peaceful continent with few wars, although high rates of violent crime remain a concern in some countries. South America occupies the southern portion of

522-682: A part of Oceania, also administered by Chile), the Galápagos Islands (administered by Ecuador , sometimes considered part of Oceania), and Tierra del Fuego (split between Argentina and Chile). In the Atlantic Ocean, Brazil administers Fernando de Noronha , Trindade and Martim Vaz , and the Saint Peter and Saint Paul Archipelago , while the Falkland Islands (Spanish: Islas Malvinas ) and South Georgia and

609-399: A phosphodiesterase molecule, which can break down over a thousand cGMP molecules per second. Thus, rods can have a large response to a small amount of light. As the retinal component of rhodopsin is derived from vitamin A , a deficiency of vitamin A causes a deficit in the pigment needed by rod cells. Consequently, fewer rod cells are able to sufficiently respond in darker conditions, and as

696-502: A population of a hundred birds in a canyon with ledges protected by vegetation. Some smaller caves and gorges are used only for roosting. While it was once thought that oilbirds always or nearly always roosted in caves, canyons or gullies, researchers placing GPS trackers on non-breeding birds found that they regularly roost in trees in the forest as well as in caves. It is a seasonal migrant across some of its range, moving from its breeding caves in search of fruit trees. It has occurred as

783-573: A rare vagrant to Costa Rica , Panama and Aruba . The Guácharo Cave (Oilbird Cave), in the mountainous Caripe district of northern Monagas , Venezuela , is where Alexander von Humboldt first studied the species. Oilbirds are nocturnal . During the day the birds rest on cave ledges and leave at night to find fruit outside the cave. It was once thought that oilbirds only roosted in caves, and indeed never saw daylight, but studies using GPS/acceleration loggers found that non-breeding birds only roosted in caves or other rock shelters one night in three,

870-578: A relatively high concentration of cyclic guanosine 3'-5' monophosphate (cGMP), which opens ion channels (largely sodium channels, though calcium can enter through these channels as well). The positive charges of the ions that enter the cell down its electrochemical gradient change the cell's membrane potential , cause depolarization , and lead to the release of the neurotransmitter glutamate . Glutamate can depolarize some neurons and hyperpolarize others, allowing photoreceptors to interact in an antagonistic manner. When light hits photoreceptive pigments within

957-481: A site called Chavín de Huantar in modern Peru at an elevation of 3,177 meters (10,423 ft). Chavín civilization spanned 900 BC to 300 BC. In the central coast of Peru, around the beginning of the 1st millennium AD, Moche (100 BC – 700 AD, at the northern coast of Peru), Paracas and Nazca (400 BC – 800 AD, Peru) cultures flourished with centralized states with permanent militia improving agriculture through irrigation and new styles of ceramic art. At

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1044-689: A subtropical climate of the dinaric type. At the highest points of the Andean region, climates are colder than the ones occurring at the highest point of the Norwegian fjords. In the Andean plateaus, the warm climate prevails, although it is tempered by the altitude, while in the coastal strip, there is an equatorial climate of the Guinean type. From this point until the north of the Chilean coast appear, successively, Mediterranean oceanic climate , temperate of

1131-405: A synaptic terminal, an inner segment, and an outer segment. The synaptic terminal forms a synapse with another neuron, usually a bipolar cell or a horizontal cell . The inner and outer segments are connected by a cilium , which lines the distal segment. The inner segment contains organelles and the cell's nucleus , while the rod outer segment (abbreviated to ROS), which is pointed toward

1218-400: Is a heap of droppings, usually above water—either a stream or the sea—on which 2–4 glossy white eggs are laid which soon become stained brown. These are rounded but with a distinctly pointed smaller end and average 41.2 millimetres (1.62 in) by 33.2 millimetres (1.31 in). The squabs become very fat before fledging, weighing around a third more than the adult birds. The Guácharo Cave

1305-526: Is because the most extensive part of the continent is in the equatorial zone (the region has more areas of equatorial plains than any other region), therefore giving the Southern Cone more oceanic influence, which moderates year round temperatures. The average annual temperatures in the Amazon basin oscillate around 27 °C (81 °F), with low thermal amplitudes and high rainfall indices. Between

1392-460: Is by far the most populous South American country, with almost half of the continent's population, followed by Colombia, Argentina, Venezuela, and Peru. In recent decades, Brazil has also generated half of the continent's GDP and has become the continent's first regional power. Most of the population lives near the continent's western or eastern coasts while the interior and the far south are sparsely populated. The geography of western South America

1479-442: Is dominated by rod cells , 1,000,000 rods per mm, the highest density of any vertebrate eye, which are organised in layers, an arrangement unique among birds but shared by deep-sea fish . They have low numbers of cone cells , and the whole arrangement would allow them to capture more light in low light conditions but probably have poor vision in daylight. Although they have specially adapted vision to forage by sight, they are among

1566-605: Is dominated by the Andes mountains; in contrast, the eastern part contains both highland regions and vast lowlands where rivers such as the Amazon , Orinoco and Paraná flow. Most of the continent lies in the tropics, except for a large part of the Southern Cone located in the middle latitudes . The continent's cultural and ethnic outlook has its origin with the interaction of Indigenous peoples with European conquerors and immigrants and, more locally, with African slaves . Given

1653-642: Is less distinct than it would be if the visual system received information from each rod cell individually. Rod cells also respond more slowly to light than cones and the stimuli they receive are added over roughly 100 milliseconds. While this makes rods more sensitive to smaller amounts of light, it also means that their ability to sense temporal changes, such as quickly changing images, is less accurate than that of cones. Experiments by George Wald and others showed that rods are most sensitive to wavelengths of light around 498 nm (green-blue), and insensitive to wavelengths longer than about 640 nm (red). This

1740-541: Is mainly reddish-brown with white spots on the nape and wings. Lower parts are cinnamon-buff with white diamond-shaped spots edged in black, these spots start small towards the throat and get larger towards the back. The stiff tail feathers are a rich brown spotted with white on either side. The feet are small and almost useless, other than for clinging to vertical surfaces. The long wings have evolved to make it capable of hovering and twisting flight, which enables it to navigate through restricted areas of its caves. For example,

1827-614: Is now Colombia. They established the Muisca Confederation of many clans, or cacicazgos , that had a free trade network among themselves. Many were goldsmiths and farmers. Other important Pre-Columbian cultures include: the Cañaris (in south central Ecuador), Chimú Empire (1300–1470, Peruvian northern coast), Chachapoyas , and the Aymaran kingdoms (1000–1450, Western Bolivia and southern Peru). Holding their capital at

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1914-480: Is one of the most biodiverse continents on Earth. It is home to many unique species of animals including the llama , anaconda , piranha , jaguar , vicuña , and tapir , and to one of the largest known insects in the world, the Titan beetle . The Amazon rainforests possess high biodiversity , with Brazil estimated to contain 10% of Earth's species . 83% of South America's large mammals ( megafauna ) became extinct at

2001-582: Is the largest country in South America, covering a little less than half of the continent's land area and encompassing around half of the continent's population. The remaining countries and territories are divided among four subregions : the Andean states , Caribbean South America , The Guianas , and the Southern Cone . Physiographically, South America also includes some of the nearby islands. The Dutch ABC islands ( Aruba , Bonaire , and Curaçao ),

2088-519: The Altiplano , Tiahuanaco or Tiwanaku (100 BC – 1200 AD, Bolivia) managed a large commercial network based on religion. Around the 7th century, both Tiahuanaco and Wari or Huari Empire (600–1200, Central and northern Peru) expanded its influence to all the Andean region, imposing the Huari urbanism and Tiahuanaco religious iconography. The Muisca were the main indigenous civilization in what

2175-586: The Archipelago of San Andrés, Providencia and Santa Catalina ( San Andrés Island , Providencia Island , and Santa Catalina Island etc., which are administered by Colombia ) are politically parts of South American countries but physiographically parts of North America. Other islands often associated with geopolitical South America are the Chiloé Archipelago and Robinson Crusoe Island (both administered by Chile), Easter Island (culturally

2262-820: The Atacama Desert ; the wettest place on earth, López de Micay in Colombia; the largest rainforest, the Amazon rainforest ; the highest capital city, La Paz , Bolivia ; the highest commercially navigable lake in the world, Lake Titicaca ; and, excluding research stations in Antarctica , the world's southernmost permanently inhabited community, Puerto Toro , Chile. South America's major mineral resources are gold, silver, copper, iron ore, tin , and petroleum. These resources have brought high income to its countries, especially in times of war or of rapid economic growth by industrialized countries elsewhere. However,

2349-717: The Bering Land Bridge (now the Bering Strait ) at least 15,000 years ago from the territory that is present-day Russia. They migrated south through North America, and eventually reached South America through the Isthmus of Panama . Amongst the oldest evidence for human presence in South America is the Monte Verde II site in Chile, suggested to date to around 14,500 years ago. From around 13,000 years ago,

2436-578: The Caribbean colonies and Brazil, as European nations built up economically slave-dependent colonies in the New World . Nearly 40% of all African slaves trafficked to the Americas went to Brazil. An estimated 4.9 million slaves from Africa came to Brazil during the period from 1501 to 1866. In contrast to other European colonies in the Americas which mainly used the labor of African slaves, Spanish colonists mainly enslaved indigenous Americans. In 1750,

2523-876: The Carrasco National Park in Bolivia . Dunston Cave , at the Asa Wright Nature Centre in Trinidad , is home to about 200 nesting pairs. The species is classified as 'Least Concern' by the IUCN red list as of October 2016, despite a decreasing population. [REDACTED] South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere , with

2610-1030: The Falkland Islands and South Georgia and the South Sandwich Islands ; and one internal territory : French Guiana . The ABC islands of the Dutch Caribbean (north of Venezuela in the Leeward Antilles ), Ascension Island (a part of Saint Helena, Ascension and Tristan da Cunha ), Bouvet Island (a dependency of Norway ), Panama , and the Caribbean island country of Trinidad and Tobago may also be considered parts of South America. South America has an area of 17,840,000 square kilometers (6,890,000 sq mi). Its population as of 2021 has been estimated at more than 434 million. South America ranks fourth in area (after Asia, Africa, and North America) and fifth in population (after Asia, Africa, Europe, and North America). Brazil

2697-470: The Fishtail projectile point style became widespread across South America, with its disappearance around 11,000 years ago coincident with the disappearance of South America's megafauna. Maize was present in northern South America by around 6,000 years ago. By 2000 BC, many agrarian communities had been settled throughout the Andes and the surrounding regions. Fishing became a widespread practice along

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2784-472: The Fortaleza area, contemporaneous with the pyramids of Ancient Egypt , one of the oldest-known civilizations in the Americas and one of the six sites where civilization separately originated in the ancient world. Caral–Supe governing class established a trade network and developed agriculture then followed by Chavín by 900 BC, according to some estimates and archaeological finds. Artifacts were found at

2871-715: The Maracaibo Lake and the mouth of the Orinoco, predominates an equatorial climate of the type Congolese, that also includes parts of the Brazilian territory. The east-central Brazilian plateau has a humid and warm tropical climate. The northern and eastern parts of the Argentine pampas have a humid subtropical climate with dry winters and humid summers of the Chinese type, while the western and eastern ranges have

2958-599: The Orinoco Llanos and in the Guianas Plateau , the precipitation levels go from moderate to high. The Pacific coast of Colombia and northern Ecuador are rainy regions, with Chocó in Colombia being the rainiest place in the world along with the northern slopes of Indian Himalayas. The Atacama Desert, along this stretch of coast, is one of the driest regions in the world. The central and southern parts of Chile are subject to extratropical cyclones , and most of

3045-547: The Portuguese Crown abolished the enslavement of indigenous peoples in colonial Brazil , under the belief that they were unfit for labor and less effective than enslaved Africans. Enslaved Africans were brought to the Americas on slave ships , under inhuman conditions and ill-treatment, and those who survived were sold in slave markets . After independence, all South American countries maintained slavery for some time. The first South American country to abolish slavery

3132-738: The Portuguese Kingdom of Brazil , Dom Pedro I (also Pedro IV of Portugal), son of the Portuguese King Dom João VI , proclaimed the independent Kingdom of Brazil in 1822, which later became the Empire of Brazil . Despite the Portuguese loyalties of garrisons in Bahia , Cisplatina and Pará , independence was diplomatically accepted by Portugal in 1825, on condition of a high compensation paid by Brazil mediated by

3219-593: The Riograndense Republic ). Rod cell Rods are a little longer and leaner than cones but have the same basic structure. Opsin -containing disks lie at the end of the cell adjacent to the retinal pigment epithelium , which in turn is attached to the inside of the eye . The stacked-disc structure of the detector portion of the cell allows for very high efficiency. Rods are much more common than cones, with about 120 million rod cells compared to 6 to 7 million cone cells. Like cones, rod cells have

3306-665: The South American Plate . South America is home to several superlatives, including the world's highest uninterrupted waterfall , Angel Falls in Venezuela; the highest single-drop waterfall Kaieteur Falls in Guyana; the largest river by volume, the Amazon River ; the longest mountain range, the Andes (whose highest mountain is Aconcagua at 6,962 m or 22,841 ft); the driest non-polar place on earth,

3393-613: The Spanish American wars of independence between the patriots, who promoted such autonomy, and the royalists , who supported Spanish authority over the Americas. The Juntas, in both Spain and the Americas, promoted the ideas of the Enlightenment . Five years after the beginning of the war, Ferdinand VII returned to the throne and began the Absolutist Restoration , as the royalists got the upper hand in

3480-457: The generic name Steatornis means 'fat bird', in reference to the fatness of the chicks. The oilbird is called a guácharo or tayo in Spanish , both terms being of indigenous origin. In Trinidad it was sometimes called diablotin (French for 'little devil'), presumably referring to its loud cries, which have been likened to those of tortured men. The common name oilbird comes from

3567-712: The native populations had no immune resistance – caused large-scale depopulation of the native population under Spanish control. Systems of forced labor, such as the haciendas and mining industry's mit'a also contributed to the depopulation. After this, enslaved Africans , who had developed immunities to these diseases, were quickly brought in to replace them. The Spaniards were committed to converting their native subjects to Christianity and were quick to purge any native cultural practices that hindered this end; however, many initial attempts at this were only partially successful, as native groups simply blended Catholicism with their established beliefs and practices. Furthermore,

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3654-417: The order Caprimulgiformes . However, the nightjars and their relatives are insectivores while the oilbird is a specialist fructivore , and it is sufficiently distinctive to be placed in a family (Steatornithidae) and suborder (Steatornithes) of its own. Some research indicates that it should even be considered a distinct order (Steatornithiformes). The specific name caripensis means 'of Caripe ', and

3741-755: The Americas. The continent is generally delimited on the northwest by the Darién watershed along the Colombia–Panama border , although some may consider the border instead to be the Panama Canal . Geopolitically and geographically, all of Panama – including the segment east of the Panama Canal in the isthmus – is typically included in North America alone and among the countries of Central America . Almost all of mainland South America sits on

3828-692: The Argentine Patagonia is desert . In the Pampas of Argentina, Uruguay and South of Brazil the rainfall is moderate, with rains well distributed during the year. The moderately dry conditions of the Chaco oppose the intense rainfall of the eastern region of Paraguay. In the semiarid coast of the Brazilian Northeast the rains are linked to a monsoon regime. Important factors in the determination of climates are sea currents, such as

3915-748: The Breton type and, already in Tierra del Fuego , cold climate of the Siberian type. The distribution of rainfall is related to the regime of winds and air masses. In most of the tropical region east of the Andes, winds blowing from the northeast, east and southeast carry moisture from the Atlantic, causing abundant rainfall. However, due to a consistently strong wind shear and a weak Intertropical Convergence Zone , South Atlantic tropical cyclones are rare. In

4002-401: The G protein and the activated receptor. Second, it serves as an adaptor protein to aid the receptor to the clathrin-dependent endocytosis machinery (to induce receptor-mediated endocytosis). A rod cell is sensitive enough to respond to a single photon of light and is about 100 times more sensitive to a single photon than cones. Since rods require less light to function than cones, they are

4089-499: The South Sandwich Islands ( biogeographically and hydrologically associated with Antarctica) have been administered as two British Overseas Territories under the Crown , whose sovereignty over the islands is disputed by Argentina . An isolated volcanic island on the South American Plate , Ascension Island is geologically a part of South America. Administered as a dependency of Saint Helena, Ascension and Tristan da Cunha ,

4176-1014: The Spaniards brought their language to the degree they did with their religion, although the Roman Catholic Church 's evangelization in Quechua , Aymara , and Guaraní actually contributed to the continuous use of these native languages albeit only in the oral form. Eventually, the natives and the Spaniards interbred, forming a mestizo class. At the beginning, many mestizos of the Andean region were offspring of Amerindian mothers and Spanish fathers. After independence, most mestizos had native fathers and European or mestizo mothers. Many native artworks were considered pagan idols and destroyed by Spanish explorers; this included many gold and silver sculptures and other artifacts found in South America, which were melted down before their transport to Spain or Portugal. Spaniards and Portuguese brought

4263-534: The Spanish and Portuguese colonies. First, Napoleon invaded Portugal, but the House of Braganza avoided capture by escaping to Brazil . Napoleon captured King Ferdinand VII of Spain, and appointed his own brother instead. This appointment provoked popular resistance, which created Juntas to rule in the name of the captured king. Many cities in the Spanish colonies, however, considered themselves equally authorized to appoint local Juntas like those of Spain. This began

4350-607: The United Kingdom. The newly independent nations began a process of fragmentation, with several civil and international wars. However, it was not as strong as in Central America. Some countries created from provinces of larger countries stayed as such up to modern times (such as Paraguay or Uruguay), while others were reconquered and reincorporated into their former countries (such as the Republic of Entre Ríos and

4437-421: The activation of transducin . Also, an inhibitory protein, arrestin , then binds to the phosphorylated rhodopsins to further inhibit the rhodopsin activity. While arrestin shuts off rhodopsin, an RGS protein (functioning as a GTPase-activating protein (GAP)) drives the transducin (G-protein) into an "off" state by increasing the rate of hydrolysis of the bonded GTP to GDP. When the cGMP concentration falls,

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4524-450: The back of the eye, contains the light-absorbing materials. A human rod cell is about 2 microns in diameter and 100 microns long. Rods are not all morphologically the same; in mice, rods close to the outer plexiform synaptic layer display a reduced length due to a shortened synaptic terminal. In vertebrates, activation of a photoreceptor cell is a hyperpolarization (inhibition) of the cell. When they are not being stimulated, such as in

4611-547: The birds prepare to emerge from a cave at dusk. The oilbird ranges from Guyana and the island of Trinidad to Venezuela , Colombia , Ecuador , Peru , Bolivia and Brazil . They range from sea-level to 3,400 m (11,200 ft). The species has highly specific habitat requirements, needing both caves to breed in and roost in frequently, and forest containing fruiting trees. Where suitable caves are absent, oilbirds will roost and breed in narrow gorges and grottos with suitable rock shelves. One such colony in Ecuador held

4698-437: The coast, helping establish fish as a primary source of food. Irrigation systems were also developed at this time, which aided in the rise of an agrarian society . South American cultures began domesticating llamas , vicuñas , guanacos , and alpacas in the highlands of the Andes circa 3500 BC. Besides their use as sources of meat and wool, these animals were used for transportation of goods. The rise of plant growing and

4785-461: The concentration in producing one, or few, major export commodities has often hindered the development and diversification of its economies. The fluctuation in the price of commodities in international markets has led historically to major highs and lows, booms and busts, in the economies of South American states, often causing political instability. This has led for calls to diversify production and increase trade within South America itself. Brazil

4872-401: The cone cells are poorly adapted for sight in the dark, night-blindness can result. Rods make use of three inhibitory mechanisms (negative feedback mechanisms) to allow a rapid revert to the resting state after a flash of light. Firstly, there exists a rhodopsin kinase (RK) which would phosphorylate the cytosolic tail of the activated rhodopsin on the multiple serines, partially inhibiting

4959-424: The conflict. The independence of South America was secured by Simón Bolívar (Venezuela) and José de San Martín (Argentina), the two most important Libertadores . Bolívar led a great uprising in the north, then led his army south towards Lima , the capital of the Viceroyalty of Peru . Meanwhile, San Martín led an army across the Andes Mountains, along with Chilean expatriates, and liberated Chile. He organized

5046-405: The current Humboldt and Falklands . The equatorial current of the South Atlantic strikes the coast of the Northeast and there is divided into two others: the current of Brazil and a coastal current that flows to the northwest towards the Antilles , where there it moves towards northeast course thus forming the most Important and famous ocean current in the world, the Gulf Stream . South America

5133-421: The dark, rod cells and cone cells depolarize and release a neurotransmitter spontaneously. This neurotransmitter hyperpolarizes the bipolar cell . Bipolar cells exist between photoreceptors and ganglion cells and act to transmit signals from the photoreceptors to the ganglion cells . As a result of the bipolar cell being hyperpolarized, it does not release its transmitter at the bipolar-ganglion synapse and

5220-427: The end of the Pleistocene around 11,000 years ago as part of the Quaternary extinction event , among the highest of any continent, with the casualties including saber-toothed cats , ground sloths , glyptodonts , gomphotheres , the equines Hippidion and Equus neogeus , and all remaining South American native ungulates . South America is thought to have been first inhabited by humans when people were crossing

5307-418: The fact that in the past chicks were captured and boiled down in order to make oil. The fossil record of the family suggests that they were once more widely distributed around the globe. The first fossil oilbird was described by Storrs Olson in 1987 from a fossil found in the Green River Formation in Wyoming. The species, Prefica nivea , was probably not adapted to hovering flight or living in caves, unlike

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5394-454: The few birds known to supplement sight by echolocation in sufficiently poor light conditions, using a series of sharp audible clicks for this purpose. The only other birds known to do this are some species of swift . [REDACTED] In addition to clicks used for echolocation, oilbirds also produce a variety of harsh screams while in their caves. Entering a cave with a light especially provokes these raucous calls; they also may be heard as

5481-502: The great city of Cusco , the Inca civilization dominated the Andes region from 1438 to 1533. Known as Tawantin suyu , and "the land of the four regions", in Quechua , the Inca Empire was highly distinct and developed. Inca rule extended to nearly a hundred linguistic or ethnic communities, some nine to fourteen million people connected by a 25,000 kilometer road system . Cities were built with precise, unmatched stonework, constructed over many levels of mountain terrain. Terrace farming

5568-461: The inhibitory PDE gamma subunits and prevents them from blocking catalytic sites on the alpha and beta subunits of PDE, leading to the activation of cGMP phosphodiesterase, which hydrolyzes cGMP (the second messenger), breaking it down into 5'-GMP. Reduction in cGMP allows the ion channels to close, preventing the influx of positive ions, hyperpolarizing the cell, and stopping the release of the neurotransmitter glutamate. Though cone cells primarily use

5655-417: The island is geopolitically a part of Africa. All of the world's major climate zones are present in South America. The distribution of the average temperatures in the region presents a constant regularity from the 30° of latitude south , when the isotherms tend, more and more, to be confused with the degrees of latitude. In temperate latitudes, winters and summers are milder than in North America. This

5742-487: The islands of Trinidad and Tobago ( Trinidad Island and Tobago Island etc.), the State of Nueva Esparta , and the Federal Dependencies of Venezuela sit on the northern portion of the South American continental shelf and are sometimes considered parts of the continent. Geopolitically, all the island countries and territories in the Caribbean have generally been grouped as a subregion of North America instead. By contrast, Aves Island (administered by Venezuela ) and

5829-466: The land outside Europe should be an exclusive duopoly between the two countries. The treaty established an imaginary line along a north–south meridian 370 leagues west of the Cape Verde Islands , roughly 46° 37' W. In terms of the treaty, all land to the west of the line (known to comprise most of the South American soil) would belong to Spain, and all land to the east, to Portugal. As accurate measurements of longitude were impossible at that time,

5916-476: The line was not strictly enforced, resulting in a Portuguese expansion of Brazil across the meridian. Beginning in the 1530s, the people and natural resources of South America were repeatedly exploited by foreign conquistadors , first from Spain and later from Portugal. These competing colonial nations claimed the land and resources as their own and divided it into colonies. European infectious diseases ( smallpox , influenza , measles , and typhus ) – to which

6003-402: The mid-17th century. It became a Dutch colony in 1667. The indigenous peoples of the Americas in various European colonies were forced to work in European plantations and mines; along with enslaved Africans who were also introduced in the proceeding centuries via the slave trade . European colonists were heavily dependent on indigenous labor during the initial phases of settlement to maintain

6090-432: The neurotransmitter substance acetylcholine , rod cells use a variety. The entire process by which light initiates a sensory response is called visual phototransduction. Activation of a single unit of rhodopsin , the photosensitive pigment in rods, can lead to a large reaction in the cell because the signal is amplified. Once activated, rhodopsin can activate hundreds of transducin molecules, each of which in turn activates

6177-417: The oilbird. Some of the same families and genera of plants the present day oilbird feeds on have been found in the Green River Formation, suggesting that prehistoric species may have eaten the same fruit and spread the same seeds. Another species from the Upper Eocene has been discovered in France. This is a large, slim bird at 40–49 cm (16–19 in), with a wing span of 95 cm (37 in). It has

6264-439: The only nocturnal flying fruit-eating birds in the world (the kākāpō , also nocturnal, is flightless). They forage at night, with specially adapted eyesight. However, they navigate by echolocation in the same way as bats , one of the few birds to do so. They produce a high-pitched clicking sound of around 2 kHz that is audible to humans. Oilbirds are related to the nightjars and have sometimes been placed with these in

6351-508: The other nights roosting in trees. The scientists responsible for the discovery also found that birds roosting in caves were highly active through the night, whereas birds roosting in the forest were far less active. They hypothesised that each environment carried costs; birds roosting in the forest were more vulnerable to predators and birds roosting in caves expended considerable energy competing with rivals and defending nesting and roosting ledges. Oilbirds are colonial cave nesters. The nest

6438-516: The photoreceptor cell, the pigment changes shape. The pigment, called rhodopsin (conopsin is found in cone cells) comprises a large protein called opsin (situated in the plasma membrane), attached to which is a covalently bound prosthetic group: an organic molecule called retinal (a derivative of vitamin A ). The retinal exists in the 11-cis-retinal form when in the dark, and stimulation by light causes its structure to change to all-trans-retinal. This structural change causes an increased affinity for

6525-427: The previously open cGMP sensitive channels close, leading to a reduction in the influx of calcium ions. The associated decrease in the concentration of calcium ions stimulates the calcium ion-sensitive proteins, which then activate the guanylyl cyclase to replenish the cGMP, rapidly restoring it to its original concentration. This opens the cGMP sensitive channels and causes a depolarization of the plasma membrane. When

6612-400: The primary source of visual information at night ( scotopic vision ). Cone cells, on the other hand, require tens to hundreds of photons to become activated. Additionally, multiple rod cells converge on a single interneuron , collecting and amplifying the signals. However, this convergence comes at a cost to visual acuity (or image resolution ) because the pooled information from multiple cells

6699-465: The regulatory protein called transducin (a type of G protein). Upon binding to rhodopsin, the alpha subunit of the G protein replaces a molecule of GDP with a molecule of GTP and becomes activated. This replacement causes the alpha subunit of the G protein to dissociate from the beta and gamma subunits of the G protein. As a result, the alpha subunit is now free to bind to the cGMP phosphodiesterase (an effector protein). The alpha subunit interacts with

6786-455: The rods are exposed to a high concentration of photons for a prolonged period, they become desensitized (adapted) to the environment. As rhodopsin is phosphorylated by rhodopsin kinase (a member of the GPCR kinases (GRKs) ), it binds with high affinity to the arrestin . The bound arrestin can contribute to the desensitization process in at least two ways. First, it prevents the interaction between

6873-421: The subsequent appearance of permanent human settlements allowed for the multiple and overlapping beginnings of civilizations in South America. One of the earliest known South American civilizations was Caral–Supe , on the central Peruvian coast. Though a pre-ceramic culture, the monumental architecture of Caral–Supe created one of the first cities of the world, generally dated to around 3500 BC, at Huaricanga in

6960-411: The subsistence economy, and natives were often captured by expeditions. The importation of African slaves began midway through the 16th century, but the enslavement of indigenous peoples continued well into the 17th and 18th centuries. The Atlantic slave trade brought enslaved Africans primarily to South American colonies, beginning with the Portuguese since 1502. The main destinations of this phase were

7047-408: The synapse is not excited. Activation of photopigments by light sends a signal by hyperpolarizing the rod cell, leading to the rod cell not sending its neurotransmitter, which leads to the bipolar cell then releasing its transmitter at the bipolar-ganglion synapse and exciting the synapse. Depolarization of rod cells (causing release of their neurotransmitter) occurs because in the dark, cells have

7134-573: The western European architectural style to the continent, and helped to improve infrastructures like bridges, roads, and the sewer system of the cities they discovered or conquered. They also significantly increased economic and trade relations, not just between the old and new world but between the different South American regions and peoples. Finally, with the expansion of the Portuguese and Spanish languages, many cultures that were previously separated became united through that of Latin American. Guyana

7221-424: The wings have deep wingtip slotting, like New World vultures , to reduce the stalling speed, and the wings have a low aspect ratio and low wing-loading, all to make the oilbird capable of flying at low speeds. The eyes of oilbirds are highly adapted to nocturnal foraging. The eyes are small, but the pupils are relatively large, allowing the highest light-gathering capacity of any bird ( f-number of 1.07). The retina

7308-472: Was Chile in 1823, Uruguay in 1830, Bolivia in 1831, Guyana in 1833, Colombia and Ecuador in 1851, Argentina in 1853, Peru and Venezuela in 1854, Suriname in 1863, Paraguay in 1869, and in 1888 Brazil was the last South American nation and the last country in western world to abolish slavery. The European Peninsular War (1807–14), a theater of the Napoleonic Wars , changed the political situation of

7395-519: Was Venezuela's first national monument and is the centerpiece of a national park; according to some estimates there may be 15,000 or more birds living there. Colombia also has a national park named after its " Cueva de los Guácharos ", near the southern border with Ecuador. Oilbirds have been reported in various other places along the Andean mountain chain, including near Ecuador's Cueva de los Tayos and in Brazil : they are known to dwell as far south as

7482-689: Was a useful form of agriculture. The Mapuche in Central and Southern Chile resisted the European and Chilean settlers, waging the Arauco War for more than 300 years. In 1494, Portugal and Spain, the two great maritime European powers of that time, on the expectation of new lands being discovered in the west, signed the Treaty of Tordesillas , by which they agreed, with the support of the Pope, that all

7569-562: Was initially colonized by the Dutch before coming under British control , though there was a brief period during the Napoleonic Wars when it was occupied by the French . The region was initially partitioned between the Dutch, French and British before fully coming under the control of Britain. Suriname was first explored by the Spanish in the 16th century and then settled by the English in

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