document_title: Alternation of generations

question_text: in terms of alternation of generations the pollen grains

text: Alternation of generations

text: Definition[edit]

text: Alternation of generations is defined as the alternation of multicellular diploid and haploid forms in the organism's life cycle, regardless of whether or not these forms are free-living.[4] In some species, such as the alga Ulva lactuca, the diploid and haploid forms are indeed both free-living independent organisms, essentially identical in appearance and therefore said to be isomorphic. The free-swimming, haploid gametes form a diploid zygote which germinates into a multicellular diploid sporophyte.  The sporophyte produces free-swimming haploid spores by meiosis that germinate into haploid gametophytes.[5]

text: However, in some other groups, either the sporophyte or the gametophyte is very much reduced and is incapable of free living. For example, in all bryophytes the gametophyte generation is dominant and the sporophyte is dependent on it.  By contrast, in all modern vascular land plants the gametophytes  are strongly reduced, although the fossil evidence indicates that they were derived from isomorphic ancestors.[3] In seed plants, the female gametophyte develops totally within the sporophyte which protects and nurtures it and the embryo sporophyte that it produces. The pollen grains, which are the male gametophytes, are reduced to only a few cells (just three cells in many cases). Here the notion of two generations is less obvious; as Bateman & Dimichele say "[s]porophyte and gametophyte effectively function as a single organism".[6] The alternative term 'alternation of phases' may then be more appropriate.[7]

text: History[edit]

text: Debates about alternation of generations in the early twentieth century can be confusing because various ways of classifying "generations" co-exist (sexual vs. asexual, gametophyte vs. sporophyte, haploid vs. diploid, etc.).[8]

text: Initially, Chamisso and Steenstrup described the succession of differently organized generations (sexual and asexual) in animals as "alternation of generations", while studying the development of tunicates, cnidarians and trematode animals.[8] This phenomenon is also known as heterogamy. Presently, the term "alternation of generations" is almost exclusively associated with the life cycles of plants, specifically with the alternation of haploid gametophytes and diploid sporophytes.[8]

text: Wilhelm Hofmeister demonstrated the morphological alternation of generations in plants,[9] between a spore-bearing generation (sporophyte) and a gamete-bearing generation (gametophyte).[10][11] By that time, a debate emerged focusing on the origin of the asexual generation of land plants (i.e., the sporophyte) and is conventionally characterized as a conflict between theories of antithetic (Čelakovský, 1874) and homologous (Pringsheim, 1876) alternation of generations.[8]  Čelakovský coined the words sporophyte and gametophyte.[citation needed]

text: Eduard Strasburger (1874) discovered the alternation between diploid and haploid nuclear phases,[8] also called cytological alternation of nuclear phases.[12] Although most often coinciding, morphological alternation and nuclear phases alternation are sometimes independent of one another, e.g., in many red algae, the same nuclear phase may correspond to two diverse morphological generations.[12] In some ferns which lost sexual reproduction, there is no change in nuclear phase, but the alternation of generations is maintained.[13]

text: Alternation of generations in plants[edit]

text: Fundamental elements[edit]

text: The diagram above shows the fundamental elements of the alternation of generations in plants. The many variations found in different groups of plants are described by use of these concepts later in the article. Starting from the right of the diagram, the processes involved are as follows:[14]

text:
Two single-celled haploid gametes, each containing n unpaired chromosomes, fuse to form a single-celled diploid zygote, which now contains n pairs of chromosomes, i.e. 2n chromosomes in total.
The single-celled diploid zygote germinates, dividing by the normal process (mitosis), which maintains the number of chromosomes at 2n. The result is a multi-cellular diploid organism, called the sporophyte (because at maturity it produces spores).
When it reaches maturity, the sporophyte produces one or more sporangia (singular: sporangium) which are the organs that produce diploid spore mother cells (sporocytes). These divide by a special process (meiosis) that reduces the number of chromosomes by a half. This initially results in four single-celled haploid spores, each containing n unpaired chromosomes.
The single-celled haploid spore germinates, dividing by the normal process (mitosis), which maintains the number of chromosomes at n. The result is a multi-cellular haploid organism, called the gametophyte (because it produces gametes at maturity).
When it reaches maturity, the gametophyte produces one or more gametangia (singular: gametangium) which are the organs that produce haploid gametes. At least one kind of gamete possesses some mechanism for reaching another gamete in order to fuse with it.

tag: ul

text: The 'alternation of generations' in the life cycle is thus between a diploid (2n) generation of sporophytes and a haploid (n) generation of gametophytes.

text: The situation is quite different from that in animals, where the fundamental process is that a diploid (2n) individual directly produces haploid (n) gametes by meiosis. Spores (i.e. haploid cells which are able to undergo mitosis) are not produced, so neither is an asexual multi-cellular generation that alternates with a sexual multi-cellular generation. (Some insects have haploid males that develop from unfertilized eggs, but the females are all diploid.)

text: Variations[edit]

text: The diagram shown above is a good representation of the life cycle of some multi-cellular algae (e.g. the genus Cladophora) which have sporophytes and gametophytes of almost identical appearance and which do not have different kinds of spores or gametes.[15]

text: However, there are many possible variations on the fundamental elements of a life cycle which has alternation of generations. Each variation may occur separately or in combination, resulting in a bewildering variety of life cycles. The terms used by botanists in describing these life cycles can be equally bewildering. As Bateman and Dimichele say "[...] the alternation of generations has become a terminological morass; often, one term represents several concepts or one concept is represented by several terms."[16]

text: Possible variations are:

text:
Relative importance of the sporophyte and the gametophyte.
Equal (homomorphy or isomorphy).Filamentous algae of the genus Cladophora, which are predominantly found in fresh water, have diploid sporophytes and haploid gametophytes which are externally indistinguishable.[17] No living land plant has equally dominant sporophytes and gametophytes, although some theories of the evolution of alternation of generations suggest that ancestral land plants did.
Unequal (heteromorphy or anisomorphy). Gametophyte of Mnium hornum, a moss.
Dominant gametophyte (gametophytic).In liverworts, mosses and hornworts, the dominant form is the haploid gametophyte. The diploid sporophyte is not capable of an independent existence, gaining most of its nutrition from the parent gametophyte, and having no chlorophyll when mature.[18] Sporophyte of Blechnum discolor, a fern.
Dominant sporophyte (sporophytic).In ferns, both the sporophyte and the gametophyte are capable of living independently, but the dominant form is the diploid sporophyte. The haploid gametophyte is much smaller and simpler in structure. In seed plants, the gametophyte is even more reduced (at the minimum to only three cells), gaining all its nutrition from the sporophyte. The extreme reduction in the size of the gametophyte and its retention within the sporophyte means that when applied to seed plants the term 'alternation of generations' is somewhat misleading: "[s]porophyte and gametophyte effectively function as a single organism".[6] Some authors have preferred the term 'alternation of phases'.[7]
Differentiation of the gametes.
Both gametes the same (isogamy).Like other species of Cladophora, C. callicoma has flagellated gametes which are identical in appearance and ability to move.[17]
Gametes of two distinct sizes (anisogamy).
Both of similar motility.Species of Ulva, the sea lettuce, have gametes which all have two flagella and so are motile. However they are of two sizes: larger 'female' gametes and smaller 'male' gametes.[19]
One large and sessile, one small and motile (oogamy). The larger sessile megagametes are eggs (ova), and smaller motile microgametes are sperm (spermatozoa, spermatozoids). The degree of motility of the sperm may be very limited (as in the case of flowering plants) but all are able to move towards the sessile eggs. When (as is almost always the case) the sperm and eggs are produced in different kinds of gametangia, the sperm-producing ones are called antheridia (singular antheridium) and the egg-producing ones archegonia (singular archegonium). Gametophyte of Pellia epiphylla with sporophytes growing from the remains of archegonia.
Antheridia and archegonia occur on the same gametophyte, which is then called monoicous. (Many sources, including those concerned with bryophytes, use the term 'monoecious' for this situation and 'dioecious' for the opposite.[20][21] Here 'monoecious' and 'dioecious' are used only for sporophytes.)The liverwort Pellia epiphylla has the gametophyte as the dominant generation. It is monoicous: the small reddish sperm-producing antheridia are scattered along the midrib while the egg-producing archegonia grow nearer the tips of divisions of the plant.[22]
Antheridia and archegonia occur on different gametophytes, which are then called dioicous.The moss Mnium hornum has the gametophyte as the dominant generation. It is dioicous: male plants produce only antheridia in terminal rosettes, female plants produce only archegonia in the form of stalked capsules.[23] Seed plant gametophytes are also dioicous. However, the parent sporophyte may be monoecious, producing both male and female gametophytes or dioecious, producing gametophytes of one gender only. Seed plant gametophytes are extremely reduced in size; the archegonium consists only of a small number of cells, and the entire male gametophyte may be represented by only two cells.[24]
Differentiation of the spores.
All spores the same size (homospory or isospory).Horsetails (species of Equisetum) have spores which are all of the same size.[25]
Spores of two distinct sizes (heterospory or anisospory): larger megaspores and smaller microspores. When the two kinds of spore are produced in different kinds of sporangia, these are called megasporangia and microsporangia. A megaspore often (but not always) develops at the expense of the other three cells resulting from meiosis, which abort.
Megasporangia and microsporangia occur on the same sporophyte, which is then called monoecious.Most flowering plants fall into this category. Thus the flower of a lily contains six stamens (the microsporangia) which produce microspores which develop into pollen grains (the microgametophytes), and three fused carpels which produce integumented megasporangia (ovules) each of which produces a megaspore which develops inside the megasporangium to produce the megagametophyte. In other plants, such as hazel, some flowers have only stamens, others only carpels, but the same plant (i.e. sporophyte) has both kinds of flower and so is monoecious. Flowers of European Holly, a dioecious species: male above, female below (leaves cut to show flowers more clearly)
Megasporangia and microsporangia occur on different sporophytes, which are then called dioecious.An individual tree of the European holly (Ilex aquifolium) produces either 'male' flowers which have only functional stamens (microsporangia) producing microspores which develop into pollen grains (microgametophytes) or 'female' flowers which have only functional carpels producing integumented megasporangia (ovules) that contain a megaspore that develops into a multicellular megagametophyte.

text: There are some correlations between these variations, but they are just that, correlations, and not absolute. For example, in flowering plants, microspores ultimately produce microgametes (sperm) and megaspores ultimately produce megagametes (eggs). However, in ferns and their allies there are groups with undifferentiated spores but differentiated gametophytes. For example, the fern Ceratopteris thalictrioides has spores of only one kind, which vary continuously in size. Smaller spores tend to germinate into gametophytes which produce only sperm-producing antheridia.[25]

text: A complex life cycle[edit]

text: The diagram shows the alternation of generations in a species which is heteromorphic, sporophytic, oogametic, dioicous, heterosporic and dioecious. A seed plant example might be a willow tree (most species of the genus Salix are dioecious).[26] Starting in the centre of the diagram, the processes involved are:

text:
An immobile egg, contained in the archegonium, fuses with a mobile sperm, released from an antheridium. The resulting zygote is either 'male' or 'female'.
A 'male' zygote develops by mitosis into a microsporophyte, which at maturity produces one or more microsporangia. Microspores develop within the microsporangium by meiosis.In a willow (like all seed plants) the zygote first develops into an embryo microsporophyte within the ovule (a megasporangium enclosed in one or more protective layers of tissue known as integument). At maturity, these structures become the seed. Later the seed is shed, germinates and grows into a mature tree. A 'male' willow tree (a microsporophyte) produces flowers with only stamens, the anthers of which are the microsporangia.
Microspores germinate producing microgametophytes; at maturity one or more antheridia are produced. Sperm develop within the antheridia.In a willow,  microspores are not liberated from the anther (the microsporangium), but develop into pollen grains (microgametophytes) within it. The whole pollen grain is moved (e.g. by an insect or by the wind) to an ovule (megagametophyte), where a sperm is produced which moves down a pollen tube to reach the egg.
A 'female' zygote develops by mitosis into a megasporophyte, which at maturity produces one or more megasporangia. Megaspores develop within the megasporangium; typically one of the four spores produced by meiosis gains bulk at the expense of the remaining three, which disappear.'Female' willow trees (megasporophytes) produce flowers with only carpels (modified leaves that bear the megasporangia).
Megaspores germinate producing megagametophytes; at maturity one or more archegonia are produced. Eggs develop within the archegonia. The carpels of a willow produce ovules, megasporangia enclosed in integuments. Within each ovule, a megaspore develops by mitosis into a megagametophyte. An archegonium develops within the megagametophyte and produces an egg. The whole of the gametophytic 'generation' remains within the protection of the sporophyte except for pollen grains (which have been reduced to just three cells contained within the microspore wall).

text: Life cycles of different plant groups[edit]

text: The term "plants" is taken here to mean the Archaeplastida, i.e. the glaucophytes, red and green algae and land plants.

text: Alternation of generations occurs in almost all multicellular red and green algae, both freshwater forms (such as Cladophora) and seaweeds (such as Ulva). In most, the generations are homomorphic (isomorphic) and free-living. Some species of red algae have a complex triphasic alternation of generations, in which there is a gametophyte phase and two distinct sporophyte phases. For further information, see Red algae: Reproduction.

text: Land plants all have heteromorphic (anisomorphic) alternation of generations, in which the sporophyte and gametophyte are distinctly different. All bryophytes, i.e. liverworts, mosses and hornworts, have the gametophyte generation as the most conspicuous. As an illustration, consider a monoicous moss. Antheridia and archegonia develop on the mature plant (the gametophyte). In the presence of water, the biflagellate sperm from the antheridia swim to the archegonia and fertilisation occurs, leading to the production of a diploid sporophyte. The sporophyte grows up from the archegonium. Its body comprises a long stalk topped by a capsule within which spore-producing cells undergo meiosis to form haploid spores. Most mosses rely on the wind to disperse these spores, although Splachnum sphaericum is entomophilous, recruiting  insects to disperse its spores. For further information, see Liverwort: Life cycle, Moss: Life cycle, Hornwort: Life cycle.

text:
Diagram of alternation of generations in liverworts.

Moss life cycle diagram

Hornwort life cycle diagram

text: In ferns and their allies, including clubmosses and horsetails, the conspicuous plant observed in the field is the diploid sporophyte. The haploid spores develop in sori on the underside of the fronds and are dispersed by the wind (or in some cases, by floating on water). If conditions are right, a spore will germinate and grow into a rather inconspicuous plant body called a prothallus. The haploid prothallus does not resemble the sporophyte, and as such ferns and their allies have a heteromorphic alternation of generations. The prothallus is short-lived, but carries out sexual reproduction, producing the diploid zygote that then grows out of the prothallus as the sporophyte. For further information, see Fern: Life cycle.

text:
Diagram of alternation of generations in ferns.

A gametophyte (prothallus) of Dicksonia sp.

A sporophyte of Dicksonia antarctica.

The underside of a Dicksonia antarctica frond showing the sori, or spore-producing structures.

text: In the spermatophytes, the seed plants, the sporophyte is the dominant multicellular phase; the gametophytes are strongly reduced in size and very different in morphology. The entire gametophyte generation, with the sole exception of pollen grains (microgametophytes), is contained within the sporophyte. The life cycle of a dioecious flowering plant (angiosperm), the willow, has been outlined in some detail in an earlier section (A complex life cycle). The life cycle of a gymnosperm is similar. However, flowering plants have in addition a phenomenon called 'double fertilization'. Two sperm nuclei from a pollen grain (the microgametophyte), rather than a single sperm, enter the archegonium of the megagametophyte; one fuses with the egg nucleus to form the zygote, the other fuses with two other nuclei of the gametophyte to form 'endosperm', which nourishes the developing embryo. For further information, see Double fertilization.

text: Evolutionary emergence of the dominant diploid phase[edit]

text: It has been proposed that the basis for the emergence of the diploid phase of the life cycle (sporophyte) as the dominant phase (e.g. as in vascular plants) is that diploidy allows masking of the expression of deleterious mutations through genetic complementation.[27][28] Thus if one of the parental genomes in the diploid cells contained mutations leading to defects in one or more gene products, these deficiencies could be compensated for by the other parental genome (which nevertheless may have its own defects in other genes).  As the diploid phase was becoming predominant, the masking effect likely allowed genome size, and hence information content, to increase without the constraint of having to improve accuracy of DNA replication.  The opportunity to increase information content at low cost was advantageous because it permitted new adaptations to be encoded. This view has been challenged, with evidence showing that selection is no more effective in the haploid than in the diploid phases of the lifecycle of mosses and angiosperms.[29]

text:
Angiosperm life cycle

Tip of tulip stamen showing pollen (microgametophytes)

Plant ovules (megagametophytes): Gymnosperm ovule on left, angiosperm ovule (inside ovary) on right

Double fertilization

text: Similar processes in other organisms[edit]

text: Rhizaria[edit]

text: Some organisms currently classified in the clade Rhizaria and thus not plants in the sense used here, exhibit alternation of generations.  Foraminifera undergo a heteromorphic alternation of generations between haploid gamont and diploid agamont forms. The single-celled haploid organism is typically much larger than the diploid organism.

text: Fungi[edit]

text: Fungal mycelia are typically haploid. When mycelia of different mating types meet, they produce two multinucleate ball-shaped cells, which join via a "mating bridge". Nuclei move from one mycelium into the other, forming a heterokaryon (meaning "different nuclei"). This process is called plasmogamy. Actual fusion to form diploid nuclei is called karyogamy, and may not occur until sporangia are formed. Karogamy produces a diploid zygote, which is a short-lived sporophyte that soon undergoes meiosis to form haploid spores. When the spores germinate, they develop into new mycelia.

text: Slime moulds[edit]

text: The life cycle of slime moulds is very similar to that of fungi. Haploid spores germinate to form swarm cells or myxamoebae.  These fuse in a process referred to as plasmogamy and karyogamy to form a diploid zygote. The zygote develops into a plasmodium, and the mature plasmodium produces, depending on the species, one to many fruiting bodies containing haploid spores.

text: Animals[edit]

text: Alternation between a multicellular diploid and a multicellular haploid generation is never encountered in animals.[30] In some animals, there is an alternation between parthenogenic and sexually reproductive phases (heterogamy).  Both phases are diploid. This has sometimes been called "alternation of generations",[31] but is quite different. In some other animals, such as hymenopterans, males are haploid and females diploid, but this is always the case rather than there being an alternation between distinct generations.


document_title: Central America

question_text: largest country in central america by land area

question_tokens: largest country in central america by land area

root

text: Central America

text: Different definitions[edit]

text: "Central America" may mean different things to various people, based upon different contexts:

tag: p

text:
The United Nations geoscheme for the Americas defines the region as all states of mainland North America south of the United States and specifically includes all of Mexico.[4]
Middle America is usually thought to comprise Mexico to the north of the 7 states of Central America as well as Colombia and Venezuela to the south. Usually the whole of the Caribbean to the north-east and sometimes the Guyanas are also included.
According to one source, the term "Central America" was used as a synonym for "Middle America" at least as recently as 1962.[5]
In Ibero-America (Latin America and Iberia), the Americas is considered a single continent, and Central America is considered a subcontinent separate from North America comprising the seven countries south of Mexico and north of Colombia.[6]
In Brazil, Central America comprises all countries between Mexico and Colombia, including those in the Caribbean.
Mexico, in whole or in part, is sometimes included by British people.[7][8][9][not in citation given][10]
For the people living in the five countries formerly part of the Federal Republic of Central America there is a distinction between the Spanish language terms "América Central" and "Centroamérica". While both can be translated into English as "Central America", "América Central" is generally used to refer to the geographical area of the seven countries between Mexico and Colombia, while "Centroamérica" is used when referring to the former members of the Federation emphasizing the shared culture and history of the region.

text: History[edit]

text: In the Pre-Columbian era, the northern areas of Central America were inhabited by the indigenous peoples of Mesoamerica. Most notable among these were the Mayans, who had built numerous cities throughout the region, and the Aztecs, who had created a vast empire. The pre-Columbian cultures of eastern El Salvador, eastern Honduras, Caribbean Nicaragua, most of Costa Rica and Panama were predominantly speakers of the Chibchan languages at the time of European contact and are considered by some[11] culturally different and grouped in the Isthmo-Colombian Area.

text: Following Christopher Columbus's voyages to the Americas, the Spanish sent many expeditions to the region, and they began their conquest of Maya territory in 1523. Soon after the conquest of the Aztec Empire, Spanish conquistador Pedro de Alvarado commenced the conquest of northern Central America for the Spanish Empire. Beginning with his arrival in Soconusco in 1523, Alvarado's forces systematically conquered and subjugated most of the major Maya kingdoms, including the K'iche', Tz'utujil, Pipil, and the Kaqchikel. By 1528, the conquest of Guatemala was nearly complete, with only the Petén Basin remaining outside the Spanish sphere of influence. The last independent Maya kingdoms – the Kowoj and the Itza people – were finally defeated in 1697, as part of the Spanish conquest of Petén.[citation needed]

text: In 1538, Spain established the Real Audiencia of Panama, which had jurisdiction over all land from the Strait of Magellan to the Gulf of Fonseca. This entity was dissolved in 1543, and most of the territory within Central America then fell under the jurisdiction of the Audiencia Real de Guatemala. This area included the current territories of Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and the Mexican state of Chiapas, but excluded the lands that would become Belize and Panama. The president of the Audiencia, which had its seat in Antigua Guatemala, was the governor of the entire area. In 1609 the area became a captaincy general and the governor was also granted the title of captain general. The Captaincy General of Guatemala encompassed most of Central America, with the exception of present-day Belize and Panama.

text: The Captaincy General of Guatemala lasted for more than two centuries, but began to fray after a rebellion in 1811 which began in the intendancy of San Salvador. The Captaincy General formally ended on 15 September 1821, with the signing of the Act of Independence of Central America. Mexican independence was achieved at virtually the same time with the signing of the Treaty of Córdoba and the Declaration of Independence of the Mexican Empire, and the entire region was finally independent from Spanish authority by 28 September 1821.

text: From its independence from Spain in 1821 until 1823, the former Captaincy General remained intact as part of the short-lived First Mexican Empire. When the Emperor of Mexico abdicated on 19 March 1823, Central America again became independent. On 1 July 1823, the Congress of Central America peacefully seceded from Mexico and declared absolute independence from all foreign nations, and the region formed the Federal Republic of Central America.[citation needed]

text: The Federal Republic of Central America was a representative democracy with its capital at Guatemala City. This union consisted of the provinces of Costa Rica, El Salvador, Guatemala, Honduras, Los Altos, Mosquito Coast, and Nicaragua. The lowlands of southwest Chiapas, including Soconusco, initially belonged to the Republic until 1824, when Mexico annexed most of Chiapas and began its claims to Soconusco. The Republic lasted from 1823 to 1838, when it disintegrated as a result of civil wars.[citation needed]

text:
Historic Coat of Arms of Central American Unions

The United Providences of Central America

United Provinces of Central America

Federal Republic of Central America

Greater Republic of Central America

text:
Coat of Arms of modern Central America

Guatemala

El Salvador

Honduras

Nicaragua

Costa Rica

Panama

Belize

text: The territory that now makes up Belize was heavily contested in a dispute that continued for decades after Guatemala achieved independence (see History of Belize (1506–1862). Spain, and later Guatemala, considered this land a Guatemalan department. In 1862, Britain formally declared it a British colony and named it British Honduras. It became independent as Belize in 1981.[citation needed]

text: Panama, situated in the southernmost part of Central America on the Isthmus of Panama, has for most of its history been culturally linked to South America. Panama was part of the Province of Tierra Firme from 1510 until 1538 when it came under the jurisdiction of the newly formed Audiencia Real de Panama. Beginning in 1543, Panama was administered as part of the Viceroyalty of Peru, along with all other Spanish possessions in South America. Panama remained as part of the Viceroyalty of Peru until 1739, when it was transferred to the Viceroyalty of New Granada, the capital of which was located at Santa Fé de Bogotá. Panama remained as part of the Viceroyalty of New Granada until the disestablishment of that viceroyalty in 1819. A series of military and political struggles took place from that time until 1822, the result of which produced the republic of Gran Colombia. After the dissolution of Gran Colombia in 1830, Panama became part of a successor state, the Republic of New Granada. From 1855 until 1886, Panama existed as Panama State, first within the Republic of New Granada, then within the Granadine Confederation, and finally within the United States of Colombia. The United States of Colombia was replaced by the Republic of Colombia in 1886. As part of the Republic of Colombia, Panama State was abolished and it became the Isthmus Department. Despite the many political reorganizations, Colombia was still deeply plagued by conflict, which eventually led to the secession of Panama on 3 November 1903. Only after that time did some begin to regard Panama as a North or Central American entity.[citation needed]

text: By the 1930s the United Fruit Company owned 3.5 million acres of land in Central America and the Caribbean and was the single largest land owner in Guatemala. Such holdings gave it great power over the governments of small countries. That was one of the factors that led to the coining of the phrase Banana Republic.[12]

text: After more than two hundred years of social unrest, violent conflict and revolution, Central America today remains in a period of political transformation. Poverty, social injustice and violence are still widespread.[13] Nicaragua is the second poorest country in the western hemisphere (only Haiti is poorer).[14]

text: Geography[edit]

text: Central America is the tapering isthmus of southern North America, with unique and varied geographic features. The Pacific Ocean lies to the southwest, the Caribbean Sea lies to the northeast, and the Gulf of Mexico lies to the north. Some physiographists define the Isthmus of Tehuantepec as the northern geographic border of Central America,[7] while others use the northwestern borders of Belize and Guatemala. From there, the Central American land mass extends southeastward to the Isthmus of Panama, where it connects to the Pacific Lowlands in northwestern South America.

text: Of the many mountain ranges within Central America, the longest are the Sierra Madre de Chiapas, the Cordillera Isabelia and the Cordillera de Talamanca. At 4,220 meters (13,850 ft), Volcán Tajumulco is the highest peak in Central America. Other high points of Central America are as listed in the table below:

text: High points in Central America

text:
Country
Name
Elevation (meters)
Range

 Belize
Doyle's Delight
1124
Cockscomb Range

 Costa Rica
Cerro Chirripó
3820
Cordillera de Talamanca

 El Salvador
Cerro El Pital
2730
Sierra Madre de Chiapas

 Guatemala
Volcán Tajumulco
4220
Sierra Madre de Chiapas

 Honduras
Cerro Las Minas
2780
Cordillera de Celaque

 Nicaragua
Mogotón
2107
Cordillera Isabelia

 Panama
Volcán Barú
3474
Cordillera de Talamanca

tag: table

text: Between the mountain ranges lie fertile valleys that are suitable for the raising of livestock and for the production of coffee, tobacco, beans and other crops. Most of the population of Honduras, Costa Rica and Guatemala lives in valleys.[15]

text: Trade winds have a significant effect upon the climate of Central America. Temperatures in Central America are highest just prior to the summer wet season, and are lowest during the winter dry season, when trade winds contribute to a cooler climate. The highest temperatures occur in April, due to higher levels of sunlight, lower cloud cover and a decrease in trade winds.[16]

text: Biodiversity[edit]

text: Central America is part of the Mesoamerican biodiversity hotspot, boasting 7% of the world's biodiversity.[17] The Pacific Flyway is a major north-south flyway for migratory birds in the Americas, extending from Alaska to Tierra del Fuego. Due to the funnel-like shape of its land mass, migratory birds can be seen in very high concentrations in Central America, especially in the spring and autumn. As a bridge between North America and South America, Central America has many species from the Nearctic and the Neotropic ecozones. However the southern countries (Costa Rica and Panama) of the region have more biodiversity than the northern countries (Guatemala and Belize), meanwhile the central countries (Honduras, Nicaragua and El Salvador) have the least biodiversity.[17] The table below shows recent statistics:

text: Biodiversity in Central America (number of different species of terrestrial vertebrate animals and vascular plants)

text:
Country
Amphibian
species
Bird
species
Mammal
species
Reptile
species
Total terrestrial
vertebrate species
Vascular plants
species
Biodiversity

 Belize[18]
46
544
147
140
877
2894
3771

 Costa Rica[19]
183
838
232
258
1511
12119
13630

 El Salvador[20]
30
434
137
106
707
2911
3618

 Guatemala[21]
133
684
193
236
1246
8681
9927

 Honduras[22]
101
699
201
213
1214
5680
6894

 Nicaragua[23]
61
632
181
178
1052
7590
8642

 Panama[24]
182
904
241
242
1569
9915
11484

text: Over 300 species of the region's flora and fauna are threatened, 107 of which are classified as critically endangered. The underlying problems are deforestation, which is estimated by FAO at 1.2% per year in Central America and Mexico combined, fragmentation of rainforests and the fact that 80% of the vegetation in Central America has already been converted to agriculture.[25]

text: Efforts to protect fauna and flora in the region are made by creating ecoregions and nature reserves. 36% of Belize's land territory falls under some form of official protected status, giving Belize one of the most extensive systems of terrestrial protected areas in the Americas. In addition, 13% of Belize's marine territory are also protected.[26] A large coral reef extends from Mexico to Honduras: the Mesoamerican Barrier Reef System. The Belize Barrier Reef is part of this. The Belize Barrier Reef is home to a large diversity of plants and animals, and is one of the most diverse ecosystems of the world. It is home to 70 hard coral species, 36 soft coral species, 500 species of fish and hundreds of invertebrate species. So far only about 10% of the species in the Belize barrier reef have been discovered.[27]

text: Flora[edit]

text: From 2001 to 2010, 5,376 square kilometers (2,076 sq mi) of forest were lost in the region. In 2010 Belize had 63% of remaining forest cover, Costa Rica 46%, Panama 45%, Honduras 41%, Guatemala 37%, Nicaragua 29%, and El Salvador 21%. Most of the loss occurred in the moist forest biome, with 12,201 square kilometers (4,711 sq mi). Woody vegetation loss was partially set off by a gain in the coniferous forest biome with 4,730 square kilometers (1,830 sq mi), and a gain in the dry forest biome at 2,054 square kilometers (793 sq mi). Mangroves and deserts contributed only 1% to the loss in forest vegetation. The bulk of the deforestation was located at the Caribbean slopes of Nicaragua with a loss of 8,574 square kilometers (3,310 sq mi) of forest in the period from 2001 to 2010. The most significant regrowth of 3,050 square kilometers (1,180 sq mi) of forest was seen in the coniferous woody vegetation of Honduras.[28]

text: The Central American pine-oak forests ecoregion, in the tropical and subtropical coniferous forests biome, is found in Central America and southern Mexico. The Central American pine-oak forests occupy an area of 111,400 square kilometers (43,000 sq mi),[29] extending along the mountainous spine of Central America, extending from the Sierra Madre de Chiapas in Mexico's Chiapas state through the highlands of Guatemala, El Salvador, and Honduras to central Nicaragua. The pine-oak forests lie between 600–1,800 metres (2,000–5,900 ft) elevation,[29] and are surrounded at lower elevations by tropical moist forests and tropical dry forests. Higher elevations above 1,800 metres (5,900 ft) are usually covered with Central American montane forests. The Central American pine-oak forests are composed of many species characteristic of temperate North America including oak, pine, fir, and cypress.

text: Laurel forest is the most common type of Central American temperate evergreen cloud forest, found in almost all Central American countries, normally more than 1,000 meters (3,300 ft) above sea level. Tree species include evergreen oaks, members of the laurel family, and species of Weinmannia, Drimys, and Magnolia.[30] The cloud forest of Sierra de las Minas, Guatemala, is the largest in Central America. In some areas of southeastern Honduras there are cloud forests, the largest located near the border with Nicaragua. In Nicaragua, cloud forests are situated near the border with Honduras, but many were cleared to grow coffee. There are still some temperate evergreen hills in the north. The only cloud forest in the Pacific coastal zone of Central America is on the Mombacho volcano in Nicaragua. In Costa Rica, there are laurel forests in the Cordillera de Tilarán and Volcán Arenal, called Monteverde, also in the Cordillera de Talamanca.

text: The Central American montane forests are an ecoregion of the tropical and subtropical moist broadleaf forests biome, as defined by the World Wildlife Fund.[31] These forests are of the moist deciduous and the semi-evergreen seasonal subtype of tropical and subtropical moist broadleaf forests and receive high overall rainfall with a warm summer wet season and a cooler winter dry season. Central American montane forests consist of forest patches located at altitudes ranging from 1,800–4,000 metres (5,900–13,100 ft), on the summits and slopes of the highest mountains in Central America ranging from Southern Mexico, through Guatemala, El Salvador, and Honduras, to northern Nicaragua. The entire ecoregion covers an area of 13,200 square kilometers (5,100 sq mi) and has a temperate climate with relatively high precipitation levels.[31]

text: Fauna[edit]

text: Ecoregions are not only established to protect the forests themselves but also because they are habitats for an incomparably rich and often endemic fauna. Almost half of the bird population of the Talamancan montane forests in Costa Rica and Panama are endemic to this region. Several birds are listed as threatened, most notably the resplendent quetzal (Pharomacrus mocinno), three-wattled bellbird (Procnias tricarunculata), bare-necked umbrellabird (Cephalopterus glabricollis), and black guan (Chamaepetes unicolor). Many of the amphibians are endemic and depend on the existence of forest. The golden toad that once inhabited a small region in the Monteverde Reserve, which is part of the Talamancan montane forests, has not been seen alive since 1989 and is listed as extinct by IUCN. The exact causes for its extincition are unknown. Global warming may have played a role, because the development of fog that is typical for this area may have been compromised. Seven small mammals are endemic to the Costa Rica-Chiriqui highlands within the Talamancan montane forest region. Jaguars, cougars, spider monkeys, as well as tapirs, and anteaters live in the woods of Central America.[30] The Central American red brocket is a brocket deer found in Central America's tropical forest.

text: Geology[edit]

text: Central America is geologically very active, with volcanic eruptions and earthquakes occurring frequently, and tsunamis occurring occasionally. Many thousands of people have died as a result of these natural disasters.

text: Most of Central America rests atop the Caribbean Plate. This tectonic plate converges with the Cocos, Nazca, and North American plates to form the Middle America Trench, a major subduction zone. The Middle America Trench is situated some 60–160 kilometers (37–99 mi) off the Pacific coast of Central America and runs roughly parallel to it. Many large earthquakes have occurred as a result of seismic activity at the Middle America Trench.[32] For example, subduction of the Cocos Plate beneath the North American Plate at the Middle America Trench is believed to have caused the 1985 Mexico City earthquake that killed as many as 40,000 people. Seismic activity at the Middle America Trench is also responsible for earthquakes in 1902, 1942, 1956, 1982, 1992, 2001, 2007, 2012, 2014, and many other earthquakes throughout Central America.

text: The Middle America Trench is not the only source of seismic activity in Central America. The Motagua Fault is an onshore continuation of the Cayman Trough which forms part of the tectonic boundary between the North American Plate and the Caribbean Plate. This transform fault cuts right across Guatemala and then continues offshore until it merges with the Middle America Trench along the Pacific coast of Mexico, near Acapulco. Seismic activity at the Motagua Fault has been responsible for earthquakes in 1717, 1773, 1902, 1976, 1980, and 2009.

text: Another onshore continuation of the Cayman Trough is the Chixoy-Polochic Fault, which runs parallel to, and roughly 80 kilometers (50 mi) to the north, of the Motagua Fault. Though less active than the Motagua Fault, seismic activity at the Chixoy-Polochic Fault is still thought to be capable of producing very large earthquakes, such as the 1816 earthquake of Guatemala.[33]

text: Managua, the capital of Nicaragua, was devastated by earthquakes in 1931 and 1972.

text: Volcanic eruptions are also common in Central America. In 1968 the Arenal Volcano, in Costa Rica, erupted killing 87 people as the 3 villages of Tabacon, Pueblo Nuevo and San Luis were buried under pyroclastic flows and debris. Fertile soils from weathered volcanic lava have made it possible to sustain dense populations in the agriculturally productive highland areas.

text: Demographics[edit]

text: The population of Central America is estimated at 47,448,333 as of 2016.[34] With an area of 523,780 square kilometers (202,230 sq mi),[2] it has a population density of 81 per square kilometer (210/sq mi).

text:
Countries of Central America

Name of territory,
with flag
Area
(km²)[35]
Population
(2016 est.)[34]
Population
density
(per km²)
Capital
Official
language
Human Development Index

 Belize
7004229660000000000♠22,966
366,954
7001130000000000000♠13
Belmopan
English
0,715 High

 Costa Rica
7004511000000000000♠51,100
4,857,274
7001820000000000000♠82
San José
Spanish
0,766 High

 El Salvador
7004210400000000000♠21,040
6,344,722
7002292000000000000♠292
San Salvador
Spanish
0,666 Medium

 Guatemala
7005108890000000000♠108,890
16,582,469
7002129000000000000♠129
Guatemala City
Spanish
0,627 Medium

 Honduras
7005112090000000000♠112,090
9,112,867
7001670000000000000♠67
Tegucigalpa
Spanish
0,606 Medium

 Nicaragua
7005130373000000000♠130,373
6,149,928
7001440000000000000♠44
Managua
Spanish
0,631 Medium

 Panama
7004782000000000000♠78,200
4,034,119
7001440000000000000♠44
Panama City
Spanish
0,780 High

Total
7005523780000000000♠523,780
7007474483330000000♠47,448,333
7001800000000000000♠80
-
-
-

text:
Largest metropolitan areas in Central America

City
Country
Population
Census Year
% of National
population

(1) Guatemala City
 Guatemala
5,700,000
2010
26%

(2) San Salvador
 El Salvador
2,415,217
2009
39%

(3) Managua
 Nicaragua
1,918,000
2012
34%

(4) Tegucigalpa
 Honduras
1,819,000
2010
24%

(5) San Pedro Sula
 Honduras
1,600,000
2010
21%+4

(6) Panama City
 Panama
1,400,000
2010
37%

(7) San José
 Costa Rica
1,275,000
2013
30%

text: Languages[edit]

text: The official language majority in all Central American countries is Spanish, except in Belize, where the official language is English. Mayan languages constitute a language family consisting of about 26 related languages. Guatemala formally recognized 21 of these in 1996. Xinca and Garifuna are also present in Central America.

text:
Languages in Central America (2010)

Pos.
Countries
Population
% Spanish
% Mayan languages
% English
% Xinca
% Garifuna

1
Guatemala
17,284,000
64.7%
34.3%
0.0%
0.7%
0.3%

2
Honduras
8,447,000
97.1%
2.0%
0.0%
0.0%
0.9%

3
El Salvador
6,108,000
99.0%
1.0%
0.0%
0.0%
0.0%

4
Nicaragua
6,028,000
87.4%
7.1%
5.5%
0.0%
0.0%

5
Costa Rica
4,726,000
97.2%
1.8%
1.0%
0.0%
0.0%

6
Panamá
3,652,000
86.8%
9.2%
4.0%
0.0
0.0%

7
Belize
334,000
52.1%
8.9%
37.0%
0.0%
2.0%

text: Ethnic groups[edit]

text: This region of the continent is very rich in terms of ethnic groups. The majority of the population is mestizo, with sizable Mayan and White populations present, including Xinca and Garifuna minorities. The immigration of Arabs, Jews, Chinese, Europeans and others brought additional groups to the area.

text:
Ethnic groups in Central America (2010)

Country
Population1
% Amerindian
% White
% Mestizo/Mixed
% Black
% Other

 Belize
324,528
6.3%
5.0%
49.6%
32.0%
4.1%

 Costa Rica
4,301,712
4.0%
65.8%
13.8%
7.2%
9.0%

 El Salvador
6,340,889
1.0%
12.0%
86.0%
0.0%
1.0%

 Guatemala
15,700,000
38.5%
18.5%
40.0%
1.0%
2.0%

 Honduras
8,143,564
6.0%
5.5%
82.0%
6.0%
0.5%

 Nicaragua
5,815,500
5.0%
17.0%
69.0%
9.0%
0.0%

 Panama
3,474,562
6.0%
10.0%
65.0%
14.0%
5.0%

Total
42,682,190
16.24%
20.18%
58.05%
4.43%
1.17%

text: Religious groups[edit]

text: The predominant religion in Central America is Christianity (95.6%).[36] Beginning with the Spanish colonization of Central America in the 16th century, Roman Catholicism became the most popular religion in the region until the first half of the 20th century. Since the 1960s, there has been an increase in other Christian groups, particularly Protestantism, as well as other religious organizations, and individuals identifying themselves as having no religion.[37]

text:
Countries
% Roman Catholicism
(2010)
% Protestantism
(2010)
% Non-affiliated
(2010)
% Other
(2010)

 Belize
40%
31%
15%
14%

 Costa Rica
69%
17%
11%
3%

 El Salvador
46%
29%
24%
1%

 Guatemala
47%
39%
12%
2%

 Honduras
52%
35%
10%
3%

 Nicaragua
58%
23%
13%
4%

 Panama
77%
14%
6%
3%

text: Culture[edit]

text:
Central American music
Central American cuisine
List of cuisines of the Americas – Central American cuisine

text: Sport[edit]

text:
Central American Games
Central American and Caribbean Games

1926 Central American and Caribbean Games – the first time this event occurred

Central American Football Union
Surfing

text: Politics[edit]

text: Central American Integration[edit]

text:
Central American
Integration System
Sistema de
Integración Centroamericana

Coat of arms

Motto(s): "Peace, Development, Liberty and Democracy"

Anthem: La Granadera

Countries

 Belize
 Costa Rica
 El Salvador
 Guatemala
 Honduras
 Nicaragua
 Panama
 Dominican Republic

Area

 • Total
560,988 km2 (216,599 sq mi)

Population

 • Total
50,807,778

 • Density
91/km2 (230/sq mi)

text: Central America is currently undergoing a process of political, economic and cultural transformation that started in 1907 with the creation of the Central American Court of Justice.

text: In 1951 the integration process continued with the signature of the San Salvador Treaty, which created the ODECA, the Organization of Central American States. However, the unity of the ODECA was limited by conflicts between several member states.

text: In 1991, the integration agenda was further advanced by the creation of the Central American Integration System (Sistema para la Integración Centroamericana, or SICA). SICA provides a clear legal basis to avoid disputes between the member states. SICA membership includes the 7 nations of Central America plus the Dominican Republic, a state that is traditionally considered part of the Caribbean.

text:
Central American flags

Guatemala

El Salvador

Honduras

Nicaragua

Costa Rica

Panama

Belize

text: On 6 December 2008 SICA announced an agreement to pursue a common currency and common passport for the member nations.[citation needed] No timeline for implementation was discussed.

text: Central America already has several supranational institutions such as the Central American Parliament, the Central American Bank for Economic Integration and the Central American Common Market.

text: On 22 July 2011 President Mauricio Funes of El Salvador became the first president pro tempore to SICA. El Salvador also became the headquarters of SICA with the inauguration of a new building.[38]

text: Foreign relations[edit]

text: Until recently, all Central American countries have maintained diplomatic relations with Taiwan instead of China. President Óscar Arias of Costa Rica, however, established diplomatic relations with China in 2007, severing formal diplomatic ties with Taiwan.[39] After breaking off relations with the Republic of China in 2017, Panama established diplomatic relations with the People's Republic of China.[40]

text: Central American Parliament[edit]

text: The Central American Parliament (also known as PARLACEN) is a political and parliamentary body of SICA. The parliament started around 1980, and its primary goal was to resolve conflicts in Nicaragua, Guatemala, and El Salvador. Although the group was disbanded in 1986, ideas of unity of Central Americans still remained, so a treaty was signed in 1987 to create the Central American Parliament and other political bodies. Its original members were Guatemala, El Salvador, Nicaragua and Honduras. The parliament is the political organ of Central America, and is part of SICA. New members have since then joined including Panama and the Dominican Republic.

text: Economy[edit]

text: Signed in 2004, the Central American Free Trade Agreement (CAFTA) is an agreement between the United States, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and the Dominican Republic. The treaty is aimed at promoting free trade among its members.

text: Guatemala has the largest economy in the region.[41][42] Its main exports are coffee, sugar, bananas, petroleum, clothing, and cardamom. Of its 10.29 billion dollar annual exports,[43] 40.2% go to the United States, 11.1% to neighboring El Salvador, 8% to Honduras, 5.5% to Mexico, 4.7% to Nicaragua, and 4.3% to Costa Rica.[44]

text: Economic growth in Central America is projected to slow slightly in 2014–15, as country-specific domestic factors offset the positive effects from stronger economic activity in the United States.[9]

text:
Economy size for Latin American countries per Gross domestic product

Country
GDP (nominal)[41][a]
GDP (nominal) per capita[45][46]
GDP (PPP)[42][a]

 Belize
1,552
$4,602
2,914

 Costa Rica
44,313
$10,432
57,955

 El Salvador
24,421
$3,875
46,050

 Guatemala
50,303
$3,512
78,012

 Honduras
18,320
$2,323
37,408

 Nicaragua
7,695
$1,839
19,827

 Panama
34,517
$10,838
55,124

text: Tourism[edit]

text: Tourism in Belize has grown considerably in more recent times, and it is now the second largest industry in the nation. Belizean Prime Minister Dean Barrow has stated his intention to use tourism to combat poverty throughout the country.[47] The growth in tourism has positively affected the agricultural, commercial, and finance industries, as well as the construction industry. The results for Belize's tourism-driven economy have been significant, with the nation welcoming almost one million tourists in a calendar year for the first time in its history in 2012.[48] Belize is also the only country in Central America with English as its official language, making this country a comfortable destination for English-speaking tourists.[49]

text: Costa Rica is the most visited nation in Central America.[50] Tourism in Costa Rica is one of the fastest growing economic sectors of the country,[51] having become the largest source of foreign revenue by 1995.[52] Since 1999, tourism has earned more foreign exchange than bananas, pineapples and coffee exports combined.[53] The tourism boom began in 1987,[52] with the number of visitors up from 329,000 in 1988, through 1.03 million in 1999, to a historical record of 2.43 million foreign visitors and $1.92-billion in revenue in 2013.[50] In 2012 tourism contributed with 12.5% of the country's GDP and it was responsible for 11.7% of direct and indirect employment.[54]

text: Tourism in Nicaragua has grown considerably recently, and it is now the second largest industry in the nation. Nicaraguan President Daniel Ortega has stated his intention to use tourism to combat poverty throughout the country.[55] The growth in tourism has positively affected the agricultural, commercial, and finance industries, as well as the construction industry. The results for Nicaragua's tourism-driven economy have been significant, with the nation welcoming one million tourists in a calendar year for the first time in its history in 2010.[56]

text: Transport[edit]

text: Roads[edit]

text: The Inter-American Highway is the Central American section of the Pan-American Highway, and spans 5,470 kilometers (3,400 mi) between Nuevo Laredo, Mexico, and Panama City, Panama. Because of the 87 kilometers (54 mi) break in the highway known as the Darién Gap, it is not possible to cross between Central America and South America in an automobile.

text: Waterways[edit]

text: Ports and harbors[edit]

text: Airports[edit]

text: Railways[edit]

text: Education[edit]

text:
List of Architecture schools in Central America
List of universities in Belize
List of universities in Costa Rica
List of universities in El Salvador
List of universities in Guatemala
List of universities in Honduras
List of universities in Nicaragua
List of universities in Panama


document_title: Einthoven's triangle

question_text: where is the positive electrode placed in lead iii

text: Einthoven's triangle

text: Einthoven's triangle is an imaginary formation of three limb leads in a triangle used in electrocardiography, formed by the two shoulders and the pubis.[1] The shape forms an inverted equilateral triangle with the heart at the center that produces zero potential when the voltages are summed. It is named after Willem Einthoven, who theorized its existence.[2]

text: Einthoven used these measuring points, by immersing the hands and foot in pails of salt water, as the contacts for his string galvanometer, the first practical ECG machine.[3]

text: Lead placements[edit]

text: Lead I — This axis goes from shoulder to shoulder, with the negative electrode placed on the right shoulder and the positive electrode placed on the left shoulder. This results in a 0 degree angle of orientation.[4]

text: Lead II — This axis goes from the right arm to the left leg, with the negative electrode on the shoulder and the positive one on the leg. This results in a +60 degree angle of orientation.[4]

text: Lead III — This axis goes from the left shoulder (negative electrode) to the right or left leg (positive electrode). This results in a +120 degree angle of orientation.[4]

text: Electrodes may be placed distally or proximally on the limb without affecting the recording.[5] The leg electrode acts as a grounding lead, and either the right or left leg can be used as a grounding lead without an effect on the ECG results.[6]

text: Each lead measures the electric field created by the heart during the depolarization and repolarization of myocytes. The electric field can be represented as a vector that changes continuously and can be measured by recording the voltage difference between electrodes.[7]

text: Using Einthoven's triangle to identify lead misplacements[edit]

text: Though Einthoven's triangle is no longer used in contemporary ECGs, Einthoven's triangle can be helpful in the identification in incorrect placement of leads. (Incorrect placement of leads can lead to error in the recording, which can ultimately lead to misdiagnosis.)

text: If the arm electrodes are reversed, lead I changes polarity, causing lead II and lead III to switch. If the right arm electrode is reversed with the leg's electrode, lead II changes polarity, causing lead I to become lead III, and vice versa. Reversal of the left arm and leg causes a change in polarity of lead III and switching of leads I and II.[6]


document_title: No man is an island

question_text: who wrote the book no man is an island

question_tokens: who wrote the book no man is an island

text: No man is an island

text: Look up no man is an island in Wiktionary, the free dictionary.

text: No man is an island may refer to:

text:
"No man is an island", a famous line from Devotions upon Emergent Occasions, a 1624 prose work by English poet John Donne
No Man Is an Island (film)
No Man is an Island (album), the 1972 debut album from reggae singer Dennis Brown
"No Man Is an Island", a 1955 book by the Trappist monk Thomas Merton
"No Man Is an Island", a 1953 episode of the Hallmark Hall of Fame, about the life of John Donne
"No Man Is an Island", a 1964 song by vocal group The Van Dykes
"No Man Is an Island", a song by Tenth Avenue North
"No Man Is an Island" (The Script song), from the album Freedom Child
Nomanisan Island, a place in the 2004 film The Incredibles

text:
This disambiguation page lists articles associated with the title No man is an island.
If an internal link led you here, you may wish to change the link to point directly to the intended article.

text: Disambiguation pages

text: All article disambiguation pagesAll disambiguation pages


document_title: Videocassette recorder

question_text: when did the first video recorder come out

question_tokens: when did the first video recorder come out

text: Videocassette recorder

text: History[edit]

text: Early machines and formats[edit]

text: The history of the videocassette recorder follows the history of videotape recording in general. In 1953, Dr. Norikazu Sawazaki developed a prototype helical scan video tape recorder.[1]

text: Ampex introduced the Quadruplex videotape professional broadcast standard format with its Ampex VRX-1000 in 1956. It became the world's first commercially successful videotape recorder using two-inch (5.1 cm)  wide tape.[2] Due to its high price of US$50,000, the Ampex VRX-1000 could be afforded only by the television networks and the largest individual stations.[3][4][5]

text: In 1959, Toshiba introduced a "new" method of recording known as helical scan, releasing the first commercial helical scan video tape recorder that year.[6] It was first implemented in reel-to-reel videotape recorders (VTRs), and later used with cassette tapes.

text: In 1963 Philips introduced their EL3400 1-inch helical scan recorder, aimed at the business and domestic user, and Sony marketed the 2" PV-100, their first reel-to-reel VTR, intended for business, medical, airline, and educational use.[7]

text: First home video recorders[edit]

text: The Telcan, produced by the UK Nottingham Electronic Valve Company in 1963, was the first home video recorder. It could be bought as a unit or in kit form for £60, equivalent to approximately £1,100 (over US$1,600) in 2014 currency. However, there were several drawbacks: it was expensive, was not easy to assemble, and could only record 20 minutes at a time. It recorded in black-and-white, the only format available in the UK at the time.[8][9][10]

text: The half-inch tape Sony model CV-2000, first marketed in 1965, was their first VTR intended for home use.[11] Ampex and RCA followed in 1965 with their own reel-to-reel monochrome VTRs priced under US$1,000 for the home consumer market.

text: The EIAJ format was a standard half-inch format used by various manufacturers. EIAJ-1 was an open-reel format. EIAJ-2 used a cartridge that contained a supply reel; the take-up reel was part of the recorder, and the tape had to be fully rewound before removing the cartridge, a slow procedure.

text: The development of the videocassette followed the replacement by cassette of other open reel systems in consumer items: the Stereo-Pak four-track audio cartridge in 1962, the compact audio cassette  and Instamatic film cartridge in 1963, the 8-track cartridge in 1965, and the Super 8 home movie cartridge in 1966.[citation needed]

text: In 1972, videocassettes of movies became available for home use.[12]

text: Sony U-matic[edit]

text: Sony demonstrated a videocassette prototype in October 1969, then set it aside to work out an industry standard by March 1970 with seven fellow manufacturers. The result, the Sony U-matic system, introduced in Tokyo in September 1971, was the world's first commercial videocassette format. Its cartridges, resembling larger versions of the later VHS cassettes, used 3/4-inch (1.9 cm) tape and had a maximum playing time of 60 minutes, later extended to 80 minutes. Sony also introduced two machines (the VP-1100 videocassette player and the VO-1700, also called the VO-1600 video-cassette recorder) to use the new tapes. U-matic, with its ease of use, quickly made other consumer videotape systems obsolete in Japan and North America, where U-matic VCRs were widely used by television newsrooms (Sony BVU-150 and Trinitron DXC 1810 video camera) schools and businesses. But the high cost - US$1,395 in 1971 for a combination TV/VCR, equivalent to over $8000 in 2014 dollars – kept it out of most homes.[13]

text: Philips "VCR" format[edit]

text: In 1970, Philips developed a home video cassette format specially made for a TV station in 1970 and available on the consumer market in 1972. Philips named this format "Video Cassette Recording" (although it is also referred to as "N1500", after the first recorder's model number).[14]

text: The format was also supported by Grundig and Loewe. It used square cassettes and half-inch (1.3 cm) tape, mounted on coaxial reels, giving a recording time of one hour. The first model, available in the United Kingdom in 1972, was equipped with a simple timer that used rotary dials. At nearly £600, it was expensive and the format was relatively unsuccessful in the home market. This was followed by a digital timer version in 1975, the N1502. In 1977 a new, incompatible, long-play version ("VCR-LP") or N1700, which could use the same blank tapes, sold quite well to schools and colleges.

text: Avco Cartrivision[edit]

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text: The Avco Cartrivision system, a combination television set and VCR from Cartridge Television Inc. that sold for US$1,350, was the first videocassette recorder to have pre-recorded tapes of popular movies available for rent. Like the Philips VCR format, the square Cartrivision cassette had the two reels of half-inch tape mounted on top of each other, but it could record up to 114 minutes, using an early form of video format that recorded every other video field and played it back three times.

text: Cassettes of major movies such as The Bridge on the River Kwai and Guess Who's Coming to Dinner were ordered via catalog at a retailer, delivered by parcel mail, and then returned to the retailer after viewing. Other cassettes on sports, travel, art, and how-to topics were available for purchase. An optional monochrome camera could be bought to make home videos. Cartrivision was first sold in June 1972, mainly through Sears, Macy's, and Montgomery Ward department stores in the United States. The system was abandoned thirteen months later after poor sales.

text: Mass-market success[edit]

text: VCR started gaining mass market traction in 1975.  Six major firms were involved in the development of the VCR: RCA, JVC, AMPEX, Matsushita Electric / Panasonic, Sony, and Toshiba.  Of these, the big winners in the growth of this industry were Japanese companies Matsushita Electric / Panasonic, JVC, and Sony, which developed more technically advanced machines with more accurate electronic timers and greater tape duration. The VCR started to become a mass market consumer product; by 1979 there were three competing technical standards using mutually incompatible tape cassettes.

text: The industry boomed in the 1980s as more and more customers bought VCRs. By 1982, 10% of households in the United Kingdom owned a VCR. The figure reached 30% in 1985 and by the end of the decade well over half of British homes owned a VCR.[15]

text: Earlier machines used mechanically-operated control switches; these were replaced by microswitches, solenoids and motor-driven mechanisms.

text: VHS vs. Betamax[edit]

text: The two major standards were Sony's Betamax (also known as Betacord or just Beta), and JVC's VHS (Video Home System), which competed for sales in what became known as the format war.[16]

text: Betamax was first to market in November 1975, and was argued by many to be technically more sophisticated in recording quality,[17] although many users did not perceive a visual difference. The first machines required an external timer, and could only record one hour, or two hours at lower quality (LP).  The timer was later incorporated within the machine as a standard feature.

text: The rival VHS format, introduced in Japan by JVC in September 1976, introduced in the United States in July 1977 by RCA, had a longer two-hour recording time with a T-120 tape, or four hours in lower-quality "long play" mode (RCA SelectaVision models, introduced in September 1977).

text: In 1978 the majority of consumers in the U.K. chose to rent rather than purchase this new expensive home entertainment technology[citation needed]. JVC introduced the HR3300 model[18] with E-30, E-60, (E-120 VHS-1 1976), E-180 minute cassette tapes with up to three hours=(VHS-2 1977)) recording time, a thinner 4 hour length (E240 tape VHS-3 1981) soon followed (E-400 VHS-5 last edition 1999).

text: The rental market was a contributing factor for acceptance of the VHS, for a variety of reasons. In those pre-digital days TV broadcasters could not offer the wide choice of a rental store, and tapes could be played as often as desired. Material was available on tape with violent or sexual scenes not available on broadcasts. Home video cameras allowed tapes to be recorded and played back.

text: Two hours and 4 hours recording times were considered enough for recording movies and sports. Although Sony later introduced L-500 (2 hour) and L-750 (3 hour) Betamax tapes in addition to the L-250 (1 hour) tape, the consumer market had swiftly moved toward the VHS system as a preferred choice. During the 1980s dual-speed (long play) models of both Beta and VHS recorders were introduced, allowing much longer recording times. The recording length on World Wide Standard on consumer video recorders (VHS) Was 8hrs with PAL colour encoding and 5hs-46mins with NTSC color encoding. The total recording length on The World Wide Standard On Professional Broadcasting (Betamax) was 3hrs 35mins on PAL colour configuration, and 5hrs on NTSC color configuration[citation needed][clarification needed].

text: Longer tapes became available a few years later, extending to 10hrs and then 12hrs LP on PAL (Europe) and 7hrs 50mins and then further extended with VHS-5 (Final edition of the Video Home System) in 1999 TO 8hrs 16mins on NTSC (North America, Japan). Betamax tape length was extended only using a DigiBetacam-40 or HDCAM cassette to 4hrs 20mins on PAL and 6hrs 30mins on NTSC models.

text: With the introduction of DVD recorders, combined VHS and DVD recorders were produced, allowing both types of media to be played, and transfer of tape material to DVD.

text: Philips Video 2000[edit]

text: A third format, Video 2000, or V2000 (also marketed as "Video Compact Cassette") was developed and introduced by Philips in 1978, sold only in Europe. Grundig developed and marketed their own models based on the V2000 format. Most V2000 models featured piezoelectric head positioning to dynamically adjust tape tracking. V2000 cassettes had two sides, and like the audio cassette could be flipped over halfway through their recording time, which gave them up to twice the recording length of VHS tapes. User switchable record-protect levers were used instead of the breakable lugs on VHS and Beta cassettes.

text: The half-inch tape used contained two parallel quarter-inch tracks, one for each side. It had a recording time of 4 hours per side, later extended to 8 hours per side on a few models. Machines had a 'real time' tape position counter with the information retained on the tape, so when tapes were loaded the position was known; this feature was only implemented on VHS recorders much later. V2000 became available in early 1979, later than its two rivals. The V2000 system did not sell well, and was discontinued in 1985.

text: Other early formats[edit]

text: Some less successful consumer videocassette formats include:

text:
V-Cord, launched by Sanyo in 1974
VX, launched by Panasonic in 1975
Compact Video Cassette (CVC), developed by Funai and Technicolor and introduced in 1980.

text: Legal challenges[edit]

text: In the early 1980s US film companies fought to suppress the VCR in the consumer market, citing concerns about copyright violations. In Congressional hearings, Motion Picture Association of America head Jack Valenti decried the "savagery and the ravages of this machine" and likened its effect on the film industry and the American public to the Boston strangler:

text: I say to you that the VCR is to the American film producer and the American public as the Boston strangler is to the woman home alone.

text: In the case Sony Corp. of America v. Universal City Studios, Inc., the Supreme Court of the United States ruled that the device was allowable for private use. Subsequently the film companies found that making and selling video recordings of their productions had become a major income source.

text: Shortcomings[edit]

text: The video cassette recorder is sensitive to changes in temperature and humidity. If the machine (or tape) was moved from a cold to a hotter environment there could be condensation of moisture on the internal parts, such as the rotating video head drum. Some later models were equipped with a moisture detector which would prevent operation in this case, but it could not detect moisture on the surface of a tape.

text: Magnetic tapes could be mechanically damaged when ejected from the machine due to moisture or other problems. Rubber drive belts and rollers hardened with age, causing malfunctions.[20] Faults such as these damaged the tape irreversibly, a particular problem with irreplaceable tapes filmed by users. VHS tapes recorded in LP or EP/SLP mode were more sensitive to minor head misalignment over time or from machine to machine. Tapes recorded on a machine made before 1995 tend to not play well on newer machines due to slight changes in helical scanning head design[citation needed].

text: Decline[edit]

text: The videocassette recorder remained in home use throughout the 1980s and 1990s, despite the advent of competing technologies such as LaserDisc (LD) and Video CD (VCD). While Laserdisc offered higher quality video and audio, the discs are heavy (weighing about one pound each), cumbersome, much more prone to damage if dropped or mishandled, and furthermore only home LD players, not recorders, were available. The VCD format found a niche with Asian film imports, but did not sell widely. Many Hollywood studios did not release feature films on VCD in North America because the VCD format had no means of preventing perfect copies being made on CD-R discs, which were already popular when the format was introduced. In an attempt to lower costs, manufacturers began dropping nonessential features from their VCR models. The built-in display was dropped in favor of on screen display for setup, programming, and status, and many buttons were eliminated from the VCR's front panel, their functions accessible only from the VCR's remote control.

text: From about 2000 DVD became the first universally successful optical medium for playback of pre-recorded video, as it gradually overtook VHS to become the most popular consumer format.  DVD recorders and other digital video recorders  dropped rapidly  in price, making the VCR obsolete.  DVD rentals in the United States first exceeded those of VHS in June 2003.[citation needed]

text: The declining market combined with a US Federal Communications Commission mandate effective March 1, 2007, that all new TV tuners in the US be ATSC tuners encouraged major electronics makers, except Funai, JVC, and Panasonic, to end production of standalone units for the US market. Most new standalone VCRs in the US since then can only record from external baseband sources (usually composite video), including CECBs which (by NTIA mandate) all have composite outputs, as well as those ATSC tuners (including TVs) and cable boxes that come with composite outputs. However, JVC did ship one model of D-VHS deck with a built-in ATSC tuner, the HM-DT100U, but it remains extremely rare, and therefore expensive. In July 2016, Funai Electric, the last remaining manufacturer of VHS recorders, announced it would cease production of VHS recorders by the end of the month.[21][22]

text: As a result of winning the format war over HD DVD, the new high definition optical disc format Blu-ray Disc was expected to replace the DVD format.  However, with many homes still having a large supply of VHS tapes and with all Blu-ray players designed to play regular DVDs and CDs by default, some manufacturers began to make VCR/Blu-ray combo players.[23]

text: Remaining niche in recording[edit]

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text: Although consumers have passed over videocassettes for home video playback in favor of DVDs since the early 2000s, VCRs still retained a significant share in home video recording during that decade. While the adoption of DVD players has been strong, DVD recorders for home theater use have been slow to pick up (although DVD recorder-writer drives became de facto standard equipment in personal computers in the mid-2000s).

text: Although technologically superior to VHS, there were several main drawbacks with recordable DVDs that slowed their adoption. When standalone DVD recorders first appeared on the Japanese consumer market in 1999, these early units were very expensive, costing between $2500 and $4000 (USD). (As of early 2007, DVD recorders from notable brands are selling for US$200 or €150 and less, with even lower "street prices".) Different DVD recordable formats also caused confusion, as early units supported only DVD-RAM and DVD-R discs, but the more recent units can record to all major formats DVD-R, DVD-RW, DVD+R, DVD+RW, DVD-R DL and DVD+R DL. Some of these DVD formats are not rewritable, whereas videocassettes could be recorded over repeatedly (notwithstanding physical wear). Another important drawback of DVD recording is that one single-layer DVD is limited to around 120 minutes of recording if the quality is not to be significantly reduced, while VHS tapes are readily available up to 210 minutes (standard play) in NTSC areas and even 300 minutes in PAL areas. Dual layer DVDs, which increase the high quality recording mode to almost four hours, are increasingly available, but the cost of this medium was still relatively high compared to standard single-layer discs. Another factor was the increasing use of digital video file formats and online video sharing, skipping physical media entirely. For these reasons, DVD recorders never took hold of the video recording market like VCRs had.

text: Digital video recorders have since come to dominate the market for home recording of television shows.

text: Special features[edit]

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text: Multi standard[edit]

text: One of the problems faced with the use of video recorders was the exchange of recordings between PAL, SECAM and NTSC countries.   Multi Standard video recorders and TV sets gradually overcame these incompatibility problems.[citation needed]

text: High quality audio (Nicam, AFM, and HiFi)[edit]

text: The U-matic machines were always made with Stereo, and both Betamax and VHS recorded the audio tracks using a fixed linear recording head. However the relatively slow tape speed of Beta and VHS was inadequate for good quality audio, and significantly limited the sound quality. Betamax's release of Beta Hi-Fi in the early 1980s was quickly followed by JVCs release of HiFi audio on VHS (model HR-D725U). Both systems delivered flat full-range frequency response (20 Hz to 20 kHz), excellent 70 dB signal-to-noise ratio (in consumer space, second only to the compact disc), dynamic range of 90 dB, and professional audio-grade channel separation (more than 70 dB). In VHS the incoming HiFi audio is frequency modulated ("Audio FM" or "AFM"), modulating the two stereo channels (L, R) on two different frequency-modulated carriers and recorded using the same high-bandwidth helical scanning technique used for the video signal. To avoid crosstalk and interference from the primary video carrier, VHS used depth multiplexing, in which the modulated audio carrier pair was placed in the hitherto-unused frequency range between the luminance and the color carrier (below 1.6 MHz), and recorded first. Subsequently, the video head erases and re-records the video signal (combined luminance and color signal) over the same tape surface, but the video signal's higher center frequency results in a shallower magnetization of the tape, allowing both the video and residual AFM audio signal to coexist on tape. (PAL versions of Beta Hi-Fi use the same technique). During playback, VHS Hi-Fi recovers the depth-recorded AFM signal by subtracting the audio head's signal (which contains the AFM signal contaminated by a weak image of the video signal) from the video head's signal (which contains only the video signal), then demodulates the left and right audio channels from their respective frequency carriers. The end result of the complex process is audio of outstanding fidelity, which was uniformly solid across all tape-speeds (EP, LP or SP.)

text: Such devices were often described as "HiFi audio", "Audio FM" / "AFM" (FM standing for "Frequency Modulation"), and sometimes informally as "Nicam" VCRs (due to their use in recording the Nicam broadcast audio signal). They remained compatible with non-HiFi VCR players since the standard audio track was also recorded, and were at times used as an alternative to audio cassette tapes due to their exceptional bandwidth, frequency range, and extremely flat frequency response.

text: The 8 mm format always used the video portion of the tape for sound, with an FM carrier between the band space of the chrominance and luminance on the tape. 8 mm could be upgraded to Stereo, by adding an extra FM signal for Stereo difference.[citation needed]

text: The professional Betacam SP format of videocassette also used AFM on the higher-end "BVW"-series of Betacam SP deck models from Sony (such as the BVW-75) to offer 2 extra tracks of audio alongside the 2 standard Dolby C-encoded linear audio tracks for the format, for a total of 4 audio tracks.   However, the 2 AFM tracks were accessible only on those decks equipped with AFM audio (like the BVW-75).

text: Quality[edit]

text: Due to the path followed by the video and Hi-Fi audio heads being striped and discontinuous—unlike that of the linear audio track—head-switching is required to provide a continuous audio signal. While the video signal can easily hide the head-switching point in the invisible vertical retrace section of the signal, so that the exact switching point is not very important, the same is obviously not possible with a continuous audio signal that has no inaudible sections. Hi-Fi audio is thus dependent on a much more exact alignment of the head switching point than is required for non-HiFi VHS machines. Misalignments may lead to imperfect joining of the signal, resulting in low-pitched buzzing.[24] The problem is known as "head chatter", and tends to increase as the audio heads wear down.

text: The sound quality of Hi-Fi VHS stereo is comparable to the quality of CD audio, particularly when recordings were made on high-end or professional VHS machines that have a manual audio recording level control. This high quality compared to other consumer audio recording formats such as compact cassette attracted the attention of amateur and hobbyist recording artists. Home recording enthusiasts occasionally recorded high quality stereo mixdowns and master recordings from multitrack audio tape onto consumer-level Hi-Fi VCRs.  However, because the VHS Hi-Fi recording process is intertwined with the VCR's video-recording function, advanced editing functions such as audio-only or video-only dubbing are impossible.  A short-lived alternative to the hifi feature for recording mixdowns of hobbyist audio-only projects was a PCM adaptor so that high-bandwidth digital video could use a grid of black-and-white dots on an analog video carrier to give pro-grade digital sounds though DAT tapes made this obsolete.

text: Copy protection[edit]

text: Introduced in 1983, Macrovision is a system that reduces the quality of recordings made from commercial video tapes, DVDs and pay-per-view broadcasts by adding random peaks of luminance to the video signal during vertical blanking. These confuse the automatic level adjustment of the recording VCR which causes the brightness of the picture to constantly change, rendering the recording unwatchable.

text: When creating a copy-protected videocassette, the Macrovision-distorted signal is stored on the tape itself by special recording equipment. By contrast, on DVDs there is just a marker asking the player to produce such a distortion during playback. All standard DVD players include this protection and obey the marker, though unofficially many models can be modified or adjusted to disable it.

text: Also, the Macrovision protection system may fail to work on older VCR's made before 1986 and some high end decks built afterwards, usually due to the lack of an AGC system.  Newer VHS and S-VHS machines (and DVD recorders) are susceptible to this signal; generally, machines of other tape formats are unaffected, such as all 3 Betamax variants.  VCRs designated for "professional" usage typically have an adjustable AGC system, a specific "Macrovision removing" circuit, or Time Base Corrector (TBC) and can thus copy protected tapes with or without preserving the protection. Such VCRs are usually overpriced and sold exclusively to certified professionals (linear editing using the 9-Pin Protocol, TV stations etc.) via controlled distribution channels in order to prevent their being used by the general public (however, said professional VCRs can be purchased reasonably by consumers on the second-hand/used market, depending on the VCR's condition). Nowadays, most DVDs still have copyright protection, but certain DVDs do not have it, usually pornography and bootlegs. However, some DVDs, such as certain DVD sets, do not have the protection against VHS copying, possibly due to the VHS format no longer used as a major retail medium for home video.

text: Flying erase heads [edit]

text: The flying erase head is a feature that may be found in some high end home VCRs as well as some broadcast grade VCRs to cleanly edit the video.

text: Normally, the tape is passed longitudinally through two fixed erase heads, one located just before the tape moves to the video head drum and the other right next to the audio/control head stack.  Upon recording, the erase heads erase any old recording contained on the tape to prevent anything already recorded on it from interfering with what is being recorded.

text: However, when trying to edit footage deck to deck, portions of the old recording's video may be between the erase head and video recording heads.  This results in a faint rainbow-like noise at and briefly after the point of the cut as the old video recording missed by the fixed erase head is never completely erased as the new recording is printed.

text: The flying erase head is so-called because an erase head is mounted on the video head drum and rotates around in the same manner as the video heads.  In the record mode, the erase head is active and erases the video precisely down to the recorded video fields.  The flying erase head runs over the tape and the video heads record the signal virtually instantly after the flying erase head has passed.

text: Since the erase head erases the old signal right before the video heads write onto the tape, there is no remnant of the old signal to cause visible distortion at and after the moment a cut is made, resulting in a clean edit.  In addition, the ability of flying erase heads to erase old video off the tape right before recording new video on it allows the ability to perform insert editing, where new footage can be placed within an existing recording with clean cuts at the beginning and end of the edit.

text: Variants[edit]

text: In addition to the standard home VCR, a number of variants have been produced over the years. These include combined "all-in-one" devices such as the TV/VCR combo (a TV and VCR in one unit) and DVD/VCR units and even TV/VCR/DVD all-in-one units.

text: Dual-deck VCRs (marketed as "double-decker") have also been sold, albeit with less success.

text: Most camcorders produced in the 20th century also feature an integrated VCR. Generally, they include neither a timer nor a TV tuner. Most of these use smaller format videocassettes, such as 8 mm, VHS-C, or MiniDV, although some early models supported full-size VHS and Betamax. In the 21st century, digital recording became the norm while videocassette tapes dwindled away gradually; tapeless camcorders use other storage media such as DVDs, or internal flash memory, hard drive, and SD card.[25]