document_title: Duluth model

question_text: the duluth model is an intervention program that emphasizes

text: Duluth model

text: Origin and theory[edit]

text: The Domestic Abuse Intervention Project was the first multi-disciplinary program designed to address the issue of domestic violence. This experimental program, conducted in Duluth in 1981, coordinated the actions of a variety of agencies dealing with domestic conflict. The Duluth model curriculum was developed by a "small group of activists in the battered women’s movement" [3] with 5 battered women and 4 men as subjects. The program has become a model for programs in other jurisdictions seeking to deal more effectively with domestic violence.[4]

text: The feminist theory underlying the Duluth Model is that men use violence within relationships to exercise power and control. This is illustrated by the "Power and Control Wheel," a graphic typically displayed as a poster in participating locations.[5][6] According to the Duluth Model, "women and children are vulnerable to violence because of their unequal social, economic, and political status in society."[7] Treatment of abusive men is focused on re-education, as "we do not see men’s violence against women as stemming from individual pathology, but rather from a socially reinforced sense of entitlement." [8] The program's philosophy is intended to help batterers work to change their attitudes and personal behavior so they would learn to be nonviolent in any relationship.

text: Implementation[edit]

text: This section is empty. You can help by adding to it. (January 2017)

text: Effectiveness[edit]

text: A U.S. study published in 2002 sponsored by the federal government found that batterers who complete programs based on the Duluth model are less likely to repeat acts of domestic violence than those who do not complete any batterers' intervention program.[9]

text: A 2003 study conducted by the U.S. National Institute of Justice found the Duluth Model to have "little or no effect."[10] However, this study had considerable shortfalls. The National Institute of Justice said in its introduction, "...response rates were low, many people dropped out of the program, and victims could not be found for subsequent interviews. The tests used to measure batterers' attitudes toward domestic violence and their likelihood to engage in future abuse were of questionable validity."[11]

text: A 2003 longitudinal, four-year evaluation by E W Gondolf, covering four cities, shows clear deescalation of reassault and other abuse, with 80% of men reaching sustained non-violence.[12]

text: A 2005 study led by Larry Bennett, a professor of social work at the University of Illinois at Chicago and an expert on batterer intervention programs, found that of the 30 batterer intervention programs in Cook County, Illinois, 15 percent of batterers who completed the programs were rearrested for domestic violence, compared with 37 percent of those who dropped out of the programs.[9] However, Bennett said the studies are largely meaningless because they lacked a proper control group.[9] He added that participants who complete domestic violence programs are likely to be more motivated than others to improve behavior and would be less inclined to offend again.[9]

text: A 2011 review of the effectiveness of batterers intervention programs (BIP) (primarily Duluth Model) found that "there is no solid empirical evidence for either the effectiveness or relative superiority of any of the current group interventions," and that "the more rigorous the methodology of evaluation studies, the less encouraging their findings."[13] That is, as BIPs in general, and Duluth Model programs in particular are subject to increasingly rigorous review, their success rate approaches zero.

text: A 2014 news report reported zero percent recidivism within 5 years for a batterers intervention program based on Nonviolent Communication, and contrasted this with a recidivism rate of 40 percent within 5 years for a batterers intervention program based on the Duluth Model as reported by the Domestic Abuse Intervention Project.[14]

text: Criticism[edit]

text: Criticism of the Duluth Model has centered on the program's insistence that men are perpetrators who are violent because they have been socialized in a patriarchy that condones male violence, and that women are victims who are violent only in self-defense.[15] Some critics argue that "programs based on the Duluth Model may ignore research linking domestic violence to substance abuse and psychological problems, such as attachment disorders, traced to childhood abuse or neglect, or the absence of a history of adequate socialization and training."[9][16] Others criticize the Duluth model as being overly confrontational rather than therapeutic, focusing solely on changing the abuser's actions and attitudes rather than dealing with underlying emotional and psychological issues.[16] Donald Dutton, a psychology professor at the University of British Columbia who has studied abusive personalities, states: "The Duluth Model was developed by people who didn't understand anything about therapy,"[9] and also points out that "lesbian battering is more frequent than heterosexual battering."[17] Philip W. Cook points out that in the case of homosexual domestic violence, the patriarchy is absent: there is no male dominance of women in same-sex relationships, and in fact, female on female abuse is reported more than twice as frequently as male on male abuse.[18] Furthermore, some critics point out that the model ignores the reality that women are sometimes the perpetrators of domestic violence in heterosexual relationships, as well.

text: Its proponents counter that the Duluth model is effective and makes best use of scarce resources.[19] However, Ellen Pence herself has written,

text: "By determining that the need or desire for power was the motivating force behind battering, we created a conceptual framework that, in fact, did not fit the lived experience of many of the men and women we were working with. The DAIP staff [...] remained undaunted by the difference in our theory and the actual experiences of those we were working with [...] It was the cases themselves that created the chink in each of our theoretical suits of armor. Speaking for myself, I found that many of the men I interviewed did not seem to articulate a desire for power over their partner. Although I relentlessly took every opportunity to point out to men in the groups that they were so motivated and merely in denial, the fact that few men ever articulated such a desire went unnoticed by me and many of my coworkers. Eventually, we realized that we were finding what we had already predetermined to find."[20]

text: The Duluth Model is featured in the documentary Power and Control: Domestic Violence in America with commentary from its authors as well as its main critics, such as Dutton.[21]

text: Erin Pizzey the founder of Chiswick Womens' Aid, the first ever refuge in the world for victims of domestic violence notes in an interview in The Red Pill that men and women are equally capable of domestic violence, though over time domestic abuse shelters have shifted to be almost exclusively for battered women. [22]

text: Their [feminists] ideology also asserts that men were impervious to any therapeutic intervention, courtesy of their deeply ingrained patriarchal privilege.

text: According to this new model they precluded anything but criminal treatment for men’s alleged violence toward women and children. Laws were passed that specifically forbade any couples intervention for men accused.[23]


document_title: Caste

question_text: who has said that caste is a closed class

root

text: Caste

text: Etymology[edit]

text: The origins of the term 'caste' are attributed to the Spanish and Portuguese casta, which, according to the John Minsheu's Spanish dictionary (1599), means "race, lineage, or breed".[5]  When the Spanish colonized the New World, they used the word to mean a "clan or lineage". However, it was the Portuguese who employed casta in the primary modern sense when they applied it to the thousands of endogamous, hereditary Indian social groups they encountered upon their arrival in India in 1498.[5][6] The use of the spelling "caste", with this latter meaning, is first attested to in English in 1613.[5]

tag: p

text: In South Asia[edit]

text: India[edit]

text: Wikimedia Commons has media related to Castes in India.

tag: table

text: Modern India's caste system is based on the social groupings called jāti and the  theoretical varna. The system of varnas appears in Hindu texts dating back to 1000 BCE and envisages the society divided into four classes: Brahmins (teachers, scholars and priests), Kashatriyas (warriors and nobles), Vaishyas (farmers, traders and artisans) and Shudras (labourers/service providers). The texts do not mention any separate, untouchable category in varna classification. Scholars believe that the system of varnas was a theoretical classification envisioned by the Brahmins, but never truly operational in the society. The practical division of the society had always been in terms of jātis (birth groups), which are not based on any specific principle, but could vary from ethnic origins to occupations. The jātis have been endogamous groups without any fixed hierarchy but subject to vague notions of rank articulated over time based on lifestyle and social, political or economic status. In many instances, as in Bengal, historically the kings and rulers had been called upon, when required, to mediate on the ranks of jātis, which might number in thousands all over the subcontinent and vary by region. In practice, the jātis may or may not fit into the varna classes and many prominent jatis, for example the Jats and Yadavs, straddled two varnas i.e. Kshatriyas and Vaishyas, and the varna status of jātis itself was subject to articulation over time.

text: Starting with the British colonial Census of 1901 led by Herbert Hope Risley, all the jātis were grouped under the theoretical varnas categories.[7] According to political scientist Lloyd Rudolph, Risley believed that varna, however ancient, could be applied to all the modern castes found in India, and "[he] meant to identify and place several hundred million Indians within it."[8] The terms varna (conceptual classification based on occupation) and jāti (groups) are two distinct concepts: while varna is the idealised four-part division envisaged by the Twice-Borns, jāti (community) refers to the thousands of actual endogamous groups prevalent across the subcontinent. The classical authors scarcely speak of anything other than the varnas, as it provided a convenient shorthand; but a problem arises when even Indologists sometimes confuse the two.[9]

text: Upon independence from Britain, the Indian Constitution listed 1,108 castes across the country as Scheduled Castes in 1950, for positive discrimination.[10] The Untouchable communities are sometimes called Scheduled Castes, Dalit or Harijan in contemporary literature.[11] In 2001, Dalits were 16.2% of India's population.[12] Most of the 15 million bonded child workers are from the lowest castes.[13][14]

text: Independent India has witnessed caste-related violence. India's National Crime Records Bureau (NCRB) records crimes against scheduled castes and scheduled tribes – the most disadvantaged groups - in a separate category. In 2005, government recorded approximately 110,000 cases of reported violent acts, including rape and murder, against Dalits [15] For 2012, the government recorded 651 murders, 3,855 injuries, 1,576 rapes, 490 kidnappings, and 214 cases of arson.[16]

text: The socio-economic limitations of the caste system are reduced due to urbanization and affirmative action. Nevertheless, the caste system still exists in endogamy and patrimony, and thrives in the politics of democracy, where caste provides ready made constituencies to politicians. The globalization and economic opportunities from foreign businesses has influenced the growth of India's middle-class population. Some members of the Chhattisgarh Potter Caste Community (CPCC) are middle-class urban professionals and no longer potters unlike the remaining majority of traditional rural potter members. The co-existence of the middle-class and traditional members in the CPCC has created intersectionality between caste and class.[17] There is persistence of caste in Indian politics. Caste associations have evolved into caste-based political parties. Political parties and the state perceive caste as an important factor for mobilization of people and policy development. It is not politics that gets caste-ridden; it is caste that gets politicized.[18]

text: Nepal[edit]

text: The Nepalese caste system resembles that of the Indian jāti system with numerous jāti divisions with a varna system superimposed for a rough equivalence. But since the culture and the society is different some of the things are different. Inscriptions attest the beginnings of a caste system during the Licchavi period.  Jayasthiti Malla (1382–95) categorized Newars into 64 castes (Gellner 2001). A similar exercise was made during the reign of Mahindra Malla (1506–75). The Hindu social code was later set up in Gorkha by Ram Shah (1603–36).

text: Pakistan[edit]

text: Religious, historical and sociocultural factors have helped define the bounds of endogamy for Muslims in some parts of Pakistan. There is a preference for endogamous marriages based on the clan-oriented nature of the society, which values and actively seeks similarities in social group identity based on several factors, including religious, sectarian, ethnic, and tribal/clan affiliation. Religious affiliation is itself multilayered and includes religious considerations other than being Muslim, such as sectarian identity (e.g. Shia or Sunni, etc.) and religious orientation within the sect (Isnashari, Ismaili, Ahmedi, etc.).[citation needed]

text: Both ethnic affiliation (e.g. Pathan, Sindhi, Baloch, Punjabi, etc.) and membership of specific biraderis or zaat/quoms are additional integral components of social identity.[19] Within the bounds of endogamy defined by the above parameters, close consanguineous unions are preferred due to a congruence of key features of group- and individual-level background factors as well as affinities. McKim Marriott claims a social stratification that is hierarchical, closed, endogamous and hereditary is widely prevalent, particularly in western parts of Pakistan. Frederik Barth in his review of this system of social stratification in Pakistan suggested that these are castes.[20][21][22]

text: Sri Lanka[edit]

text: The caste system in Sri Lanka is a division of society into strata,[23] influenced by the textbook varnas and jāti system found in India. Ancient Sri Lankan texts such as the Pujavaliya, Sadharmaratnavaliya and Yogaratnakaraya and inscriptional evidence show that the above hierarchy prevailed throughout the feudal period. The repetition of the same caste hierarchy even as recently as the 18th century, in the British/Kandyan period Kadayimpoth - Boundary books as well, indicates the continuation of the tradition right up to the end of Sri Lanka's monarchy.

text: Southeast Asia[edit]

text: Indonesia[edit]

text: Balinese caste structure has been described in early 20th-century European literature to be based on three categories – triwangsa (thrice born) or the nobility, dwijāti (twice born) in contrast to ekajāti (once born) the low folks. Four statuses were identified in these sociological studies, spelled a bit differently from the caste categories for India:[24]

text:
Brahmanas - priest
Satrias - knighthood
Wesias - commerce
Sudras - servitude

tag: ul

text: The Brahmana caste was further subdivided by these Dutch ethnographers into two: Siwa and Buda. The Siwa caste was subdivided into five – Kemenuh, Keniten, Mas, Manuba and Petapan. This classification was to accommodate the observed marriage between higher-caste Brahmana men with lower-caste women. The other castes were similarly further sub-classified by these 19th-century and early-20th-century ethnographers based on numerous criteria ranging from profession, endogamy or exogamy or polygamy, and a host of other factors in a manner similar to castas in Spanish colonies such as Mexico, and caste system studies in British colonies such as India.[24]

text: East Asia[edit]

text: China and Mongolia[edit]

text: During the period of Yuan Dynasty, ruler Kublai Khan enforced a Four Class System, which was a legal caste system. The order of four classes of people was maintained by the information of the descending order were:-

text:
Mongolian
Semu people
Han people (in the northern areas of China)
Southerners (people of the former Southern Song dynasty)

text: Some scholars notes that it was a kind of psychological indication that the earlier they submitted to Mongolian people, the higher social status they would have. The 'Four Class System' and its people received different treatment in political, legal, and military affairs.[25][26]

text: Today, the Hukou system is considered by various sources as the current caste system of China.[27][28][29]

text: There is also significant controversy over the social classes of Tibet, especially with regards to the serfdom in Tibet controversy.

text: Japan[edit]

text: In Japan's history, social strata based on inherited position rather than personal merit, was rigid and highly formalized in a system called mibunsei (身分制). At the top were the Emperor and Court nobles (kuge), together with the Shogun and daimyo. Below them, the population was divided into four classes: samurai, peasants, craftsmen and merchants. Only samurai were allowed to bear arms. A samurai had a right to kill any peasants, craftsman or merchant who he felt were disrespectful. Merchants were the lowest caste because they did not produce any products. The castes were further sub-divided; for example, peasants were labelled as furiuri, tanagari, mizunomi-byakusho among others. As in Europe, the castes and sub-classes were of the same race, religion and culture.

text: Howell, in his review of Japanese society notes that if a Western power had colonized Japan in the 19th century, they would have discovered and imposed a rigid four-caste hierarchy in Japan.[30]

text: De Vos and Wagatsuma observe that Japanese society had a systematic and extensive caste system. They discuss how alleged caste impurity and alleged racial inferiority, concepts often  assumed to be different, are superficial terms, and are due to identical inner psychological processes, which expressed themselves in Japan and elsewhere.[31]

text: Endogamy was common because marriage across caste lines was socially unacceptable.[31][32]

text: Japan had its own untouchable caste, shunned and ostracized, historically referred to by the insulting term Eta, now called Burakumin. While modern law has officially abolished the class hierarchy, there are reports of discrimination against the Buraku or Burakumin underclasses.[33] The Burakumin are regarded as "ostracised."[34] The burakumin are one of the main minority groups in Japan, along with the Ainu of Hokkaidō and those of residents of Korean and Chinese descent.

text: Korea[edit]

text: The baekjeong (백정) were an “untouchable” outcaste of Korea. The meaning today is that of butcher. It originates in the Khitan invasion of Korea in the 11th century. The defeated Khitans who surrendered were settled in isolated communities throughout Goryeo to forestall rebellion.  They were valued for their skills in hunting, herding, butchering, and making of leather, common skill sets among nomads.  Over time, their ethnic origin was forgotten, and they formed the bottom layer of Korean society.

text: In 1392, with the foundation of the Confucian Joseon dynasty, Korea systemised its own native class system. At the top were the two official classes, the Yangban, which literally means "two classes." It was composed of scholars (munban) and warriors (muban). Scholars had a significant social advantage over the warriors. Below were the jung-in (중인-中人: literally "middle people". This was a small class of specialized professions such as medicine, accounting, translators, regional bureaucrats, etc. Below that were the sangmin (상민-常民: literally 'commoner'), farmers working their own fields. Korea also had a serf population known as the nobi. The nobi population could fluctuate up to about one-third of the population, but on average the nobi made up about 10% of the total population.[35] In 1801, the vast majority of government nobi were emancipated,[36] and by 1858 the nobi population stood at about 1.5 percent of the total population of Korea.[37] The hereditary nobi system was officially abolished around 1886–87 and the rest of the nobi system was abolished with the Gabo Reform of 1894,[37] but traces remained until 1930.

text: The opening of Korea to foreign Christian missionary activity in the late 19th century saw some improvement in the status of the baekjeong. However, everyone was not equal under the Christian congregation, and even so protests erupted when missionaries tried to integrate baekjeong into worship, with non-baekjeong finding this attempt insensitive to traditional notions of hierarchical advantage.[citation needed] Around the same time, the baekjeong began to resist open social discrimination.[38] They focused on social and economic injustices affecting them, hoping to create an egalitarian Korean society. Their efforts included attacking social discrimination by upper class, authorities, and "commoners," and the use of degrading language against children in public schools.[39]

text: With the Gabo reform of 1896, the class system of Korea was officially abolished. Following the collapse of the Gabo government, the new cabinet, which became the Gwangmu government after the establishment of the Korean Empire, introduced systematic measures for abolishing the traditional class system. One measure was the new household registration system, reflecting the goals of formal social equality, which was implemented by the loyalists’ cabinet. Whereas the old registration system signified household members according to their hierarchical social status, the new system called for an occupation.[40]

text: While most Koreans by then had surnames and even bongwan, although still substantial number of cheonmin, mostly consisted of serfs and slaves, and untouchables did not. According to the new system, they were then required to fill in the blanks for surname in order to be registered as constituting separate households. Instead of creating their own family name, some cheonmins appropriated their masters’ surname, while others simply took the most common surname and its bongwan in the local area. Along with this example, activists within and outside the Korean government had based their visions of a new relationship between the government and people through the concept of citizenship, employing the term inmin ("people") and later, kungmin ("citizen").[40]

text: North Korea[edit]

text: The Committee for Human Rights in North Korea reported that "Every North Korean citizen is assigned a heredity-based class and socio-political rank over which the individual exercises no control but which determines all aspects of his or her life."[41] Regarded as Songbun, Barbara Demick describes this "class structure" as an updating of the hereditary "caste system", combining Confucianism and Stalinism.[42]  She claims that a bad family background is called "tainted blood", and that by law this "tainted blood" lasts for three generations.[43]

text: Tibet[edit]

text: Heidi Fjeld has put forth the argument that pre-1950s Tibetan society was functionally a caste system, in contrast to previous scholars who defined the Tibetan social class system as similar to European feudal serfdom, as well as non-scholarly western accounts which seek to romanticize a supposedly 'egalitarian' ancient Tibetan society.

text: Middle East[edit]

text: Yezidi society is hierarchical. The secular leader is a hereditary emir or prince, whereas a chief sheikh heads the religious hierarchy. The Yazidi are strictly endogamous; members of the three Yazidi castes, the murids, sheikhs and pirs, marry only within their group.

text: Ancient Egypt[edit]

text: The Ancient Egyptians were divided into four social classes:[44][45]

text:
the royalty and nobles
artisans, craftworkers and merchants
workers
slaves

tag: ol

text: Iran[edit]

text:
Pre-Islamic Sassanid society was immensely complex, with separate systems of social organization governing numerous different groups within the empire.[46] Historians believe society comprised four[47][48][49]
social classes:

text:
Priests (Persian: Asravan)
Warriors (Persian: Arteshtaran)
Secretaries (Persian: Dabiran)
Commoners (Persian: Vastryoshan)

text: Yemen[edit]

text: In Yemen there exists a hereditary caste, the African-descended Al-Akhdam who are kept as perennial manual workers. Estimates put their number at over 3.5 million residents who are discriminated, out of a total Yemeni population of around 22 million.[50]

text: Africa[edit]

text: Various sociologists have reported caste systems in Africa.[51][52][53] The specifics of the caste systems have varied in ethnically and culturally diverse Africa, however the following features are common - it has been a closed system of social stratification, the social status is inherited, the castes are hierarchical, certain castes are shunned while others are merely endogamous and exclusionary.[54] In some cases, concepts of purity and impurity by birth have been prevalent in Africa. In other cases, such as the Nupe of Nigeria, the Beni Amer of East Africa, and the Tira of Sudan, the exclusionary principle has been driven by evolving social factors.[55]

text: West Africa[edit]

text: Among the Igbo of Nigeria - especially Enugu, Anambra, Imo, Abia, Ebonyi, Edo and Delta states of the country - Obinna finds Osu caste system has been and continues to be a major social issue. The Osu caste is determined by one's birth into a particular family irrespective of the religion practised by the individual. Once born into Osu caste, this Nigerian person is an outcast, shunned and ostracized, with limited opportunities or acceptance, regardless of his or her ability or merit. Obinna discusses how this caste system-related identity and power is deployed within government, Church and indigenous communities.[51]

text: The osu class systems of eastern Nigeria and southern Cameroon are derived from indigenous religious beliefs and discriminate against the "Osus" people as "owned by deities" and outcasts.

text: The Songhai economy was based on a caste system. The most common were metalworkers, fishermen, and carpenters. Lower caste participants consisted of mostly non-farm working immigrants, who at times were provided special privileges and held high positions in society. At the top were noblemen and direct descendants of the original Songhai people, followed by freemen and traders.[56]

text: In a review of social stratification systems in Africa, Richter reports that the term caste has been used by French and American scholars to many groups of West African artisans. These groups have been described as inferior, deprived of all political power, have a specific occupation, are hereditary and sometimes despised by others. Richter illustrates caste system in Ivory Coast, with six sub-caste categories. Unlike other parts of the world, mobility is sometimes possible within sub-castes, but not across caste lines. Farmers and artisans have been, claims Richter, distinct castes. Certain sub-castes are shunned more than others. For example, exogamy is rare for women born into families of woodcarvers.[57]

text: Similarly, the Mandé societies in Gambia, Ghana, Guinea, Ivory Coast, Liberia, Senegal and Sierra Leone have social stratification systems that divide society by ethnic ties. The Mande class system regards the jonow slaves as inferior. Similarly, the Wolof in Senegal is divided into three main groups, the geer (freeborn/nobles), jaam (slaves and slave descendants) and the underclass neeno. In various parts of West Africa, Fulani societies also have class divisions. Other castes include Griots, Forgerons, and Cordonniers.

text: Tamari has described endogamous castes of over fifteen West African peoples, including the Tukulor, Songhay, Dogon, Senufo, Minianka, Moors, Manding, Soninke, Wolof, Serer, Fulani, and Tuareg. Castes appeared among the Malinke people no later than 14th century, and was present among the Wolof and Soninke, as well as some Songhay and Fulani populations, no later than 16th century. Tamari claims that wars, such as the Sosso-Malinke war described in the Sunjata epic, led to the formation of blacksmith and bard castes among the people that ultimately became the Mali empire.

text: As West Africa evolved over time, sub-castes emerged that acquired secondary specializations or changed occupations. Endogamy was prevalent within a caste or among a limited number of castes, yet castes did not form demographic isolates according to Tamari. Social status according to caste was inherited by off-springs automatically; but this inheritance was paternal. That is, children of higher caste men and lower caste or slave concubines would have the caste status of the father.[53]

text: Central Africa[edit]

text: Ethel M. Albert in 1960 claimed that the societies in Central Africa were caste-like social stratification systems.[58] Similarly, in 1961, Maquet notes that the society in Rwanda and Burundi can be best described as castes.[59] The Tutsi, noted Maquet, considered themselves as superior, with the more numerous Hutu and the least numerous Twa regarded, by birth, as respectively, second and third in the hierarchy of Rwandese society. These groups were largely endogamous, exclusionary and with limited mobility.[60] Maquet's theories have been controversial.

text: Horn of Africa[edit]

text: In a review published in 1977, Todd reports that numerous scholars report a system of social stratification in different parts of Africa that resembles some or all aspects of caste system. Examples of such caste systems, he claims, are to be found in Ethiopia in communities such as the Gurage and Konso. He then presents the Dime of Southwestern Ethiopia, amongst whom there operates a system which Todd claims can be unequivocally labelled as caste system. The Dime have seven castes whose size varies considerably. Each broad caste level is a hierarchical order that is based on notions of purity, non-purity and impurity. It uses the concepts of defilement to limit contacts between caste categories and to preserve the purity of the upper castes. These caste categories have been exclusionary, endogamous and the social identity inherited.[62] Alula Pankhurst has published a study of caste groups in SW Ethiopia.[63]

text: Among the Kafa, there were also traditionally groups labeled as castes. "Based on research done before the Derg regime, these studies generally presume the existence of a social hierarchy similar to the caste system. At the top of this hierarchy were the Kafa, followed by occupational groups including blacksmiths (Qemmo), weavers (Shammano), bards (Shatto), potters, and tanners (Manno). In this hierarchy, the Manjo were commonly referred to as hunters, given the lowest status equal only to slaves."[64]

text: The Borana Oromo of southern Ethiopia in the Horn of Africa also have a class system, wherein the Wata, an acculturated hunter-gatherer group, represent the lowest class. Though the Wata today speak the Oromo language, they have traditions of having previously spoken another language before adopting Oromo.[65]

text: The traditionally nomadic Somali people are divided into clans, wherein the Rahanweyn agro-pastoral clans and the occupational clans such as the Madhiban were traditionally sometimes treated as outcasts.[66] As Gabboye, the Madhiban along with the Yibir and Tumaal (collectively referred to as sab) have since obtained political representation within Somalia, and their general social status has improved with the expansion of urban centers.[61]

text: Europe[edit]

text: Medieval Europe's caste system had the following order:[67][68]

text:
Nobility, royalty
Knights, squires, pages, clergy
Artisans
Peasants, slaves, serfs

text: Basque country[edit]

text: For centuries, through the modern times, the majority regarded Cagots who lived primarily in the Basque region of France and Spain as an inferior caste, the untouchables. While they had the same skin color and religion as the majority, in the churches they had to use segregated doors, drink from segregated fonts, and receive communion on the end of long wooden spoons. It was a closed social system. The socially isolated Cagots were endogamous, and chances of social mobility non-existent.[69][70]

text: United Kingdom[edit]

text: In July 2013, the UK government announced its intention to amend the Equality Act 2010 to "introduce legislation on caste, including any necessary exceptions to the caste provisions, within the framework of domestic discrimination law".[71] Section 9(5) of the Equality Act 2010 provides that "a Minister may by order amend the statutory definition of race to include caste and may provide for exceptions in the Act to apply or not to apply to caste".

text: From September 2013 to February 2014, Meena Dhanda led a project on ‘Caste in Britain’ for the UK Equality and Human Rights Commission (EHRC).[72]


document_title: Pangaea

question_text: what land mass was north america a part of about 300 million years ago

text: Pangaea

text: Origin of the concept

text: The name "Pangaea/Pangea" is derived from Ancient Greek pan (πᾶν, "all, entire, whole") and Gaia (Γαῖα, "Mother Earth, land").[5][10] The concept that the continents once formed a continuous land mass was first proposed by Alfred Wegener, the originator of the scientific theory of continental drift, in his 1912 publication The Origin of Continents (Die Entstehung der Kontinente).[11] He expanded upon his hypothesis in his 1915 book The Origin of Continents and Oceans (Die Entstehung der Kontinente und Ozeane), in which he postulated that, before breaking up and drifting to their present locations, all the continents had formed a single supercontinent that he called the "Urkontinent".

text: The name "Pangea" occurs in the 1920 edition of Die Entstehung der Kontinente und Ozeane, but only once, when Wegener refers to the ancient supercontinent as "the Pangaea of the Carboniferous".[12] Wegener used the Germanized form "Pangäa", but the name entered German and English scientific literature (in 1922[13] and 1926, respectively) in the Latinized form "Pangaea" (of the Greek "Pangaia"), especially due to a symposium of the American Association of Petroleum Geologists in November 1926.[14]

text: Formation

text: The forming of supercontinents and their breaking up appears to have been cyclical through Earth's history. There may have been many others before Pangaea. The fourth-last supercontinent, called Columbia or Nuna, appears to have assembled in the period 2.0–1.8 Ga.[15][16] Columbia/Nuna broke up and the next supercontinent, Rodinia, formed from the accretion and assembly of its fragments. Rodinia lasted from about 1.1 billion years ago (Ga) until about 750 million years ago, but its exact configuration and geodynamic history are not nearly as well understood as those of the later supercontinents, Pannotia and Pangaea.

text: When Rodinia broke up, it split into three pieces: the supercontinent of Proto-Laurasia, the supercontinent of Proto-Gondwana, and the smaller Congo craton. Proto-Laurasia and Proto-Gondwana were separated by the Proto-Tethys Ocean. Next Proto-Laurasia itself split apart to form the continents of Laurentia, Siberia and Baltica. Baltica moved to the east of Laurentia, and Siberia moved northeast of Laurentia. The splitting also created two new oceans, the Iapetus Ocean and Paleoasian Ocean. Most of the above masses coalesced again to form the relatively short-lived supercontinent of Pannotia. This supercontinent included large amounts of land near the poles and, near the equator, only a relatively small strip connecting the polar masses. Pannotia lasted until 540 Ma, near the beginning of the Cambrian period and then broke up, giving rise to the continents of Laurentia, Baltica, and the southern supercontinent of Gondwana.

text: In the Cambrian period, the continent of Laurentia, which would later become North America, sat on the equator, with three bordering oceans: the Panthalassic Ocean to the north and west, the Iapetus Ocean to the south and the Khanty Ocean to the east. In the Earliest Ordovician, around 480 Ma, the microcontinent of Avalonia – a landmass incorporating fragments of what would become eastern Newfoundland, the southern British Isles, and parts of Belgium, northern France, Nova Scotia, New England, South Iberia and northwest Africa – broke free from Gondwana and began its journey to Laurentia.[17] Baltica, Laurentia, and Avalonia all came together by the end of the Ordovician to form a minor supercontinent called Euramerica or Laurussia, closing the Iapetus Ocean. The collision also resulted in the formation of the northern Appalachians. Siberia sat near Euramerica, with the Khanty Ocean between the two continents. While all this was happening, Gondwana drifted slowly towards the South Pole. This was the first step of the formation of Pangaea.[18]

text: The second step in the formation of Pangaea was the collision of Gondwana with Euramerica. By Silurian time, 440 Ma, Baltica had already collided with Laurentia, forming Euramerica. Avalonia had not yet collided with Laurentia, but as Avalonia inched towards Laurentia, the seaway between them, a remnant of the Iapetus Ocean, was slowly shrinking. Meanwhile, southern Europe broke off from Gondwana and began to move towards Euramerica across the newly formed Rheic Ocean. It collided with southern Baltica in the Devonian, though this microcontinent was an underwater plate. The Iapetus Ocean's sister ocean, the Khanty Ocean, shrank as an island arc from Siberia collided with eastern Baltica (now part of Euramerica). Behind this island arc was a new ocean, the Ural Ocean.

text: By late Silurian time, North and South China split from Gondwana and started to head northward, shrinking the Proto-Tethys Ocean in their path and opening the new Paleo-Tethys Ocean to their south. In the Devonian Period, Gondwana itself headed towards Euramerica, causing the Rheic Ocean to shrink. In the Early Carboniferous, northwest Africa had touched the southeastern coast of Euramerica, creating the southern portion of the Appalachian Mountains, the Meseta Mountains and the Mauritanide Mountains. South America moved northward to southern Euramerica, while the eastern portion of Gondwana (India, Antarctica and Australia) headed toward the South Pole from the equator. North and South China were on independent continents. The Kazakhstania microcontinent had collided with Siberia. (Siberia had been a separate continent for millions of years since the deformation of the supercontinent Pannotia in the Middle Carboniferous.)

text: Western Kazakhstania collided with Baltica in the Late Carboniferous, closing the Ural Ocean between them and the western Proto-Tethys in them (Uralian orogeny), causing the formation of not only the Ural Mountains but also the supercontinent of Laurasia. This was the last step of the formation of Pangaea. Meanwhile, South America had collided with southern Laurentia, closing the Rheic Ocean and forming the southernmost part of the Appalachians and Ouachita Mountains. By this time, Gondwana was positioned near the South Pole and glaciers were forming in Antarctica, India, Australia, southern Africa and South America. The North China block collided with Siberia by Late Carboniferous time, completely closing the Proto-Tethys Ocean.

text: By early Permian time, the Cimmerian plate split from Gondwana and headed towards Laurasia, thus closing the Paleo-Tethys Ocean, but forming a new ocean, the Tethys Ocean, in its southern end. Most of the landmasses were all in one. By the Triassic Period, Pangaea rotated a little and the Cimmerian plate was still travelling across the shrinking Paleo-Tethys, until the Middle Jurassic time. The Paleo-Tethys had closed from west to east, creating the Cimmerian Orogeny. Pangaea, which looked like a C, with the new Tethys Ocean inside the C, had rifted by the Middle Jurassic, and its deformation is explained below.

text: Evidence of existence

text: Fossil evidence for Pangaea includes the presence of similar and identical species on continents that are now great distances apart. For example, fossils of the therapsid Lystrosaurus have been found in South Africa, India and Antarctica, alongside members of the Glossopteris flora, whose distribution would have ranged from the polar circle to the equator if the continents had been in their present position; similarly, the freshwater reptile Mesosaurus has been found in only localized regions of the coasts of Brazil and West Africa.[19]

text: Additional evidence for Pangaea is found in the geology of adjacent continents, including matching geological trends between the eastern coast of South America and the western coast of Africa. The polar ice cap of the Carboniferous Period covered the southern end of Pangaea. Glacial deposits, specifically till, of the same age and structure are found on many separate continents which would have been together in the continent of Pangaea.[20]

text: Paleomagnetic study of apparent polar wandering paths also support the theory of a supercontinent. Geologists can determine the movement of continental plates by examining the orientation of magnetic minerals in rocks; when rocks are formed, they take on the magnetic properties of the Earth and indicate in which direction the poles lie relative to the rock. Since the magnetic poles drift about the rotational pole with a period of only a few thousand years, measurements from numerous lavas spanning several thousand years are averaged to give an apparent mean polar position. Samples of sedimentary rock and intrusive igneous rock have magnetic orientations that are typically an average of the "secular variation" in the orientation of magnetic north because their remanent magnetizations are not acquired instantaneously. Magnetic differences between sample groups whose age varies by millions of years is due to a combination of true polar wander and the drifting of continents. The true polar wander component is identical for all samples, and can be removed, leaving geologists with the portion of this motion that shows continental drift and can be used to help reconstruct earlier continental positions.[21]

text: The continuity of mountain chains provides further evidence for Pangaea. One example of this is the Appalachian Mountains chain which extends from the southeastern United States to the Caledonides of Ireland, Britain, Greenland, and Scandinavia.[22]

text: Rifting and break-up

text: There were three major phases in the break-up of Pangaea. The first phase began in the Early-Middle Jurassic (about 175 Ma), when Pangaea began to rift from the Tethys Ocean in the east to the Pacific in the west. The rifting that took place between North America and Africa produced multiple failed rifts. One rift resulted in a new ocean, the North Atlantic Ocean.[22]

text: The Atlantic Ocean did not open uniformly; rifting began in the north-central Atlantic. The South Atlantic did not open until the Cretaceous when Laurasia started to rotate clockwise and moved northward with North America to the north, and Eurasia to the south. The clockwise motion of Laurasia led much later to the closing of the Tethys Ocean and the widening of the "Sinus Borealis", which later became the Arctic Ocean. Meanwhile, on the other side of Africa and along the adjacent margins of east Africa, Antarctica and Madagascar, new rifts were forming that would lead to the formation of the southwestern Indian Ocean that would open up in the Cretaceous.

text: The second major phase in the break-up of Pangaea began in the Early Cretaceous (150–140 Ma), when the minor supercontinent of Gondwana separated into multiple continents (Africa, South America, India, Antarctica, and Australia). The subduction at Tethyan Trench probably caused Africa, India and Australia to move northward, causing the opening of a "South Indian Ocean". In the Early Cretaceous, Atlantica, today's South America and Africa, finally separated from eastern Gondwana (Antarctica, India and Australia). Then in the Middle Cretaceous, Gondwana fragmented to open up the South Atlantic Ocean as South America started to move westward away from Africa. The South Atlantic did not develop uniformly; rather, it rifted from south to north.

text: Also, at the same time, Madagascar and India began to separate from Antarctica and moved northward, opening up the Indian Ocean. Madagascar and India separated from each other 100–90 Ma in the Late Cretaceous. India continued to move northward toward Eurasia at 15 centimeters (6 in) a year (a plate tectonic record), closing the eastern Tethys Ocean, while Madagascar stopped and became locked to the African Plate. New Zealand, New Caledonia and the rest of Zealandia began to separate from Australia, moving eastward toward the Pacific and opening the Coral Sea and Tasman Sea.

text: The third major and final phase of the break-up of Pangaea occurred in the early Cenozoic (Paleocene to Oligocene). Laurasia split when North America/Greenland (also called Laurentia) broke free from Eurasia, opening the Norwegian Sea about 60–55 Ma. The Atlantic and Indian Oceans continued to expand, closing the Tethys Ocean.

text: Meanwhile, Australia split from Antarctica and moved quickly northward, just as India had done more than 40 million years before. Australia is currently on a collision course with eastern Asia. Both Australia and India are currently moving northeast at 5–6 centimeters (2–3 in) a year. Antarctica has been near or at the South Pole since the formation of Pangaea about 280 Ma. India started to collide with Asia beginning about 35 Ma, forming the Himalayan orogeny, and also finally closing the Tethys Seaway; this collision continues today. The African Plate started to change directions, from west to northwest toward Europe, and South America began to move in a northward direction, separating it from Antarctica and allowing complete oceanic circulation around Antarctica for the first time. This motion, together with decreasing atmospheric carbon dioxide concentrations, caused a rapid cooling of Antarctica and allowed glaciers to form. This glaciation eventually coalesced into the kilometers-thick ice sheets seen today.[23] Other major events took place during the Cenozoic, including the opening of the Gulf of California, the uplift of the Alps, and the opening of the Sea of Japan. The break-up of Pangaea continues today in the Red Sea Rift and East African Rift.

text: Tectonic plate shift

text: Pangaea's formation is now commonly explained in terms of plate tectonics. The involvement of plate tectonics in Pangaea's[24] separation helps to show how it did not separate all at once, but at different times, in sequences. Additionally, after these separations, it has also been discovered that the separated land masses may have also continued to break apart multiple times. The formation of each environment and climate on Pangaea is due to plate tectonics, and thus, it is as a result of these shifts and changes different climatic pressures were placed on the life on Pangaea. Although plate tectonics was paramount in the formation of later land masses, it was also essential in the placement, climate, environments, habitats, and overall structure of Pangaea.[25]

text: What can also be observed in relation to tectonic plates and Pangaea, is the formations to such plates. Mountains and valleys form due to tectonic collisions as well as earthquakes and chasms. Consequentially, this shaped Pangaea and animal adaptations. Furthermore, plate tectonics can contribute to volcanic activity,[26] which is responsible for extinctions and adaptations which have evidently affected life over time, and without doubt on Pangaea.

text: Life

text: For the approximately 160 million years Pangaea existed, many species had fruitful times whereas others struggled. The Traversodontidae[27] is an example of such prospering animals, eating a diet of only plants. Plants dependent on spore reproduction had been taken out of the ecosystems, and replaced by the gymnosperm plant, which reproduces through the use of seeds instead. Later on, insects (beetles, dragonflies, mosquitos) also thrived during the Permian period 299 to 252 million years ago.[28] However, the Permian extinction at 252 Mya greatly impacted these insects in mass extinction, being the only mass extinction to affect insects. When the Triassic Period came, many reptiles were able to also thrive, including Archosaurs, which were an ancestor to modern-day crocodiles and birds.

text: Little is known about marine life during the existence of Pangaea. Scientists are unable to find substantial evidence or fossilized remains in order to assist them in answering such questions. However, a couple of marine animals have been determined to have existed at the time- the Ammonites and Brachiopods. Additionally, evidence pointing towards massive reefs with varied ecosystems, especially in the species of sponges and coral, have also been discovered.[citation needed]

text: Climate change after Pangaea

text: Pangaea has tremendously affected the setup of the world now. In the post Pangaea time period, the reconfiguration of continents and oceans has changed the climate of many areas. There is scientific evidence that proves that climate was drastically altered. When the continents separated and reformed themselves, it changed the flow of the oceanic currents and winds. The scientific reasoning behind all of the changes is Continental Drift. The theory of Continental Drift, created by Alfred Wegener, explained how the continents shifted Earth’s surface and how that affected many aspects such as climate, rock formations found on different continents and plant and animal fossils.[29] Wegener studied plant fossils from the frigid Arctic of Svalbard, Norway. He determined that such plants were not meant to adapt to a glacial climate. The fossils he found were from tropical plants that were meant to adapt and thrive in warmer and tropical climate.[30] Because we would not assume that the plant fossils were capable of traveling to a different place we suspect that Svalbard possibly had a warmer, less frigid climate in the past.[31]

text: When Pangaea separated, the reorganization of the continents changed the function of the oceans and seaways. The restructuring of the continents, changed and altered the distribution of warmth and coolness of the oceans. When North America and South America connected, it stopped equatorial currents from passing from the Atlantic Ocean to the Pacific Ocean.[32] Researchers have found evidence by using computer hydrological models to show that this strengthened the Gulf Stream by diverting more warm currents towards Europe. Warm waters at high latitudes led to an increased evaporation and eventually atmospheric moisture. Increased evaporation and atmospheric moisture resulted in increased precipitation. Evidence of increased precipitation is the development of snow and ice that covers Greenland, which led to an accumulation of the icecap. Greenland’s growing ice cap led to further global cooling.[32] Scientists also found evidence of global cooling through the separation of Australia and Antarctica and the formation of the Antarctic Ocean. Ocean currents in the newly formed Antarctic or Southern Ocean created a circumpolar current.[32] The creation of the new ocean that caused a circumpolar current eventually led to atmospheric currents that rotated from west to east. Atmospheric and oceanic currents stopped the transfer of warm, tropical air and water to the higher latitudes. As a result of the warm air and currents moving northward, Antarctica cooled down so much that it became frigid.

text: Although many of Alfred Wegener’s theories and conclusions were valid, scientists are constantly coming up with new innovative ideas or reasoning behind why certain things happen. Wegener’s theory of Continental Drift was later replaced by the theory of tectonic plates.[33]

text: Implications of extinction

text: There is evidence to suggest that the deterioration of northern Pangaea contributed to the Permian Extinction, one of Earth’s five major mass extinction events, which resulted in the loss of over 90% of marine and 70% of terrestrial species. There were three main sources of environmental deterioration which are believed to have had a hand in the extinction event.

text: The first of these sources is a loss of oxygen concentration in the ocean which caused deep water regions called the lysocline to grow shallower. With the lysocline shrinking, there were fewer places for calcite to dissolve in the ocean, considering calcite only dissolves at deep ocean depths. This led to the extinction of carbonate producers such as brachiopods and corals that relied on dissolved calcite to survive. The second source is the eruption of the Siberian Traps, a large volcanic event which is argued to be the result of Pangaean tectonic movement.[34] This had several negative repercussions on the environment, including metal loading and excess atmospheric carbon. Metal loading, the release of toxic metals from volcanic eruptions into the environment, led to acid rain and general stress on the environment. These toxic metals are known to infringe on vascular plants’ ability to photosynthesize, which may have resulted in the loss of Permian-era flora. Excess carbon dioxide in the atmosphere is believed to be the main cause of the shrinking of lysocline areas.

text: The third cause of this extinction event that can be attributed to northern Pangaea is the beginnings of anoxic ocean environments, or oceans with very low oxygen concentrations. The mix of anoxic oceans and ocean acidification due to metal loading led to increasingly acidic oceans,[35] which ultimately led to the extinction of Benthos.[36]


document_title: Capsid

question_text: what is the function of a viral capsid

question_tokens: what is the function of a viral capsid

text: Capsid

text: Specific shapes[edit]

text: Icosahedral[edit]

text:
The icosahedral structure is extremely common among viruses. The number and arrangement of capsomeres in an icosahedral capsid can be classified using the "quasi-equivalence principle" proposed by Donald Caspar and Aaron Klug.[10] Like the Goldberg polyhedra, an icosahedral structure can be regarded as being constructed from pentamers and hexamers. The structures can be indexed by two integers h and k, with

h
≥
1

{\displaystyle h\geq 1}

 and

k
≥
0

{\displaystyle k\geq 0}

; the structure can be thought of as taking h steps from the edge of a pentamer, turning 60 degrees counterclockwise, then taking k steps to get to the next pentamer. The triangulation number T for the capsid is defined as:

text: Icosahedral capsids contain 12 pentamers plus 10(T − 1) hexamers. [11][12] The T-number is representative of the size and complexity of the capsid proteins: all know viruses with T > 7 require auxillary proteins for assembly.[13] Geometric examples for many values of h, k, and T can be found at List of geodesic polyhedra and Goldberg polyhedra. Although this classification can be applied to the majority of known viruses, exceptions are known including the retroviruses where point mutations disrupt the symmetry.[12]

text: T-numbers can be represented in different ways, for example T = 1 can only be represented as an icosahedron or a dodecahedron and, depending on the type of quasi-symmetry, T = 3 can be presented as a truncated dodecahedron, an icosidodecahedron, or a truncated icosahedron and their respective duals a triakis icosahedron, a rhombic triacontahedron, or a pentakis dodecahedron.[14][clarification needed]

text: Prolate[edit]

text: An elongated icosahedron is a common shape for the heads of bacteriophages. Such a structure is composed of a cylinder with a cap at either end. The cylinder is composed of 10 triangles. The Q number, which can be any positive integer[dubious – discuss], specifies the number of triangles, composed of asymmetric subunits, that make up the 10 triangles of the cylinder. The caps are classified by the T number.[15]

text: Helical[edit]

text: Many rod-shaped and filamentous plant viruses have capsids with helical symmetry.[16] The helical structure can be described as a set of n 1-D molecular helices related by an n-fold axial symmetry.[17] The helical transformation are classified into two categories: one-dimensional and two-dimensional helical systems.[17] Creating an entire helical structure relies on a set of translational and rotational matrices which are coded in the protein data bank.[17] Helical symmetry is given by the formula P = μ x ρ, where μ is the number of structural units per turn of the helix, ρ is the axial rise per unit and P is the pitch of the helix. The structure is said to be open due to the characteristic that any volume can be enclosed by varying the length of the helix.[18] The most understood helical virus is the tobacco mosaic virus.[16] The virus is a single molecule of (+) strand RNA. Each coat protein on the interior of the helix bind three nucleotides of the RNA genome. Influenza A viruses differ by comprising multiple ribonucleoproteins, the viral NP protein organizes the RNA into a helical structure. The size is also different the tobacco mosaic virus has a 16.33 protein subunits per helical turn,[16] while the influenza A virus has a 28 amino acid tail loop.[citation needed]

text: Functions[edit]

text: The functions of the virion are to:

text:
protect the genome,
deliver the genome, and
interact with the host.

text: The virion must assemble a stable, protective protein shell to protect the genome from lethal chemical and physical agents. These include forms of natural radiation, extremes of pH or temperature and proteolytic and nucleolytic enzymes. Delivery of the genome is also important by specific binding to external receptors of the host cell, transmission of specific signals that induce uncoating of the genome, and induction of fusion with host cell membranes.[18][clarification needed]

text: Chemical properties[edit]

text: The viral particle must be metastable so that interactions can be readily reversed when entering and uncoating a new host cell. If it attains the minimum free energy state conformation will be irreversible associated with attachment and entry.[clarification needed] Each subunit of the capsid has identical bonding contacts with its neighbors, and the two binding contacts are usually noncovalent. The non-covalent bonding holds the structural unit together. The reversible formation of non-covalent bonds between properly folded subunits leads to error-free assembly and minimizes free energy.[18]

text: Origin and evolution[edit]

text: It has been suggested that many viral capsid proteins have evolved on multiple occasions from functionally diverse cellular proteins.[19] The recruitment of cellular proteins appears to have occurred at different stages of evolution, so that some cellular proteins were captured and refunctionalized prior to the divergence of cellular organisms into the three contemporary domains of life, whereas others were hijacked relatively recently. As a result, some capsid proteins are widespread in viruses infecting distantly related organisms (e.g., capsid proteins with the jelly-roll fold), whereas others are restricted to a particular group of viruses (e.g., capsid proteins of alphaviruses).[19]


document_title: Cell division

question_text: who discovered cells divide to make new cells

text: Cell division

text: Phases of cell division[edit]

text: This article relies too much on references to primary sources. Please improve this by adding secondary or tertiary sources. (July 2017) (Learn how and when to remove this template message)

text: Interphase[edit]

text: Interphase is the process a cell must go through before mitosis, meiosis, and cytokinesis.[5] Interphase consists of four main stages: G1, S, G0, and G2. G1 is a time of growth for the cell. If the cell does not progress through G1, the cell then enters a stage called G0. In G0, cells are still living but they are put on hold. The cells may later be called back into interphase if needed at a later time. There are checkpoints during interphase that allow the cell to be either progressed or denied further development. In S phase, the chromosomes are replicated in order for the genetic content to be maintained. During G2, the cell undergoes the final stages of growth before it enters the M phase. The M phase, can be either mitosis or meiosis depending on the type of cell. Germ cells undergo meiosis, while somatic cells will undergo mitosis. After the cell proceeds successfully through the M phase, it may then undergo cell division through cytokinesis. The control of each checkpoint is controlled by cyclin and cyclin dependent kinases. The progression of interphase is the result of the increased amount of cyclin. As the amount of cyclin increases, more and more cyclin dependent kinases attach to cyclin signaling the cell further into interphase. The peak of the cyclin attached to the cyclin dependent kinases this system pushes the cell out of interphase and into the M phase, where mitosis, meiosis, and cytokinesis occur.

text: Prophase[edit]

text: Prophase is the first stage of division. The nuclear envelope is broken down, long strands of chromatin condense to form shorter more visible strands called chromosomes, the nucleolus disappears, and microtubules attach to the chromosomes at the kinetochores present in the centromere.[6] Microtubules associated with the alignment and separation of chromosomes are referred to as the spindle and spindle fibers. Chromosomes will also be visible under a microscope and will be connected at the centromere. During this condensation and alignment period, homologous chromosomes may swap portions of their DNA in a process known as crossing over.

text: Metaphase[edit]

text: Metaphase is the stage in cell division when the chromosomes line up in the middle of the cell by MTOCs ( microtubule organizing center) by pushing and pulling on centromeres of both chromatids which causes the chromosome to move to the center. The chromosomes are still condensing and are currently at one step away from being the most coiled and condensed they will be.[7] Spindle and spindle fibers have already connected to the kinetochores. At this point, the chromosomes are ready to split into opposite poles of the cell towards the spindle to which they are connected. [8]

text: Anaphase[edit]

text: Anaphase is a very short stage of the cell cycle and occurs after the chromosomes align at the mitotic plate. After the chromosomes line up in the middle of the cell, the spindle fibers will pull them apart. The chromosomes are split apart as the sister chromatids move to opposite sides of the cell.[9]

text: Telophase[edit]

text: Telophase is the last stage of the cell cycle. Two cells form around the chromatin at the two poles of the cell. Two nuclear membranes begin to reform and the chromatin begin to unwind.[10]

text: Variants[edit]

text: Cells are broadly classified into two main categories: simple, non-nucleated prokaryotic cells, and complex, nucleated eukaryotic cells. Owing to their structural differences, eukaryotic and prokaryotic cells do not divide in the same way. Also, the pattern of cell division that transforms eukaryotic stem cells into gametes (sperm cells in males or egg cells in females), termed meiosis, is different from that of the division of somatic cells in the body.

text: Degradation[edit]

text: Multicellular organisms replace worn-out cells through cell division. In some animals, however, cell division eventually halts. In humans this occurs, on average, after 52 divisions, known as the Hayflick limit. The cell is then referred to as senescent. Cells stop dividing because the telomeres, protective bits of DNA on the end of a chromosome required for replication, shorten with each copy, eventually being consumed.[citation needed] Cancer cells, on the other hand, are not thought to degrade in this way, if at all. An enzyme called telomerase, present in large quantities in cancerous cells, rebuilds the telomeres, allowing division to continue indefinitely.

text: History[edit]

text: A cell division under microscope was first discovered by German botanist Hugo von Mohl in 1835 as he worked over Green algae Cladophora glomerata.[12]