Human Genetics

"Human Genetics" redirects here. For the journal, see Human Genetics (journal).

For a non-technical introduction to the topic, see Introduction to genetics.

A small piece of humanDNA

Human genetics is the study of inheritance as it occurs in human beings. Human genetics encompasses a variety of overlapping fields including:classical genetics, cytogenetics, molecular genetics, biochemical genetics, genomics, population genetics, developmental genetics, clinical genetics, and genetic counseling.

Genes can be the common factor of the qualities of most human-inherited traits. Study of human genetics can be useful as it can answer questions about human nature, understand the diseases and development of effective disease treatment, and understand genetics of human life. This article describes only basic features of human genetics; for the genetics of disorders please see: Medical genetics.

Human Heart Information

The human heart is an organ that provides a continuous blood circulation through the cardiac cycle and is a vital organ in the human body.^[1] The heart is divided into four main chambers: the two upper chambers are called the left atrium and the right atrium (plural atria) and the two lower chambers are called the right and the left ventricle.^[2] There is a thick wall of muscle separating the right side and the left side of the heart called the septum. Normally with each heartbeat, the right ventricle pumps the same amount of blood into the lungs that the left ventricle pumps out into the body. Physicians commonly refer to the right atrium and right ventricle together as the right heart and to the left atrium and left ventricle as the left heart.^[3]

The electric energy that stimulates the heart occurs in the sinoatrial node, which produces a definite potential and then discharges, sending an impulse across the atria.

It is not very well known how the electric signal moves in the atria. It seems that it moves in a radial way, but Bachmann's bundle and coronary sinus muscle play a role in conduction between the two atria, which have a nearly simultaneous systole.^[4][5][6] While in the ventricles, the signal is carried by specialized tissue called the Purkinje fibers which then transmit the electric charge to themyocardium.^[7]

The human embryonic heart begins beating at around 21 days after conception, or five weeks after the last normal menstrual period(LMP). The first day of the LMP is normally used to date the start of the gestation (pregnancy).

The human heart begins beating at a rate near the mother’s, about 75–80 beats per minute (BPM). The embryonic heart rate (EHR) then accelerates by approximately 100 BPM during the first month to peak at 165–185 BPM during the early seventh week after conception (early ninth week after the LMP). This acceleration is approximately 3.3 BPM per day, or about 10 BPM every three days, which is an increase of 100 BPM in the first month.^[8][9][10] The regression formula, which describes this acceleration before the embryo reaches 25 mm in crown-rump length, or 9.2 LMP weeks, is: the age in days = EHR(0.3)+6.^[11]

After 9.1 weeks after the LMP, it decelerates to about 152 BPM (±25 BPM) during the 15th week after LMP. After the 15th week, the deceleration slows to an average rate of about 145 (±25 BPM) BPM, at term. There is no difference in female and male heart rates before birth.

The human heart and its disorders (cardiopathies) are studied primarily by cardiologists.

Human Skeleton

The human skeleton is composed of 270 bones at birth^[1][2][3] and by the time adulthood is reached, some bones have fused together to give a total of 206 bones in the body. The human skeleton can be divided into the axial skeleton and the appendicular skeleton. The axial skeleton is formed by the vertebral column, the rib cage and theskull. The appendicular skeleton, which is attached to the axial skeleton, is formed by the pectoral girdles, the pelvic girdle and the bones of the upper and lower limbs.

The human skeleton serves six major functions; support, movement, protection, production of blood cells, storage of ions and endocrine regulation.

The human skeleton is not as sexually dimorphic as that of many other primate species, but subtle differences between sexes in the morphology of the skull, dentition, long bones, and pelves exist. In general, female skeletal elements tend to be smaller and less robust than corresponding male elements within a given population. The pelvis in female skeletons is also different from that of males in order to facilitate child birth.

Marine Aquarium

See also: Reef aquarium

A marine aquarium

Corals in a marine aquarium

A marine aquarium is an aquarium that keeps marine plants and animals in a contained environment. Marine aquaria are further subdivided by hobbyists into fish only (FO), fish only with live rock (FOWLR), and reef aquaria. Fish only tanks often showcase large or aggressive marine fish species and generally rely on mechanical and chemical filtration. FOWLR and reef tanks use live rock, a material composed of coral skeletons harboring beneficial nitrogen waste metabolizing bacteria, as a means of more natural biological filtration.

Marine fishkeeping is different from its freshwater counterpart because of the fundamental differences in the constitution of saltwater and the resulting differences in the adaptation of its inhabitants. A stable marine aquarium requires more equipment than freshwater systems, and generally requires more stringent water quality monitoring.^[1] The inhabitants of a marine aquarium are often difficult to acquire and are usually more expensive than freshwater aquarium inhabitants. However, the inhabitants of saltwater aquariums are usually much more spectacular than freshwater aquarium fish.

Marine reef aquarium at the London aquarium

Biography of William Shakespeare

This article is about the poet and playwright. For other persons of the same name, see William Shakespeare (disambiguation). For other uses of "Shakespeare", seeShakespeare (disambiguation).

William Shakespeare
The Chandos portrait, artist and authenticity unconfirmed. National Portrait Gallery, London.
Born	Baptised 26 April 1564 (birth date unknown) Stratford-upon-Avon, Warwickshire,England
Died	23 April 1616 (aged 52) Stratford-upon-Avon, Warwickshire, England
Occupation	Playwright, poet, actor
Period	English Renaissance
Spouse(s)	Anne Hathaway (m. 1582–1616)
Children	Susanna Hall Hamnet Shakespeare Judith Quiney
Relative(s)	John Shakespeare (father) Mary Shakespeare (mother)

William Shakespeare (26 April 1564 (baptised) – 23 April 1616)^{[nb 1]} was an English poet and playwright, widely regarded as the greatest writer in the English language and the world's pre-eminent dramatist.^[1] He is often called England's national poet and the "Bard of Avon".^{[2][nb 2]} His extant works, including some collaborations, consist of about 38 plays,^{[nb 3]} 154 sonnets, two longnarrative poems, and a few other verses, the authorship of some of which is uncertain. His plays have been translated into every major living language and are performed more often than those of any other playwright.^[3]

Shakespeare was born and brought up in Stratford-upon-Avon. At the age of 18, he married Anne Hathaway, with whom he had three children: Susanna, and twins Hamnet and Judith. Between 1585 and 1592, he began a successful career in London as an actor, writer, and part-owner of a playing company called the Lord Chamberlain's Men, later known as the King's Men. He appears to have retired to Stratford around 1613 at age 49, where he died three years later. Few records of Shakespeare's private life survive, and there has been considerable speculation about such matters as his physical appearance, sexuality, religious beliefs, and whether the works attributed to him were written by others.^[4]

Shakespeare produced most of his known work between 1589 and 1613.^{[5][nb 4]} His early plays were mainly comedies and histories, genres he raised to the peak of sophistication and artistry by the end of the 16th century. He then wrote mainly tragedies until about 1608, including Hamlet, King Lear, Othello, and Macbeth, considered some of the finest works in the English language. In his last phase, he wrote tragicomedies, also known as romances, and collaborated with other playwrights.

Many of his plays were published in editions of varying quality and accuracy during his lifetime. In 1623, John Heminges and Henry Condell, two friends and fellow actors of Shakespeare, published the First Folio, a collected edition of his dramatic works that included all but two of the plays now recognised as Shakespeare's. It was prefaced with a poem by Ben Jonson, in which Shakespeare is hailed, presciently, as "not of an age, but for all time."^[6]

Shakespeare was a respected poet and playwright in his own day, but his reputation did not rise to its present heights until the 19th century. The Romantics, in particular, acclaimed Shakespeare's genius, and the Victorians worshipped Shakespeare with a reverence that George Bernard Shaw called "bardolatry".^[7] In the 20th century, his work was repeatedly adopted and rediscovered by new movements in scholarship and performance. His plays remain highly popular today and are constantly studied, performed, and reinterpreted in diverse cultural and political contexts throughout the world.

Biography of John Milton

For other people named John Milton, see John Milton (disambiguation).

John Milton
Portrait of John Milton in National Portrait Gallery, London ca. 1629. Unknown artist (detail)
Born	9 December 1608 (Old style) Bread Street, Cheapside, London, England
Died	8 November 1674 (aged 65) Bunhill, London, England
Resting place	St Giles-without-Cripplegate
Occupation	Poet, prose polemicist, civil servant
Language	English, Latin, French, German,Greek, Hebrew, Italian, Spanish,Aramaic, Syriac
Nationality	English
Alma mater	Christ's College, University of Cambridge
Signature

John Milton (9 December 1608 – 8 November 1674) was an English poet, polemicist, a scholarly man of letters, and a civil servant for the Commonwealth of England under Oliver Cromwell. He wrote at a time of religious flux and political upheaval, and is best known for his epic poem Paradise Lost.

Milton's poetry and prose reflect deep personal convictions, a passion for freedom and self-determination, and the urgent issues and political turbulence of his day. Writing in English, Latin, and Italian, he achieved international renown within his lifetime, and his celebrated Areopagitica (written in condemnation of pre-publication censorship) is among history's most influential and impassioned defenses of free speech and freedom of the press.

William Hayley's 1796 biography called him the "greatest English author,"^[1] and he remains generally regarded "as one of the preeminent writers in the English language,"^[2] though critical reception has oscillated in the centuries since his death (often on account of his republicanism). Samuel Johnson praised Paradise Lost as "a poem which...with respect to design may claim the first place, and with respect to performance, the second, among the productions of the human mind," though he (a Tory and recipient of royal patronage) described Milton's politics as those of an "acrimonious and surly republican".^[3]

Because of his republicanism, Milton has been the subject of centuries of British partisanship (a "nonconformist" biography by John Toland, a hostile account by Anthony à Wood

Biography of Marcus Aurelius

Marcus Aurelius Antoninus Augustus
16th Emperor of the Roman Empire
Bust of Marcus Aurelius in the Musée Saint-Raymond, Toulouse.
Reign	8 March 161–169 (with Lucius Verus); 169–177 (alone); 177 – March 180 (with Commodus)
Full name	Marcus Annius Catilius Severus (or Marcus Catilius Severus; birth to marriage) Marcus Annius Verus (marriage to adoption byAntoninus Pius) Marcus Aelius Aurelius Verus Caesar (as imperial heir) Caesar Marcus Aurelius Antoninus Augustus (as emperor)
Born	26 April 121
Birthplace	Rome
Died	17 March 180 (aged 58)
Place of death	Vindobona or Sirmium
Buried	Hadrian's Mausoleum
Predecessor	Antoninus Pius
Successor	Commodus (alone)
Wife	Faustina the Younger
Issue	14, incl. Commodus, Marcus Annius Verus, Antoninus andLucilla
Dynasty	Antonine
Father	Marcus Annius Verus
Mother	Domitia Lucilla

Marcus Aurelius (Latin: Marcus Aurelius Antoninus Augustus;^{[1][notes 1]} 26 April 121 AD – 17 March 180 AD) was a Roman Emperorfrom 161 to 180. He ruled with Lucius Verus as co-emperor from 161 until Verus' death in 169. He was the last of the Five Good Emperors, and is also considered one of the most important Stoic philosophers.

During his reign, the Empire defeated a revitalized Parthian Empire in the East; Aurelius' general Avidius Cassius sacked the capitalCtesiphon in 164. In central Europe, Aurelius fought the Marcomanni, Quadi, and Sarmatians with success during the Marcomannic Wars, with the threat of the Germanic tribes beginning to represent a troubling reality for the Empire. A revolt in the East led by Avidius Cassius failed to gain momentum and was suppressed immediately.

Marcus Aurelius' Stoic tome Meditations, written in Greek while on campaign between 170 and 180, is still revered as a literary monument to a philosophy of service and duty, describing how to find and preserve equanimity in the midst of conflict by following nature as a source of guidance and inspiration.

                                                                                   
 

Biography of King Arthur

"Arthur Pendragon" redirects here. For other uses, see Arthur Pendragon (disambiguation).

For other uses, see King Arthur (disambiguation).

Statue of King Arthur,Hofkirche, Innsbruck, designed byAlbrecht Dürer and cast by Peter Vischer the Elder, 1520s^[1]

King Arthur of Britain, byHoward Pyle from The Story of King Arthur and His Knights. (1903)

King Arthur is a legendary British leader of the late 5th and early 6th centuries, who, according to medieval histories and romances, led the defence of Britain against Saxon invaders in the early 6th century. The details of Arthur's story are mainly composed of folklore and literary invention, and his historical existence is debated and disputed by modern historians.^[2] The sparse historical background of Arthur is gleaned from various sources, including the Annales Cambriae, the Historia Brittonum, and the writings of Gildas. Arthur's name also occurs in early poetic sources such as Y Gododdin.^[3]

The legendary Arthur developed as a figure of international interest largely through the popularity of Geoffrey of Monmouth's fanciful and imaginative 12th-century Historia Regum Britanniae (History of the Kings of Britain).^[4] Some Welsh and Breton tales and poems relating the story of Arthur date from earlier than this work; in these works, Arthur appears either as a great warrior defending Britain from human and supernatural enemies or as a magical figure of folklore, sometimes associated with the Welsh Otherworld, Annwn.^[5] How much of Geoffrey's Historia(completed in 1138) was adapted from such earlier sources, rather than invented by Geoffrey himself, is unknown.

Although the themes, events and characters of the Arthurian legend varied widely from text to text, and there is no one canonical version, Geoffrey's version of events often served as the starting point for later stories. Geoffrey depicted Arthur as a king of Britain who defeated the Saxons and established an empire over Britain, Ireland, Iceland, Norway and Gaul. Many elements and incidents that are now an integral part of the Arthurian story appear in Geoffrey's Historia, including Arthur's father Uther Pendragon, the wizard Merlin, Arthur's wife Guinevere, the swordExcalibur, Arthur's conception at Tintagel, his final battle against Mordred at Camlann and final rest in Avalon. The 12th-century French writerChrétien de Troyes, who added Lancelot and the Holy Grail to the story, began the genre of Arthurian romance that became a significant strand ofmedieval literature. In these French stories, the narrative focus often shifts from King Arthur himself to other characters, such as various Knights of the Round Table. Arthurian literature thrived during the Middle Ages but waned in the centuries that followed until it experienced a major resurgence in the 19th century. In the 21st century, the legend lives on, not only in literature but also in adaptations for theatre, film, television, comics and other media.