Africa is the world's second largest and second most-populous continent, being behind Asia in both categories. At about 30.3 million km2 including adjacent islands, it covers 6% of Earth's total surface area and 20% of its land area. With 1.2 billion people as of 2016, it accounts for about 16% of the world's human population. The continent is surrounded by the Mediterranean Sea to the north, the Isthmus of Suez and the Red Sea to the northeast, the Indian Ocean to the southeast and the Atlantic Ocean to the west; the continent includes various archipelagos. It contains 54 recognised sovereign states, nine territories and two de facto independent states with limited or no recognition; the majority of the continent and its countries are in the Northern Hemisphere, with a substantial portion and number of countries in the Southern Hemisphere. Africa's average population is the youngest amongst all the continents. Algeria is Africa's largest country by area, Nigeria is its largest by population. Africa central Eastern Africa, is accepted as the place of origin of humans and the Hominidae clade, as evidenced by the discovery of the earliest hominids and their ancestors as well as ones that have been dated to around 7 million years ago, including Sahelanthropus tchadensis, Australopithecus africanus, A. afarensis, Homo erectus, H. habilis and H. ergaster—the earliest Homo sapiens, found in Ethiopia, date to circa 200,000 years ago.
Africa encompasses numerous climate areas. Africa hosts a large diversity of ethnicities and languages. In the late 19th century, European countries colonised all of Africa. African nations cooperate through the establishment of the African Union, headquartered in Addis Ababa. Afri was a Latin name used to refer to the inhabitants of then-known northern Africa to the west of the Nile river, in its widest sense referred to all lands south of the Mediterranean; this name seems to have referred to a native Libyan tribe, an ancestor of modern Berbers. The name had been connected with the Phoenician word ʿafar meaning "dust", but a 1981 hypothesis has asserted that it stems from the Berber word ifri meaning "cave", in reference to cave dwellers; the same word may be found in the name of the Banu Ifran from Algeria and Tripolitania, a Berber tribe from Yafran in northwestern Libya. Under Roman rule, Carthage became the capital of the province it named Africa Proconsularis, following its defeat of the Carthaginians in the Third Punic War in 146 BC, which included the coastal part of modern Libya.
The Latin suffix -ica can sometimes be used to denote a land. The Muslim region of Ifriqiya, following its conquest of the Byzantine Empire's Exarchatus Africae preserved a form of the name. According to the Romans, Africa lay to the west of Egypt, while "Asia" was used to refer to Anatolia and lands to the east. A definite line was drawn between the two continents by the geographer Ptolemy, indicating Alexandria along the Prime Meridian and making the isthmus of Suez and the Red Sea the boundary between Asia and Africa; as Europeans came to understand the real extent of the continent, the idea of "Africa" expanded with their knowledge. Other etymological hypotheses have been postulated for the ancient name "Africa": The 1st-century Jewish historian Flavius Josephus asserted that it was named for Epher, grandson of Abraham according to Gen. 25:4, whose descendants, he claimed, had invaded Libya. Isidore of Seville in his 7th-century Etymologiae XIV.5.2. Suggests "Africa comes from the Latin aprica, meaning "sunny".
Massey, in 1881, stated that Africa is derived from the Egyptian af-rui-ka, meaning "to turn toward the opening of the Ka." The Ka is the energetic double of every person and the "opening of the Ka" refers to a womb or birthplace. Africa would be, for the Egyptians, "the birthplace." Michèle Fruyt in 1976 proposed linking the Latin word with africus "south wind", which would be of Umbrian origin and mean "rainy wind". Robert R. Stieglitz of Rutgers University in 1984 proposed: "The name Africa, derived from the Latin *Aphir-ic-a, is cognate to Hebrew Ophir." Ibn Khallikan and some other historians claim that the name of Africa came from a Himyarite king called Afrikin ibn Kais ibn Saifi called "Afrikus son of Abrahah" who subdued Ifriqiya. Africa is considered by most paleoanthropologists to be the oldest inhabited territory on Earth, with the human species originating from the continent. During the mid-20th century, anthropologists discovered many fossils and evidence of human occupation as early as 7 million years ago.
Fossil remains of several species of early apelike humans thought to have evolved into modern man, such as Australopithecus afarensis (radiometrically dated to 3.9–3.0 million years BP, Paranthropus boisei and Homo ergaster have been discovered. After the evolution of Homo sapiens sapiens 150,000 to 100,000 years BP in Africa, the continent was populated by groups of hunter-gatherers; these first modern humans left Africa and populated the rest of the globe during the Out of Africa II migration dated to 50,000 years BP, exiting the continent eith
In botany, phyllotaxis or phyllotaxy is the arrangement of leaves on a plant stem. Phyllotactic spirals form a distinctive class of patterns in nature; the term was coined by Charles Bonnet to describe the arrangement of leaves on a plant. The basic arrangements of leaves on a stem are alternate. Leaves may be whorled if several leaves arise, or appear to arise, from the same level on a stem. With an opposite leaf arrangement, two leaves arise from the stem at the same level, on opposite sides of the stem. An opposite leaf pair can be thought of as a whorl of two leaves. With an alternate pattern, each leaf arises at a different point on the stem. Distichous phyllotaxis called "two-ranked leaf arrangement" is a special case of either opposite or alternate leaf arrangement where the leaves on a stem are arranged in two vertical columns on opposite sides of the stem. Examples include various bulbous plants such as Boophone, it occurs in other plant habits such as those of Gasteria or Aloe seedlings, in mature plants of related species such as Kumara plicatilis.
In an opposite pattern, if successive leaf pairs are 90 degrees apart, this habit is called decussate. It is common in members of the family Crassulaceae Decussate phyllotaxis occurs in the Aizoaceae. In genera of the Aizoaceae, such as Lithops and Conophytum, many species have just two developed leaves at a time, the older pair folding back and dying off to make room for the decussately oriented new pair as the plant grows; the whorled arrangement is unusual on plants except for those with short internodes. Examples of trees with whorled phyllotaxis are Brabejum stellatifolium and the related genus Macadamia. A whorl can occur as a basal structure where all the leaves are attached at the base of the shoot and the internodes are small or nonexistent. A basal whorl with a large number of leaves spread out in a circle is called a rosette; the rotational angle from leaf to leaf in a repeating spiral can be represented by a fraction of a full rotation around the stem. Alternate distichous leaves will have an angle of 1/2 of a full rotation.
In beech and hazel the angle is 1/3, in oak and apricot it is 2/5, in sunflowers and pear, it is 3/8, in willow and almond the angle is 5/13. The numerator and denominator consist of a Fibonacci number and its second successor; the number of leaves is sometimes called rank, in the case of simple Fibonacci ratios, because the leaves line up in vertical rows. With larger Fibonacci pairs, the pattern becomes non-repeating; this tends to occur with a basal configuration. Examples can be found in composite flowers and seed heads; the most famous example is the sunflower head. This phyllotactic pattern creates an optical effect of criss-crossing spirals. In the botanical literature, these designs are described by the number of counter-clockwise spirals and the number of clockwise spirals; these turn out to be Fibonacci numbers. In some cases, the numbers appear to be multiples of Fibonacci numbers because the spirals consist of whorls; the pattern of leaves on a plant is controlled by the local depletion of the plant hormone auxin in certain areas of the meristem.
Leaves become initiated in localized areas. When a leaf is initiated and begins development, auxin begins to flow towards it, thus depleting auxin from another area on the meristem where a new leaf is to be initiated; this gives rise to a self-propagating system, controlled by the ebb and flow of auxin in different regions of the meristematic topography. Insight into the mechanism had to wait until Wilhelm Hofmeister proposed a model in 1868. A primordium, the nascent leaf, forms at the least crowded part of the shoot meristem; the golden angle between successive leaves is the blind result of this jostling. Since three golden arcs add up to more than enough to wrap a circle, this guarantees that no two leaves follow the same radial line from center to edge; the generative spiral is a consequence of the same process that produces the clockwise and counter-clockwise spirals that emerge in densely packed plant structures, such as Protea flower disks or pinecone scales. In modern times, researchers such as Snow and Snow have continued these lines of inquiry.
Computer modeling and morphological studies have refined Hoffmeister's ideas. Questions remain about the details. Botanists are divided on whether the control of leaf migration depends on chemical gradients among the primordia or purely mechanical forces. Lucas rather than Fibonacci numbers have been observed in a few plants and the leaf positioning appears to be random. Physical models of phyllotaxis date back to Airy's experiment of packing hard spheres. Gerrit van Iterson diagrammed. Douady et al. showed that phyllotactic patterns emerge as self-organizing processes in dynamic systems. In 1991, Levitov proposed that lowest energy configurations of repulsive particles in cylindrical geometries reproduce the spirals of botanical phyllotaxis. More Nisoli et al. showed that to be true by constructing a "magnetic cactus" made of magnetic dipoles mounted on bearings stacked along a "stem". They demonstrated that these interacting particles can access novel dynamical phenomena beyond what botany yields: a "Dynamical Phyllotaxis" family of non local topological solitons emerge in the nonlinear regime of these systems, as well as purely classical rotons and maxons in the spectrum of linear excitations.
Close packing of spheres generates a dodecahedral tessellation with pentaprismic fac
The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
The Zygophyllales are an order of dicotyledonous plants, comprising the following two families: Family Zygophyllaceae Family KrameriaceaeAccording to the Angiosperm Phylogeny Group both families are unplaced to order, but included in the Eurosids I. The APG III system of 2009, recognized this order. If the monogeneric family Krameriaceae shares little common traits with the family Zygophyllaceae, researchers see little advantage in keeping it as a separate family; the name Zygophyllales can be used. The order keeps unchanged in the APG IV system. Under the Cronquist system, the Zygophyllaceae were included within the Sapindales, the Krameriaceae within the Polygalales
Wikispecies is a wiki-based online project supported by the Wikimedia Foundation. Its aim is to create a comprehensive free content catalogue of all species. Jimmy Wales stated that editors are not required to fax in their degrees, but that submissions will have to pass muster with a technical audience. Wikispecies is available under the GNU Free Documentation License and CC BY-SA 3.0. Started in September 2004, with biologists across the world invited to contribute, the project had grown a framework encompassing the Linnaean taxonomy with links to Wikipedia articles on individual species by April 2005. Benedikt Mandl co-ordinated the efforts of several people who are interested in getting involved with the project and contacted potential supporters in early summer 2004. Databases were evaluated and the administrators contacted, some of them have agreed on providing their data for Wikispecies. Mandl defined two major tasks: Figure out how the contents of the data base would need to be presented—by asking experts, potential non-professional users and comparing that with existing databases Figure out how to do the software, which hardware is required and how to cover the costs—by asking experts, looking for fellow volunteers and potential sponsorsAdvantages and disadvantages were discussed by the wikimedia-I mailing list.
The board of directors of the Wikimedia Foundation voted by 4 to 0 in favor of the establishment of a Wikispecies. The project is hosted at species.wikimedia.org. It was merged to a sister project of Wikimedia Foundation on September 14, 2004. On October 10, 2006, the project exceeded 75,000 articles. On May 20, 2007, the project exceeded 100,000 articles with a total of 5,495 registered users. On September 8, 2008, the project exceeded 150,000 articles with a total of 9,224 registered users. On October 23, 2011, the project reached 300,000 articles. On June 16, 2014, the project reached 400,000 articles. On January 7, 2017, the project reached 500,000 articles. On October 30, 2018, the project reached 600,000 articles, a total of 1.12 million pages. Wikispecies comprises taxon pages, additionally pages about synonyms, taxon authorities, taxonomical publications, institutions or repositories holding type specimen. Wikispecies asks users to use images from Wikimedia Commons. Wikispecies does not allow the use of content.
All Species Foundation Catalogue of Life Encyclopedia of Life Tree of Life Web Project List of online encyclopedias The Plant List Wikispecies, The free species directory that anyone can edit Species Community Portal The Wikispecies Charter, written by Wales
The rosids are members of a large clade of flowering plants, containing about 70,000 species, more than a quarter of all angiosperms. The clade is divided into 16 to 20 orders, depending upon circumscription and classification; these orders, in turn, together comprise about 140 families. Fossil rosids are known from the Cretaceous period. Molecular clock estimates indicate that the rosids originated in the Aptian or Albian stages of the Cretaceous, between 125 and 99.6 million years ago. The name is based upon the name "Rosidae", understood to be a subclass. In 1967, Armen Takhtajan showed that the correct basis for the name "Rosidae" is a description of a group of plants published in 1830 by Friedrich Gottlieb Bartling; the clade was renamed "Rosidae" and has been variously delimited by different authors. The name "rosids" is informal and not assumed to have any particular taxonomic rank like the names authorized by the ICBN; the rosids are monophyletic based upon evidence found by molecular phylogenetic analysis.
Three different definitions of the rosids were used. Some authors included the orders Vitales in the rosids. Others excluded both of these orders; the circumscription used in this article is that of the APG IV classification, which includes Vitales, but excludes Saxifragales. The rosids and Saxifragales form the superrosids clade; this is one of three groups that compose the Pentapetalae, the others being Dilleniales and the superasterids. The rosids consist of two groups: the eurosids; the eurosids, in turn, are divided into two groups: malvids. The rosids consist of 17 orders. In addition to Vitales, there are 8 orders in malvids; some of the orders have only been recognized. These are Vitales, Crossosomatales and Huerteales; the phylogeny of Rosids shown below is adapted from the Angiosperm Phylogeny Group website. The nitrogen-fixing clade contains a high number of actinorhizal plants. Not all plants in this clade are actinorhizal, however. Media related to Rosids at Wikimedia Commons
Zygophyllaceae is a family, of flowering plants, that contain the bean-caper and caltrop. The family includes around 285 species in 22 genera. In the APG III system of classification, the families Zygophyllaceae and Krameriaceae compose the order Zygophyllales. In the previous version of their classification system, the Angiosperm Phylogeny Group had included the option of placing Krameria within Zygophyllaceae. Zygophyllaceae are divided into five subfamilies. Molecular phylogenies of the family were published in 2000, 2018. Phylogenies of groups within the family the predominantly southern African species of Zygophylloideae have been published. Plants in the family Zygophyllaceae may be shrubs, or herbs, they are found in dry habitats. The leaves are opposite with stipules and spines; some are cultivated as ornamental plants, such as Guaiacum, Zygophyllum and Larrea species. King Clone, a creosote bush in California, may be the oldest living organism. Peganum was in Zygophyllaceae before being moved to the newly created family Nitrariaceae.
Modern molecular phylogenetics suggest the following relationships: Family Zygophyllaceae Flowers in Israel Chilean Zygophyllaceae Chileflora