Central Africa is the core region of the African continent which includes Burundi, the Central African Republic, the Democratic Republic of the Congo, and Rwanda. All of the states in the UN subregion of Middle Africa, plus those otherwise commonly reckoned in Central Africa, since its independence in 2011, South Sudan has been commonly included in the region. The Central African Federation, called the Federation of Rhodesia and Nyasaland, was made up of what are now the nations of Malawi and these states are now typically considered part of Southern Africa. Archeological finds in Central Africa have been discovered dating back over 100,000 years, according to Zangato and Holl, there is evidence of iron-smelting in the Central African Republic and Cameroon that may date back to 3000 to 2500 BCE. Extensive walled settlements have recently found in Northeast Nigeria, approximately 60 km southwest of Lake Chad dating to the first millennium BCE. Trade and improved agricultural techniques supported more sophisticated societies, leading to the civilizations of Sao, Bornu, Baguirmi.
Around 1000 BCE, Bantu migrants had reached the Great Lakes Region in Central Africa, halfway through the first millennium BCE, the Bantu had settled as far south as what is now Angola. The Sao civilization flourished from ca. the sixth century BCE to as late as the sixteenth century CE in northern Central Africa, the Sao lived by the Chari River south of Lake Chad in territory that became part of Cameroon and Chad. They are the earliest people to have clear traces of their presence in the territory of modern Cameroon. Today, several groups of northern Cameroon and southern Chad. Sao artifacts show that they were skilled workers in bronze, finds include bronze sculptures and terra cotta statues of human and animal figures, funerary urns, household utensils, highly decorated pottery, and spears. The largest Sao archaeological finds have been south of Lake Chad. The Kanem-Bornu Empire was centered in the Chad Basin and it was known as the Kanem Empire from the 9th century CE onward and lasted as the independent kingdom of Bornu until 1900.
The history of the Empire is mainly known from the Royal Chronicle or Girgam discovered in 1851 by the German traveller Heinrich Barth, Kanem rose in the 8th century in the region to the north and east of Lake Chad. The Kanem empire went into decline, and in the 14th century was defeated by Bilala invaders from the Lake Fitri region, the Kanuri people led by the Sayfuwa migrated to the west and south of the lake, where they established the Bornu Empire. By the late 16th century the Bornu empire had expanded and recaptured the parts of Kanem that had been conquered by the Bulala, satellite states of Bornu included the Damagaram in the west and Baguirmi to the southeast of Lake Chad. The Shilluk Kingdom was centered in South Sudan from the 15th century from along a strip of land along the bank of White Nile. The capital and royal residence was in the town of Fashoda, the kingdom was founded during the mid-fifteenth century CE by its first ruler, Nyikang
The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician.
The first ammonites, species of molluscs, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common.
The Devonian Period is formally broken into Early and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers
The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe.
Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms. During the Permian, all the Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment.
The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, arthropods, the period saw a massive desert covering the interior of Pangaea
Trilobites are a fossil group of extinct marine arachnomorph arthropods that form the class Trilobita. Trilobites form one of the earliest known groups of arthropods, Trilobites finally disappeared in the mass extinction at the end of the Permian about 250 million years ago. The trilobites were among the most successful of all early animals, by the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, a fossil record was left behind. The study of fossils has facilitated important contributions to biostratigraphy, evolutionary biology. Trilobites are often placed within the arthropod subphylum Schizoramia within the superclass Arachnomorpha, Trilobites had many lifestyles, some moved over the sea bed as predators, scavengers, or filter feeders, and some swam, feeding on plankton. Most lifestyles expected of modern marine arthropods are seen in trilobites, some trilobites are even thought to have evolved a symbiotic relationship with sulfur-eating bacteria from which they derived food.
The earliest trilobites known from the record are redlichiids and ptychopariid bigotinids dated to some 540 to 520 million years ago. Contenders for the earliest trilobites include Profallotaspis jakutensis, Fritzaspis spp, all trilobites are thought to have originated in present-day Siberia, with subsequent distribution and radiation from this location. All Olenellina lack facial sutures, and this is thought to represent the original state, other groups show secondary lost facial sutures, such as all Agnostina and some Phacopina. Earlier trilobites may be found and could shed light on the origin of trilobites. Three specimens of a trilobite from Morocco, Megistaspis hammondi, dated 478 million years old contain fossilized soft parts. Early trilobites show all the features of the group as a whole. Morphological similarities between early trilobites and other Cambrian arthropods make analysis of ancestral relationships difficult, that trilobites share a common ancestor with other arthropods before the Ediacaran-Cambrian boundary is still reasonable to assume.
Changes included narrowing of the thorax and increasing or decreasing numbers of thoracic segments, specific changes to the cephalon are noted, variable glabella size and shape, position of eyes and facial sutures, and hypostome specialization. Several morphologies appeared independently within different major taxa, the loss of surface detail in the cephalon, pygidium, or the thoracic furrows, is a common evolutionary trend. Notable examples of this were the orders Agnostida and Asaphida, effacement is believed to be an indication of either a burrowing lifestyle or a pelagic one. Effacement poses a problem for taxonomists since the loss of details can make the determination of phylogenetic relationships difficult, tectonic breakup of Pannotia allowed for the diversification and radiation expressed in the Cambrian as the distinctive olenellid province and the separate redlichid province
In paleogeography, Gondwanaland, is the name given to an ancient supercontinent. It is believed to have sutured about 600 to 530 million years ago, Gondwana formed prior to Pangaea, and became part of it. Around 335 to 250 million years ago Gondwana and Laurasia joined together to form the supercontinent Pangaea, Gondwana separated from Laurasia in the breakup of Pangaea, drifting farther south after the split. Gondwana itself also broke apart, the continent of Gondwana was named by Austrian scientist Eduard Suess, after the Gondwana region of central northern India which is derived from Sanskrit for forest of the Gonds. The name had previously used in a geological context, first by H. B. From which the Gondwana sedimentary sequences are described, for example, the plant family Proteaceae, known only from southern South America, South Africa and New Zealand, is considered to have a Gondwanan distribution. This pattern is considered to indicate an archaic, or relict. The assembly of Gondwana was a protracted process, several orogenies led to its final amalgamation 550 to 500 million years ago at the end of the Ediacaran, and into the Cambrian.
These include the Brasiliano Orogeny, the East African Orogeny, the Malagasy Orogeny, the final stages of Gondwanan assembly overlapped with the opening of the Iapetus Ocean between Laurentia and western Gondwana. During this interval, the Cambrian explosion occurred and this is the Famatinian block and it formerly continued the line of the Appalachians southwards. One of the sites of Gondwanan amalgamation was the East African Orogeny. The East African Orogeny at about 650–630 Mya affected a part of Arabia, north-eastern Africa, East Africa. Collins and Windley propose that in this orogeny, Azania collided with the Congo–Tanzania–Bangweulu Block, the Malagasy orogeny at about 550–515 Mya affected Madagascar, eastern East Africa and southern India. In it, Neoproterozoic India collided with the already combined Azania and Congo–Tanzania–Bangweulu Block, at the same time, in the Kunga Orogeny Neoproterozoic India collided with the Australia/Mawson continent. Other large continental masses, including the core cratons of North America, when Pangaea broke up, two large masses and Laurasia, were formed.
During the late Paleozoic, Gondwana extended from a point at or near the South Pole to near the Equator, across much of Gondwana, the climate was mild. During the Mesozoic, the world was on average warmer than it is today. Gondwana was host to a variety of flora and fauna for many millions of years
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as coal, can be regarded as metamorphic rock because of exposure to elevated temperature and pressure. Coal is composed primarily of carbon, along with quantities of other elements, chiefly hydrogen, oxygen. A fossil fuel, coal forms when plant matter is converted into peat, which in turn is converted into lignite, sub-bituminous coal, after that bituminous coal. This involves biological and geological processes that take place over time, throughout history, coal has been used as an energy resource, primarily burned for the production of electricity and heat, and is used for industrial purposes, such as refining metals. Coal is the largest source of energy for the generation of electricity worldwide, the extraction of coal, its use in energy production and its byproducts are all associated with environmental and health effects including climate change.
Coal is extracted from the ground by coal mining, since 1983, the worlds top coal producer has been China. In 2015 China produced 3,747 million tonnes of coal –47. 7% of 7,861 million tonnes world coal production, in 2015 other large producers were United States, European Union and Australia. The word originally took the col in Old English, from Proto-Germanic *kula. In Old Turkic languages, kül is ash, cinders, öčür is quench, the compound charcoal in Turkic is öčür kül, literally quenched ashes, coals with elided anlaut ö- and inflection affixes -ülmüş. At various times in the geologic past, the Earth had dense forests in low-lying wetland areas, due to natural processes such as flooding, these forests were buried underneath soil. As more and more soil deposited over them, they were compressed, the temperature rose as they sank deeper and deeper. As the process continued the plant matter was protected from biodegradation and oxidation and this trapped the carbon in immense peat bogs that were eventually covered and deeply buried by sediments.
Under high pressure and high temperature, dead vegetation was slowly converted to coal, as coal contains mainly carbon, the conversion of dead vegetation into coal is called carbonization. The wide, shallow seas of the Carboniferous Period provided ideal conditions for coal formation, the exception is the coal gap in the Permian–Triassic extinction event, where coal is rare. Coal is known from Precambrian strata, which predate land plants — this coal is presumed to have originated from residues of algae, in its dehydrated form, peat is a highly effective absorbent for fuel and oil spills on land and water. It is used as a conditioner for soil to make it able to retain. Lignite, or brown coal, is the lowest rank of coal, jet, a compact form of lignite, is sometimes polished and has been used as an ornamental stone since the Upper Palaeolithic
A fish is any member of a group of animals that consist of all gill-bearing aquatic craniate animals that lack limbs with digits. They form a group to the tunicates, together forming the olfactores. Included in this definition are the living hagfish and cartilaginous, tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered obsolete or paraphyletic by excluding the tetrapods, because in this manner the term fish is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology. The traditional term pisces is considered a typological, but not a phylogenetic classification, the earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts, fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms.
Many fish of the Paleozoic developed external armor that protected them from predators, the first fish with jaws appeared in the Silurian period, after which many became formidable marine predators rather than just the prey of arthropods. Fish are abundant in most bodies of water and they can be found in nearly all aquatic environments, from high mountain streams to the abyssal and even hadal depths of the deepest oceans. With 33,100 described species, fish exhibit greater species diversity than any group of vertebrates. Fish are an important resource for humans worldwide, especially as food and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean. They are caught by fishers, kept as pets, raised by fishkeepers. Fish have had a role in culture through the ages, serving as deities, religious symbols, fish do not represent a monophyletic group, and therefore the evolution of fish is not studied as a single event. Early fish from the record are represented by a group of small, jawless.
Jawless fish lineages are mostly extinct, an extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils, the diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways. The first ancestors of fish may have kept the form into adulthood. Fish are a group, that is, any clade containing all fish contains the tetrapods
Diapsids are a group of amniote tetrapods that developed two holes in each side of their skulls about 300 million years ago during the late Carboniferous period. The diapsids are extremely diverse, and include all crocodiles, snakes, turtles, although some diapsids have lost either one hole, or both holes, or have a heavily restructured skull, they are still classified as diapsids based on their ancestry. At least 7,925 species of diapsid reptiles exist in environments around the world today, the name Diapsida means two arches, and diapsids are traditionally classified based on their two ancestral skull openings posteriorly above and below the eye. This arrangement allows for the attachment of larger, stronger jaw muscles, a more obscure ancestral characteristic is a relatively long lower arm bone compared to the upper arm bone. Diapsids were originally classified as one of four subclasses of the class Reptilia, all of which were based on the number, the other three subclasses were Synapsida and Euryapsida.
With the advent of phylogenetic nomenclature, this system of classification was heavily modified, the synapsids are often not considered true reptiles, while Euryapsida were found to be an unnatural assemblage of diapsids that had lost one of their skull openings. Genetic studies have shown that this is the case in turtles, in phylogenetic systems, birds are considered to be members of this group. Some modern studies of relationships have preferred to use the name diapsid to refer to the crown group of all modern diapsid reptiles. However, many researchers have favored a more traditional definition that includes the prehistoric araeoscelidians. In 1991, Laurin defined Diapsida as a clade, the most recent common ancestor of araeoscelidians and archosaurs, below is a cladogram showing the relations of the major groups of diapsids. Cladogram after Bickelmann et al.2009 and Reisz et al,2011, Vertebrate paleontology Synapsida Anapsida Euryapsida Data related to Diapsid at Wikispecies Diapsida. Michel Laurin and Jacques A.
Gauthier, Diapsida Cladogram at Mikkos Phylogeny Archive
The molluscs compose the large phylum Mollusca of invertebrate animals. Around 85,000 extant species of molluscs are recognized, molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs live in freshwater and terrestrial habitats and they are highly diverse, not just in size and in anatomical structure, but in behaviour and in habitat. The phylum is divided into 9 or 10 taxonomic classes. The gastropods are by far the most numerous molluscs in terms of classified species, the three most universal features defining modern molluscs are a mantle with a significant cavity used for breathing and excretion, the presence of a radula, and the structure of the nervous system. Other than these things, molluscs express great morphological diversity, so many textbooks base their descriptions on an ancestral mollusc. This has a single, limpet-like shell on top, which is made of proteins and chitin reinforced with calcium carbonate, the underside of the animal consists of a single muscular foot.
Although molluscs are coelomates, the coelom tends to be small, the main body cavity is a hemocoel through which blood circulates, their circulatory systems are mainly open. The generalized mollusc has two paired nerve cords, or three in bivalves, the brain, in species that have one, encircles the esophagus. Most molluscs have eyes, and all have sensors to detect chemicals, the simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur. All produce eggs, from which may emerge trochophore larvae, more complex veliger larvae, good evidence exists for the appearance of gastropods and bivalves in the Cambrian period 541 to 485.4 million years ago. Molluscs have, for centuries, been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye and their shells have been used as money in some preindustrial societies. Mollusc species can represent hazards or pests for human activities, the bite of the blue-ringed octopus is often fatal, and that of Octopus apollyon causes inflammation that can last for over a month.
Stings from a few species of large tropical cone shells can kill, schistosomiasis is transmitted to humans via water snail hosts, and affects about 200 million people. Snails and slugs can be serious pests, and accidental or deliberate introduction of some snail species into new environments has seriously damaged some ecosystems. The words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, molluscus was itself an adaptation of Aristotles τα μαλακά, the soft things, which he applied to cuttlefish. The scientific study of molluscs is accordingly called malacology, as it is now known these groups have no relation to molluscs, and very little to one another, the name Molluscoida has been abandoned. The most universal features of the structure of molluscs are a mantle with a significant cavity used for breathing and excretion
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures.
As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages.
It is named after Wenlock Edge in Shropshire, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway
North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can be considered a subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16. 5% of the land area. North America is the third largest continent by area, following Asia and Africa, and the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 565 million people in 23 independent states, or about 7. 5% of the worlds population, North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge. The so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago, the Classic stage spans roughly the 6th to 13th centuries. The Pre-Columbian era ended with the migrations and the arrival of European settlers during the Age of Discovery.
Present-day cultural and ethnic patterns reflect different kind of interactions between European colonists, indigenous peoples, African slaves and their descendants, European influences are strongest in the northern parts of the continent while indigenous and African influences are relatively stronger in the south. Because of the history of colonialism, most North Americans speak English, Spanish or French, the Americas are usually accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass previously unknown by Europeans. In 1507, Waldseemüller produced a map, in which he placed the word America on the continent of South America. He explained the rationale for the name in the accompanying book Cosmographiae Introductio, for Waldseemüller, no one should object to the naming of the land after its discoverer.
He used the Latinized version of Vespuccis name, but in its feminine form America, following the examples of Europa and Africa. Later, other mapmakers extended the name America to the continent, In 1538. Some argue that the convention is to use the surname for naming discoveries except in the case of royalty, a minutely explored belief that has been advanced is that America was named for a Spanish sailor bearing the ancient Visigothic name of Amairick. Another is that the name is rooted in a Native American language, the term North America maintains various definitions in accordance with location and context. In Canadian English, North America may be used to refer to the United States, usage sometimes includes Greenland and Mexico, as well as offshore islands
The Phanerozoic Eon is the current geologic eon in the geologic time scale, and the one during which abundant animal and plant life has existed. It covers 541 million years to the present, and began with the Cambrian Period when diverse hard-shelled animals first appeared. Its name was derived from the Ancient Greek words φανερός and ζωή, meaning life, since it was once believed that life began in the Cambrian. The time before the Phanerozoic, called the Precambrian supereon, is now divided into the Hadean, land plant life appeared in the early Phanerozoic eon. During this time span, tectonic forces caused the continents to move and eventually collect into a landmass known as Pangaea. The Proterozoic-Phanerozoic boundary is at 541 million years ago, the three different dividing points are within a few million years of each other. The Phanerozoic is divided into three eras, the Paleozoic and Cenozoic, which are subdivided into 12 periods. The Paleozoic features the rise of fish and reptiles, the Mesozoic is ruled by the reptiles, and features the evolution of mammals and more famously, dinosaurs.
The Cenozoic is the time of the mammals, and more recently, the Paleozoic is a time in Earths history when complex life forms evolved, took their first breath of oxygen on dry land, and when the forerunners of all life on Earth began to diversify. There are six periods in the Paleozoic era, Ordovician, Devonian, the Cambrian is the first period of the Paleozoic Era and starts from 541 to 485 million years ago. The Cambrian sparked a rapid expansion in evolution in an event known as the Cambrian Explosion during which the greatest number of creatures evolved in a period in the history of Earth. Plants like algae evolved, and the fauna was dominated by armored arthropods, almost all marine phyla evolved in this period. During this time, the super-continent Pannotia began to break up, the Ordovician spans from 485 million years to 440 million years. The Ordovician was a time in Earths history in many species still prevalent today evolved, such as primitive fish, cephalopods. The most common forms of life, were trilobites, more importantly, the first arthropods crept ashore to colonize Gondwana, a continent empty of animal life.
By the end of the Ordovican, Gondwana had moved from the equator to the South Pole, the glaciation of Gondwana resulted in a major drop in sea level, killing off all life that had established along its coast. Glaciation caused a snowball Earth, leading to the Ordovician-Silurian extinction, during which 60% of marine invertebrates and this is considered the first mass extinction and the second deadliest in the history of Earth. The Silurian spans from 440 million years to 415 million years, fully terrestrial life evolved, which included early arachnids and centipedes