The American alligator, sometimes referred to colloquially as a gator or common alligator, is a large crocodilian reptile endemic to the southeastern United States. It is one of two living species in the genus Alligator within the family Alligatoridae. Adult male American alligators measure 3.4 to 4.6 m in length, can weigh up to 453 kg. Females are smaller; the American alligator inhabits freshwater wetlands, such as marshes and cypress swamps from Texas to southeastern and coastal Virginia. It is distinguished from the sympatric American crocodile by its broader snout, with overlapping jaws and darker coloration, is less tolerant of saltwater but more tolerant of cooler climates than the American crocodile, found only in tropical climates. American alligators are apex predators and consume fish, reptiles and mammals. Hatchlings feed on invertebrates, they play an important role as ecosystem engineers in wetland ecosystems through the creation of alligator holes, which provide both wet and dry habitats for other organisms.
Throughout the year, in particular during the breeding season, American alligators bellow to declare territory and locate suitable mates. Male American alligators use infrasound to attract females. Eggs are laid in a nest of vegetation, sticks and mud in a sheltered spot in or near the water. Young are born with yellow bands around their bodies and are protected by their mother for up to one year; the conservation status of the American alligator is listed as Least Concern by the International Union for Conservation of Nature. Hunting had decimated their population, the American alligator was listed as an endangered species by the Endangered Species Act of 1973. Subsequent conservation efforts have allowed their numbers to increase and the species was removed from endangered status in 1987. American alligators are now harvested for their skins and meat; the species is the official state reptile of three states: Florida and Mississippi. The American alligator was first classified by French zoologist François Marie Daudin as Crocodilus mississipiensis in 1801.
In 1807 Georges Cuvier created the genus Alligator. They are grouped in the family Alligatoridae with the caimans; the superfamily Alligatoroidea includes all crocodilians that are more related to the American alligator than to either the Nile crocodile or the gharial. Members of this superfamily first arose in about 100 -- 66 million years ago. Leidyosuchus of Alberta is the earliest known fossil, from the Campanian era 83 to 72 million years ago. Fossil alligatoroids have been found throughout Eurasia, because bridges across both the North Atlantic and the Bering Strait connected North America to Eurasia about 66 to 23 million years ago. Alligators and caimans split in North America during the late Cretaceous, the caimans reached South America by the Paleogene, before the closure of the Isthmus of Panama during the Neogene period, from about 23 to 2.58 million years ago. The Chinese alligator descended from a lineage that crossed the Bering land bridge during the Neogene. Fossils identical to the existing American alligator are found throughout the Pleistocene, from 2.5 million to 11.7 thousand years ago.
In 2016, a Miocene fossil skull of an alligator was found at Florida. Unlike the other extinct alligator species of in the same genus, the fossil skull was indistinguishable from that of the modern American alligator; this alligator and the American alligator are now considered to be sister taxa, meaning that the Alligator mississippiensis lineage has existed in North America for over 8 million years. The alligator's full mitochondrial genome was sequenced in the 1990s and it suggests the animal evolved at a rate similar to mammals and greater than birds and most cold-blooded vertebrates. However, the full genome, published in 2014, suggests that the alligator evolved much more than mammals and birds. Domestic American alligators range from long and slender to short and robust in response to variations in factors such as growth rate and climate; the American alligator is a large species of crocodilian. On average it is the second largest species in the family Alligatoridae, behind only the black caiman.
Weight varies depending on length, health and available food sources. Similar to many other reptiles that range expansively into temperate zones, American alligators from the northern end of their range, such as southern Arkansas and northern North Carolina, tend to reach smaller sizes. Large adult American alligators tend to be robust and bulky compared to other length crocodilians, for example captive males measuring 3 to 4 m were found to weigh 200 to 350 kg - although captive specimens may outweigh wild specimens due to lack of hunting behavior and other stressors; as with all crocodilians, as opposed to many mammals where size diminishes with old age, healthy American alligators may continue to expand throughout their lives and the oldest specimens are the largest. Old, large male American alligators reach an expected maximum size of up to 4.6 m in length, weighing up to 453 kg, while females reach a maximum of 3 m. On rare occasions, a large, old male may grow to an greater length. During the 19th and 20th centuries, larger males reaching 5 to 6 m (16 ft 5 in to 19 ft 8
Jacksonville is the most populous city in Florida, the most populous city in the southeastern United States and the largest city by area in the contiguous United States. It is the seat of Duval County, with which the city government consolidated in 1968. Consolidation gave Jacksonville its great size and placed most of its metropolitan population within the city limits; as of 2017 Jacksonville's population was estimated to be 892,062. The Jacksonville metropolitan area has a population of 1,523,615 and is the fourth largest in Florida. Jacksonville is centered on the banks of the St. Johns River in the First Coast region of northeast Florida, about 25 miles south of the Georgia state line and 328 miles north of Miami; the Jacksonville Beaches communities are along the adjacent Atlantic coast. The area was inhabited by the Timucua people, in 1564 was the site of the French colony of Fort Caroline, one of the earliest European settlements in what is now the continental United States. Under British rule, settlement grew at the narrow point in the river where cattle crossed, known as Wacca Pilatka to the Seminole and the Cow Ford to the British.
A platted town was established there in 1822, a year after the United States gained Florida from Spain. Harbor improvements since the late 19th century have made Jacksonville a major military and civilian deep-water port, its riverine location facilitates Naval Station Mayport, Naval Air Station Jacksonville, the U. S. Marine Corps Blount Island Command, the Port of Jacksonville, Florida's third largest seaport. Jacksonville's military bases and the nearby Naval Submarine Base Kings Bay form the third largest military presence in the United States. Significant factors in the local economy include services such as banking, insurance and logistics; as with much of Florida, tourism is important to the Jacksonville area tourism related to golf. People from Jacksonville may be called "Jacksonvillians" or "Jaxsons"; the area of the modern city of Jacksonville has been inhabited for thousands of years. On Black Hammock Island in the national Timucuan Ecological and Historic Preserve, a University of North Florida team discovered some of the oldest remnants of pottery in the United States, dating to 2500 BC.
In the 16th century, the beginning of the historical era, the region was inhabited by the Mocama, a coastal subgroup of the Timucua people. At the time of contact with Europeans, all Mocama villages in present-day Jacksonville were part of the powerful chiefdom known as the Saturiwa, centered around the mouth of the St. Johns River. One early map shows. French Huguenot explorer Jean Ribault charted the St. Johns River in 1562, calling it the River of May because, the month of his discovery. Ribault erected a stone column at his landing site near the river's mouth, claiming the newly discovered land for France. In 1564, René Goulaine de Laudonnière established the first European settlement, Fort Caroline, on the St. Johns near the main village of the Saturiwa. Philip II of Spain ordered Pedro Menéndez de Avilés to protect the interest of Spain by attacking the French presence at Fort Caroline. On September 20, 1565, a Spanish force from the nearby Spanish settlement of St. Augustine attacked Fort Caroline, killed nearly all the French soldiers defending it.
The Spanish renamed the fort San Mateo, following the ejection of the French, St. Augustine's position as the most important settlement in Florida was solidified; the location of Fort Caroline is subject to debate but a reconstruction of the fort was established on the St. Johns River in 1964. Spain ceded Florida to the British in 1763 after the French and Indian War, the British soon constructed the King's Road connecting St. Augustine to Georgia; the road crossed the St. Johns River at a narrow point, which the Seminole called Wacca Pilatka and the British called the Cow Ford; the British introduced the cultivation of sugar cane and fruits, as well the export of lumber. As a result, the northeastern Florida area prospered economically more than it had under the Spanish. Britain ceded control of the territory to Spain in 1783, after being defeated in the American Revolutionary War, the settlement at the Cow Ford continued to grow. After Spain ceded the Florida Territory to the United States in 1821, American settlers on the north side of the Cow Ford decided to plan a town, laying out the streets and plats.
They named the town Jacksonville, after President Andrew Jackson. Led by Isaiah D. Hart, residents wrote a charter for a town government, approved by the Florida Legislative Council on February 9, 1832. During the American Civil War, Jacksonville was a key supply point for hogs and cattle being shipped from Florida to feed the Confederate forces; the city was blockaded by Union forces. Though no battles were fought in Jacksonville proper, the city changed hands several times between Union and Confederate forces. In the Skirmish of the Brick Church in 1862, Confederates won their first victory in the state. However, Union forces captured a Confederate position at the Battle of St. Johns Bluff, occupied Jacksonville in 1862. Slaves escaped to freedom in Union lines. In February 1864 Union forces left Jacksonville and confronted a Confederate Army at the Battle of Olustee, going down to defeat. Union forces held the city for the remainder of the war. In Ma
The bald eagle is a bird of prey found in North America. A sea eagle, it forms a species pair with the white-tailed eagle, its range includes most of Canada and Alaska, all of the contiguous United States, northern Mexico. It is found near large bodies of open water with an abundant food supply and old-growth trees for nesting; the bald eagle is an opportunistic feeder which subsists on fish, which it swoops down and snatches from the water with its talons. It builds the largest nest of any North American bird and the largest tree nests recorded for any animal species, up to 4 m deep, 2.5 m wide, 1 metric ton in weight. Sexual maturity is attained at the age of four to five years. Bald eagles are not bald; the adult is brown with a white head and tail. The sexes are identical in plumage; the beak is hooked. The plumage of the immature is brown; the bald eagle is both the national bird and national animal of the United States of America. The bald eagle appears on its seal. In the late 20th century it was on the brink of extirpation in the contiguous United States.
Populations have since recovered and the species was removed from the U. S. government's list of endangered species on July 12, 1995 and transferred to the list of threatened species. It was removed from the List of Endangered and Threatened Wildlife in the Lower 48 States on June 28, 2007; the plumage of an adult bald eagle is evenly dark brown with a white tail. The tail is moderately long and wedge-shaped. Males and females are identical in plumage coloration, but sexual dimorphism is evident in the species, in that females are 25% larger than males; the beak and irises are bright yellow. The legs are feather-free, the toes are short and powerful with large talons; the developed talon of the hind toe is used to pierce the vital areas of prey while it is held immobile by the front toes. The beak is hooked, with a yellow cere; the adult bald eagle is unmistakable in its native range. The related African fish eagle has a brown body, white head and tail, but differs from the bald in having a white chest and black tip to the bill.
The plumage of the immature is a dark brown overlaid with messy white streaking until the fifth year, when it reaches sexual maturity. Immature bald eagles are distinguishable from the golden eagle, the only other large, non-vulturine raptorial bird in North America, in that the former has a larger, more protruding head with a larger beak, straighter edged wings which are held flat and with a stiffer wing beat and feathers which do not cover the legs; when seen well, the golden eagle is distinctive in plumage with a more solid warm brown color than an immature bald eagle, with a reddish-golden patch to its nape and a contrasting set of white squares on the wing. Another distinguishing feature of the immature bald eagle over the mature bird is its black, yellow-tipped beak; the bald eagle has sometimes been considered the largest true raptor in North America. The only larger species of raptor-like bird is the California condor, a New World vulture which today is not considered a taxonomic ally of true accipitrids.
However, the golden eagle, averaging 4.18 kg and 63 cm in wing chord length in its American race, is 455 g lighter in mean body mass and exceeds the bald eagle in mean wing chord length by around 3 cm. Additionally, the bald eagle's close cousins, the longer-winged but shorter-tailed white-tailed eagle and the overall larger Steller's sea eagle, may wander to coastal Alaska from Asia; the bald eagle has a body length of 70–102 cm. Typical wingspan is between 1.8 and 2.3 m and mass is between 3 and 6.3 kg. Females are about 25% larger than males, averaging as much as 5.6 kg, against the males' average weight of 4.1 kg. The size of the bird varies by location and corresponds with Bergmann's rule, since the species increases in size further away from the Equator and the tropics. For example, eagles from South Carolina average 3.27 kg in mass and 1.88 m in wingspan, smaller than their northern counterparts. One field guide in Florida listed small sizes for bald eagles there, at about 4.13 kg. Of intermediate size, 117 migrant bald eagles in Glacier National Park were found to average 4.22 kg but this was juvenile eagles, with 6 adults here averaging 4.3 kg.
Wintering eagles in Arizona were found to average 4.74 kg. The largest eagles are from Alaska, where large females may weigh more than 7 kg and span 2.44 m across the wings. A survey of adult weights in Alaska showed that females there weighed on average 5.35 kg and males weighed 4.23 kg against immatures which averaged 5.09 kg and 4.05 kg in the two sexes. An Alaskan adult female eagle, considered outsized we
This article is about a single species of tortoise. For related species in North America that are called gopher tortoises, see Gopherus The gopher tortoise is a species of the Gopherus genus native to the southeastern United States; the gopher tortoise is seen as a keystone species because it digs burrows that provide shelter for at least 360 other animal species. They are threatened by habitat destruction; the gopher tortoise is a representative of the genus Gopherus, which contains the only tortoises native to North America. This species of gopher tortoise is the state tortoise of Florida; the gopher tortoise is a large terrestrial reptile which possesses forefeet well adapted for burrowing, elephantine hind feet. These features are common to most tortoises; the front legs have scales to protect the tortoise while burrowing. They are dark brown to gray-black with a yellow plastron. A gular projection is evident on the anterior plastron. Sexual dimorphism is evident, with male gopher tortoises having concave plastrons, while those of females are flat.
In addition, the gular projection on male plastrons is longer than in females. Carapace length can range with a height of 15 -- 37 cm. Body mass averages 4 kg, with a range of 2–6 kg. Gopher tortoises are herbivore scavengers, their diets contains over 300 species of plants. They consume a wide range of plants, but eat broad-leaved grass, regular grass and terrestrial legumes, they eat mushrooms, fruits such as gopher apple, pawpaw and saw palmetto berries. In addition, gopher tortoises eat flowers from the genera Cnidoscolus, Tillandsia and Dyschoriste. Juvenile tortoises tend to eat more legumes, which are higher in protein, fewer grasses and tough, fibrous plants than mature tortoises. Gopher tortoises have been known to eat excrement; as gopher tortoises get water from the food they eat, they only drink standing water in times of extreme drought. Gopher tortoises, like other tortoises of the genus Gopherus, are known for their digging ability. Gopher tortoises spend most of their time in long burrows, up to 14.5 metres in length and 3 metres deep.
In these burrows, the tortoises are protected from summer heat, winter cold and predators. The burrows are common in longleaf pine savannas, where the tortoises are the primary grazers, playing an essential role in their ecosystem. Except during breeding season, gopher tortoises are solitary animals. Within their range they dig several burrows. On average, each gopher tortoise needs about 4 acres to live. Sexual reproduction involves courtship rituals. During the mating season between April and November, females lay their eggs in the open; the sex of the eggs is determined by the temperature where they are incubated in a nest laid below sand. If the sand is over 30 degrees Celsius, it's a female and if below 30 degrees Celsius, the egg is a male. Incubation period can last from 110 days in South Carolina. Gopher tortoises can live more than 40 years. One current specimen, has been living continuously in captivity at the Nova Scotia Museum of Natural History in Halifax for 75 years as of 2018 and is believed to have hatched between 1920 and 1925.
Additionally, there are journalistic reports of a specimen in North Texas with a verified age of 75–78 years old. The gopher tortoise reaches maturity at about 10–15 years of age, when their shells are around 9 inches long, they may mate from February with a peak throughout May and June. Females may lay clutches of 3–14 eggs, depending on body size, in a sandy mound close to the entrance of their burrow. Ninety percent of clutches may be destroyed by predators such as armadillos, foxes and alligators before the eggs hatch, less than 6% of eggs are expected to grow into tortoises that live one year or more after hatching. Since July 7, 1987, the U. S. Fish and Wildlife Service has listed Gopherus polyphemus as "Threatened" wherever the tortoises are found west of the Mobile and Tombigbee Rivers in Alabama and Louisiana, its status is listed as "Under Review" in Florida and in other locations. On November 9, 2009, the U. S. Fish and Wildlife Service proposed rulemaking to include the eastern population of Gopherus polyphemus in the List of Threatened Wildlife.
G. polyphemus appears on the IUCN Red List as a "Vulnerable" species. In July 2011, United States Fish & Wildlife Service determined that listing the eastern population of the tortoise as Threatened under the Endangered Species Act is warranted, however, it is precluded from doing so at this time due to higher priority actions and a lack of sufficient funds to commence proposed rule development. In the interim period of time the USFWS will place the eastern population of the tortoise on its candidate species list until sufficient funding is available to initiate a proposed listing rule; the University of Florida Conservation Clinic Center for Governmental Responsibility Levin College of Law describe five main threats to the tortoise population, they are: Habitat loss through human development, habitat loss through poor supervision, human desire to use it as a pet or meat, relocation causing popu
Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. Modern amphibians are all Lissamphibia, they inhabit a wide variety of habitats, with most species living within terrestrial, arboreal or freshwater aquatic ecosystems. Thus amphibians start out as larvae living in water, but some species have developed behavioural adaptations to bypass this; the young undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely on their skin, they are superficially similar to lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are ecological indicators; the earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land.
They diversified and became dominant during the Carboniferous and Permian periods, but were displaced by reptiles and other vertebrates. Over time, amphibians shrank in size and decreased in diversity, leaving only the modern subclass Lissamphibia; the three modern orders of amphibians are Anura and Apoda. The number of known amphibian species is 8,000, of which nearly 90% are frogs; the smallest amphibian in the world is a frog from New Guinea with a length of just 7.7 mm. The largest living amphibian is the 1.8 m Chinese giant salamander, but this is dwarfed by the extinct 9 m Prionosuchus from the middle Permian of Brazil. The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology; the word "amphibian" is derived from the Ancient Greek term ἀμφίβιος, which means "both kinds of life", ἀμφί meaning "of both kinds" and βιος meaning "life". The term was used as a general adjective for animals that could live on land or in water, including seals and otters.
Traditionally, the class Amphibia includes all tetrapod vertebrates. Amphibia in its widest sense was divided into three subclasses, two of which are extinct: Subclass Lepospondyli† Subclass Temnospondyli† Subclass Lissamphibia Salientia: Jurassic to present—6,200 current species in 53 families Caudata: Jurassic to present—652 current species in 9 families Gymnophiona: Jurassic to present—192 current species in 10 families The actual number of species in each group depends on the taxonomic classification followed; the two most common systems are the classification adopted by the website AmphibiaWeb, University of California and the classification by herpetologist Darrel Frost and the American Museum of Natural History, available as the online reference database "Amphibian Species of the World". The numbers of species cited above follows Frost and the total number of known amphibian species as of March 31, 2019 is 8,000, of which nearly 90% are frogs. With the phylogenetic classification, the taxon Labyrinthodontia has been discarded as it is a polyparaphyletic group without unique defining features apart from shared primitive characteristics.
Classification varies according to the preferred phylogeny of the author and whether they use a stem-based or a node-based classification. Traditionally, amphibians as a class are defined as all tetrapods with a larval stage, while the group that includes the common ancestors of all living amphibians and all their descendants is called Lissamphibia; the phylogeny of Paleozoic amphibians is uncertain, Lissamphibia may fall within extinct groups, like the Temnospondyli or the Lepospondyli, in some analyses in the amniotes. This means that advocates of phylogenetic nomenclature have removed a large number of basal Devonian and Carboniferous amphibian-type tetrapod groups that were placed in Amphibia in Linnaean taxonomy, included them elsewhere under cladistic taxonomy. If the common ancestor of amphibians and amniotes is included in Amphibia, it becomes a paraphyletic group. All modern amphibians are included in the subclass Lissamphibia, considered a clade, a group of species that have evolved from a common ancestor.
The three modern orders are Anura and Gymnophiona. It has been suggested that salamanders arose separately from a Temnospondyl-like ancestor, that caecilians are the sister group of the advanced reptiliomorph amphibians, thus of amniotes. Although the fossils of several older proto-frogs with primitive characteristics are known, the oldest "true frog" is Prosalirus bitis, from the Early Jurassic Kayenta Formation of Arizona, it is anatomically similar to modern frogs. The oldest known caecilian is another Early Jurassic species, Eocaecilia micropodia from Arizona; the earliest salamander is Beiyanerpeton jianpingensis from the Late Jurassic of northeastern China. Authorities disagree as to whether Salientia is a superorder that includes the order Anura, or whether
Human prehistory is the period between the use of the first stone tools c. 3.3 million years ago by hominins and the invention of writing systems. The earliest writing systems appeared c. 5,300 years ago, but it took thousands of years for writing to be adopted, it was not used in some human cultures until the 19th century or until the present. The end of prehistory therefore came at different dates in different places, the term is less used in discussing societies where prehistory ended recently. Sumer in Mesopotamia, the Indus valley civilization, ancient Egypt were the first civilizations to develop their own scripts and to keep historical records. Neighboring civilizations were the first to follow. Most other civilizations reached the end of prehistory during the Iron Age; the three-age system of division of prehistory into the Stone Age, followed by the Bronze Age and Iron Age, remains in use for much of Eurasia and North Africa, but is not used in those parts of the world where the working of hard metals arrived abruptly with contact with Eurasian cultures, such as the Americas, Oceania and much of Sub-Saharan Africa.
These areas with some exceptions in Pre-Columbian civilizations in the Americas, did not develop complex writing systems before the arrival of Eurasians, their prehistory reaches into recent periods. The period when a culture is written about by others, but has not developed its own writing is known as the protohistory of the culture. By definition, there are no written records from human prehistory, so dating of prehistoric materials is crucial. Clear techniques for dating were not well-developed until the 19th century; this article is concerned with human prehistory, the time since behaviorally and anatomically modern humans first appeared until the beginning of recorded history. Earlier periods are called "prehistoric". Beginning The term "prehistory" can refer to the vast span of time since the beginning of the Universe or the Earth, but more it refers to the period since life appeared on Earth, or more to the time since human-like beings appeared. End The date marking the end of prehistory is defined as the advent of the contemporary written historical record.
The date varies from region to region depending on the date when relevant records become a useful academic resource. For example, in Egypt it is accepted that prehistory ended around 3200 BCE, whereas in New Guinea the end of the prehistoric era is set much more at around 1900 common era. In Europe the well-documented classical cultures of Ancient Greece and Ancient Rome had neighbouring cultures, including the Celts and to a lesser extent the Etruscans, with little or no writing, historians must decide how much weight to give to the highly prejudiced accounts of these "prehistoric" cultures in Greek and Roman literature. Time periods In dividing up human prehistory in Eurasia, historians use the three-age system, whereas scholars of pre-human time periods use the well-defined geologic record and its internationally defined stratum base within the geologic time scale; the three-age system is the periodization of human prehistory into three consecutive time periods, named for their respective predominant tool-making technologies: Stone Age Bronze Age Iron Age The notion of "prehistory" began to surface during the Enlightenment in the work of antiquarians who used the word'primitive' to describe societies that existed before written records.
The first use of the word prehistory in English, occurred in the Foreign Quarterly Review in 1836. The use of the geologic time scale for pre-human time periods, of the three-age system for human prehistory, is a system that emerged during the late nineteenth century in the work of British and Scandinavian archeologists and anthropologists; the main source for prehistory is archaeology, but some scholars are beginning to make more use of evidence from the natural and social sciences. This view has been articulated by advocates of deep history; the primary researchers into human prehistory are archaeologists and physical anthropologists who use excavation and geographic surveys, other scientific analysis to reveal and interpret the nature and behavior of pre-literate and non-literate peoples. Human population geneticists and historical linguists are providing valuable insight for these questions. Cultural anthropologists help provide context for societal interactions, by which objects of human origin pass among people, allowing an analysis of any article that arises in a human prehistoric context.
Therefore, data about prehistory is provided by a wide variety of natural and social sciences, such as paleontology, archaeology, geology, comparative linguistics, molecular genetics and many others. Human prehistory differs from history not only in terms of its chronology but in the way it deals with the activities of archaeological cultures rather than named nations or individuals. Restricted to material processes and artifacts rather than written records, prehistory is anonymous; because of this, reference terms that prehistorians use, such as Neanderthal or Iron Age are modern labels with definitions sometimes subject to debate. The concept of a "Stone Age" is found useful in the archaeology of most of the world, though in the archaeology of the Americas it is called by different names and begins with a Lithic sta
Nature, in the broadest sense, is the natural, physical, or material world or universe. "Nature" can refer to the phenomena of the physical world, to life in general. The study of nature is a large, part of science. Although humans are part of nature, human activity is understood as a separate category from other natural phenomena; the word nature is derived from the Latin word natura, or "essential qualities, innate disposition", in ancient times meant "birth". Natura is a Latin translation of the Greek word physis, which related to the intrinsic characteristics that plants and other features of the world develop of their own accord; the concept of nature as a whole, the physical universe, is one of several expansions of the original notion. This usage continued during the advent of modern scientific method in the last several centuries. Within the various uses of the word today, "nature" refers to geology and wildlife. Nature can refer to the general realm of living plants and animals, in some cases to the processes associated with inanimate objects—the way that particular types of things exist and change of their own accord, such as the weather and geology of the Earth.
It is taken to mean the "natural environment" or wilderness—wild animals, forest, in general those things that have not been altered by human intervention, or which persist despite human intervention. For example, manufactured objects and human interaction are not considered part of nature, unless qualified as, for example, "human nature" or "the whole of nature"; this more traditional concept of natural things which can still be found today implies a distinction between the natural and the artificial, with the artificial being understood as that, brought into being by a human consciousness or a human mind. Depending on the particular context, the term "natural" might be distinguished from the unnatural or the supernatural. Earth is the only planet known to support life, its natural features are the subject of many fields of scientific research. Within the solar system, it is third closest to the sun, its most prominent climatic features are its two large polar regions, two narrow temperate zones, a wide equatorial tropical to subtropical region.
Precipitation varies with location, from several metres of water per year to less than a millimetre. 71 percent of the Earth's surface is covered by salt-water oceans. The remainder consists of continents and islands, with most of the inhabited land in the Northern Hemisphere. Earth has evolved through geological and biological processes that have left traces of the original conditions; the outer surface is divided into several migrating tectonic plates. The interior remains active, with a thick layer of plastic mantle and an iron-filled core that generates a magnetic field; this iron core is composed of a solid inner phase, a fluid outer phase. Convective motion in the core generates electric currents through dynamo action, these, in turn, generate the geomagnetic field; the atmospheric conditions have been altered from the original conditions by the presence of life-forms, which create an ecological balance that stabilizes the surface conditions. Despite the wide regional variations in climate by latitude and other geographic factors, the long-term average global climate is quite stable during interglacial periods, variations of a degree or two of average global temperature have had major effects on the ecological balance, on the actual geography of the Earth.
Geology is the study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, physical properties and history of Earth materials, the processes by which they are formed and changed; the field is a major academic discipline, is important for mineral and hydrocarbon extraction, knowledge about and mitigation of natural hazards, some Geotechnical engineering fields, understanding past climates and environments. The geology of an area evolves through time as rock units are deposited and inserted and deformational processes change their shapes and locations. Rock units are first emplaced either by deposition onto the surface or intrude into the overlying rock. Deposition can occur when sediments settle onto the surface of the Earth and lithify into sedimentary rock, or when as volcanic material such as volcanic ash or lava flows, blanket the surface. Igneous intrusions such as batholiths, laccoliths and sills, push upwards into the overlying rock, crystallize as they intrude.
After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed. Deformation occurs as a result of horizontal shortening, horizontal extension, or side-to-side motion; these structural regimes broadly relate to convergent boundaries, divergent boundaries, transform boundaries between tectonic plates. Earth is estimated to have formed 4.54 billion years ago from the solar nebula, along with the Sun and other planets. The moon formed 20 million years later. Molten, the outer layer of the Earth cooled, resulting in the solid crust. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, most or all of which came from ice delivered by comets, produced the oceans and other water sources; the energetic chemistry is believed to have produced a self-replicat