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Nature is an inherent character or constitution, particularly of the ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, elements and phenomenon of the physical world, including life. Although humans are part of nature, human activity or humans as a whole are often described as at times at odds, or outright Anthropocentrism to nature.
During the advent of modern scientific method in the last several centuries, nature became the passive reality, organized and moved by divine laws.Isaac Newton's Philosophiae Naturalis Principia Mathematica (1687), for example, is translated "Mathematical Principles of Natural Philosophy", and reflects the then-current use of the words "natural philosophy", akin to "systematic study of nature"The etymology of the word "physical" shows its use as a synonym for "natural" in about the mid-15th century: With the Industrial Revolution, nature increasingly became seen as the part of reality deprived from intentional intervention: it was hence considered as sacred by some traditions (Rousseau, American transcendentalism) or a mere decorum for divine providence or human history (Hegel, Marx). However, a vitalist vision of nature, closer to the pre-Socratic one, got reborn at the same time, especially after Charles Darwin.
Within the various uses of the word today, "nature" often refers to geology and wildlife. Nature can refer to the general realm of life, and 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 often taken to mean the "natural environment" or wilderness—wild animals, rocks, forest, and in general those things that have not been substantially altered by human intervention, or which persist despite human intervention. For example, manufactured objects and human interaction generally 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 that can still be found today implies a distinction between the natural and the artificial, with the artificial being understood as that which has been brought into being by a human consciousness or a human mind. Depending on the particular context, the term "natural" might also be distinguished from the or the supernatural.
Earth has evolved through geological and biological processes that have left few traces of the original conditions. The outer surface is divided into several gradually migrating . 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, and a fluid outer phase. Convection motion in the outer core generates electric currents through Dynamo theory action, and these, in turn, generate the geomagnetic field.
The atmosphere conditions have been significantly 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, and variations of a degree or two of average global temperature have historically had major effects on the ecological balance, and on the actual geography of the Earth.
Rock units are first emplaced either by deposition onto the surface or intrude into the overlying rock. Deposition can occur when settle onto the surface of the Earth and later lithification into sedimentary rock, or when as volcanic rock such as volcanic ash or lava flows, blanket the surface. Igneous such as , , dikes, and sills, push upwards into the overlying rock, and crystallize as they intrude.
After the initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphism. Deformation typically occurs as a result of horizontal shortening, horizontal extension, or side-to-side (strike-slip) motion. These structural regimes broadly relate to convergent boundaries, divergent boundaries, and transform boundaries, respectively, between plate tectonics.
During the Neoproterozoic era, freezing temperatures covered much of the Earth in and ice sheets. This hypothesis has been termed the "Snowball Earth", and it is of particular interest as it precedes the Cambrian explosion in which multicellular life forms began to proliferate about 530–540 million years ago.
Since the Cambrian explosion there have been five distinctly identifiable Extinction event. The last mass extinction occurred some 66 million years ago, when a meteorite collision probably triggered the extinction of the Bird and other large reptiles, but spared small animals such as . Over the past 66 million years, mammalian life diversified.
Several million years ago, a species of small African ape gained the ability to stand upright. The subsequent advent of human life, and the development of agriculture and further civilization allowed humans to affect the Earth more rapidly than any previous life form, impacting both the nature and quantity of other organisms as well as global climate. By comparison, the Great Oxygenation Event, produced by the proliferation of algae during the Siderian period, required about 400 million years to culminate.
The present era is classified as part of a mass extinction event, the Holocene extinction event, the fastest ever to have occurred. Some, such as E. O. Wilson of Harvard University, predict that human destruction of the biosphere could cause the extinction of one-half of all species in the next 100 years. The extent of the current extinction event is still being researched, debated and calculated by biologists.
Terrestrial weather occurs almost exclusively in the troposphere, and serves as a convective system for redistributing heat. Weather is a Chaos theory that is readily modified by small changes to the environment, so accurate Meteorology is limited to only a few days. Weather is also influenced by the seasons, which result from the Earth's axis being axial tilt relative to its orbital plane. Thus, at any given time during the summer or winter, one part of the Earth is more directly exposed to the rays of the sun. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the Northern and Southern Hemispheres experience opposite seasons.
Weather can have both beneficial and harmful effects. Lightning strikes can cause , while heavy rain can cause and . Extremes in weather, such as or and , can expend large amounts of energy along their paths, and produce devastation. Surface vegetation has evolved a dependence on the seasonal variation of the weather, and sudden changes lasting only a few years can have a stress effect on the plants. These pose a threat to the animals that depend on its growth for their food.
Climate is a measure of the long-term trends in the weather. Various factors are known to influence the climate, including , surface albedo, , variations in the solar luminosity, and changes to the Earth's orbit. Based on historical and geological records, the Earth is known to have undergone drastic in the past, including . In the present day, two things are happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes.
Ocean currents are an important factor in determining climate, particularly the major underwater thermohaline circulation which distributes heat energy from the equatorial oceans to the polar regions. These currents help to moderate the differences in temperature between winter and summer in the temperate zones. Also, without the redistributions of heat energy by the ocean currents and atmosphere, the tropics would be much hotter, and the much colder.
The climate of a region depends on a number of factors, including Geomorphology, , proximity to a large body of water, and especially latitude. A latitudinal band of the surface with similar climatic attributes forms a climate region. There are a number of such regions, ranging from the tropical climate at the equator to the polar climate in the northern and southern extremes. The latter regions are typically below the freezing temperature of water for much of the year, which can allow frozen water to accumulate in and thereby changing the surface albedo.
The major oceanic divisions are determined by the various , , and other criteria. In descending order of size, they are the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Southern Ocean, and the Arctic Ocean. Smaller regions of the oceans are called seas, gulfs, and other names. There are also , which are smaller bodies of landlocked saltwater that are not interconnected with the World Ocean. Two notable examples of salt lakes are the Great Salt Lake and the Caspian Sea. No other planet in the Solar System has surface oceans, although there are 15 moons that are suspected of having ice-covered oceans.
The only world other than Earth known to harbor lakes is Titan, Saturn's largest moon, which has lakes of ethane, most likely mixed with methane. It is not known if Titan's lakes are fed by rivers, though Titan's surface is carved by numerous river beds. Natural lakes on Earth are generally found in mountainous areas, , and areas with ongoing or recent glacier. Other lakes are found in , along the courses of mature rivers, or human-made behind . In some parts of the world, there are many lakes because of chaotic drainage patterns left over from the last ice age. All lakes are temporary over geologic time scales, as they will slowly fill in with sediments or spill out of the basin containing them.
Small bodies of Water stagnation, typically less than , are termed a pond or pool. They can be natural or human-made. A wide variety of human-made bodies of water are classified as ponds, including designed for aesthetic ornamentation, designed for commercial fish breeding, and designed to store thermal energy. Ponds and lakes are distinguished from streams via current speed. While currents in streams are easily observed, ponds possess thermally driven micro-currents and moderate wind driven currents. These features distinguish a pond from many other aquatic terrain features, such as and .
There is no general rule that defines what can be called a river. Smaller scale water flows with a steady current are termed a stream, creek, brook, rivulet, or rill. These are confined within a stream bed and stream bank. Many names for small rivers are specific to geographic location; one example is Burn in Scotland and North-east England. In US naming, sometimes a river is said to be larger than a creek, but this is not always the case, due to vagueness in the language; consequently the US Geographic Names Information System calls all "linear flowing bodies of water" streams.
Streams are important as conduits in the water cycle, instruments in groundwater recharge, and they serve as corridors for fish and wildlife migration. The biological habitat in the immediate vicinity of a stream is called a riparian zone. Given the status of the ongoing Holocene extinction, streams play an important corridor role in connecting fragmented habitats and thus in conserving biodiversity. The study of streams and waterways in general involves many branches of inter-disciplinary natural science and engineering, including hydrology, geomorphology, aquatic ecology, Freshwater fish, riparian, and others.
Central to the ecosystem concept is the idea that interact with every other element in their local environment. Eugene Odum, a founder of ecology, stated: "Any unit that includes all of the organisms (i.e.: the "community") in a given area interacting with the physical environment so that a flow of energy leads to clearly defined trophic structure, biotic diversity, and material cycles (i.e.: exchange of materials between living and nonliving parts) within the system is an ecosystem." Within the ecosystem, species are connected and dependent upon one another in the food chain, and exchange energy and matter between themselves as well as with their environment. The human ecosystem concept is based on the human/nature dichotomy and the idea that all species are ecologically dependent on each other, as well as with the abiotic constituents of their biotope.
A smaller unit of size is called a microecosystem. For example, a microsystem can be a stone and all the life under it. A macroecosystem might involve a whole ecoregion, with its drainage basin.
Present day organisms from to humans possess a self-replicating informational molecule (genome), either DNA or RNA (as in some viruses), and such an informational molecule is probably intrinsic to life. It is likely that the earliest forms of life were based on a self-replicating informational molecule (genome), perhaps RNA or a molecule more primitive than RNA or DNA.
The biosphere is the part of Earth's outer shell—including land, surface rocks, water, air and the atmosphere—within which life occurs, and which Biology processes in turn alter or transform. From the broadest Geophysiology point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere (rocks), hydrosphere (water), and atmosphere (air). The entire Earth contains over 75 billion tons (150 trillion pounds or about ) of biomass (life), which lives within various environments within the biosphere.The figure "about one-half of one percent" takes into account the following (See, e.g., , which takes global average weight as 60 kg.), the total human biomass is the average weight multiplied by the current human population of approximately 6.5 billion (see, e.g., ): Assuming 60–70 kg to be the average human mass (approximately 130–150 lb on the average), an approximation of total global human mass of between 390 billion () and 455 billion kg (between 845 billion and 975 billion lb, or about 423 million–488 million ). The total biomass of all kinds on earth is estimated to be in excess of (75 billion short tons). By these calculations, the portion of total biomass accounted for by humans would be very roughly 0.6%.
Over nine-tenths of the total biomass on Earth is plant life, on which animal life depends very heavily for its existence. More than 2 million species of plant and animal life have been identified to date, and estimates of the actual number of existing species range from several million to well over 50 million."Animal." World Book Encyclopedia. 16 vols. Chicago: World Book, 2003. This source gives an estimate of from 2 to 50 million. The number of individual species of life is constantly in some degree of flux, with new species appearing and others ceasing to exist on a continual basis. Website based on the contents of the book: The total number of species is in rapid decline.
Species that were unable to adapt to the changing environment and competition from other life forms became extinct. However, the fossil record retains evidence of many of these older species. Current fossil and DNA evidence shows that all existing species can trace a continual ancestry back to the first primitive life forms.
When basic forms of plant life developed the process of photosynthesis the sun's energy could be harvested to create conditions which allowed for more complex life forms. The resultant oxygen accumulated in the atmosphere and gave rise to the ozone layer. The incorporation of smaller cells within larger ones resulted in the development of yet more complex cells called eukaryotes. Cells within colonies became increasingly specialized, resulting in true multicellular organisms. With the ozone layer absorbing harmful ultraviolet radiation, life colonized the land surface of Earth.
These life forms are found in almost every location on the Earth where there is liquid water, including in the Earth's interior.
Their reproduction is both rapid and profuse. The combination of a high mutation rate and a horizontal gene transfer ability makes them highly adaptable, and able to survive in new and sometimes very harsh environments, including outer space. They form an essential part of the planetary ecosystem. However, some microorganisms are and can post health risk to other organisms.
Virus are pathogen, but they are not autonomous life forms, as it is the case for viroid, satellites, DPIs and prion.
Among the many ways of classifying plants are by regional , which, depending on the purpose of study, can also include fossil flora, remnants of plant life from a previous era, including pollen. People in many regions and countries take great pride in their individual arrays of characteristic flora, which can vary widely across the globe due to differences in climate and terrain.
Regional floras commonly are divided into categories such as native flora or agricultural and garden flora. Some types of "native flora" actually have been introduced centuries ago by people migrating from one region or continent to another, and become an integral part of the native, or natural flora of the place to which they were introduced. These invasive species are examples of how human interaction with the ecosystem can blur the boundary of what is considered nature.
Another category of plant has historically been carved out for weeds. Though the term has fallen into disfavor among Botany as a formal way to categorize "useless" plants, the informal use of the word "weeds" to describe those plants that are deemed worthy of elimination is illustrative of the general tendency of people and societies to seek to alter or shape the course of nature. Similarly, animals are often categorized in ways such as domestic, laboratory, farm animals, wild animals, pests, etc. according to their relationship to human life.
Animals as a category have several characteristics that generally set them apart from other living things. Animals are eukaryote and usually multicellular, which separates them from bacteria, archaea, and most . They are , generally digesting food in an internal chamber, which separates them from plants and . They are also distinguished from plants, algae, and fungus by lacking .
With a few exceptions—most notably the two Phylum consisting of and —animals have bodies that are differentiated into tissues. These include , which are able to contract and control locomotion, and a nervous system, which sends and processes signals. There is also typically an internal digestion chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of collagen and elastic . This may be calcified to form structures like Exoskeleton, , and spicules, a framework upon which cells can move about and be reorganized during development and maturation, and which supports the complex anatomy required for mobility.
The development of technology by the human race has allowed the greater exploitation of natural resources and has helped to alleviate some of the risk from natural hazards. However, in spite of this progress, the fate of human civilization remains closely linked to changes in the environment. There exists a highly complex feedback loop between the use of advanced technology and changes to the environment. Human-made threats to the Earth's natural environment include pollution, deforestation, and disasters such as oil spills. Humans have contributed to the extinction of many plants and animals, with roughly 1 million species threatened with extinction within decades. The loss of biodiversity and ecosystem functions over the last half century have impacted the extent that nature can contribute to human quality of life, and continued declines could pose a major threat to the existence of human civilization, unless a rapid course correction is made. The value of natural resources to society is often poorly reflected in market failure, because whilst there are extraction costs, natural resources themselves are typically available free of charge. This distorts market pricing of natural resources and at the same time leads to underinvestment in our natural assets. The annual global cost of public subsidies that damage nature is conservatively estimated at $4–6 trillion (million million). Institutional protections of these natural goods, such as the oceans and rainforests, are lacking. Governments have not prevented these economic externalities.UK Government Official Documents, February 2021, "The Economics of Biodiversity: The Dasgupta Review Headline Messages" p. 2
Humans employ nature for both leisure and economic activities. The acquisition of natural resources for industrial use remains a sizable component of the world's economic system. Some activities, such as hunting and fishing, are used for both sustenance and leisure, often by different people. Agriculture was first adopted around the 9th millennium BCE. Ranging from food production to energy, nature influences economic wealth.
Although early humans gathered uncultivated plant materials for food and employed the medicinal plant for healing, most modern human use of plants is through agriculture. The land conversion of land for crop growth has led to a significant reduction in the amount available of forestation and wetlands, resulting in the loss of habitat for many plant and animal species as well as increased erosion.
Although natural wonders are celebrated in the Psalms and the Book of Job, in the West, wilderness portrayals in art became more prevalent in the 1800s, especially in the works of the Romantic movement. British artists John Constable and J. M. W. Turner turned their attention to capturing the beauty of the natural world in their paintings. Before that, paintings had been primarily of religious scenes or of human beings. William Wordsworth's poetry described the wonder of the natural world, which had formerly been viewed as a threatening place. Increasingly the valuing of nature became an aspect of Western culture. This artistic movement also coincided with the Transcendentalist movement in the Western world. A common classical idea of beautiful art involves the word mimesis, the imitation of nature. Also in the realm of ideas about beauty in nature is that the perfect is implied through perfect mathematical Substantial form and more generally by patterns in nature. As David Rothenburg writes, "The beautiful is the root of science and the goal of art, the highest possibility that humanity can ever hope to see".
The behaviour of matter and energy throughout the observable universe appears to follow well-defined , or scientific law, which scientists seek to understand. These laws have been employed to produce cosmological models that successfully explain the structure and the evolution of the universe we can observe. The mathematical expressions of the laws of physics employ a set of twenty physical constants that appear to be static across the observable universe. The values of these constants have been carefully measured, but the reason for their specific values remains a mystery. The anthropic principle argues that the physical constants have the observed values precisely because intelligent life is here to observe them.
Outer space is saturated by blackbody radiation left over from the Big Bang and the origin of the universe. It contains a near-perfect vacuum of predominantly hydrogen and helium plasma, and is permeated by electromagnetic radiation, , and ; the latter include various atomic nucleus and subatomic particles. Regions enriched by matter expelled by is sparsely filled with cosmic dust and numerous types of organic discovered to date by microwave spectroscopy. Near the Earth, there are signs of human life in outer space today, such as material left over from previous crewed and uncrewed launches which are a potential hazard to spacecraft. Some of this space debris re-enters the atmosphere periodically.
At the largest scale, the visible universe follows the Cosmological principle, appearing uniformly isotropic and homogeneous in all directions. On smaller scales, observable matter is organized in a hierarchy of structures due to the cumulative effect of gravity. Stars are formed in galaxy structures that typically span up to 100,000 in scale. These in turn are organized in larger scale and groups spanning tens of millions of light years, then that extend hundreds of millions of light years across. The largest known structures are the that link together superclusters. In the open regions between these structures are vast, nearly empty voids. Individual galaxies have numerous groupings of stars called Star cluster. All stars can appear individually or in hierarchical systems of co-orbiting stars. Each star can have orbiting sub-stellar bodies at various scales: , , moons, asteroids and comets, down to meteoroids.
A major question in astronomy concerns the existence of life elsewhere in the universe. Although Earth is the only body within the Solar System known to support life, evidence suggests that in the distant past the planet Mars possessed bodies of liquid water on the surface. For a brief period in Mars' history, it may have also been capable of forming life. At present though, most of the water remaining on Mars is frozen.
If life exists at all on Mars, it is most likely to be located underground where liquid water can still exist. Conditions on the other terrestrial planets, Mercury and Venus, appear to be too harsh to support life as we know it. But it has been conjectured that Europa, the fourth-largest moon of Jupiter, may possess a sub-surface ocean of liquid water and could potentially host life. Astronomers have discovered extrasolar – planets that lie in the habitable zone of space surrounding a star, and therefore could possibly host life. However the requirements for life are not completely known and astronomical observations provide limited information.
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Historical perspective
Earth is estimated to have formed 4.54 billion years ago from the solar nebula, along with the Sun and other . The Moon formed roughly 20 million years later. Initially molten, the outer layer of the Earth cooled, resulting in the solid crust. Outgassing and Volcano activity produced the primordial atmosphere. Condensing water vapor, most or all of which came from ice delivered by , produced the oceans and other water sources.
The highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago.
Continents formed, then broke up and reformed as the surface of Earth reshaped over hundreds of millions of years, occasionally combining to make a supercontinent. Roughly 750 million years ago, the earliest known supercontinent Rodinia, began to break apart. The continents later recombined to form Pannotia which broke apart about 540 million years ago, then finally Pangaea, which broke apart about 180 million years ago.
Atmosphere, climate, and weather
The Earth's atmosphere is a key factor in sustaining the ecosystem. The thin layer of gases that envelops the Earth is held in place by gravity. Air is mostly nitrogen, oxygen, water vapor, with much smaller amounts of carbon dioxide, argon, etc. The atmospheric pressure and density declines steadily with altitude. The ozone layer plays an important role in depleting the amount of ultraviolet (UV) radiation that reaches the surface. As DNA is readily damaged by UV light, this serves to protect life at the surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes.
Water on Earth
Water is a chemical substance that is composed of hydrogen and oxygen (H2O) and is vital for all known forms of life. In typical usage, "water" refers only to its liquid form, but it also has a solid state, ice, and a state, water vapor, or steam. Water covers 71% of the Earth's surface. On Earth, it is found mostly in oceans and other large bodies of water, with 1.6% of water below ground in and 0.001% in the atmosphere as vapor, clouds, and precipitation. Oceans hold 96.5% of surface water; and polar , 2.4%; and other land surface water such as rivers, lakes, ponds, underground , and groundwater, 1%. The smallest freshwater reserve is the 0.1% in the atmosphere. Through subduction processes in the Earth's crust, an equivalent mass of the planet's surface water has been interred in the upper mantle alone.
Oceans
An ocean is a major body of Seawater, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface (an area of some 361 million square kilometers) is covered by ocean, a World Ocean that is customarily divided into several principal oceans and smaller seas. More than half of this area is over deep. Average oceanic salinity is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt. Though generally recognized as several 'separate' oceans, these waters comprise one global, interconnected body of salt water often referred to as the World Ocean or global ocean. This is a fundamental concept in oceanography: a global-spanning ocean that functions as a continuous body of water with relatively free interchange among its bodies.
Lakes and ponds
A lake (from Latin word lacus) is a terrain feature (or physical feature), a body of liquid on the surface of a world that is localized to the bottom of basin (another type of landform or terrain feature; that is, it is not global) and moves slowly if it moves at all. On Earth, a body of water is considered a lake when it is inland, not part of the ocean, is larger and deeper than a pond, and is fed by a river.
(2025). 9780123706263, Academic Press. ISBN 9780123706263
Rivers and streams
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. A river is part of the hydrological cycle. Water within a river is generally collected from precipitation through surface runoff, groundwater recharge, springs, and the release of stored water in natural ice and snowpacks (i.e., from ). Where a river merges with a slow-moving body of water, the deposited sedimentation can build up to form a River delta.
Ecosystems
Ecosystems are composed of a variety of biotic component and abiotic components that function in an interrelated way. The structure and composition is determined by various environmental factors that are interrelated. Variations of these factors will initiate dynamic modifications to the ecosystem. Some of the more important components are soil, atmosphere, radiation from the sun, water, and living organisms.
Wilderness
Wilderness is generally defined as areas that have not been significantly modified by human activity. Wilderness areas can be found in preserves, estates, farms, conservation preserves, ranches, national forests, , and even in urban areas along rivers, gulches, or otherwise undeveloped areas. Wilderness areas and protected parks are considered important for the survival of certain species, ecological studies, conservation, and solitude. Some nature writers believe wilderness areas are vital for the human spirit and creativity, and some ecologists consider wilderness areas to be an integral part of the Earth's self-sustaining natural ecosystem (the biosphere). They may also preserve historic genetics traits and that they provide habitat for wild flora and fauna that may be difficult or impossible to recreate in , , or laboratory.
Life
Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by Organism, metabolism, cell growth, adaptation, response to stimuli, and reproduction. Life may also be said to be simply the characteristic state of . The latter can then be defined in terms of biochemistry, genetics, or thermodynamics. Properties common to terrestrial organisms (plants, animals, Fungus, , archaea, and bacteria) are that they are cellular and based on a complex chemical organization. However, not every definition of life considers these properties to be essential. Human-made Artificial life may also be considered to be life.
(2025). 9783319935836 ISBN 9783319935836 The specific nucleotide sequence in each organism contains information that functions to promotes survival, reproduction, and the capacity to acquire resources necessary for reproduction; such sequences probably emerged early in the evolution of life. Survival functions present early in the evolution of life likely also included genomic sequences that promote the avoidance of damage to the self-replicating molecule and also the capability to DNA repair that do occur. Repair of some genome damages may have involved using information from another similar molecule by a process of recombination (a primitive form of sexual interaction).
Evolution
The origin of life on Earth is not well understood, but it is known to have occurred at least 3.5 billion years ago, during the hadean or archean eons on a Early Earth that had a substantially different environment than is found at present. These life forms possessed the basic traits of self-replication and inheritable traits. Once life had appeared, the process of evolution by natural selection resulted in the development of ever-more diverse life forms.
Microbes
The first form of life to develop on the Earth were unicellular, and they remained the only form of life until about a billion years ago when multi-cellular organisms began to appear. Microorganisms or microbes are microscopic, and smaller than the human eye can see. can be single-celled, such as Bacteria, Archaea, many , and a minority of Fungus.
Plants and animals
Originally Aristotle divided all living things between plants, which generally do not move fast enough for humans to notice, and animals. In Carl Linnaeus' system, these became the kingdoms Vegetabilia (later ) and . Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungus and several groups of were removed to new kingdoms. However, these are still often considered plants in many contexts. Bacterial life is sometimes included in flora, and some classifications use the term bacterial flora separately from plant flora.
Human interrelationship
Human impact
Although humans comprise a minuscule proportion of the total living biomass on Earth, the human effect on nature is disproportionately large. Because of the extent of human influence, the boundaries between what humans regard as nature and "made environments" is not clear cut except at the extremes. Even at the extremes, the amount of natural environment that is free of discernible human influence is diminishing at an increasingly rapid pace. A 2020 study published in Nature found that anthropogenic mass (human-made materials) outweighs all living biomass on earth, with plastic alone exceeding the mass of all land and marine animals combined. And according to a 2021 study published in Frontiers in Forests and Global Change, only about 3% of the planet's terrestrial surface is ecologically and intact, with a low human footprint and healthy populations of native animal species. Philip Cafaro, professor of philosophy at the School of Global Environmental Sustainability at Colorado State University, wrote in 2022 that "the cause of global biodiversity loss is clear: other species are being displaced by a rapidly growing human economy."
Aesthetics and beauty
Beauty in nature has historically been a prevalent theme in art and books, filling large sections of libraries and bookstores. That nature has been depicted and celebrated by so much art, photography, poetry, and other literature shows the strength with which many people associate nature and beauty. Reasons why this association exists, and what the association consists of, are studied by the branch of philosophy called aesthetics. Beyond certain basic characteristics that many philosophers agree about to explain what is seen as beautiful, the opinions are virtually endless. Nature and wildness have been important subjects in various eras of world history. An early tradition of landscape art began in China during the Tang Dynasty (618–907). The tradition of representing nature as it is became one of the aims of Chinese painting and was a significant influence in Asian art.
Matter and energy
Matter is defined as a substance that has mass and takes up a volume of space, while energy is a property that can make matter perform work. At the quantum mechanical scale of the very tiny, both matter and energy exibit the property of wave–particle duality, and they are related to each other through mass–energy equivalence. Matter constitutes the observable universe, which is made visible by the radiation of energy waves. The visible components of the universe are now believed to compose only 4.9 percent of the total mass. The remainder is in an unknown form that is believed to consist of 26.8 percent cold dark matter and 68.3 percent dark energy. The exact nature of these unseen components is under intensive investigation by physicists.
Beyond Earth
Outer space, also simply called space, refers to the relatively empty regions of the universe outside the of celestial bodies. Outer space is used to distinguish it from airspace (and terrestrial locations). There is no discrete boundary between Earth's atmosphere and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the Solar System is called interplanetary space, which passes over into interstellar space at what is known as the heliopause.
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