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80-402: 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 laws , elements and phenomena 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 separate and even superior to nature. During

160-488: 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 gaseous 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 aquifers and 0.001% in

240-435: 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 living beings , 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

320-496: 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. 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

400-440: A continual basis. The total number of species is in rapid decline. 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 primordial 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,

480-496: A daily basis. All living organisms that exist within a given ecosphere. J.B. Lamarck defined the term biosphere. When modern biologists mention the biosphere they usually mean the best part of the Earth's crust, which is the lithosphere and hydrosphere, and of the lower parts of the Earth's lower parts, which is the troposphere. All these together and the living organisms make up the biosphere. Other authorities go further and define

560-463: 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. Geology is the science and study of the solid and liquid matter that constitutes the Earth. The field of geology encompasses the study of the composition, structure , physical properties , dynamics, and history of Earth materials , and the processes by which they are formed, moved, and changed. The field

640-406: A dependence on the seasonal variation of the weather, and sudden changes lasting only a few years can have a dramatic effect, both on the vegetation and on the animals which 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 ocean currents, surface albedo , greenhouse gases , variations in

720-651: 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 unnatural or the supernatural . The word nature is borrowed from the Old French nature and is derived from the Latin word natura , or "essential qualities, innate disposition", and in ancient times, literally meant " birth ". In ancient philosophy, natura

800-587: A dynamic dimension then, especially for Heraclitus ), and has steadily gained currency ever since. Earth is the only planet known to support life , and its natural features are the subject of many fields of scientific research. Within the Solar System , it is third closest to the Sun; it is the largest terrestrial planet and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow temperate zones, and

880-485: A metabolism, a capacity to grow, respond to stimuli, and reproduce. An entity with these properties is generally considered life. However, not every definition of life considers all of these properties to be essential. Human-made analogs of life may also be considered to be life. 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 biotic processes in turn alter or transform. From

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960-444: A meteorite collision probably triggered the extinction of the non-avian dinosaurs and other large reptiles, but spared small animals such as mammals . 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

1040-431: A minority of Fungi . 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

1120-435: A pond from many other aquatic terrain features, such as stream pools and tide pools . 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. Small rivers may also be called by several other names, including stream, creek, brook, rivulet, and rill; there

1200-462: A solid and spherical layer known as the Crust (geology) . This includes rocks and minerals that are present on the Earth as well as parts of soil and skeletal remains of animals that have become fossilized over the years. This is all about process how rocks metamorphosize. They go through solids to weathered to washing away and back to being buried and resurrected. The primary agent driving these processes

1280-420: A variety of biotic 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. Central to the ecosystem concept

1360-501: A wide equatorial tropical to subtropical region. Precipitation varies widely 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

1440-454: Is a major academic discipline , and is also important for mineral and hydrocarbon extraction, knowledge about and mitigation of natural hazards , some Geotechnical engineering fields, and 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

1520-527: Is a planet's "original" crust. It forms from solidification of a magma ocean. Toward the end of planetary accretion , the terrestrial planets likely had surfaces that were magma oceans. As these cooled, they solidified into crust. This crust was likely destroyed by large impacts and re-formed many times as the Era of Heavy Bombardment drew to a close. The nature of primary crust is still debated: its chemical, mineralogic, and physical properties are unknown, as are

1600-563: 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 . 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 , national parks , and even in urban areas along rivers, gulches, or otherwise undeveloped areas. Wilderness areas and protected parks are considered important for

1680-405: Is continuously subjected to plasma flow. The plasma flow is the solar wind that is propelled from the Sun. The interaction between solar wind and geomagnetic field eventually combine to result in the formation of an electrical current layer, which is called the magnetopause. This electric current layer confines the Earth's magnetic field. The region in which the magnetopause is enclosed in is known as

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1760-495: Is debated. The anorthosite highlands of the Moon are primary crust, formed as plagioclase crystallized out of the Moon's initial magma ocean and floated to the top; however, it is unlikely that Earth followed a similar pattern, as the Moon was a water-less system and Earth had water. The Martian meteorite ALH84001 might represent primary crust of Mars; however, again, this is debated. Like Earth, Venus lacks primary crust, as

1840-475: Is estimated to have formed 4.54 billion years ago from the solar nebula , along with the Sun and other planets . The Moon formed roughly 20 million years later. Initially 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

1920-441: 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 , farm animals , wild animals , pests , etc. according to their relationship to human life. Ecosphere (planetary) The layer of an ecosphere that exists at a Terrestrial planet 's Center of mass and which extends radially outward until ending in

2000-546: Is mostly used as the Latin translation of the Greek word physis (φύσις), which originally related to the intrinsic characteristics of plants, animals, and other features of the world to develop of their own accord. The concept of nature as a whole, the physical universe , is one of several expansions of the original notion; it began with certain core applications of the word φύσις by pre-Socratic philosophers (though this word had

2080-496: Is needed to create tertiary crust, and Earth is the only planet in the Solar System with plate tectonics. Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is the top component of the lithosphere , a division of Earth's layers that includes the crust and the upper part of the mantle . The lithosphere is broken into tectonic plates that move, allowing heat to escape from

2160-533: Is no general rule that defines what can be called a river. Many names for small rivers are specific to geographic location; one example is Burn in Scotland and North-east England. Sometimes a river is said to be larger than a creek, but this is not always the case, due to vagueness in the language. A river is part of the hydrological cycle . Water within a river is generally collected from precipitation through surface runoff , groundwater recharge, springs , and

2240-503: Is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by organization , metabolism , growth , adaptation , response to stimuli , and reproduction . Life may also be said to be simply the characteristic state of organisms . Present day organisms from viruses to humans possess a self-replicating informational molecule (genome), either DNA or RNA (as in some viruses), and such an informational molecule

2320-415: 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, rift zones , and areas with ongoing or recent glaciation . Other lakes are found in endorheic basins or along the courses of mature rivers. In some parts of the world, there are many lakes because of chaotic drainage patterns left over from

2400-501: 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 specific deoxyribonucleotide / ribonucleotide sequence in each currently extant individual organism contains sequence information that functions to promotes survival, reproduction , and the capacity to acquire resources necessary for reproduction, and such sequences probably emerged early in

2480-446: Is the idea that living organisms interact with every other element in their local environment . Eugene Odum, a founder of ecology, stated: "Any unit that includes all of the organisms (ie: 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

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2560-438: Is the movement of Earth’s tectonic plates, which creates mountains, volcanoes, and ocean basins. The inner core of the Earth contains liquid iron, which is an important factor in the geosphere as well as the magnetosphere. The total mass of water , regardless of phase (e.g. liquid, solid, gas), that exists within an ecosphere. It's possible for the hydrosphere to be highly distributed throughout other component spheres such as

2640-797: The Indian Ocean , the Southern Ocean , and the Arctic Ocean . Smaller regions of the oceans are called seas, gulfs, bays and other names. There are also salt lakes , which are smaller bodies of landlocked saltwater that are not interconnected with the World Ocean. Two notable examples of salt lakes are the Aral Sea and the Great Salt Lake . A lake (from Latin word lacus ) is a terrain feature (or physical feature ),

2720-573: The Moon and other planetary bodies formed via igneous processes and were later modified by erosion , impact cratering , volcanism, and sedimentation. Most terrestrial planets have fairly uniform crusts. Earth, however, has two distinct types: continental crust and oceanic crust . These two types have different chemical compositions and physical properties and were formed by different geological processes. Planetary geologists divide crust into three categories based on how and when it formed. This

2800-661: The Neoproterozoic era, freezing temperatures covered much of the Earth in glaciers 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 mass extinctions . The last mass extinction occurred some 66 million years ago, when

2880-455: The Northern and Southern Hemispheres experience opposite seasons. Weather is a chaotic system that is readily modified by small changes to the environment , so accurate weather forecasting is limited to only a few days. Overall, two things are happening worldwide: (1) temperature is increasing on the average; and (2) regional climates have been undergoing noticeable changes. Water is

2960-584: The World Ocean or global ocean. This concept of a global ocean as a continuous body of water with relatively free interchange among its parts is of fundamental importance to oceanography . The major oceanic divisions are defined in part by the continents , various archipelagos , and other criteria: these divisions are (in descending order of size) the Pacific Ocean , the Atlantic Ocean ,

3040-421: The adiabatic rise of mantle causes partial melting. Tertiary crust is more chemically-modified than either primary or secondary. It can form in several ways: The only known example of tertiary crust is the continental crust of the Earth. It is unknown whether other terrestrial planets can be said to have tertiary crust, though the evidence so far suggests that they do not. This is likely because plate tectonics

3120-420: The air as vapor , clouds, and precipitation . Oceans hold 97% of surface water, glaciers , and polar ice caps 2.4%, and other land surface water such as rivers, lakes, and ponds 0.6%. Additionally, a minute amount of the Earth's water is contained within biological bodies and manufactured products. An ocean is a major body of saline water , and a principal component of the hydrosphere. Approximately 71% of

3200-415: The geosphere and atmosphere . There are about 1.4 billion km of water on Earth. That includes liquid water in the ocean, lakes, and rivers. It includes frozen water in snow, ice, and glaciers, and water that’s underground in soils and rocks. It also includes water that is in the atmosphere as clouds and vapor. Water is always on the move changing from a solid to vapor to ice and back to water. Water stays on

3280-508: The kingdoms Vegetabilia (later Plantae ) and Animalia . Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungi and several groups of algae 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 . Among

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3360-738: 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. A pond is a body of standing water , either natural or human-made, that is usually smaller than a lake. A wide variety of human-made bodies of water are classified as ponds, including water gardens designed for aesthetic ornamentation, fish ponds designed for commercial fish breeding, and solar ponds designed to store thermal energy. Ponds and lakes are distinguished from streams via current speed. While currents in streams are easily observed, ponds and lakes possess thermally driven micro-currents and moderate wind driven currents. These features distinguish

3440-457: The tropical climate at the equator to the polar climate in the northern and southern extremes. Weather is also influenced by the seasons, which result from the Earth 's axis being tilted 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,

3520-433: The Earth for various amounts of time. It can be minutes, days or years and it doesn't have any set schedule. A drop of water can be in the ocean for years, or evaporate after a few days. Water is constantly changing and moving forms. Climate change can alter the life of a drop of water. With global warming, water evaporates faster and the cycle keeps moving at faster rates. The key here is the water cycle and how this works on

3600-400: 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 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

3680-593: The Earth more rapidly than any previous life form, affecting 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 300 million years to culminate. The present era is classified as part of a mass extinction event , the Holocene extinction event,

3760-552: The Earth's surface (an area of some 361 million square kilometers) is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas. More than half of this area is over 3,000 meters (9,800 feet) 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

3840-419: The Earth, the density of the atmosphere decreases outward, which pushes the oxygen inward allowing humans to breathe without consequence. The general circulation of the atmosphere is defined as the zonally and temporally averaged wind and temperature fields. The magnetic field of an ecosphere along with the charged particles that are being controlled by that magnetic field. The Earth is one large magnet that

3920-528: The advent of modern scientific method in the last several centuries, nature became the passive reality , organized and moved by divine laws. 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,

4000-409: The biosphere as " the space of our planet that is taken up by living beings" or as " that part of the Earth's crust, of its hydrosphere and atmosphere, that builds the environment for life". The layer of an ecosphere that exists as a gas. The atmosphere is the most distant component sphere of matter from the planet's Center of mass , beyond which is Outer space . The whole mass of air surrounding

4080-471: The biosphere. 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. The number of individual species of life is constantly in some degree of flux, with new species appearing and others ceasing to exist on

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4160-445: The broadest geophysiological 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 6.8×10 kilograms) of biomass (life), which lives within various environments within

4240-423: The crust ranges between about 20 and 120 km. Crust on the far side of the Moon averages about 12 km thicker than that on the near side . Estimates of average thickness fall in the range from about 50 to 60 km. Most of this plagioclase-rich crust formed shortly after formation of the Moon, between about 4.5 and 4.3 billion years ago. Perhaps 10% or less of the crust consists of igneous rock added after

4320-453: The entire planet has been repeatedly resurfaced and modified. Secondary crust is formed by partial melting of mostly silicate materials in the mantle, and so is usually basaltic in composition. This is the most common type of crust in the Solar System. Most of the surfaces of Mercury, Venus, Earth, and Mars comprise secondary crust, as do the lunar maria . On Earth secondary crust forms primarily at mid-ocean spreading centers , where

4400-553: 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 polar regions much colder. Weather can have both beneficial and harmful effects. Extremes in weather, such as tornadoes or hurricanes and cyclones , can expend large amounts of energy along their paths, and produce devastation. Surface vegetation has evolved

4480-621: 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 repair such damages 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 ). Properties common to terrestrial organisms (plants, animals, fungi , protists , archaea , and bacteria) are that they are cellular, carbon-and-water-based with complex organization, having

4560-438: 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. The Earth's atmosphere is a key factor in sustaining the ecosystem . The thin layer of gases that envelops

4640-529: 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

4720-463: The formation of the initial plagioclase-rich material. The best-characterized and most voluminous of these later additions are the mare basalts formed between about 3.9 and 3.2 billion years ago. Minor volcanism continued after 3.2 billion years, perhaps as recently as 1 billion years ago. There is no evidence of plate tectonics . Study of the Moon has established that a crust can form on a rocky planetary body significantly smaller than Earth. Although

4800-412: The geomagnetic field. The atmospheric 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

4880-491: The igneous mechanisms that formed them. This is because it is difficult to study: none of Earth's primary crust has survived to today. Earth's high rates of erosion and crustal recycling from plate tectonics has destroyed all rocks older than about 4 billion years , including whatever primary crust Earth once had. However, geologists can glean information about primary crust by studying it on other terrestrial planets. Mercury's highlands might represent primary crust, though this

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4960-503: 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 , fluvial geomorphology , aquatic ecology , fish biology , riparian ecology , and others. Ecosystems are composed of

5040-406: The initial sequence of rocks has been deposited, the rock units can be deformed and/or metamorphosed . 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 tectonic plates . Earth

5120-416: The interior of Earth into space. A theoretical protoplanet named " Theia " is thought to have collided with the forming Earth, and part of the material ejected into space by the collision accreted to form the Moon. As the Moon formed, the outer part of it is thought to have been molten, a " lunar magma ocean ". Plagioclase feldspar crystallized in large amounts from this magma ocean and floated toward

5200-416: The magnetosphere. Crust (geology) In geology , the crust is the outermost solid shell of a planet , dwarf planet , or natural satellite . It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be distinguished based on its phase (solid crust vs. liquid mantle). The crusts of Earth , Mercury , Venus , Mars , Io ,

5280-649: The many ways of classifying plants are by regional floras , which, depending on the purpose of study, can also include fossil flora , remnants of plant life from a previous era. 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

5360-461: The native, or natural flora of the place to which they were introduced. This is an example of how human interaction with nature 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 botanists 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

5440-616: 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. During

5520-420: The original conditions. The outer surface is divided into several gradually 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, and a fluid outer phase. Convective motion in the core generates electric currents through dynamo action, and these, in turn, generate

5600-462: The ozone layer absorbing harmful ultraviolet radiation , life colonized the surface of Earth. 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. Microorganisms can be single-celled , such as Bacteria , Archaea , many Protista , and

5680-440: The planetary ecosystem. However, some microorganisms are pathogenic and can post health risk to other organisms. Viruses are infectious agents , but they are not autonomous life forms , as it is the case for viroids , satellites , DPIs and prions . Originally Aristotle divided all living things between plants, which generally do not move fast enough for humans to notice, and animals. In Linnaeus ' system, these became

5760-411: The process of evolution by natural selection resulted in the development of ever-more diverse life forms. 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

5840-528: The release of stored water in natural ice and snowpacks (i.e., from glaciers ). A stream is a flowing body of water with a current , confined within a bed and stream banks . In the United States, a stream is classified as a watercourse less than 60 feet (18 metres) wide. 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

5920-418: The solar luminosity, and changes to the Earth's orbit. Based on historical and geological records, the Earth is known to have undergone drastic climate changes in the past, including ice ages . The climate of a region depends on a number of factors, 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

6000-419: The surface or intrude into the overlying rock . Deposition can occur when sediments settle onto the surface of the Earth and later 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 , dikes , and sills , push upwards into the overlying rock, and crystallize as they intrude. After

6080-444: The surface. The cumulate rocks form much of the crust. The upper part of the crust probably averages about 88% plagioclase (near the lower limit of 90% defined for anorthosite ): the lower part of the crust may contain a higher percentage of ferromagnesian minerals such as the pyroxenes and olivine , but even that lower part probably averages about 78% plagioclase. The underlying mantle is denser and olivine-rich. The thickness of

6160-424: The surface. The atmosphere also retains heat during the night, thereby reducing the daily temperature extremes. Terrestrial weather occurs almost exclusively in the lower part of the atmosphere , and serves as a convective system for redistributing heat. Ocean currents are another important factor in determining climate, particularly the major underwater thermohaline circulation which distributes heat energy from

6240-534: 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 genetic traits and that they provide habitat for wild flora and fauna that may be difficult or impossible to recreate in zoos , arboretums , or laboratories . Although there

6320-438: 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

6400-537: 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

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