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Nature, in the broadest sense, is the natural, physical, material world or
universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxy, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development ...

universe
. "Nature" can refer to the
phenomena A phenomenon (; plural phenomena) is an observable fact or event. The term came into its modern philosophical Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, existence, knowledge ...
of the physical world, and also to life in general. The study of nature is a large, if not the only, part of
science Science () is a systematic enterprise that builds and organizes knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is something that is truth, true. The usual test for a statement of ...

science
. Although humans are part of nature, human activity is often understood as a separate category from other natural phenomena. The word ''nature'' is borrowed from the
Old French Old French (, , ; Modern French French ( or ) is a Romance language The Romance languages, less commonly Latin or Neo-Latin languages, are the modern languages that evolved from Vulgar Latin Vulgar Latin, also known as Popular o ...
''nature'' and is derived from the
Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the power of the Roman Republic, it became ...

Latin
word ''natura'', or "essential qualities, innate disposition", and in ancient times, literally meant "
birth Birth is the act or process of bearing or bringing forth offspring, also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fe ...

birth
". In ancient philosophy, ''natura'' is mostly used as the Latin translation of the Greek word ''
physis Physis (; grc, φύσις Physis (; grc, φύσις ) is a Greek philosophical Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, existence, knowledge Knowledge is a familia ...
'' (φύσις), which originally related to the intrinsic characteristics that plants, animals, and other features of the world develop of their own accord. The concept of nature as a whole, the physical
universe The universe ( la, universus) is all of space and time and their contents, including planets, stars, galaxy, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development ...

universe
, is one of several expansions of the original notion; it began with certain core applications of the word φύσις by
pre-Socratic Pre-Socratic philosophy is ancient Greek philosophy Ancient Greek philosophy arose in the 6th century BC, at a time when the inhabitants of ancient Greece were struggling to repel devastating invasions from the east. Greek philosophy continued t ...
philosophers (though this word had a dynamic dimension then, especially for
Heraclitus Heraclitus of Ephesus (; grc-gre, Ἡράκλειτος ; , ) was an Ancient Greek Ancient Greek includes the forms of the Greek language Greek ( el, label=Modern Greek Modern Greek (, , or , ''Kiní Neoellinikí Glóssa''), ...

Heraclitus
), and has steadily gained currency ever since. During the advent of modern
scientific method The scientific method is an empirical Empirical evidence for a proposition is evidence, i.e. what supports or counters this proposition, that is constituted by or accessible to sense experience or experimental procedure. Empirical evidence ...

scientific method
in the last several centuries, nature became the passive reality, organized and moved by divine laws. With the
Industrial revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Continental Europe or mainland Europe is the contiguous continent A continent is any of several large landmasse ...
, nature increasingly became seen as the part of reality deprived from intentional intervention: it was hence considered as sacred by some traditions (
Rousseau Jean-Jacques Rousseau (, ; ; 28 June 1712 – 2 July 1778) was a Republic of Geneva, Genevan philosopher, writer, and composer. His political philosophy influenced the progress of the Age of Enlightenment, Enlightenment throughout Europe, as w ...

Rousseau
, American
transcendentalism Transcendentalism is a philosophical movement that developed in the late 1820s and 1830s in the eastern United States. "Transcendentalism is an American literary, political, and philosophical movement of the early nineteenth century, centered arou ...
) or a mere decorum for divine providence or human history (
Hegel Georg Wilhelm Friedrich Hegel (; ; 27 August 1770 – 14 November 1831) was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citi ...

Hegel
,
Marx Karl Heinrich Marx (; 5 May 1818 – 14 March 1883) was a German philosopher A philosopher is someone who practices philosophy Philosophy (from , ) is the study of general and fundamental questions, such as those about reason, M ...

Marx
). However, a vitalist vision of nature, closer to the presocratic one, got reborn at the same time, especially after
Charles Darwin Charles Robert Darwin (; ; 12 February 1809 – 19 April 1882) was an English naturalist Natural history is a domain of inquiry involving organism In biology, an organism () is any organic, life, living system that fu ...

Charles Darwin
. Within the various uses of the word today, "nature" often refers to geology and
wildlife Wildlife traditionally refers to undomesticated animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functi ...

wildlife
. Nature can refer to the general realm of living plants and animals, 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 Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth
. It is often taken to mean the "
natural environment The natural environment or natural world encompasses all life, living and non-living things occurring nature, naturally, meaning in this case not Artificiality, artificial. The term is most often applied to the Earth or some parts of Earth. Th ...

natural environment
" or
wilderness Wilderness or wildlands (usually in the plural), are natural environments on Earth that have not been significantly modified by human activity or any nonurbanized land not under extensive agricultural cultivation. The term has traditionally re ...

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 Consciousness, at its simplest, is sentience or awareness of internal and external existence. Despite millennia of analyses, definitions, explanations and debates by philosophers and scientists, consciousness remains puzzling and controversial ...

consciousness
or a human
mind The mind is the set of faculties responsible for mental phenomena A phenomenon (; plural phenomena) is an observable fact or event. The term came into its modern philosophical Philosophy (from , ) is the study of general and fun ...

mind
. Depending on the particular context, the term "natural" might also be distinguished from the unnatural or the
supernatural The supernatural encompasses supposed phenomena or entities that are not subject to the Scientific law, laws of nature. This term is attributed to non-physical entity, non-physical entities, such as angels, demons, gods, and ghost, spirits. It ...

supernatural
.


Earth

Earth is the only
planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and ...

planet
known to support life, and its natural features are the subject of many fields of scientific research. Within the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

Solar System
, it is third closest to the Sun; it is the largest
terrestrial planet A terrestrial planet, telluric planet, or rocky planet, is a planet that is composed primarily of silicate Rock (geology), rocks or metals. Within the Solar System, the terrestrial planets accepted by the IAU are the inner planets closest to the Su ...
and the fifth largest overall. Its most prominent climatic features are its two large polar regions, two relatively narrow
temperate In geography Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its populati ...
zones, and a wide
equator The Equator is a circle of latitude, about in circumference, that divides Earth into the Northern Hemisphere, Northern and Southern Hemisphere, Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the N ...

equator
ial tropical to
subtropical The subtropical zones or subtropics are geographical Geography (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country locat ...

subtropical
region.
Precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology dates back , though significant progress in meteorology did not begin until the 18th century. The 19th century saw mod ...
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 The Northern Hemisphere is the half of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remain ...

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 gradually migrating
tectonic plate This is a list of tectonic plates on Earth's surface Earth is the third planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibri ...
s. The interior remains active, with a thick layer of plastic
mantle Mantle may refer to: *Mantle (geology) A mantle is a layer inside a planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a n ...
and an iron-filled core that generates a
magnetic field A magnetic field is a vector field In vector calculus and physics, a vector field is an assignment of a vector to each point in a subset of space. For instance, a vector field in the plane can be visualised as a collection of arrows with ...

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 the geomagnetic field. The
atmospheric An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet A planet is an astronomical body orbi ...

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 In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use the ...

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.


Geology

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 A structure is an arrangement and organization of interrelated elements in a material object or system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. ...
,
physical properties A physical property is any Property (philosophy), property that is Measurement, measurable, whose value describes a state of a physical system. The changes in the physical properties of a system can be used to describe its changes between momenta ...
, dynamics, and
history History (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxima ...
of Earth materials, and the processes by which they are formed, moved, and changed. The field is a major
academic discipline An academic discipline or academic field is a subdivision of knowledge Knowledge is a familiarity or awareness, of someone or something, such as facts A fact is an occurrence in the real world. The usual test for a statement of fact is ...
, and is also important for
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
and
hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, prop ...
extraction, knowledge about and mitigation of
natural hazard A natural hazard is a natural phenomenon Types of natural phenomena include: Weather, fog, thunder, tornadoes; biological processes, decomposition, germination seedlings, three days after germination. Germination is the process by which ...
s, some
Geotechnical engineering Geotechnical engineering, also known as geotechnics, is the branch of concerned with the engineering behavior of . It uses the principles of and for the solution of its respective problems. It also relies on knowledge of , , , and other rel ...
fields, and understanding past climates and environments.


Geological evolution

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 Deposition may refer to: * Deposition (law), taking testimony outside of court * List of deposed politicians, Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual ...
onto the surface or intrude into the
overlying rock visible at far right). Note the man standing in front of the formation, for scale. New Jersey, U.S.A. In structural geology, an anticline is a type of Fold (geology), fold that is an arch-like shape and has its oldest Bed (geology), beds at its ...
. Deposition can occur when
sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently sediment transport, transported by the action of wind, water, or ice or by the force of gravity acting on the particles. ...

sediment
s settle onto the surface of the Earth and later lithify into
sedimentary rock Sedimentary rocks are types of rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the minerals included, its Chemical compoun ...

sedimentary rock
, or when as
volcanic material A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Ear ...

volcanic material
such as
volcanic ash Volcanic ash consists of fragments of rock, mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure ...
or
lava Lava is magma once it has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fracture in the Crust (geology), crust, ...

lava
flows, blanket the surface. Igneous s such as
batholith A batholith (from Greek ''bathos'', depth + ''lithos'', rock) is a large mass of intrusive Intrusive may refer to: * Intrusiveness, a typically unwelcome behavior, interrupting and disturbing to others * Intrusive rock; intrusion of molten magm ...
s,
laccolith A laccolith is a sheet-like intrusion (or concordant pluton) that has been injected within or between layers of sedimentary rock Sedimentary rocks are types of Rock (geology), rock that are formed by the accumulation or deposition of mineral o ...

laccolith
s,
dikes Dyke or dike may refer to: General uses * Dyke (slang) The term ''dyke'' is a slang Slang is language (words, phrases, and usages) of an informal register. It also sometimes refer to the language generally exclusive to the members of ...
, 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
metamorphosed Metamorphic rocks arise from the transformation of existing rock Rock most often refers to: * Rock (geology) A rock is any naturally occurring solid mass or aggregate of minerals or mineraloid matter. It is categorized by the mineral ...
. Deformation typically occurs as a result of horizontal shortening, horizontal extension, or side-to-side (
strike-slip In geology Geology (from the γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is a branch of concerned with both the liquid and , the of which it is composed, and the processes by which they change over t ...
) motion. These structural regimes broadly relate to convergent boundaries, divergent boundaries, and
transform boundaries A transform fault or transform boundary is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either anot ...
, respectively, between
tectonic plates This is a list of tectonic plates on Earth's surface. Tectonic plates are pieces of Earth's crust 350px, Plates in the crust of Earth Earth's crust is a thin shell on the outside of Earth, accounting for less than 1% of Earth's volume. It is ...
.


Historical perspective

Earth is estimated to have formed 4.54 billion years ago from the
solar nebula The formation and evolution of the Solar System The Solar SystemCapitalization Capitalization ( North American English) or capitalisation ( British English) is writing a word with its first letter as a capital letter (uppercase letter) ...
, along with the
Sun The Sun is the star A star is an astronomical object consisting of a luminous spheroid of plasma (physics), plasma held together by its own gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many othe ...

Sun
and other
planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilibrium, rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and ...

planet
s. 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 A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet ar ...

volcanic
activity produced the primordial atmosphere. Condensing
water vapor (99.9839 °C) , - , Boiling point The boiling point of a substance is the temperature at which the vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating th ...
, most or all of which came from
ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , eve ...

ice
delivered by
comet A comet is an icy, small Solar System body A small Solar System body (SSSB) is an object in the Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astr ...

comet
s, 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 In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the proces ...
. Roughly 750 million years ago, the earliest known supercontinent
Rodinia Rodinia (from the Russian родить, ''rodit'', meaning "to beget, to give birth", or родина, ''rodina'', meaning "motherland, birthplace") was a Neoproterozoic supercontinent that assembled 1.1–0.9 billion years ago and broke up 750 ...

Rodinia
, began to break apart. The continents later recombined to form
Pannotia Pannotia (from Greek: ''pan- Pan may refer to: Prefix *''Pan-'', a prefix from the Greek language, Greek πᾶν, ''pan'', meaning "all", "of everything", or "involving all members" of a group ** , most but not all using the prefix People * Pan ...

Pannotia
which broke apart about 540 million years ago, then finally
Pangaea Pangaea or Pangea () was a supercontinent In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology) ...

Pangaea
, which broke apart about 180 million years ago. During the
Neoproterozoic The Neoproterozoic Era is the unit of geologic time The geologic time scale (GTS) is a system of chronological datingChronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such ob ...
era, freezing temperatures covered much of the Earth in
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
s and ice sheets. This hypothesis has been termed the "
Snowball Earth The Snowball Earth hypothesis proposes that, during one or more of Earth's Greenhouse and icehouse Earth, icehouse climates, the Earth's surface, planet's surface became entirely or nearly entirely frozen. It is believed that this occurred someti ...
", 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 An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity Biodiversity is the biological variety and Genetic variability, variability of life, life on Earth. Biodiversity is ...
. The last mass extinction occurred some 66 million years ago, when a meteorite collision probably triggered the extinction of the
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 annum, million years ago, although the exact origin and timing of the evolution ...

dinosaur
s and other large reptiles, but spared small animals such as
mammal Mammals (from Latin Latin (, or , ) is a classical language A classical language is a language A language is a structured system of communication Communication (from Latin ''communicare'', meaning "to share" or "to be i ...
s. Over the past 66 million years, mammalian life diversified. Several million years ago, a species of small African
ape Apes (Hominoidea ) are a branch The branches and leaves of a tree. A branch ( or , ) or tree branch (sometimes referred to in botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of bi ...

ape
gained the ability to stand upright. The subsequent advent of human life, and the development of agriculture and further
civilization  A civilization (or civilisation) is a complex society A complex society is a concept that is shared by a range of disciplines including anthropology, archaeology, history and sociology to describe a stage of social formation. The concep ...

civilization
allowed humans to affect 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 upright=2, O2 build-up in the Earth's atmosphere. Red and green lines represent the range of the estimates while time is measured in billions of years ago (Ga). The Great Oxidation Event (GOE), sometimes also called the Great Oxygenation Even ...
, produced by the proliferation of
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
during the
Siderian The Siderian Period (; el, σίδηρος, translit=sídēros, meaning "iron") is the first geologic period in the Paleoproterozoic Era and lasted from Ma to Ma (million years ago). Instead of being based on stratigraphy through Jurassic ...
period, required about 300 million years to culminate. The present era is classified as part of a mass
extinction event An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity Biodiversity is the biological variety and Genetic variability, variability of life, life on Earth. Biodiversity ...
, the
Holocene extinction The Holocene extinction, otherwise referred to as the sixth mass extinction or Anthropocene extinction, is an ongoing extinction event of species during the present Holocene epoch (geology), epoch (with the more recent time sometimes called Anthr ...
event, the fastest ever to have occurred. Some, such as
E. O. Wilson Edward Osborne Wilson (born June 10, 1929), usually cited as E. O. Wilson, is an American biologist Francesco Redi, the founder of biology, is recognized to be one of the greatest biologists of all time A biologist is a professional who has ...
of
Harvard University Harvard University is a private Private or privates may refer to: Music * "In Private "In Private" was the third single in a row to be a charting success for United Kingdom, British singer Dusty Springfield, after an absence of nearly t ...

Harvard University
, predict that human destruction of the
biosphere The biosphere (from βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all s. It can also be termed the zo ...
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.


Atmosphere, climate, and weather

The Earth's atmosphere is a key factor in sustaining the
ecosystem An ecosystem (or ecological system) consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the syst ...
. The thin layer of gases that envelops the Earth is held in place by gravity. Air is mostly
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
,
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
,
water vapor (99.9839 °C) , - , Boiling point The boiling point of a substance is the temperature at which the vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating th ...
, with much smaller amounts of carbon dioxide, argon, etc. The atmospheric pressure declines steadily with altitude. The plays an important role in depleting the amount of
ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, ...

ultraviolet
(UV) radiation that reaches the surface. As
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

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. Terrestrial weather occurs almost exclusively in the lower part of the atmosphere, and serves as a convective system for redistributing heat.
Ocean current An ocean current is a continuous, directed movement of sea water generated by a number of forces acting upon the water, including wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range ...
s are another important factor in determining climate, particularly the major underwater
thermohaline circulation Thermohaline circulation (THC) is a part of the large-scale Ocean current, ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective ''thermohaline'' derives from ''wikt:thermo-, t ...

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
polar region The Polar Regions, also called the frigid zones Zone or The Zone may refer to: Places Climate and altitude zones * Death zone (originally the lethal zone), altitudes above a certain point where the amount of oxygen is insufficient to sustain ...
s much colder. Weather can have both beneficial and harmful effects. Extremes in weather, such as
tornado A tornado is a violently rotating column of air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lower pie represents trace gases that together compose about 0.043391% of the atmos ...

tornado
es or
hurricane A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation Atmospheric circulation is the large-scale movement of Atmosphere of Earth, air and together with oc ...

hurricane
s and
cyclone In meteorology, a cyclone () is a large scale air mass that rotates around a strong center of low atmospheric pressure, counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere as viewed from above (opposite to an ...

cyclone
s, 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 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 Albedo (prounounced ; la, albedo, meaning 'whiteness') is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiat ...

albedo
,
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhou ...
es, variations in the solar luminosity, and changes to the Earth's orbit. Based on historical records, the Earth is known to have undergone drastic climate changes in the past, including
ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents an ...

ice age
s. The climate of a region depends on a number of factors, especially
latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth and planets. The first person to use the ...

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 Tropical climate is one of the five major climate groups in the . Tropical climates are characterized by monthly average temperatures of 18 °C (64.4 °F) or higher year-round and feature hot temperatures. Annual precipitation is often ...
at the equator to the
polar climate The polar climate regions are characterized by a lack of warm summer Summer is the hottest of the four temperate In geography, the temperate climates of Earth Earth is the third planet from the Sun and the only astrono ...
in the northern and southern extremes. Weather is also influenced by the seasons, which result from the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth
's
axis Axis may refer to: Politics *Axis of evil The phrase "axis of evil" was first used by U.S. President George W. Bush in his State of the Union address on January 29, 2002, less than five months after the 9/11 attacks, and often repeated t ...
being tilted relative to its
orbital plane The orbital plane of a revolving body is the geometric plane in which its orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet around a star or a natural satel ...
. 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 The Sun is the star A star is an astronomical object consisting of a luminous spheroid of plasma (physics), plasma held together by its own gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many othe ...

sun
. This exposure alternates as the Earth revolves in its orbit. At any given time, regardless of season, the and
southern The name Southern may refer to: * South South is one of the cardinal directions or compass points. South is the opposite of north and is perpendicular to the east and west. Etymology The word ''south'' comes from Old English ''sūþ'', from earl ...

southern
hemispheres experience opposite seasons. Weather is a
chaotic system Chaos theory is an interdisciplinary scientific theory and branch of mathematics focused on underlying patterns and deterministic Scientific law, laws highly sensitive to initial conditions in dynamical systems that were thought to have complet ...
that is readily modified by small changes to the
environment Environment most often refers to: __NOTOC__ * Natural environment, all living and non-living things occurring naturally * Biophysical environment, the physical and biological factors along with their chemical interactions that affect an organism or ...

environment
, so accurate
weather forecasting Weather forecasting is the application of science and technology to predict the conditions of the atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' o ...
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 on the Earth

Water is a
chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ultimately composed of atoms, which ...
that is composed of
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
and
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
(H2O) and is vital for all known forms of life. In typical usage, ''water'' refers only to its liquid form or
state State may refer to: Arts, entertainment, and media Literature * ''State Magazine'', a monthly magazine published by the U.S. Department of State * The State (newspaper), ''The State'' (newspaper), a daily newspaper in Columbia, South Carolina, Un ...
, but the substance also has a solid state,
ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , eve ...

ice
, and a
gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

gas
eous state,
water vapor (99.9839 °C) , - , Boiling point The boiling point of a substance is the temperature at which the vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating th ...
, or
steam Steam is water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fl ...

steam
. Water covers 71% of the
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

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
aquifer An aquifer is an underground layer of -bearing , rock fractures or unconsolidated materials (, , or ). can be extracted using a water . The study of water flow in aquifers and the characterization of aquifers is called . Related terms include a ...

aquifer
s and 0.001% in the
air File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lower pie represents trace gases that together compose about 0.043391% of the atmosphere (0.04402961% at April 2019 concentration ). Number ...

air
as
vapor In physics, a vapor (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of variety (linguistics), varieties of the English language native to the United St ...
, clouds, and
precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology dates back , though significant progress in meteorology did not begin until the 18th century. The 19th century saw mod ...
. Oceans hold 97% of surface water,
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
s, and polar
ice cap In glaciology Lateral moraine on a glacier joining the Gorner Glacier, Zermatt">Gorner_Glacier.html" ;"title="moraine on a glacier joining the Gorner Glacier">moraine on a glacier joining the Gorner Glacier, Zermatt, Swiss Alps. The moraine is ...
s 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.


Oceans

An ocean is a major body of
saline water Saline water (more commonly known as salt water) is water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere an ...

saline water
, 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 continuous body of water that is customarily divided into several principal oceans and smaller seas. More than half of this area is over deep. Average oceanic
salinity Salinity () is the saltiness or amount of salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific ...

salinity
is around 35
parts per thousand In science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Testability, testable explanations and predictio ...
(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 The ocean (also the sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.Distribution of land and water on the planet
"
UN Atlas of the Oceans
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 Oceanography (from the Ancient Greek Ancient Greek includes the forms of the used in and the from around 1500 BC to 300 BC. It is often roughly divided into the following periods: (), Dark Ages (), the period (), and the period ...
. The major oceanic divisions are defined in part by the
continent A continent is any of several large landmass A landmass, or land mass, is a large region In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of th ...

continent
s, various
archipelago An archipelago ( ), sometimes called an island group or island chain, is a chain, cluster or collection of island An island (or isle) is an isolated piece of habitat that is surrounded by a dramatically different habitat, such as ...

archipelago
s, and other criteria: these divisions are (in descending order of size) the
Pacific Ocean The Pacific Ocean is the largest and deepest of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. ...

Pacific Ocean
, the , the
Indian Ocean The Indian Ocean is the third-largest of the world's five ocean The ocean (also the or the world ocean) is the body of that covers approximately 70.8% of the surface of and contains 97% of . Another definition is "any of the large ...

Indian Ocean
, the
Southern Ocean The Southern Ocean, also known as the Antarctic Ocean, comprises the southernmost waters of the World Ocean, generally taken to be south of 60° S latitude and encircling Antarctica. As such, it is regarded as the second-smallest of t ...

Southern Ocean
, and the
Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major s. It spans an area of approximately and is also known as the coldest of all the oceans. The (IHO) recognizes it as an ocean, although some call it the Arctic Medit ...

Arctic Ocean
. Smaller regions of the oceans are called seas, gulfs,
bay A bay is a recessed, coastal body of water that directly connects to a larger main body of water, such as an ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface ...

bay
s and other names. There are also
salt lake A salt lake or saline lake is a landlocked body of water (Lysefjord) in Norway Norway, officially the Kingdom of Norway,Names in the official and recognised languages: Bokmål Bokmål (, ; literally "book tongue") is an official wr ...

salt lake
s, 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 The Aral Sea (Aral ; kk, Aral teńizi, Арал теңізі, uz, Orol dengizi, Орол денгизи, kaa, Aral ten'izi, Арал теңизи, russian: Аральское море) was an endorheic lake lying between Kazakhstan Kaza ...

Aral Sea
and the
Great Salt Lake The Great Salt Lake, located in the northern part of the U.S. state of Utah, is the largest salt water lake in the Western Hemisphere, and the eighth-largest terminal lake in the world. In an average year the lake covers an area of approximat ...

Great Salt Lake
.


Lakes

A lake (from Latin word ''lacus'') is a
terrain feature A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws ...
(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. The only world other than Earth known to harbor lakes is
Titan Titan most often refers to: * Titan (moon), the largest moon of Saturn * Titans, a race of deities in Greek mythology Titan or Titans may also refer to: Arts and entertainment Fictional entities Fictional locations * Titan in fiction, fictional ...
, Saturn's largest moon, which has lakes of
ethane Ethane ( or ) is an organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ (anatomy), organ Chemistry * Organic matter, matter that has come from a once-living ...
, most likely mixed with
methane Methane (, ) is a chemical compound with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes a ...
. 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,
rift zone upright=1.2, East Rift Zone on Kīlauea, Hawaii A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a set of linear cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined re ...
s, and areas with ongoing or recent
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the o ...

glaciation
. Other lakes are found in
endorheic basin An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin A drainage basin is any area of land where precipitation In meteorology Meteorology is a branch of the atmospheric sciences Atmospheri ...
s 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 the last
Ice Age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents an ...

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.


Ponds

A pond is a
body Body may refer to: In science * Physical body, an object in physics that represents a large amount, has mass or takes up space * Body (biology), the physical material of an organism * Body plan, the physical features shared by a group of animals ...

body
of
standing water Water stagnation occurs when water Water (chemical formula H2O) is an inorganic, transparent, tasteless, odorless, and nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all k ...
, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including
water garden Water garden or aquatic garden, is a term sometimes used for gardens, or parts of gardens, where any type of water feature is a principal or dominant element. The primary focus is on plants, but they will sometimes also house waterfowl, or orname ...
s designed for aesthetic ornamentation,
fish pond A fish pond, or fishpond, is a controlled pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake A lake is an area filled with water, localized in a basin, surrounded by land, apart from an ...

fish pond
s designed for commercial fish breeding, and s designed to store thermal energy. Ponds and lakes are distinguished from streams via
current Currents or The Current may refer to: Science and technology * Current (fluid) A current in a fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied shear stress, or external force. ...
speed. While currents in streams are easily observed, ponds and lakes possess thermally driven micro-currents and moderate wind driven currents. These features distinguish a pond from many other aquatic terrain features, such as
stream pool A stream pool, in hydrology, is a stretch of a river or stream in which the water depth is above average and the water velocity is below average. Formation A stream pool may be bedded with sediment or Armor (hydrology), armoured with gravel, and ...
s and
tide pool Tide pools or rock pools are shallow pools of seawater that form on the rocky intertidal shore. Many of these pools exist as separate bodies of water only at low tide. Many tide pools are habitat In ecology Ecology (from e ...
s.


Rivers

A river is a natural
watercourse A watercourse is the channel Channel, channels, channeling, etc., may refer to: Geography * Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water. Australia * Channel Cou ...

watercourse
, usually
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in ...
, 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 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 (meteorology), precipitation through surface runoff, groundwater recharge, Spring (hydrology), springs, and the release of stored water in natural ice and snowpacks (i.e., from
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
s).


Streams

A stream is a flowing body of water with a Current (stream), current, confined within a stream bed, bed and stream banks. In the United States, a stream is classified as a watercourse less than wide. Streams are important as conduits in the water cycle, instruments in groundwater recharge, and they serve as corridors for fish and
wildlife Wildlife traditionally refers to undomesticated animal Animals (also called Metazoa) are multicellular A multicellular organism is an organism In biology, an organism () is any organic, life, living system that functi ...

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 The Holocene extinction, otherwise referred to as the sixth mass extinction or Anthropocene extinction, is an ongoing extinction event of species during the present Holocene epoch (geology), epoch (with the more recent time sometimes called Anthr ...
, streams play an important wildlife corridor, corridor role in connecting Habitat fragmentation, 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, fluvial geomorphology, aquatic ecology, Freshwater fish, fish biology, riparian, riparian ecology, and others.


Ecosystems

Ecosystems are composed of a variety of biotic component, 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 The Sun is the star A star is an astronomical object consisting of a luminous spheroid of plasma (physics), plasma held together by its own gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many othe ...

sun
, water, and living organisms. Central to the ecosystem concept is the idea that living organisms interact with every other element in their local environment (biophysical), 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 the system is an ecosystem."Odum, EP (1971) ''Fundamentals of ecology'', 3rd edition, Saunders New York 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.


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, 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 the survival of certain species, ecological studies, Habitat conservation, conservation, and solitude. Some nature writers believe wilderness areas are vital for the human spirit and creativity,Botkin, Daniel B. (2000) ''No Man's Garden'', Island Press, pp. 155–57, . and some ecologists consider wilderness areas to be an integral part of the Earth's self-sustaining natural ecosystem (the
biosphere The biosphere (from βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all s. It can also be termed the zo ...
). They may also preserve historic genetics, genetic traits and that they provide habitat for wild flora (plants), flora and fauna (animals), fauna that may be difficult or impossible to recreate in zoos, arboretums, or laboratory, laboratories.


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, organization, metabolism, cell growth, growth, adaptation, response to stimulus (physiology), stimuli, and reproduction. Life may also be said to be simply the characteristic state of organisms. Properties common to terrestrial organisms (plants, animals, Fungus, fungi, protists, archaea, and bacteria) are that they are cellular, carbon-and-water-based with complex organization, having 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 Artificial life, analogs of life may also be considered to be life. The
biosphere The biosphere (from βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all s. It can also be termed the zo ...
is the part of Earth's outer shell—including land, surface rocks, water, air and the atmosphere—within which life occurs, and which Biology, biotic processes in turn alter or transform. From the broadest Geophysiology, 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 6.8×1013 kilograms) of biomass (ecology), biomass (life), which lives within various environments within 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 a continual basis. The total number of species is in rapid decline.


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, 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, 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 Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

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 Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
accumulated in the atmosphere and gave rise to the . The incorporation of smaller cells within larger ones resulted in the endosymbiotic theory, 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 surface of Earth.


Microbes

The first form of life to develop on the Earth were microbes, and they remained the only form of life until about a billion years ago when multi-cellular organisms began to appear. Microorganisms are single-celled organisms that are generally microscopic, and smaller than the human eye can see. They include Bacteria, Fungus, Fungi, Archaea, and Protista. 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 environments, including outer space. They form an essential part of the planetary ecosystem. However, some microorganisms are pathogenic and can post health risk to other organisms.


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, Linnaeus' system, these became the kingdom (biology), kingdoms Vegetabilia (later Plantae) and Animalia. Since then, it has become clear that the Plantae as originally defined included several unrelated groups, and the fungus, 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 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'' and ''agricultural and garden flora'', the lastly mentioned of which are intentionally grown and cultivated. 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. 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 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. Animals as a category have several characteristics that generally set them apart from other living things. Animals are eukaryote, eukaryotic and usually multicellular (although see Myxozoa), which separates them from bacteria, archaea, and most protists. They are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungus, fungi by lacking cell walls. With a few exceptions—most notably the two Phylum, phyla consisting of sponges and placozoans—animals have bodies that are differentiated into biological tissue, tissues. These include muscles, which are able to contract and control locomotion, and a nervous system, which sends and processes signals. There is also typically an internal digestion, digestive chamber. The eukaryotic cells possessed by all animals are surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. This may be calcified to form structures like Animal shell, shells, bones, and spicule (sponge), 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.


Human interrelationship


Human impact

Although humans comprise only a minuscule proportion of the total living Biomass (ecology), biomass on Earth, the human impact on the environment, 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 (journal), Nature'' found that anthropogenic mass (human-made materials) outweighs all living biomass on earth, with Plastic pollution, 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 faunally intact, with a low human footprint and healthy populations of native animal species. 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. In spite of this progress, however, the fate of human
civilization  A civilization (or civilisation) is a complex society A complex society is a concept that is shared by a range of disciplines including anthropology, archaeology, history and sociology to describe a stage of social formation. The concep ...

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 that are only slowly becoming understood. Man-made threats to the Earth's natural environment include pollution, deforestation, and disasters such as oil spills. Humans have contributed to the Holocene extinction, extinction of many plants and animals, with roughly 1 million species threatened with extinction within decades. The biodiversity loss, 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 continued existence of human civilization, unless a rapid course correction is made. The value of natural resources to human society is not reflected in market failure, market prices because mostly natural resources are 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. 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#History, 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, medicinal properties of vegetation for healing, most modern human use of plants is through agriculture. The land conversion, clearance of large tracts 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.


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 art, 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. Although natural wonders are celebrated in the Psalms and the Book of Job,
wilderness Wilderness or wildlands (usually in the plural), are natural environments on Earth that have not been significantly modified by human activity or any nonurbanized land not under extensive agricultural cultivation. The term has traditionally re ...

wilderness
portrayals in art became more prevalent in the 1800s, especially in the works of the Romantic movement. Kingdom of Great Britain, 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.History of Conservation
BC Spaces for Nature. Accessed: May 20, 2006.
This artistic movement also coincided with the Transcendentalism, 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, forms 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".


Matter and energy

Some fields of science see nature as matter in motion, obeying certain laws of nature which science seeks to understand. For this reason the most fundamental science is generally understood to be "physics"—the name for which is still recognizable as meaning that it is the "''study of nature''". Matter is commonly defined as the substance of which physical objects are composed. It constitutes the observable universe. The visible components of the universe are now believed to compose only 4.9 percent of the total mass. The remainder is believed to consist of 26.8 percent cold dark matter and 68.3 percent dark energy. The exact arrangement of these components is still unknown and is under intensive investigation by physicists. The behaviour of matter and energy throughout the observable universe appears to follow well-defined physical laws. These laws have been employed to produce Physical cosmology, 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.


Beyond Earth

Outer space, also simply called ''space'', refers to the relatively empty regions of the Universe outside the atmospheres of celestial bodies. ''Outer'' space is used to distinguish it from airspace (and terrestrial locations). There is no discrete boundary between atmosphere of Earth, Earth's atmosphere and space, as the atmosphere gradually attenuates with increasing altitude. Outer space within the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

Solar System
is called interplanetary medium, interplanetary space, which passes over into interstellar medium, interstellar space at what is known as the Heliosphere#Heliopause, heliopause. Outer space is sparsely filled with several dozen types of organic chemistry, organic molecules discovered to date by rotational spectroscopy, microwave spectroscopy, cosmic microwave background, blackbody radiation left over from the Big Bang and the origin of the universe, and cosmic rays, which include ionized atomic nucleus, atomic nuclei and various subatomic particles. There is also some gas, plasma (physics), plasma and dust, and small meteors. Additionally, 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, debris re-enters the atmosphere periodically. Although Earth is the only body within the
Solar System The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...

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 (planet), Mercury and Venus, appear to be too harsh to support life as we know it. But it has been conjectured that Europa (moon), Europa, the fourth-largest moon of Jupiter, may possess a sub-surface ocean of liquid water and could potentially host life. Astronomers have started to discover extrasolar Earth analogs – planets that lie in the circumstellar habitable zone, habitable zone of space surrounding a star, and therefore could possibly host life as we know it.


See also

* Force of nature (disambiguation), Force of nature * Human nature * Natural history * Naturalism (disambiguation), Naturalism * Natural landscape * Natural law * Natural resource * Natural science * Natural theology * Nature reserve * Nature versus nurture * Nature worship * Naturism * Rewilding (conservation biology), Rewilding Media: * ''Natural History (Pliny), Natural History'', by Pliny the Elder * ''Nature (essay), Nature'', by Ralph Waldo Emerson * ''Nature (journal), Nature'', a prominent scientific journal * ''National Wildlife (magazine), National Wildlife'', a publication of the National Wildlife Federation * ''Nature (TV series), Nature'' (TV series) * ''Natural World (TV series), Natural World'' (TV series) Organizations: * The Nature Conservancy * Nature Detectives Philosophy: * Mother Nature * Nature (philosophy) * Naturalism (philosophy), Naturalism, any of several philosophical stances, typically those descended from materialism and pragmatism that do not distinguish the supernatural from nature;Papineau, David (2016
"Naturalism"
The Stanford Encyclopedia of Philosophy, Edward N. Zalta (ed.), >
this includes the ''methodological naturalism'' of natural science, which makes the methodology, methodological assumption that observation, observable events in nature are explained only by natural causes, without assuming either the existence or non-existence of the supernatural * Balance of nature (biological fallacy), a discredited concept of natural equilibrium in predator–prey dynamics


Notes and references


Further reading

* * Farber, Paul Lawrence (2000), ''Finding Order in Nature: The Naturalist Tradition from Linnaeus to E. O. Wilson''. Johns Hopkins University Press: Baltimore. * * *


External links


The IUCN Red List of Threatened Species (iucnredlist.org)
* {{Authority control Nature, Environmental science Environmental social science concepts Main topic articles