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123-514: The name shows the range's great importance as a source of drinking water , and the waters supply a great number of important cities in the southeast of Brazil. From its brooks are formed the Jaguari River , which supplies the northern region of Greater São Paulo ; most left-bank tributaries of the Paraíba do Sul River , which crosses a densely populated and highly industrialized region; and

246-420: A double helix . The two DNA strands are known as polynucleotides since they are composed of simpler units called nucleotides . Each nucleotide is composed of a nitrogen-containing nucleobase —either cytosine (C), guanine (G), adenine (A), or thymine (T)—as well as a sugar called deoxyribose and a phosphate group . The nucleotides are joined to one another in a chain by covalent bonds between

369-420: A living systems theory viewpoint that does not necessarily depend on molecular chemistry. One systemic definition of life is that living things are self-organizing and autopoietic (self-producing). Variations of this include Stuart Kauffman 's definition as an autonomous agent or a multi-agent system capable of reproducing itself, and of completing at least one thermodynamic work cycle . This definition

492-428: A nucleus and other membrane-bound organelles , although they have circular DNA and ribosomes . Bacteria and Archaea are two domains of prokaryotes. The other primary type is the eukaryote cell, which has a distinct nucleus bound by a nuclear membrane and membrane-bound organelles, including mitochondria , chloroplasts , lysosomes , rough and smooth endoplasmic reticulum , and vacuoles . In addition, their DNA

615-474: A solvent ). It is vital for all known forms of life , despite not providing food energy or organic micronutrients . Its chemical formula, H 2 O , indicates that each of its molecules contains one oxygen and two hydrogen atoms , connected by covalent bonds . The hydrogen atoms are attached to the oxygen atom at an angle of 104.45°. In liquid form, H 2 O is also called "water" at standard temperature and pressure . Because Earth's environment

738-601: A 1 cm sample cell. Aquatic plants , algae , and other photosynthetic organisms can live in water up to hundreds of meters deep, because sunlight can reach them. Practically no sunlight reaches the parts of the oceans below 1,000 metres (3,300 ft) of depth. The refractive index of liquid water (1.333 at 20 °C (68 °F)) is much higher than that of air (1.0), similar to those of alkanes and ethanol , but lower than those of glycerol (1.473), benzene (1.501), carbon disulfide (1.627), and common types of glass (1.4 to 1.6). The refraction index of ice (1.31)

861-407: A common origin. All life forms require certain core chemical elements for their biochemical functioning. These include carbon , hydrogen , nitrogen , oxygen , phosphorus , and sulfur —the elemental macronutrients for all organisms. Together these make up nucleic acids , proteins and lipids , the bulk of living matter. Five of these six elements comprise the chemical components of DNA,

984-528: A consequence of these microbial activities, the physical-chemical environment on Earth has been changing on a geologic time scale , thereby affecting the path of evolution of subsequent life. For example, the release of molecular oxygen by cyanobacteria as a by-product of photosynthesis induced global changes in the Earth's environment. Because oxygen was toxic to most life on Earth at the time, this posed novel evolutionary challenges, and ultimately resulted in

1107-442: A host cell to make new products. Virus self-assembly within host cells has implications for the study of the origin of life , as it may support the hypothesis that life could have started as self-assembling organic molecules . Some of the earliest theories of life were materialist, holding that all that exists is matter, and that life is merely a complex form or arrangement of matter. Empedocles (430 BC) argued that everything in

1230-481: A large amount of sediment transport that occurs on the surface of the earth. Deposition of transported sediment forms many types of sedimentary rocks , which make up the geologic record of Earth history . The water cycle (known scientifically as the hydrologic cycle) is the continuous exchange of water within the hydrosphere , between the atmosphere , soil water, surface water , groundwater, and plants. Water moves perpetually through each of these regions in

1353-472: A matter of debate; viruses lack characteristics of life such as cell membranes, metabolism and the ability to grow or respond to their environments. Viruses have been classed into "species" based on their genetics , but many aspects of such a classification remain controversial. The original Linnaean system has been modified many times, for example as follows: The attempt to organise the Eukaryotes into

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1476-535: A month in a simulated Martian environment . Beyond the Solar System, the region around another main-sequence star that could support Earth-like life on an Earth-like planet is known as the habitable zone . The inner and outer radii of this zone vary with the luminosity of the star, as does the time interval during which the zone survives. Stars more massive than the Sun have a larger habitable zone, but remain on

1599-477: A property that is exploited by cetaceans and humans for communication and environment sensing ( sonar ). Metallic elements which are more electropositive than hydrogen, particularly the alkali metals and alkaline earth metals such as lithium , sodium , calcium , potassium and cesium displace hydrogen from water, forming hydroxides and releasing hydrogen. At high temperatures, carbon reacts with steam to form carbon monoxide and hydrogen. Hydrology

1722-452: A resurgence of interest in the work of Russell, Barge and colleagues. Hylomorphism is a theory first expressed by the Greek philosopher Aristotle (322 BC). The application of hylomorphism to biology was important to Aristotle, and biology is extensively covered in his extant writings . In this view, everything in the material universe has both matter and form, and the form of a living thing

1845-809: A set of 355 genes from the last universal common ancestor was tentatively identified. The biosphere is postulated to have developed, from the origin of life onwards, at least some 3.5 billion years ago. The earliest evidence for life on Earth includes biogenic graphite found in 3.7 billion-year-old metasedimentary rocks from Western Greenland and microbial mat fossils found in 3.48 billion-year-old sandstone from Western Australia . More recently, in 2015, "remains of biotic life " were found in 4.1 billion-year-old rocks in Western Australia. In 2017, putative fossilised microorganisms (or microfossils ) were announced to have been discovered in hydrothermal vent precipitates in

1968-619: A short period Linnaeus had classified them in the taxon Vermes in Animalia, but later placed them back in Plantae. Herbert Copeland classified the Fungi in his Protoctista , including them with single-celled organisms and thus partially avoiding the problem but acknowledging their special status. The problem was eventually solved by Whittaker , when he gave them their own kingdom in his five-kingdom system . Evolutionary history shows that

2091-467: A small number of kingdoms has been challenged. The Protozoa do not form a clade or natural grouping, and nor do the Chromista (Chromalveolata). The ability to sequence large numbers of complete genomes has allowed biologists to take a metagenomic view of the phylogeny of the whole tree of life . This has led to the realisation that the majority of living things are bacteria, and that all have

2214-530: A state of death , and none is immortal . Many philosophical definitions of living systems have been proposed, such as self-organizing systems. Viruses in particular make definition difficult as they replicate only in host cells. Life exists all over the Earth in air, water, and soil , with many ecosystems forming the biosphere . Some of these are harsh environments occupied only by extremophiles . Life has been studied since ancient times, with theories such as Empedocles 's materialism asserting that it

2337-440: A structure of rigid oxygen atoms in which hydrogen atoms flowed freely. When sandwiched between layers of graphene , ice forms a square lattice. The details of the chemical nature of liquid water are not well understood; some theories suggest that its unusual behavior is due to the existence of two liquid states. Pure water is usually described as tasteless and odorless, although humans have specific sensors that can feel

2460-412: A swimming pool when the light source is sunlight reflected from the pool's white tiles. In nature, the color may also be modified from blue to green due to the presence of suspended solids or algae. In industry, near-infrared spectroscopy is used with aqueous solutions as the greater intensity of the lower overtones of water means that glass cuvettes with short path-length may be employed. To observe

2583-408: A thousand years. In the late 1740s, Carl Linnaeus introduced his system of binomial nomenclature for the classification of species. Linnaeus attempted to improve the composition and reduce the length of the previously used many-worded names by abolishing unnecessary rhetoric, introducing new descriptive terms and precisely defining their meaning. The fungi were originally treated as plants. For

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2706-461: A variety of applications including high-temperature electrochemistry and as an ecologically benign solvent or catalyst in chemical reactions involving organic compounds. In Earth's mantle, it acts as a solvent during mineral formation, dissolution and deposition. The normal form of ice on the surface of Earth is ice I h , a phase that forms crystals with hexagonal symmetry . Another with cubic crystalline symmetry , ice I c , can occur in

2829-977: Is transported by boats through seas, rivers, lakes, and canals. Large quantities of water, ice, and steam are used for cooling and heating in industry and homes. Water is an excellent solvent for a wide variety of substances, both mineral and organic; as such, it is widely used in industrial processes and in cooking and washing. Water, ice, and snow are also central to many sports and other forms of entertainment, such as swimming , pleasure boating, boat racing , surfing , sport fishing , diving , ice skating , snowboarding , and skiing . The word water comes from Old English wæter , from Proto-Germanic * watar (source also of Old Saxon watar , Old Frisian wetir , Dutch water , Old High German wazzar , German Wasser , vatn , Gothic 𐍅𐌰𐍄𐍉 ( wato )), from Proto-Indo-European * wod-or , suffixed form of root * wed- ( ' water ' ; ' wet ' ). Also cognate , through

2952-489: Is visibly blue due to absorption of light in the region c. 600–800 nm. The color can be easily observed in a glass of tap-water placed against a pure white background, in daylight. The principal absorption bands responsible for the color are overtones of the O–H stretching vibrations . The apparent intensity of the color increases with the depth of the water column, following Beer's law . This also applies, for example, with

3075-439: Is 917 kg/m (57.25 lb/cu ft), an expansion of 9%. This expansion can exert enormous pressure, bursting pipes and cracking rocks. In a lake or ocean, water at 4 °C (39 °F) sinks to the bottom, and ice forms on the surface, floating on the liquid water. This ice insulates the water below, preventing it from freezing solid. Without this protection, most aquatic organisms residing in lakes would perish during

3198-473: Is a mechanistic explanation for the origin of species by means of natural selection . At the beginning of the 20th century Stéphane Leduc (1853–1939) promoted the idea that biological processes could be understood in terms of physics and chemistry, and that their growth resembled that of inorganic crystals immersed in solutions of sodium silicate. His ideas, set out in his book La biologie synthétique , were widely dismissed during his lifetime, but has incurred

3321-472: Is a part of the Atlantic Forest ecosystem. Despite the clearing of the land for livestock raising, the difficult access to many areas has made possible for sanctuaries of well-preserved forest to still exist, with trees such as the jacarandá , Spanish cedar , canjerana , guatambu , ipê , canela, angico , jequitibá , and also the araucaria , more typical of subtropical South America but found in

3444-561: Is about 4.54 billion years . Life on Earth has existed for at least 3.5 billion years, with the oldest physical traces of life dating back 3.7 billion years. Estimates from molecular clocks, as summarised in the TimeTree public database, place the origin of life around 4.0 billion years ago. Hypotheses on the origin of life attempt to explain the formation of a universal common ancestor from simple organic molecules via pre-cellular life to protocells and metabolism. In 2016,

3567-493: Is at a temperature of 273.16 K (0.01 °C; 32.02 °F) and a pressure of 611.657 pascals (0.00604 atm; 0.0887 psi); it is the lowest pressure at which liquid water can exist. Until 2019 , the triple point was used to define the Kelvin temperature scale . The water/vapor phase curve terminates at 647.096 K (373.946 °C; 705.103 °F) and 22.064 megapascals (3,200.1 psi; 217.75 atm). This

3690-479: Is being simulated and explored by scientists and engineers. The definition of life has long been a challenge for scientists and philosophers. This is partially because life is a process, not a substance. This is complicated by a lack of knowledge of the characteristics of living entities, if any, that may have developed outside Earth. Philosophical definitions of life have also been put forward, with similar difficulties on how to distinguish living things from

3813-558: Is capable of forming the various specialised cells that form the adult organism. This specialisation allows multicellular organisms to exploit resources more efficiently than single cells. About 800 million years ago, a minor genetic change in a single molecule, the enzyme GK-PID , may have allowed organisms to go from a single cell organism to one of many cells. Cells have evolved methods to perceive and respond to their microenvironment, thereby enhancing their adaptability. Cell signalling coordinates cellular activities, and hence governs

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3936-422: Is considered the starting point of modern organic chemistry . It is of historical significance because for the first time an organic compound was produced in inorganic reactions. During the 1850s Hermann von Helmholtz , anticipated by Julius Robert von Mayer , demonstrated that no energy is lost in muscle movement, suggesting that there were no "vital forces" necessary to move a muscle. These results led to

4059-421: Is extended by the evolution of novel functions over time. Death is the termination of all vital functions or life processes in an organism or cell. One of the challenges in defining death is in distinguishing it from life. Death would seem to refer to either the moment life ends, or when the state that follows life begins. However, determining when death has occurred is difficult, as cessation of life functions

4182-428: Is greater than the repulsion between the hydrogen atoms. The O–H bond length is about 0.096 nm. Other substances have a tetrahedral molecular structure, for example methane ( CH 4 ) and hydrogen sulfide ( H 2 S ). However, oxygen is more electronegative than most other elements, so the oxygen atom has a negative partial charge while the hydrogen atoms are partially positively charged. Along with

4305-435: Is important in many geological processes. Groundwater is present in most rocks , and the pressure of this groundwater affects patterns of faulting . Water in the mantle is responsible for the melt that produces volcanoes at subduction zones . On the surface of the Earth, water is important in both chemical and physical weathering processes. Water, and to a lesser but still significant extent, ice, are also responsible for

4428-470: Is it a noble gas (and therefore is not removed from the atmosphere through chemical reactions with other elements), but comparisons between the abundances of its nine stable isotopes in the modern atmosphere reveal that the Earth lost at least one ocean of water early in its history, between the Hadean and Archean eons. Any water on Earth during the latter part of its accretion would have been disrupted by

4551-425: Is its soul (Greek psyche , Latin anima ). There are three kinds of souls: the vegetative soul of plants, which causes them to grow and decay and nourish themselves, but does not cause motion and sensation; the animal soul , which causes animals to move and feel; and the rational soul , which is the source of consciousness and reasoning, which (Aristotle believed) is found only in man. Each higher soul has all of

4674-498: Is known as the critical point . At higher temperatures and pressures the liquid and vapor phases form a continuous phase called a supercritical fluid . It can be gradually compressed or expanded between gas-like and liquid-like densities; its properties (which are quite different from those of ambient water) are sensitive to density. For example, for suitable pressures and temperatures it can mix freely with nonpolar compounds , including most organic compounds . This makes it useful in

4797-413: Is lower than that of liquid water. In a water molecule, the hydrogen atoms form a 104.5° angle with the oxygen atom. The hydrogen atoms are close to two corners of a tetrahedron centered on the oxygen. At the other two corners are lone pairs of valence electrons that do not participate in the bonding. In a perfect tetrahedron, the atoms would form a 109.5° angle, but the repulsion between the lone pairs

4920-407: Is most likely to exist, within wide bounds of uncertainty. A "Confidence of Life Detection" scale (CoLD) for reporting evidence of life beyond Earth has been proposed. Artificial life is the simulation of any aspect of life, as through computers, robotics , or biochemistry . Synthetic biology is a new area of biotechnology that combines science and biological engineering . The common goal

5043-476: Is not only plausible, but probable or inevitable, possibly resulting in a biophysical cosmology instead of a mere physical cosmology . Other planets and moons in the Solar System and other planetary systems are being examined for evidence of having once supported simple life, and projects such as SETI are trying to detect radio transmissions from possible alien civilisations. Other locations within

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5166-428: Is often not simultaneous across organ systems. Such determination, therefore, requires drawing conceptual lines between life and death. This is problematic because there is little consensus over how to define life. The nature of death has for millennia been a central concern of the world's religious traditions and of philosophical inquiry. Many religions maintain faith in either a kind of afterlife or reincarnation for

5289-485: Is organised into chromosomes . All species of large complex organisms are eukaryotes, including animals, plants and fungi, though with a wide diversity of protist microorganisms . The conventional model is that eukaryotes evolved from prokaryotes, with the main organelles of the eukaryotes forming through endosymbiosis between bacteria and the progenitor eukaryotic cell. The molecular mechanisms of cell biology are based on proteins . Most of these are synthesised by

5412-422: Is poor at dissolving nonpolar substances. This allows it to be the " solvent of life": indeed, water as found in nature almost always includes various dissolved substances, and special steps are required to obtain chemically pure water . Water is the only common substance to exist as a solid , liquid, and gas in normal terrestrial conditions. Along with oxidane , water is one of the two official names for

5535-481: Is rare, but it has been recorded a few times, such as in the winter of 1994, when it snowed in the Itatiaia massif. Water Water is an inorganic compound with the chemical formula H 2 O . It is a transparent, tasteless, odorless, and nearly colorless chemical substance . It is the main constituent of Earth 's hydrosphere and the fluids of all known living organisms (in which it acts as

5658-430: Is relatively close to water's triple point , water exists on Earth as a solid , a liquid , and a gas . It forms precipitation in the form of rain and aerosols in the form of fog . Clouds consist of suspended droplets of water and ice , its solid state. When finely divided, crystalline ice may precipitate in the form of snow . The gaseous state of water is steam or water vapor . Water covers about 71% of

5781-417: Is the design and construction of new biological functions and systems not found in nature. Synthetic biology includes the broad redefinition and expansion of biotechnology, with the ultimate goals of being able to design and build engineered biological systems that process information, manipulate chemicals, fabricate materials and structures, produce energy, provide food, and maintain and enhance human health and

5904-458: Is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography . The study of the distribution and movement of groundwater is hydrogeology , of glaciers is glaciology , of inland waters is limnology and distribution of oceans is oceanography . Ecological processes with hydrology are in the focus of ecohydrology . The collective mass of water found on, under, and over

6027-434: Is to define life as "a self-sustained chemical system capable of undergoing Darwinian evolution ", a definition adopted by a NASA committee attempting to define life for the purposes of exobiology , based on a suggestion by Carl Sagan . This definition, however, has been widely criticised because according to it, a single sexually reproducing individual is not alive as it is incapable of evolving on its own. Others take

6150-509: Is unlikely or impossible. Organisms that have a wide range of tolerance are more widely distributed than organisms with a narrow range of tolerance. To survive, some microorganisms have evolved to withstand freezing , complete desiccation , starvation , high levels of radiation exposure , and other physical or chemical challenges. These extremophile microorganisms may survive exposure to such conditions for long periods. They excel at exploiting uncommon sources of energy. Characterization of

6273-748: The Grande River , which is the source of the Paraná River , one of the longest and most important in South America and the river with the world's largest hydroelectric output, through a series of power plants way down the river to Argentina and Paraguay . Many springs of mineral water lie in the regions of Caxambu and São Lourenço in Minas Gerais , and Campos do Jordão and Serra Negra in São Paulo . The Serra da Mantiqueira

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6396-714: The International Ocean Discovery Program found unicellular life in 120 °C sediment 1.2 km below seafloor in the Nankai Trough subduction zone. According to one researcher, "You can find microbes everywhere—they're extremely adaptable to conditions, and survive wherever they are." The inert components of an ecosystem are the physical and chemical factors necessary for life—energy (sunlight or chemical energy ), water, heat, atmosphere , gravity , nutrients , and ultraviolet solar radiation protection . In most ecosystems,

6519-485: The Moon-forming impact (~4.5 billion years ago), which likely vaporized much of Earth's crust and upper mantle and created a rock-vapor atmosphere around the young planet. The rock vapor would have condensed within two thousand years, leaving behind hot volatiles which probably resulted in a majority carbon dioxide atmosphere with hydrogen and water vapor . Afterward, liquid water oceans may have existed despite

6642-504: The Nuvvuagittuq Belt of Quebec, Canada that were as old as 4.28 billion years, the oldest record of life on Earth, suggesting "an almost instantaneous emergence of life" after ocean formation 4.4 billion years ago , and not long after the formation of the Earth 4.54 billion years ago. Evolution is the change in heritable characteristics of biological populations over successive generations. It results in

6765-458: The Solar System that may host microbial life include the subsurface of Mars , the upper atmosphere of Venus , and subsurface oceans on some of the moons of the giant planets . Investigation of the tenacity and versatility of life on Earth, as well as an understanding of the molecular systems that some organisms utilise to survive such extremes, is important for the search for extraterrestrial life. For example, lichen could survive for

6888-504: The azure jay , the toucan , the scaly-headed parrot ( maitaca ), the inhambu , the jacana , the seriema and the crested caracara . The Mantiqueira is a popular region for mountain climbers and trekkers, where in winter, which is the dry season, one can climb some of the highest peaks in the country: Here are also some of the highest Brazilian cities: Due to altitude, winter in the Serra da Mantiqueira sees low temperatures , with

7011-432: The elements hydrogen and oxygen by passing an electric current through it—a process called electrolysis . The decomposition requires more energy input than the heat released by the inverse process (285.8 kJ/ mol , or 15.9 MJ/kg). Liquid water can be assumed to be incompressible for most purposes: its compressibility ranges from 4.4 to 5.1 × 10  Pa in ordinary conditions. Even in oceans at 4 km depth, where

7134-529: The molar volumes of the liquid and solid phases, and L f {\displaystyle L_{\text{f}}} is the molar latent heat of melting. In most substances, the volume increases when melting occurs, so the melting temperature increases with pressure. However, because ice is less dense than water, the melting temperature decreases. In glaciers, pressure melting can occur under sufficiently thick volumes of ice, resulting in subglacial lakes . The Clausius-Clapeyron relation also applies to

7257-480: The soul , or resurrection of the body at a later date. Whether or not viruses should be considered as alive is controversial. They are most often considered as just gene coding replicators rather than forms of life. They have been described as "organisms at the edge of life" because they possess genes , evolve by natural selection, and replicate by making multiple copies of themselves through self-assembly. However, viruses do not metabolise and they require

7380-467: The structure and metabolic diversity of microbial communities in such extreme environments is ongoing. The first classification of organisms was made by the Greek philosopher Aristotle (384–322 BC), who grouped living things as either plants or animals, based mainly on their ability to move. He distinguished animals with blood from animals without blood, which can be compared with the concepts of vertebrates and invertebrates respectively, and divided

7503-458: The water cycle consisting of the following transfer processes: Life Life on Earth: Life is a quality that distinguishes matter that has biological processes , such as signaling and self-sustaining processes, from matter that does not. It is defined descriptively by the capacity for homeostasis , organisation , metabolism , growth , adaptation , response to stimuli , and reproduction . All life over time eventually reaches

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7626-419: The 1740s. Living things are composed of biochemical molecules , formed mainly from a few core chemical elements . All living things contain two types of large molecule, proteins and nucleic acids , the latter usually both DNA and RNA : these carry the information needed by each species, including the instructions to make each type of protein. The proteins, in turn, serve as the machinery which carries out

7749-444: The Earth was younger and less massive , water would have been lost to space more easily. Lighter elements like hydrogen and helium are expected to leak from the atmosphere continually, but isotopic ratios of heavier noble gases in the modern atmosphere suggest that even the heavier elements in the early atmosphere were subject to significant losses. In particular, xenon is useful for calculations of water loss over time. Not only

7872-513: The Earth's surface, with seas and oceans making up most of the water volume (about 96.5%). Small portions of water occur as groundwater (1.7%), in the glaciers and the ice caps of Antarctica and Greenland (1.7%), and in the air as vapor , clouds (consisting of ice and liquid water suspended in air), and precipitation (0.001%). Water moves continually through the water cycle of evaporation , transpiration ( evapotranspiration ), condensation , precipitation, and runoff , usually reaching

7995-538: The Indo-European root, with Greek ύδωρ ( ýdor ; from Ancient Greek ὕδωρ ( hýdōr ), whence English ' hydro- ' ), Russian вода́ ( vodá ), Irish uisce , and Albanian ujë . One factor in estimating when water appeared on Earth is that water is continually being lost to space. H 2 O molecules in the atmosphere are broken up by photolysis , and the resulting free hydrogen atoms can sometimes escape Earth's gravitational pull. When

8118-459: The Sun-like "main sequence" of stellar evolution for a shorter time interval. Small red dwarfs have the opposite problem, with a smaller habitable zone that is subject to higher levels of magnetic activity and the effects of tidal locking from close orbits. Hence, stars in the intermediate mass range such as the Sun may have a greater likelihood for Earth-like life to develop. The location of

8241-403: The abandonment of scientific interest in vitalistic theories, especially after Eduard Buchner 's demonstration that alcoholic fermentation could occur in cell-free extracts of yeast. Nonetheless, belief still exists in pseudoscientific theories such as homoeopathy , which interprets diseases and sickness as caused by disturbances in a hypothetical vital force or life force. The age of Earth

8364-466: The appearance of new species and often the disappearance of old ones. Evolution occurs when evolutionary processes such as natural selection (including sexual selection ) and genetic drift act on genetic variation, resulting in certain characteristics increasing or decreasing in frequency within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation . Fossils are

8487-488: The area because of altitude. At its closest point, the region is only 100 km (62 mi) from the city of São Paulo. It is also the habitat of a varied fauna: pampas deer (locally known as veado campeiro ), maned wolves ( lobo guará ), cougars ( onça-parda or suçuarana ), bush dogs ( cachorro-vinagre ), ocelots ( jaguatirica ), pacas , howler monkeys ( bugio ), Atlantic titis ( sauá ), squirrels , and hedgehogs can still be found there. Birds of note are

8610-450: The attributes of the lower ones. Aristotle believed that while matter can exist without form, form cannot exist without matter, and that therefore the soul cannot exist without the body. This account is consistent with teleological explanations of life , which account for phenomena in terms of purpose or goal-directedness. Thus, the whiteness of the polar bear's coat is explained by its purpose of camouflage. The direction of causality (from

8733-399: The basic functions of multicellular organisms. Signaling between cells can occur through direct cell contact using juxtacrine signalling , or indirectly through the exchange of agents as in the endocrine system . In more complex organisms, coordination of activities can occur through a dedicated nervous system . Though life is confirmed only on Earth, many think that extraterrestrial life

8856-577: The bent structure, this gives the molecule an electrical dipole moment and it is classified as a polar molecule . Water is a good polar solvent , dissolving many salts and hydrophilic organic molecules such as sugars and simple alcohols such as ethanol . Water also dissolves many gases, such as oxygen and carbon dioxide —the latter giving the fizz of carbonated beverages, sparkling wines and beers. In addition, many substances in living organisms, such as proteins , DNA and polysaccharides , are dissolved in water. The interactions between water and

8979-436: The biosphere, including soil , hot springs , inside rocks at least 19 km (12 mi) deep underground, the deepest parts of the ocean, and at least 64 km (40 mi) high in the atmosphere. For example, spores of Aspergillus niger have been detected in the mesosphere at an altitude of 48 to 77 km. Under test conditions, life forms have been observed to survive in the vacuum of space. Life forms thrive in

9102-457: The blooded animals into five groups: viviparous quadrupeds ( mammals ), oviparous quadrupeds (reptiles and amphibians ), birds, fishes and whales . The bloodless animals were divided into five groups: cephalopods , crustaceans , insects (which included the spiders, scorpions , and centipedes ), shelled animals (such as most molluscs and echinoderms ), and " zoophytes " (animals that resemble plants). This theory remained dominant for more than

9225-537: The boiling point, but with the liquid/gas transition the vapor phase has a much lower density than the liquid phase, so the boiling point increases with pressure. Water can remain in a liquid state at high temperatures in the deep ocean or underground. For example, temperatures exceed 205 °C (401 °F) in Old Faithful , a geyser in Yellowstone National Park . In hydrothermal vents ,

9348-785: The chemical compound H 2 O ; it is also the liquid phase of H 2 O . The other two common states of matter of water are the solid phase, ice , and the gaseous phase, water vapor or steam . The addition or removal of heat can cause phase transitions : freezing (water to ice), melting (ice to water), vaporization (water to vapor), condensation (vapor to water), sublimation (ice to vapor) and deposition (vapor to ice). Water differs from most liquids in that it becomes less dense as it freezes. In 1 atm pressure, it reaches its maximum density of 999.972 kg/m (62.4262 lb/cu ft) at 3.98 °C (39.16 °F), or almost 1,000 kg/m (62.43 lb/cu ft) at almost 4 °C (39 °F). The density of ice

9471-412: The conditions vary during the day and from one season to the next. To live in most ecosystems, then, organisms must be able to survive a range of conditions, called the "range of tolerance". Outside that are the "zones of physiological stress", where the survival and reproduction are possible but not optimal. Beyond these zones are the "zones of intolerance", where survival and reproduction of that organism

9594-422: The deep Mariana Trench , and inside rocks up to 580 m (1,900 ft; 0.36 mi) below the sea floor under 2,590 m (8,500 ft; 1.61 mi) of ocean off the coast of the northwestern United States, and 2,400 m (7,900 ft; 1.5 mi) beneath the seabed off Japan. In 2014, life forms were found living 800 m (2,600 ft; 0.50 mi) below the ice of Antarctica. Expeditions of

9717-433: The desired result. Conversely, a pressure cooker can be used to decrease cooking times by raising the boiling temperature. In a vacuum, water will boil at room temperature. On a pressure/temperature phase diagram (see figure), there are curves separating solid from vapor, vapor from liquid, and liquid from solid. These meet at a single point called the triple point , where all three phases can coexist. The triple point

9840-523: The exception being sulfur. The latter is a component of the amino acids cysteine and methionine . The most abundant of these elements in organisms is carbon, which has the desirable attribute of forming multiple, stable covalent bonds . This allows carbon-based (organic) molecules to form the immense variety of chemical arrangements described in organic chemistry . Alternative hypothetical types of biochemistry have been proposed that eliminate one or more of these elements, swap out an element for one not on

9963-486: The force of gravity . This property is relied upon by all vascular plants , such as trees. Water is a weak solution of hydronium hydroxide—there is an equilibrium 2H 2 O ⇌ H 3 O + OH , in combination with solvation of the resulting hydronium and hydroxide ions. Pure water has a low electrical conductivity , which increases with the dissolution of a small amount of ionic material such as common salt . Liquid water can be split into

10086-409: The formation of colonies of identical cells. These cells can form group organisms through cell adhesion . The individual members of a colony are capable of surviving on their own, whereas the members of a true multi-cellular organism have developed specialisations, making them dependent on the remainder of the organism for survival. Such organisms are formed clonally or from a single germ cell that

10209-474: The formation of Earth's major animal and plant species. This interplay between organisms and their environment is an inherent feature of living systems. The biosphere is the global sum of all ecosystems. It can also be termed as the zone of life on Earth, a closed system (apart from solar and cosmic radiation and heat from the interior of the Earth), and largely self-regulating. Organisms exist in every part of

10332-450: The fundamental stretching absorption spectrum of water or of an aqueous solution in the region around 3,500 cm (2.85 μm) a path length of about 25 μm is needed. Also, the cuvette must be both transparent around 3500 cm and insoluble in water; calcium fluoride is one material that is in common use for the cuvette windows with aqueous solutions. The Raman-active fundamental vibrations may be observed with, for example,

10455-406: The fungi are more closely related to animals than to plants. As advances in microscopy enabled detailed study of cells and microorganisms, new groups of life were revealed, and the fields of cell biology and microbiology were created. These new organisms were originally described separately in protozoa as animals and protophyta/thallophyta as plants, but were united by Ernst Haeckel in

10578-480: The future to the past) is in contradiction with the scientific evidence for natural selection, which explains the consequence in terms of a prior cause. Biological features are explained not by looking at future optimal results, but by looking at the past evolutionary history of a species, which led to the natural selection of the features in question. Spontaneous generation was the belief that living organisms can form without descent from similar organisms. Typically,

10701-426: The given environment. This implies all or most of the following traits: From a physics perspective, an organism is a thermodynamic system with an organised molecular structure that can reproduce itself and evolve as survival dictates. Thermodynamically, life has been described as an open system which makes use of gradients in its surroundings to create imperfect copies of itself. Another way of putting this

10824-434: The idea was that certain forms such as fleas could arise from inanimate matter such as dust or the supposed seasonal generation of mice and insects from mud or garbage. The theory of spontaneous generation was proposed by Aristotle , who compiled and expanded the work of prior natural philosophers and the various ancient explanations of the appearance of organisms; it was considered the best explanation for two millennia. It

10947-496: The information to be preserved during reproduction and cell division. Within cells, DNA is organised into long structures called chromosomes . During cell division these chromosomes are duplicated in the process of DNA replication , providing each cell its own complete set of chromosomes. Eukaryotes store most of their DNA inside the cell nucleus . Cells are the basic unit of structure in every living thing, and all cells arise from pre-existing cells by division . Cell theory

11070-642: The kingdom Protista ; later, the prokaryotes were split off in the kingdom Monera , which would eventually be divided into two separate groups, the Bacteria and the Archaea . This led to the six-kingdom system and eventually to the current three-domain system , which is based on evolutionary relationships. However, the classification of eukaryotes, especially of protists, is still controversial. As microbiology developed, viruses, which are non-cellular, were discovered. Whether these are considered alive has been

11193-416: The liquid is known as boiling ). Sublimation and deposition also occur on surfaces. For example, frost is deposited on cold surfaces while snowflakes form by deposition on an aerosol particle or ice nucleus. In the process of freeze-drying , a food is frozen and then stored at low pressure so the ice on its surface sublimates. The melting and boiling points depend on pressure. A good approximation for

11316-753: The liquid or solid state can form up to four hydrogen bonds with neighboring molecules. Hydrogen bonds are about ten times as strong as the Van der Waals force that attracts molecules to each other in most liquids. This is the reason why the melting and boiling points of water are much higher than those of other analogous compounds like hydrogen sulfide. They also explain its exceptionally high specific heat capacity (about 4.2 J /(g·K)), heat of fusion (about 333 J/g), heat of vaporization ( 2257 J/g ), and thermal conductivity (between 0.561 and 0.679 W/(m·K)). These properties make water more effective at moderating Earth's climate , by storing heat and transporting it between

11439-563: The list, or change required chiralities or other chemical properties. Deoxyribonucleic acid or DNA is a molecule that carries most of the genetic instructions used in the growth, development, functioning and reproduction of all known living organisms and many viruses. DNA and RNA are nucleic acids ; alongside proteins and complex carbohydrates , they are one of the three major types of macromolecule that are essential for all known forms of life. Most DNA molecules consist of two biopolymer strands coiled around each other to form

11562-423: The many chemical processes of life. The cell is the structural and functional unit of life. Smaller organisms, including prokaryotes (bacteria and archaea ), consist of small single cells. Larger organisms , mainly eukaryotes , can consist of single cells or may be multicellular with more complex structure. Life is only known to exist on Earth but extraterrestrial life is thought probable . Artificial life

11685-508: The middle of the 19th century. It appealed to philosophers such as Henri Bergson , Friedrich Nietzsche , and Wilhelm Dilthey , anatomists like Xavier Bichat , and chemists like Justus von Liebig . Vitalism included the idea that there was a fundamental difference between organic and inorganic material, and the belief that organic material can only be derived from living things. This was disproved in 1828, when Friedrich Wöhler prepared urea from inorganic materials. This Wöhler synthesis

11808-448: The non-living. Legal definitions of life have been debated, though these generally focus on the decision to declare a human dead, and the legal ramifications of this decision. At least 123 definitions of life have been compiled. Since there is no consensus for a definition of life, most current definitions in biology are descriptive. Life is considered a characteristic of something that preserves, furthers or reinforces its existence in

11931-411: The occurrence of fog in early morning and frost , giving the landscape the appearance of regions with a much colder climate. In winter, it is common for the temperatures to reach near 0 °C (32 °F), and then sub-freezing temperatures not rarely occur in the region's towns. On top of the highest peaks, the cold can be even more intense, and temperatures can drop to -10 °C (14 °F). Snow

12054-418: The oceans and the atmosphere. The hydrogen bonds of water are around 23 kJ/mol (compared to a covalent O-H bond at 492 kJ/mol). Of this, it is estimated that 90% is attributable to electrostatics, while the remaining 10% is partially covalent. These bonds are the cause of water's high surface tension and capillary forces. The capillary action refers to the tendency of water to move up a narrow tube against

12177-538: The oceans may have always been on the Earth since the beginning of the planet's formation . Water ( H 2 O ) is a polar inorganic compound . At room temperature it is a tasteless and odorless liquid , nearly colorless with a hint of blue . The simplest hydrogen chalcogenide , it is by far the most studied chemical compound and is sometimes described as the "universal solvent" for its ability to dissolve more substances than any other liquid, though it

12300-566: The oldest from the Archaean Eon, up to 3.4 billion years old. Extinction is the process by which a species dies out. The moment of extinction is the death of the last individual of that species. Because a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively after a period of apparent absence. Species become extinct when they are no longer able to survive in changing habitat or against superior competition. Over 99% of all

12423-609: The parent cell divides into two or more daughter cells. For prokaryotes, cell division occurs through a process of fission in which the DNA is replicated, then the two copies are attached to parts of the cell membrane. In eukaryotes , a more complex process of mitosis is followed. However, the result is the same; the resulting cell copies are identical to each other and to the original cell (except for mutations ), and both are capable of further division following an interphase period. Multicellular organisms may have first evolved through

12546-402: The presence of water in their mouths, and frogs are known to be able to smell it. However, water from ordinary sources (including mineral water ) usually has many dissolved substances that may give it varying tastes and odors. Humans and other animals have developed senses that enable them to evaluate the potability of water in order to avoid water that is too salty or putrid . Pure water

12669-473: The preserved remains or traces of organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in layers ( strata ) of sedimentary rock is known as the fossil record . A preserved specimen is called a fossil if it is older than the arbitrary date of 10,000 years ago. Hence, fossils range in age from the youngest at the start of the Holocene Epoch to

12792-437: The pressure is 400 atm, water suffers only a 1.8% decrease in volume. The viscosity of water is about 10 Pa· s or 0.01 poise at 20 °C (68 °F), and the speed of sound in liquid water ranges between 1,400 and 1,540 metres per second (4,600 and 5,100 ft/s) depending on temperature. Sound travels long distances in water with little attenuation , especially at low frequencies (roughly 0.03 dB /km for 1 k Hz ),

12915-587: The rate of change of the melting temperature with pressure is given by the Clausius–Clapeyron relation : d T d P = T ( v L − v S ) L f {\displaystyle {\frac {dT}{dP}}={\frac {T\left(v_{\text{L}}-v_{\text{S}}\right)}{L_{\text{f}}}}} where v L {\displaystyle v_{\text{L}}} and v S {\displaystyle v_{\text{S}}} are

13038-460: The ribosomes through an enzyme-catalyzed process called protein biosynthesis . A sequence of amino acids is assembled and joined based upon gene expression of the cell's nucleic acid. In eukaryotic cells, these proteins may then be transported and processed through the Golgi apparatus in preparation for dispatch to their destination. Cells reproduce through a process of cell division in which

13161-404: The sea. Water plays an important role in the world economy . Approximately 70% of the fresh water used by humans goes to agriculture . Fishing in salt and fresh water bodies has been, and continues to be, a major source of food for many parts of the world, providing 6.5% of global protein. Much of the long-distance trade of commodities (such as oil, natural gas, and manufactured products)

13284-435: The soul, like everything else, was composed of fiery atoms. He elaborated on fire because of the apparent connection between life and heat, and because fire moves. Plato , in contrast, held that the world was organised by permanent forms , reflected imperfectly in matter; forms provided direction or intelligence, explaining the regularities observed in the world. The mechanistic materialism that originated in ancient Greece

13407-493: The species that have ever lived are now extinct. Mass extinctions may have accelerated evolution by providing opportunities for new groups of organisms to diversify. The diversity of life on Earth is a result of the dynamic interplay between genetic opportunity , metabolic capability, environmental challenges, and symbiosis . For most of its existence, Earth's habitable environment has been dominated by microorganisms and subjected to their metabolism and evolution. As

13530-488: The star within a galaxy may also affect the likelihood of life forming. Stars in regions with a greater abundance of heavier elements that can form planets, in combination with a low rate of potentially habitat -damaging supernova events, are predicted to have a higher probability of hosting planets with complex life. The variables of the Drake equation are used to discuss the conditions in planetary systems where civilisation

13653-413: The subunits of these biomacromolecules shape protein folding , DNA base pairing , and other phenomena crucial to life ( hydrophobic effect ). Many organic substances (such as fats and oils and alkanes ) are hydrophobic , that is, insoluble in water. Many inorganic substances are insoluble too, including most metal oxides , sulfides , and silicates . Because of its polarity, a molecule of water in

13776-408: The sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone . According to base pairing rules (A with T, and C with G), hydrogen bonds bind the nitrogenous bases of the two separate polynucleotide strands to make double-stranded DNA. This has the key property that each strand contains all the information needed to recreate the other strand, enabling

13899-488: The surface of a planet is called the hydrosphere . Earth's approximate water volume (the total water supply of the world) is 1.386 billion cubic kilometres (333 million cubic miles). Liquid water is found in bodies of water , such as an ocean, sea, lake, river, stream, canal , pond, or puddle . The majority of water on Earth is seawater . Water is also present in the atmosphere in solid, liquid, and vapor states. It also exists as groundwater in aquifers . Water

14022-537: The surface temperature of 230 °C (446 °F) due to the increased atmospheric pressure of the CO 2 atmosphere. As the cooling continued, most CO 2 was removed from the atmosphere by subduction and dissolution in ocean water, but levels oscillated wildly as new surface and mantle cycles appeared. Geological evidence also helps constrain the time frame for liquid water existing on Earth. A sample of pillow basalt (a type of rock formed during an underwater eruption)

14145-403: The temperature can exceed 400 °C (752 °F). At sea level , the boiling point of water is 100 °C (212 °F). As atmospheric pressure decreases with altitude, the boiling point decreases by 1 °C every 274 meters. High-altitude cooking takes longer than sea-level cooking. For example, at 1,524 metres (5,000 ft), cooking time must be increased by a fourth to achieve

14268-413: The universe is made up of a combination of four eternal "elements" or "roots of all": earth, water, air, and fire. All change is explained by the arrangement and rearrangement of these four elements. The various forms of life are caused by an appropriate mixture of elements. Democritus (460 BC) was an atomist ; he thought that the essential characteristic of life was having a soul ( psyche ), and that

14391-458: The upper atmosphere. As the pressure increases, ice forms other crystal structures . As of 2024, twenty have been experimentally confirmed and several more are predicted theoretically. The eighteenth form of ice, ice XVIII , a face-centred-cubic, superionic ice phase, was discovered when a droplet of water was subject to a shock wave that raised the water's pressure to millions of atmospheres and its temperature to thousands of degrees, resulting in

14514-441: The winter. Water is a diamagnetic material. Though interaction is weak, with superconducting magnets it can attain a notable interaction. At a pressure of one atmosphere (atm), ice melts or water freezes (solidifies) at 0 °C (32 °F) and water boils or vapor condenses at 100 °C (212 °F). However, even below the boiling point, water can change to vapor at its surface by evaporation (vaporization throughout

14637-535: Was composed of four eternal elements , and Aristotle 's hylomorphism asserting that living things have souls and embody both form and matter. Life originated at least 3.5 billion years ago, resulting in a universal common ancestor . This evolved into all the species that exist now, by way of many extinct species, some of which have left traces as fossils . Attempts to classify living things, too, began with Aristotle . Modern classification began with Carl Linnaeus 's system of binomial nomenclature in

14760-414: Was decisively dispelled by the experiments of Louis Pasteur in 1859, who expanded upon the investigations of predecessors such as Francesco Redi . Disproof of the traditional ideas of spontaneous generation is no longer controversial among biologists. Vitalism is the belief that there is a non-material life-principle. This originated with Georg Ernst Stahl (17th century), and remained popular until

14883-495: Was formulated by Henri Dutrochet , Theodor Schwann , Rudolf Virchow and others during the early nineteenth century, and subsequently became widely accepted. The activity of an organism depends on the total activity of its cells, with energy flow occurring within and between them. Cells contain hereditary information that is carried forward as a genetic code during cell division. There are two primary types of cells, reflecting their evolutionary origins. Prokaryote cells lack

15006-809: Was recovered from the Isua Greenstone Belt and provides evidence that water existed on Earth 3.8 billion years ago. In the Nuvvuagittuq Greenstone Belt , Quebec, Canada, rocks dated at 3.8 billion years old by one study and 4.28 billion years old by another show evidence of the presence of water at these ages. If oceans existed earlier than this, any geological evidence has yet to be discovered (which may be because such potential evidence has been destroyed by geological processes like crustal recycling ). More recently, in August 2020, researchers reported that sufficient water to fill

15129-486: Was revived and revised by the French philosopher René Descartes (1596–1650), who held that animals and humans were assemblages of parts that together functioned as a machine. This idea was developed further by Julien Offray de La Mettrie (1709–1750) in his book L'Homme Machine . In the 19th century the advances in cell theory in biological science encouraged this view. The evolutionary theory of Charles Darwin (1859)

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