In a general sense, biospheres are any closed, self-regulating systems containing ecosystems. This includes artificial biospheres such as Biosphere 2 and BIOS-3, and potentially ones on other planets or moons.
Origin and use of the term
The term "biosphere" was coined by geologist Eduard Suess in 1875, which he defined as the place on Earth's surface where life dwells.
While the concept has a geological origin, it is an indication of the effect of both Charles Darwin and Matthew F. Maury on the Earth sciences. The biosphere's ecological context comes from the 1920s (see Vladimir I. Vernadsky), preceding the 1935 introduction of the term "ecosystem" by Sir Arthur Tansley (see ecology history). Vernadsky defined ecology as the science of the biosphere. It is an interdisciplinary concept for integrating astronomy, geophysics, meteorology, biogeography, evolution, geology, geochemistry, hydrology and, generally speaking, all life and Earth sciences.
Narrow definition
Geochemists define the biosphere as being the total sum of living organisms (the "biomass" or "biota" as referred to by biologists and ecologists). In this sense, the biosphere is but one of four separate components of the geochemical model, the other three being geosphere, hydrosphere, and atmosphere. When these four component spheres are combined into one system, it is known as the Ecosphere. This term was coined during the 1960s and encompasses both biological and physical components of the planet.
The Second International Conference on Closed Life Systems defined biospherics as the science and technology of analogs and models of Earth's biosphere; i.e., artificial Earth-like biospheres. Others may include the creation of artificial non-Earth biospheres—for example, human-centered biospheres or a native Martian biosphere—as part of the topic of biospherics.
Earth's biosphere
Age
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 fossilized microorganisms (or microfossils) were announced to have been discovered in hydrothermal vent precipitates in 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. According to biologist Stephen Blair Hedges, "If life arose relatively quickly on Earth... then it could be common in the universe."
Extent
Every part of the planet, from the polar ice caps to the equator, features life of some kind. Recent advances in microbiology have demonstrated that microbes live deep beneath the Earth's terrestrial surface, and that the total mass of microbial life in so-called "uninhabitable zones" may, in biomass, exceed all animal and plant life on the surface. The actual thickness of the biosphere on earth is difficult to measure. Birds typically fly at altitudes as high as 1,800 m (5,900 ft; 1.1 mi) and fish live as much as 8,372 m (27,467 ft; 5.202 mi) underwater in the Puerto Rico Trench.
There are more extreme examples for life on the planet: Rüppell's vulture has been found at altitudes of 11,300 m (37,100 ft; 7.0 mi); bar-headed geese migrate at altitudes of at least 8,300 m (27,200 ft; 5.2 mi); yaks live at elevations as high as 5,400 m (17,700 ft; 3.4 mi) above sea level; mountain goats live up to 3,050 m (10,010 ft; 1.90 mi). Herbivorous animals at these elevations depend on lichens, grasses, and herbs.
Life forms live in every part of the Earth's 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. Microorganisms, under certain test conditions, have been observed to survive the vacuum of outer space. The total amount of soil and subsurface bacterial carbon is estimated as 5 × 1017 g, or the "weight of the United Kingdom". The mass of prokaryote microorganisms—which includes bacteria and archaea, but not the nucleated eukaryote microorganisms—may be as much as 0.8 trillion tons of carbon (of the total biosphere mass, estimated at between 1 and 4 trillion tons). Barophilic marine microbes have been found at more than a depth of 10,000 m (33,000 ft; 6.2 mi) in the Mariana Trench, the deepest spot in the Earth's oceans. In fact, single-celled life forms have been found in the deepest part of the Mariana Trench, by the Challenger Deep, at depths of 11,034 m (36,201 ft; 6.856 mi). Other researchers reported related studies that microorganisms thrive 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, as well as 2,400 m (7,900 ft; 1.5 mi) beneath the seabed off Japan. Culturable thermophilic microbes have been extracted from cores drilled more than 5,000 m (16,000 ft; 3.1 mi) into the Earth's crust in Sweden, from rocks between 65–75 °C (149–167 °F). Temperature increases with increasing depth into the Earth's crust. The rate at which the temperature increases depends on many factors, including type of crust (continental vs. oceanic), rock type, geographic location, etc. The greatest known temperature at which microbial life can exist is 122 °C (252 °F) (Methanopyrus kandleri Strain 116), and it is likely that the limit of life in the "deep biosphere" is defined by temperature rather than absolute depth. On 20 August 2014, scientists confirmed the existence of microorganisms living 800 m (2,600 ft; 0.50 mi) below the ice of Antarctica. According to one researcher, "You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are."
Our biosphere is divided into a number of biomes, inhabited by fairly similar flora and fauna. On land, biomes are separated primarily by latitude. Terrestrial biomes lying within the Arctic and Antarctic Circles are relatively barren of plant and animal life, while most of the more populous biomes lie near the equator.
Distribution of life
It constitutes a thin layer of irregular dimensions, just as the density of biomass, diversity and primary production is irregular. It spans the surface and the bottom of the oceans and seas, where it first developed, by the surface of the continents, and on the surface levels of the earth's crust, where life thrives, with low density, between pores and interstices of the rocks.
Oceans
In the oceans the life is concentrated in the surface layer, photic zone, into which the light. The trophic chain starts here with photosynthesizers that are mostly cyanobacteria and protists, usually unicellular and planktonic. The limiting factors for the development of life are here some essential nutrients, such as iron, which are scarce, and maximum productivitywe find it in the cold seas and in certain tropical regions, contiguous to the continents, in which the currents bring out nutrients from the bottom of the sea. Outside those places, the pelagic (offshore) regions of the warm latitudes are biological deserts, with low density of life. The richest and most complex marine ecosystems are, however, tropical, and they are those that develop at a very shallow depth, only a few meters, rich in benthic life, near the shore; The clearest example is the coral reefs.
In addition to the photic zone, there is a thriving marine life in each of the dark and extensive ocean bottoms, which depends, for its nutrition, on the organic matter that falls from above, in the form of waste and corpses. In some places where the geotectonic processes bring out hot waters laden with salts, the primary, autotrophic producers, who obtain the energy of chemical reactions based on inorganic substrates, are important; the type of matabolism that we call chemosynthesis.
Against certain prejudices, the average density of life is greater in the continents than in the oceans in the current biosphere; although as the ocean is much more extensive, corresponds approximately 50% of the total primary production of the planet.
Continents
In the continents the trophic chain starts from the terrestrial plants, photosynthesizers that obtain mineral nutrients from the soil thanks to the same structures with which they are anchored, the roots, making water circulate towards the foliage, where they evaporate it. For this reason the main limiting factor in the continents is the availability of water in the soil, at the same time as the temperature, which is more variable than in the seas, where the high specific heat of the water ensures a very homogeneous thermal environment and stable in time.
For the indicated reason, biomass, gross productivity and ecological diversity, is distributed:
Following a gradient, with a maximum towards the equator and a minimum in the polar regions, in correlation with the available energy.
Concentrated in three latitudinally extended bands. The first one is the equatorial one, where the rains produced by the intertropical front, which are of the zenith type, occur all year round or alternate with a dry season. The other two, more or less symmetrical, cover the middle or temperate latitudes, where there is a greater or lesser abundance of cyclonal rains, which accompany the storms.
Among these humid areas and dense life, there are two symmetrical bands of tropical desert or semi-desert regions, where although biomass is low, biodiversity is high. In the high latitudes of both hemispheres we have, finally, the polar regions, where the poverty of life is explained by the shortage of liquid water as well as the lack of energy.
Deep biosphere
Until recently the level was set as limit for life, a few meters deep, to where the roots of the plants extend. Now we have verified that not only in the oceanic bottoms there are ecosystems dependent on chemoautotrophic organisms, but that life of this type extends to deep levels of the crust. It consists of bacteria and extremophile archaea, which extract energy from inorganic chemical processes (chemosynthesis). They thrive no doubt better in places where certain unstable mineral mixtures appear, which offer a potential for chemical energy; but the Earth is geologically a still alive planet, where the internal processes still generate constantly situations of that type.
Extension
The sheath-like biosphere begins about 60 km above the Earth's surface and ends about 5 km below the Earth's surface. It begins in the lower hemisphere of the mesosphere, pervades the remaining layers of the Earth's atmosphere and the upper parts of the hydrosphere, penetrates the pedosphere and ends in the upper part of the lithosphere, after a few kilometers in the Earth's crust. At least when attention is paid to microorganisms, the biosphere extends over the entire surface of the earth, the oceans and seabeds.
Vertical extension
According to current knowledge, the upper limit of the terrestrial biosphere is slightly above the stratopause, in the lowest mesosphere at 60 km altitude. There are still certain microorganisms in permanent stages before. At these atmospheric altitudes they defy the low temperatures ranging from about -50 ° C (lower stratosphere) to about 0 ° C (lower mesosphere), as well as the almost complete lack of water and the strong ultraviolet radiation, At present, it is assumed that the microorganisms found do not go through their entire life cycle so far from the earth's surface. Instead, they should only be swirled up the Earth's surface in various ways and then remain in the stratosphere and lowest mesosphere for some time.
Below the stratosphere is the troposphere, the densest and lowest Earth's atmosphere layer. Here the air has higher air temperatures thanks to the natural greenhouse effect and is relatively low in radiation due to the stratospheric ozone layer above. For these reasons, there are the habitats of terrestrial creatures in the troposphere, temperature-induced mostly even just below the nival altitudinal zone.
Below the troposphere, on the one hand, the bottoms of the pedosphere and, on the other hand, the waters of the hydrosphere follow. The soils are inhabited by a variety of soil organisms. Their habitat is limited to the bottom by the supply of soil water and soil air, with microorganisms penetrate the deepest. Intact, but frozen microorganisms find themselves still deep in the permafrost. In the waters life forms exist to the bottom and once more many meters into the muddy body of water. In fact, a larger proportion of theEarth's total biomass in the form of archaea and bacteria in ocean sediments. But the more prominent members of the aquatic life keep in the top and light-filled water layers of epipelagial on. Beyond that, species and individuals densities can become very small. This is especially true for the deep sea. However, their cold darkness is interrupted by volcanic islands and atolls, which rise above the water surface. Submarine, Guyots and Seamounts provide habitats to many organisms, some of these undersea mountains can rise to the epipelagial. Seen worldwide, seamounts occur very frequently and occupy an area the size of Europe. Collectively, they are likely to be one of the major major biomes. Depending on the depth of the water, volcanic islands, atolls, seamounts and guyots can find diverse communities that interrupt the desert life of the deep sea in this way.
Below the soils and muddy watercourses, the rocks of the lithosphere join. Here caves were found to contain simple cave ecosystems consisting of microorganisms and some multicellular organisms. All other communities of the lithosphere consist exclusively of microorganisms. Some live in oil deposits, coal seams, gas hydrates, in deep aquifers, or in fine pores directly in the bedrock. Furthermore, at least certain microbial long-term stages also occur in salt domes. It can be assumed that the biosphere in the lithosphere pulls down to the depth from which the ambient temperature rises geothermally above 150 ° C. At this temperature, it should become too hot even for hyperthermophilic microbes. As a rule of thumb, it is assumed that the ambient temperature increases by 3 ° C per 100 meters of depth. Thus, the biosphere would have to end in about 5 km lithosphere depth. However, there are strong regional deviations from this rule of thumb.
Microbial ecosystems can also be found in sub-glacial lakes, which are completely isolated from the environment by the overlapping glacial ice. Microorganisms are also found deep in the glacier ice itself. It remains unclear to what extent they only survive or show active life processes there.
Horizontal extension
The living things do not distribute themselves evenly over the biosphere. First, there are biomes with large species and individuals densities. These include, for example, the tropical rainforests and coral reefs. On the other hand, there are also areas with very sparse macroscopic and limited microscopic life. These include cold deserts and dry deserts in the countryside and seabeds in the oceans of the lightless and cold deep seas (Bathyal, Abyssal, Hadal). However, within the desert areas scattered inland areas of higher biodiversity: water oases in the dry deserts, post-volcanic phenomena (Thermal springs, solfatars, fumaroles, mofettes) in the cold deserts, as well as hydrothermal sources (Black Smokers, White Smokers),, and methane sources (Cold Seeps), on deep seabeds,
Construction
Only a thin shell of the earth is space with life. Measured by the total earth volume, the biosphere has only a tiny volume. For earthly organisms have certain claims to their abiotic environment. Most parts of the world can not meet the demands.
The claims of the living beings begin with the space requirement. They can only stay in places that provide enough space for their body sizes. If enough space is available, the place must also offer suitable possibilities of staying in the room. Which options are suitable differs from life form to life form. For example, trees need enough rooting space and tang attachment sites on the seabed, while phytoplankton already get along with the free body of water. The whereabouts claims can change seasonally and age-dependently.
Example: Adult King Albatrosses need some space for their three-meter-wide wings. They roam the low air layers over the open ocean. There they mainly catch octopuses, drink seawater, sleep in the air or float on the sea surface. Adult king algae broods do not need any solid settlement opportunity. However, that changes seasonally. Because they fly to the mainland every two years. There they brag, occupy a breeding ground, incubate her an egg for 79 days and protect the very defenseless young birds in the first five weeks of life. Afterwards, the parents fly out to the sea again. However, they return at irregular intervals to the breeding site to feed the young birds. The young birds must persevere on land,
Furthermore, the abiotic eco-factors (physio-system, location) must move into bandwidths that are tolerable on earthly life forms. This applies in an outstanding way to the offers of thermal energy and liquid water and downstream of the other abiotic eco-factors. In addition, the whereabouts must also ensure the nutrition of the living beings. Autotrophic organisms must have sufficient nutrients and heterotrophic organisms sufficient nutrients.
In the course of Earth's history, the life forms have evolved very different body sizes, settlement methods, Physiosystemansprüche and diets. Now, the same conditions do not prevail everywhere within the biosphere. Therefore no living thing occurs in all places of the biosphere. Life forms with similar or complementary adaptations are found together in the same location. Together they form ecoregions (Eu-biome) and ecozones (zonobioms).
The location of the ecological zones of the mainland depends on the climate. The climate depends on the degree of latitude (→ lighting zones), the distance to the sea (→ oceanicity / continentality) and possibly of high mountains that prevent precipitation (→ climate glacier). Overall, the ecozones run approximately broad circle parallel.
The location of the ecozones of the oceans (realms) depends on the near-surface water temperature. It should also be borne in mind that, for many marine organisms, the continental shores or sheer vastness of the oceans are barriers that restrict their spread. A total of twelve marine eco-zones are distinguished worldwide. Within a marine ecology, desert-like ecoregions are next to ecoregions of great organismic abundance. This is because the same trophic conditions do not prevail everywhere in the oceans: phytoplankton can only thrive extensively in sections of the sea with a rich supply of building materials. The phytoplankton is at the base of the marine food webs, Consequently, there are also the other marine life forms especially numerous. Sea areas with high concentrations of building materials are areas of upwelling in which building-rich deep water rises to the surface of the water. Large amounts of runot can produce a similar effect (whale pump).
Organismic structure
The size of the biosphere is determined primarily by microorganisms. At the outer borders of the biosphere, only permanent stages of microbes are found, which are immune to inhospitable conditions. This applies to the mesosphere and stratosphere as well as to permafrost soils, salt domes and deep glacial ice. But even within the biosphere boundaries many ecosystems can be found that consist exclusively of microorganisms. This applies to all communities within the lithosphere, ie for deposits of crude oil, coal and gas hydrate as well as for deep aquifers, deeper sediments of the ocean and for ecosystems in simple solid rock. In addition, the microorganisms occupy all rooms that are alsoinhabitedby multicellular organisms. They even live on and in these metabionts, on skin and rhizosphere as well as on leaves and in digestive tracts. The terrestrial biosphere proves to be a sphere of microorganisms everywhere, especially in its more extreme areas. In comparison, the habitat of metabionts appears very limited.
Trophic construction
Strictly speaking, the biosphere consists of many ecosystems that are more or less closely interlinked. In every ecosystem, living things fulfill one of three different trophic functions: Primary producers - also called autotrophs - build up biomass from low-energy building materials. This biomass is then consumed by consumers. During production and consumption, large quantities of waste material are collected. The inventory waste is from organisms of the third trophic function, the Destruenten, mined down to the low-energy building materials. The building materials can then be used again by the primary producers to build new biomass.
The existence of consumers and destructors depends on the presence of primary producers. Complete ecosystems can only be developed in places where primary producers find suitable living conditions. This ultimately applies to the entire biosphere. The extent and existence of the entire biosphere is spatiotemporal depending on the presence of primary producers.
The most striking and important primary producers of the terrestrial biosphere are the photoautotrophic organisms. They operate photosynthesis in order to produce their biomass from low-energy building materials with the help of light. Among the best known photoautotrophic organisms are land plants and algae (→ phototrophic organisms), where more than 99% of the total plant biomass is produced by land plants. The photoautotrophic primary production of the oceans is mainly done by non-calcifying haptophytes and cyanobacteria.
Photoautotrophic organisms are at the base of many terrestrial ecosystems. The biosphere shows its most species- and individual-rich ecosystems in locations where plants or other photoautotrophic life forms can exist. In the countryside in places where daylight comes in, but outside the cold deserts, outside the dry deserts and below the nivalen altitude level. In the water in the euphotic zone of the epipelagial.
Beyond the areas of daylight, long-term relationships can only be established if their phototrophic primary producers are satisfied with only scant volcanic activity - or if they become completely independent of photoautotrophically generated biomass. At the basis of such completely light-independent ecosystems are then chemoautotrophicPrimary producers. Chemoautotrophic organisms also grow their biomass from low-energy building materials. They gain the necessary energy not from light, but from certain chemical reactions. The ecosystems that rely on primary chemoautotrophic producers include hydrothermal (black smokers, white smokers), cold seeps, sub-glacial lakes, caves completely isolated from the outside world, and various microbial ecosystems deep in the bedrock (→ Endolites).
However, the biosphere also includes spaces that are not directly associated with the photoautotrophic or chemoautotrophic ecosystems. Instead, they lie between and outside of them. Due to unfavorable living conditions, the rooms can not be colonized by primary producers. However, these inhospitable areas can be temporarily taken over by consumers, who then return to autotrophically maintained ecosystems.
Example: Many migratory birds pass through their habitats with extremely sparse autotrophic life on their annual migrations. So white storks fly through the dry desert Sahara. Striped geese cross the vegetation-free main ridge of the Himalayas. However, both bird species choose their winter and breeding areas again in habitats inhabited by plants. So they only stay temporarily outside photoautotrophically maintained ecosystems.
The vertical migration is similar to annual bird migration: depending on the time of day, many aquatic organisms migrate back and forth between the epipelagial and the low-lying layers of water below. Some members of the phytoplankton migrate down at night to acquire building materials in the deeper water layers. At daybreak, they return to the water surface. At the same time there is an opposite movement of zooplankton and some larger animals. They swim in the shelter of darkness to the surface of the water to make prey, and return at dawn to the depth to be safe even from larger predators.
In addition, waste from the autotrophically maintained ecosystems is constantly flowing away. The waste can be recycled by destructors beyond the actual limits of those ecosystems. In this way, ecosystems can emerge - and thus expand the biosphere - which are not based directly on present primary producers, but on waste waste. Typical examples of such ecosystems are the soils, which are subject to a constant diversity of terrestrial living stock. But also water bodies and deeper water layers below the euphotic zone belong to it, to which inventory waste trickles down from the Epipelagial and from the banks. Particularly worth mentioning are the whale falls: Dead whales sink to the bottom of the sea and deliver large amounts of usable waste for deep-sea dwellers. The walkadavers also serve as intermediate stations for deep-sea organisms on their migrations between the chemoautotroph-based ecosystems of the widely spread hydrothermal (smokers) and methane sources (cold seeps). The reduction of marine waste in the sea occurs at lower rates even in the oxygen-depleted zones (oxygen minimum zone s) by appropriately adapted organisms. In addition to soils and far-off water bodies, many caves are among the waste-based ecosystems, as far as they are not completely isolated from the outside world. In the caves inventory waste is entered in many ways, a prominent example is bat guano.
Artificial biospheres
Experimental biospheres, also called closed ecological systems, have been created to study ecosystems and the potential for supporting life outside the earth. These include spacecraft and the following terrestrial laboratories:
Biosphere 2 in Arizona, United States, 3.15 acres (13,000 m2).
BIOS-1, BIOS-2 and BIOS-3 at the Institute of Biophysics in Krasnoyarsk, Siberia, in what was then the Soviet Union.
Biosphere J (CEEF, Closed Ecology Experiment Facilities), an experiment in Japan.
Micro-Ecological Life Support System Alternative (MELiSSA) at Universitat Autònoma de Barcelona
Extraterrestrial biospheres
No biospheres have been detected beyond the Earth; therefore, the existence of extraterrestrial biospheres remains hypothetical. The rare Earth hypothesis suggests they should be very rare, save ones composed of microbial life only. On the other hand, Earth analogs may be quite numerous, at least in the Milky Way galaxy, given the large number of planets. Three of the planets discovered orbiting TRAPPIST-1 could possibly contain biospheres. Given limited understanding of abiogenesis, it is currently unknown what percentage of these planets actually develop biospheres.
Based on observations by the Kepler Space Telescope team, it has been calculated that provided the probability of abiogenesis is higher than 1 to 1000, the closest alien biosphere should be within 100 light-years from the Earth.
It is also possible that artificial biospheres will be created during the future, for example on Mars. The process of creating an uncontained system that mimics the function of Earth's biosphere is called terraforming.
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