Biosphere

For other uses, see Biosphere (disambiguation).
A false-color composite of global oceanic and terrestrial photoautotroph abundance, from September 1997 to August 2000. Provided by the SeaWiFS Project, NASA/Goddard Space Flight Center and ORBIMAGE.

The biosphere is the global sum of all ecosystems. It can also be termed 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.[1] By the most general biophysiological definition, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, geosphere, hydrosphere, and atmosphere. The biosphere is postulated to have evolved, beginning with a process of biopoesis (life created naturally from non-living matter such as simple organic compounds) or biogenesis (life created from living matter), at least some 3.5 billion years ago.[2][3] The earliest evidence for life on Earth includes biogenic graphite found in 3.7 billion-year-old metasedimentary rocks from Western Greenland[4] and microbial mat fossils found in 3.48 billion-year-old sandstone from Western Australia.[5][6]

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.[7]

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.[8]

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

A beach scene on Earth, simultaneously showing the lithosphere (ground), hydrosphere (ocean) and atmosphere (air)

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 lithosphere, hydrosphere, and atmosphere. The word ecosphere, coined during the 1960s, 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.

Extent of Earth's biosphere

Water covers 71% of the Earth's surface. Image is the Blue Marble photographed from Apollo 17.

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 of 650 to 1,800 metres, and fish that live deep underwater can be found down to -8,372 metres in the Puerto Rico Trench.[2]

There are more extreme examples for life on the planet: Rüppell's vulture has been found at altitudes of 11,300 metres; bar-headed geese migrate at altitudes of at least 8,300 metres; yaks live at elevations between 3,200 to 5,400 metres above sea level; mountain goats live up to 3,050 metres. Herbivorous animals at these elevations depend on lichens, grasses, and herbs.

Microscopic organisms live at such extremes that, taking them into consideration, the thickness of the biosphere is much greater. Culturable microbes have been found in the Earth's upper atmosphere as high as 41 km (25 mi).[9] It is unlikely, however, that microbes are active at such altitudes, where temperatures and air pressure are extremely minor and ultraviolet radiation very intense. More likely, these microbes were brought into the upper atmosphere by winds or possibly volcanic eruptions. Barophilic marine microbes have been found at more than 10 km (6 mi) depth in the Mariana Trench.[10] In fact, single-celled life forms have been found in the deepest part of the Mariana Trench, Challenger Deep, at depths of 36,201 feet (11,034 meters).[11] Microbes are not limited to the air, water or the Earth's surface. Culturable thermophilic microbes have been extracted from cores drilled more than 5 km (3 mi) into the Earth's crust in Sweden,[12] from rocks between 65-75 °C.

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 (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.

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. Terrestrial organisms in temperate and Arctic biomes have relatively small amounts of total biomass, smaller energy requirements, and display prominent adaptations to cold, including world-spanning migrations, social adaptations, homeothermy, estivation and multiple layers of insulation.

Specific biospheres

For this list, if a word is followed by a number, it is usually referring to a specific system or number. Thus:

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.[15] On the other hand, Earth analogs may be quite numerous, at least in the Milky Way galaxy.[16] Given limited understanding of abiogenesis, it is currently unknown what percentage of these planets actually develop biospheres.

It is also possible that artificial biospheres will be created during the future, for example on Mars.[17] The process of creating an uncontained system that mimics the function of Earth's biosphere is called terraforming.[18]

See also

References

  1. ↑ The Columbia Encyclopedia, Sixth Edition. Columbia University Press. 2004. Retrieved 2010-11-12.
  2. ↑ 2.0 2.1 Campbell, Neil A.; Brad Williamson; Robin J. Heyden (2006). Biology: Exploring Life. Boston, Massachusetts: Pearson Prentice Hall. ISBN 0-13-250882-6.
  3. ↑ Zimmer, Carl (3 October 2013). "Earth’s Oxygen: A Mystery Easy to Take for Granted". New York Times. Retrieved 3 October 2013.
  4. ↑ Yoko Ohtomo, Takeshi Kakegawa, Akizumi Ishida, Toshiro Nagase, Minik T. Rosing (8 December 2013). "Evidence for biogenic graphite in early Archaean Isua metasedimentary rocks". Nature Geoscience. doi:10.1038/ngeo2025. Retrieved 9 Dec 2013.
  5. ↑ Borenstein, Seth (13 November 2013). "Oldest fossil found: Meet your microbial mom". AP News. Retrieved 15 November 2013.
  6. ↑ Noffke, Nora; Christian, Daniel; Wacey, David; Hazen, Robert M. (8 November 2013). "Microbially Induced Sedimentary Structures Recording an Ancient Ecosystem in the ca. 3.48 Billion-Year-Old Dresser Formation, Pilbara, Western Australia". Astrobiology (journal) 13 (12): 1103–24. doi:10.1089/ast.2013.1030. PMC 3870916. PMID 24205812. Retrieved 15 November 2013.
  7. ↑ "Meaning of biosphere". WebDictionary.co.uk. WebDictionary.co.uk. Retrieved 2010-11-12.
  8. ↑ Seuss, E. (1875) Die Entstehung Der Alpen [The Origin of the Alps]. Vienna: W. Braunmuller.
  9. ↑ Wainwright et al, (2003). "Microorganisms cultured from stratospheric air samples obtained at 41 km." FEMS Microbiology Letters 218, 161-165.
  10. ↑ Takamia et al (1997). "Microbial flora in the deepest sea mud of the Mariana Trench." FEMS Microbiology Letters 152 (2), 279-285.
  11. ↑ National Geographic, 2005
  12. ↑ Szewzyk, U; Szewzyk, R; Stenstrom, TR. (1994). "Thermophilic, anaerobic bacteria isolated from a deep borehole in granite in Sweden". Proceedings of the National Academy of Sciences of the USA 91 (5): 1810–1813. doi:10.1073/pnas.91.5.1810. PMC 43253. PMID 11607462.
  13. ↑ Nakano et al. (1998). "Dynamic Simulation of Pressure Control System for the Closed Ecology Experiment Facility". Transactions of the Japan Society of Mechanical Engineers 64: 107–114. doi:10.1299/kikaib.64.107.
  14. ↑ "Institute for Environmental Sciences". Ies.or.jp. Retrieved 2011-11-08.
  15. ↑ P. Ward, D.E. Brownlee. 2000. Rare Earth: Why Complex Life Is Uncommon in the Universe
  16. ↑ Space.com
  17. ↑ R. Zubrin. 1996. The Case for Mars: The Plan to Settle the Red Planet and Why We Must
  18. ↑ Fogg, M.J. (1998). "Terraforming Mars: A review of current research". Advances in Space Research 22 (3): 415–420. doi:10.1016/S0273-1177(98)00166-5. ISSN 0273-1177.

External links

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