From Wikipedia, the free encyclopedia - View original article

Jump to: navigation, search

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, 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 evidences for life on Earth are graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland[4] and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia.[5][6]

In a general sense, biospheres are any closed, self-regulating systems containing ecosystems; including artificial ones such as Biosphere 2 and BIOS-3; and, potentially, ones on other planets or moons.[7]

Origin and use of the term[edit]

The term "biosphere" was coined by geologist Eduard Suess in 1875, which he defined as:[8]

"The place on Earth's surface where life dwells."

While this 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[edit]


Geochemists define the biosphere as being the total sum of living organisms (the "biomass" or "biota" as referred to by biologists and ecologists).[citation needed] 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.[citation needed]

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.[citation needed] 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.[citation needed]

Gaia hypothesis[edit]

During the early 1970s, the British chemist James Lovelock and Lynn Margulis, a microbiologist from the United States, added to the hypothesis, specifically noting the ties between the biosphere and other Earth systems. For example, when carbon dioxide amounts increase in the atmosphere, plants grow more quickly. As their growth continues, they remove more and more carbon dioxide from the atmosphere.

Many scientists[who?] are now involved with new topics of study that examine interactions between biotic and abiotic factors in the biosphere, such as geobiology and geomicrobiology.

Ecosystems occur when communities and their physical environment work together as a system. The difference between this and a biosphere is simple—the biosphere is everything in general terms.

Extent of Earth's biosphere[edit]

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) (Wainwright et al., 2003, in FEMS Microbiology Letters).[citation needed] 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 (Takamia et al., 1997, in FEMS Microbiology Letters).[citation needed] 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).[9] 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,[10][11] 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[edit]

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

Extraterrestrial biospheres[edit]

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.[14] On the other hand, new research suggests that Earth analogs may be quite numerous, at least in the Milky Way galaxy.[15] 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.[16]

See also[edit]


  1. ^ The Columbia Encyclopedia, Sixth Edition. Columbia University Press. 2004. Retrieved 2010-11-12. 
  3. ^ Zimmer, Carl (3 October 2013). "Earth’s Oxygen: A Mystery Easy to Take for Granted". New York Times. Retrieved 3 October 2013. 
  7. ^ "Meaning of biosphere". Retrieved 2010-11-12. 
  8. ^ Seuss, E. (1875) Die Entstehung Der Alpen [The Origin of the Alps]. Vienna: W. Braunmuller.
  9. ^ National Geographic, 2005
  10. ^ Gold T. 1992. The deep, hot biosphere. Proceedings of the National Academy of the USA 89(13): 6045-6049.
  11. ^ 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.
  12. ^ 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.
  13. ^ "Institute for Environmental Sciences". Retrieved 2011-11-08. 
  14. ^ P. Ward, D.E. Brownlee. 2000. Rare Earth: Why Complex Life Is Uncommon in the Universe
  15. ^
  16. ^ R. Zubrin. 1996. The Case for Mars: The Plan to Settle the Red Planet and Why We Must

External links[edit]