Biosphere

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.

Biosphere is historically and most commonly defined as that part of the Earth in which living organisms exist. As such, it is viewed as a place or supporting stratum that overlaps with the inner portion of the atmosphere, the upper part of the geosphere, and much of the hydrosphere (Mayhew 2004; Margulis and Sagan 2002). Another concept of the biosphere is as simply "life on earth," in other words, the total of all living things on earth (Knight and Schlager 2002). As such, the biosphere is one of four mutually exclusive spheres, the others being the atmosphere, geosphere, and hydrosphere. Yet other definitions of biosphere include both the living organisms and their environment (McGraw-Hill 2005).

Viewed as a place, the biosphere takes up a relatively small portion of the earth, perhaps with the overall dimensions of a hollow sphere about twenty-three kilometers wide, or about 0.0007 percent of the volume of the plant (6371 kilometer radius) (Margulis and Sagan 2002). Viewed as limited to only the living organisms, the biosphere occupies about 0.00008 percent of the mass of the earth (Knight and Schlager 2002).

Origin and use of the term

A familiar scene on Earth which simultaneously shows the lithosphere, hydrosphere and atmosphere.

The term "biosphere" was coined by geologist Eduard Suess in 1875. He defined biosphere as (Seuss 1875):

The place on earth's surface where life dwells.

Many current definitions reflect this historical concept. Margulis and Sagan (2002) define biosphere as "the place where life exists," and Mayhew (2004) as "the zone where life is found." As a particular stratum of earth, it includes part of the atmosphere, much of the hydrosphere, and part of the geosphere or lithosphere.

While this concept has a geological origin, it is an indication of the impact of both [[Charles Darwin (1809 - 1882) and American oceanographer and meterologist Matthew Maury (1806 - 1873) on the earth sciences.

Biosphere is an interdisciplinary concept for integrating astronomy, geophysics, meteorology, biogeography, evolution, geology, geochemistry, hydrology and, generally speaking, all life and earth sciences.

Other concepts of biosphere

Biosphere as life on earth definition. Some life scientists and earth scientists use biosphere in the sense of "life on earth"; that is, 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 overall earth system, the other three being geosphere (or lithosphere), hydrosphere, and atmosphere. The biosphere works in concert with these other major earth systems (Knight and Schlager 2002).

Biosphere as life and its environment. A broader meaning of biosphere is both the all of the living organisms and their environment. Included is all of the environments capable of sustaining life as well as all living organisms (McGraw Hill 2005). In this sense, biosphere overlaps almost the entire hydrosphere, as well as parts of the atmosphere and lithosphere (McGraw Hill 2005). Characteristic of this sense of the term is the interrelationships of living things and their environments (McGraw Hill 2005). Some might prefer the word ecosphere, coined in the 1960s, as all encompassing of both biological and physical components of the planet. The biosphere's ecological context comes from the 1920s, preceding the 1935 introduction of the term "ecosystem" by Sir Arthur Tansley. Soviet mineralogist and geochemist Vladimir Vernadsky (1863 - 1945) defined ecology as the science of the biosphere. He is most noted for his 1926 book The Biosphere in which he inadvertently worked to popularize Eduard Suess’ term biosphere, by hypothesizing that life is the geological force that shapes the earth.

Gaia's biosphere. The concept that the biosphere is itself a living organism, either actually or metaphorically, is known as the Gaia hypothesis. James Lovelock, an atmospheric scientist from the United Kingdom, proposed the Gaia hypothesis to explain how biotic and abiotic factors interact in the biosphere. This hypothesis considers Earth itself a kind of living organism. Its atmosphere, geosphere, and hydrosphere are cooperating systems that yield a biosphere full of life. In the early 1970s, 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 levels increase in the atmosphere, plants grow more quickly. As their growth continue, they remove more and more carbon dioxide from the atmosphere.

Extent of Earth's biosphere

Nearly every part of the upper part of the lithosphere and lower part of the atmosphere supports life of some kind, from the polar ice caps to the Equator. 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 hard to measure. Birds typically fly at altitudes of 650 to 2000 meters, and fish that live deep underwater can be found down to -8,372 meters 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 meters. Bar-headed Geese migrate at altitudes of at least 8,300 meters (over Mount Everest). Yaks live at elevations between 3,200 to 5,400 meters above sea level. Mountain goats live up to 3,050 meters. Herbivorous animals at these elevations depend on lichens, grasses, and herbs, but the biggest tree is the Tine palm or mountain coconut found 3,400 meters above sea level.

Microscopic organisms live at such extremes that, taking them into consideration puts the thickness of the biosphere much greater. Culturable microbes have been found in the Earth's upper atmosphere as high as 41 kilometers (Wainwright et al, 2003). It is unlikely, however, that microbes are active at such altitudes, where temperatures and air pressure are extremely low and ultraviolet radiation very high. 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 kilometer depth depth (10,897 meters) in the Marianas Trench (Takamia et al, 1997).

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 kilometers into the Earth's crust in Sweden (Gold 1992; Szewzyk 1994) from rocks between 65 to 75 degrees centigrade. Temperature increases rapidly with increasing depth into the Earth's crust. The speed at which the temperature increases depends on many factors, including type of crust (continental vs. oceanic), rock type, geographic location, and so forth. The upper known limit of microbial is 121 degrees centigrade (Kashefi and Lovely 2003), 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 broadly 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 budgets, and display prominent adaptations to cold, including world-spanning migrations, social adaptations, homeothermy, estivation and multiple layers of insulation.

Biomass accounts for about 3.7 kg carbon per square meter of the earth's surface averaged over land and sea, making a total of about 1900 gigatonnes of carbon.

Specific biospheres

When the word Biosphere is followed by a number, it is usually referring to a specific system. Thus:

• Biosphere 1 - The planet Earth
• Biosphere 2 - A laboratory in Arizona which contains 3.15 acres (13,000 m²) of closed ecosystem.
• BIOS-3 was a closed ecosystem 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.

Hyperbaric biosphere

In 1999, Carl Baugh patented a small "hyperbaric biosphere" chamber, designed to emulate the conditions thought by him to exist on the early earth, providing double atmospheric pressure, enhanced oxygen, and protection from ultraviolet radiation, while magnetic coils attempt to make up for earth's reduced magnetic field.

See also

• Back-contamination
• Biome
• Biosphere reserve
• Cryosphere
• Earth's atmosphere
• Geosphere
• Homeostasis
• Hydrosphere
• Life support system
• Lithosphere
• Noosphere
• Shadow biosphere
• Thomas Gold
• Montreal Biosphère

References

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Kashefi K, Lovley DR (2003) Extending the upper temperature limit for life. Science 301:934.

The deep, hot biosphere T Gold PNAS July 1, 1992 vol. 89 no. 13 6045-6049

Thermophilic, anaerobic bacteria isolated from a deep borehole in granite in Sweden. U Szewzyk, R Szewzyk, and T A Stenström PNAS March 1, 1994 vol. 91 no. 5 1810-1813

Knight, Judson, and Neil Schlager. 2002. Science of everyday things. Detroit: Gale Group. ISBN 0787656313.

McGraw-Hill concise encyclopedia of science & technology. 2005. New York: McGraw-Hill. 0071429573

Mayhew, Susan. 2004. A dictionary of geography: over 3000 entries. Oxford: Oxford Univ. Press. OCLC 163502775.

FEMS Microbiology Letters Volume 152 Issue 2, Pages 279 - 285 Published Online: 17 Jan 2006 Microbial flora in the deepest sea mud of the Mariana Trench Hideto Takamia*, Akira Inouea, Fumie Fujia, Koki Horikoshia http://www3.interscience.wiley.com/journal/119173470/abstract

Wainwright et al. (2003). Microoganisms cultured from stratospheric air samples obtained at 41km. FEMS Micorbiology Letters. 218,161-165.

External links

• Article on the Biosphere at Encyclopedia of Earth
• GLOBIO.info, an ongoing programme to map the past, current and future impacts of human activities on the biosphere
• Paul Crutzen Interview Freeview video of Paul Crutzen Nobel Laureate for his work on decomposition of ozone talking to Harry Kroto Nobel Laureate by the Vega Science Trust.

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