The biosphere is that part of a planet earth's outer shell—including air, land, and water—within which life occurs, and which biotic processes in turn alter or transform. From the broadest geophysiological point of view, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere (rocks), hydrosphere (water), and atmosphere (air).
The term "biosphere" was coined by a geologist, Eduard Suess, in 1875. The concept of biosphere has thus a geological origin and is an indication of the impact of Darwin on the earth sciences. An ecological concept of the biosphere comes from the 1920s (see Vladimir I. Vernadsky), preceding the 1935 introduction of the term "ecosystem" by Sir Arthur Tansley (see ecology history). The biosphere is an important concept in astronomy, geophysics, meteorology, biogeography, evolution, geology, geochemistry, and, generally speaking, all life and earth sciences.
Some life sciences and earth sciences use biosphere in a more limited sense. For example, geochemists define the biosphere as being the total sum of living organisms (the "biomass" or "biota" of biologists and ecologists). In this sense, the biosphere is but one of the four components of the geochemical model, the other three being the lithosphere, hydrosphere, and atmosphere.
Some consider that the semantic and conceptual confusion surrounding the term "biosphere" is reflected in the current debates related to biodiversity and sustainable development. The meaning used by geochemists is one of the consequences of specialization in modern science. Some might prefer the word "ecosphere", coined in the 1960s, as all ecompassing of both biological and physical components of the planet.
Vernadsky defined ecology as the science of the biosphere. 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. Some also include the creation of artificial non-Earth biospheres—for example, human-centered biospheres or a native Martian biosphere—in the field of biospherics.
Biosphere 1, Biosphere 2, Biosphere 3
When the word Biosphere is followed by a number, it is usually referring to a specific system.
- Biosphere 1 - The planet Earth.
Biosphere 2 - A laboratory in Arizona which contains 3.15 acres (13,000 m²) of closed ecosystem.
Biosphere 3 - Experiment conducted by Russians in 1967-8. 
--- See also: biome, cryosphere, Biosphere Reserve, noosphere, geosphere, eco-evolution, homeostasis, life support system
Earth is the only place where life is known to exist. The planet's lifeforms are said to form a "biosphere". This biosphere is generally believed to have evolved beginning some 3.5 billion years ago.
The 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 populus 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.
Some theorists therefore postulate that the Earth is poorly suited to life. However, every part of the planet supports life, from the polar ice caps to the Equator. Recent advances in microbiology have proven that microscopic life lives deep under the Earth's surface, and that the total mass of microbial life in so-called "uninhabitable zones" may, in terms of sheer biomass, outweigh all animal and plant life combined on the surface of the Earth.
Oceans mediate the cold and distribute nutrients. The Antarctic krill, Euphausia superba, for example, is generally considered to be the most successful animal of the planet, with a biomass probably over 500 million tonnes (c.f. human biomass of about 250 million tonnes).
For important major components of Earth's biosphere, see: Ocean; Forest; Desert; Steppe; Lake; River; Atmosphere.
Last updated: 10-23-2005 11:10:51