The study of planetary habitability is partly based upon hypothesis formulation from knowledge of the Earth’s conditions, as the Earth is the only planet currently known to harbour life.
The hypothesis was formulated by the chemist James Lovelock and co-developed by the microbiologist Lynn Margulis in the 1970s. Gaian hypotheses suggest that organisms co-evolve with their environment: that is, they «influence their abiotic environment, and that environment in turn influences the biota by Darwinian process». A reduced version of the hypothesis has been called «influential Gaia» in «Directed Evolution of the Biosphere: Biogeochemical Selection or Gaia? Lapenis, which states the biota influence certain aspects of the abiotic world, e.
Since barriers existed throughout the Twentieth Century between Russia and the rest of the world, it is only relatively recently that the early Russian scientists who introduced concepts overlapping the Gaia hypothesis have become better known to the Western scientific community. Less accepted versions of the hypothesis claim that changes in the biosphere are brought about through the coordination of living organisms and maintain those conditions through homeostasis. In some versions of Gaia philosophy, all lifeforms are considered part of one single living planetary being called Gaia. The Gaia hypothesis was an influence on the deep ecology movement. The Gaia hypothesis posits that the Earth is a self-regulating complex system involving the biosphere, the atmosphere, the hydrospheres and the pedosphere, tightly coupled as an evolving system. Gaia evolves through a cybernetic feedback system operated unconsciously by the biota, leading to broad stabilization of the conditions of habitability in a full homeostasis.
The existence of a planetary homeostasis influenced by living forms had been observed previously in the field of biogeochemistry, and it is being investigated also in other fields like Earth system science. Processing of the greenhouse gas CO2, explained below, plays a critical role in the maintenance of the Earth temperature within the limits of habitability. The CLAW hypothesis, inspired by the Gaia hypothesis, proposes a feedback loop that operates between ocean ecosystems and the Earth’s climate. Currently the increase in human population and the environmental impact of their activities, such as the multiplication of greenhouse gases may hypothesis formulation negative feedbacks in the environment to become positive feedback. James Lovelock and Andrew Watson developed the mathematical model Daisyworld, in which temperature regulation arises from a simple ecosystem consisting of two species whose activity varies in response to the planet’s environment. Daisyworld examines the energy budget of a planet populated by two different types of plants, black daisies and white daisies.
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The colour of the daisies influences the albedo of the planet such that black daisies absorb light and warm the planet, while white daisies reflect light and cool the planet. It has been suggested that the results were predictable because Lovelock and Watson selected examples that produced the responses they desired. Ocean salinity has been constant at about 3. The constant ocean salinity was a long-standing mystery, because no process counterbalancing the salt influx from rivers was known. In the biogeochemical processes of the earth, sources and sinks are the movement of elements.
The elements that comprise salinity do not readily change and are a conservative property of seawater. Hsue a correspondence author in 2001. The «desiccation» of the Mediterranean is the evidence of a functioning kidney. Levels of gases in the atmosphere in 420,000 years of ice core data from Vostok, Antarctica research station.
Current period is at the left. The Gaia hypothesis states that the Earth’s atmospheric composition is kept at a dynamically steady state by the presence of life. The atmospheric composition provides the conditions that contemporary life has adapted to. The stability of the atmosphere in Earth is not a consequence of chemical equilibrium. Oxygen is a reactive compound, and should eventually combine with gases and minerals of the Earth’s atmosphere and crust. Gaia scientists see the participation of living organisms in the carbon cycle as one of the complex processes that maintain conditions suitable for life. One of these organisms is Emiliania huxleyi, an abundant coccolithophore algae which also has a role in the formation of clouds.
Lichen and other organisms accelerate the weathering of rocks in the surface, while the decomposition of rocks also happens faster in the soil, thanks to the activity of roots, fungi, bacteria and subterranean animals. The flow of carbon dioxide from the atmosphere to the soil is therefore regulated with the help of living beings. The idea of the Earth as an integrated whole, a living being, has a long tradition. In the eighteenth century, as geology consolidated as a modern science, James Hutton maintained that geological and biological processes are interlinked. Also in the turn to the 20th century Aldo Leopold, pioneer in the development of modern environmental ethics and in the movement for wilderness conservation, suggested a living Earth in his biocentric or holistic ethics regarding land.
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