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Gaia Hypothesis

Gaia hypothesis

The Gaia (pronounced GAY-ah) hypothesis is the idea that Earth is a living organism and can regulate its own environment. This idea argues that Earth is able to maintain conditions that are favorable for life to survive on it, and that it is the living things on Earth that give the planet this ability.

Mother Earth

The idea that Earth and its atmosphere are some sort of "superorganism" was actually first proposed by Scottish geologist (a person specializing in the study of Earth) James Hutton (17261797), although this was not one of his more accepted and popular ideas. As a result, no one really pursued this notion until some 200 years later, when the English chemist James Lovelock (1919 ) put forth a similar idea in his 1979 book, Gaia: A New Look at Life on Earth. Gaia is the name of the Greek goddess of Earth and mother of the Titans. In modern times, the name has come to symbolize "Earth Mother" or "Living Earth." In this book, Lovelock proposed that Earth's biosphere (all the parts of Earth that make up the living world) acts as a single living system that if left alone, can regulate itself.

As to the name Gaia, the story goes that Lovelock was walking in the countryside surrounding his home in Wilshire, England, and met his neighbor, English novelist William Golding (19111993), author of Lord of the Flies and several other books. Telling Golding of his new theory, he then asked his advice about choosing a suitable name for it, and the result of this meeting was that the term "Gaia" was chosen because of its real connection to the Greek goddess who pulled the living world together out of chaos or complete disorder.

Origin of Earth's atmosphere

Lovelock arrived at this hypothesis by studying Earth's neighboring planets, Mars and Venus. Suggesting that chemistry and physics seemed to argue that these barren and hostile planets should have an atmosphere just like that of Earth, Lovelock stated that Earth's atmosphere is different because it has life on it. Both Mars and Venus have an atmosphere with about 95 percent carbon dioxide, while Earth's is about 79 percent nitrogen and 21 percent oxygen. He explained this dramatic difference by saying that Earth's atmosphere was probably very much like that of its neighbors at first, and that it was a world with hardly any life on it. The only form that did exist was what many consider to be the first forms of lifeanaerobic (pronounced ANN-ay-roe-bik) bacteria that lived in the ocean. This type of bacteria cannot live in an oxygen environment, and its only job is to convert nitrates to nitrogen gas. This accounts for the beginnings of a nitrogen build-up in Earth's atmosphere.

Words to Know

Biosphere: The sum total of all lifeforms on Earth and the interaction among those lifeforms.

Feedback: Information that tells a system what the results of its actions are.

Homeostasis: State of being in balance; the tendency of an organism to maintain constant internal conditions despite large changes in the external environment.

Photosynthesis: Chemical process by which plants containing chlorophyll use sunlight to manufacture their own food by converting carbon dioxide and water to carbohydrates, releasing oxygen as a by-product.

Symbiosis: A pattern in which two or more organisms live in close connection with each other, often to the benefit of both or all organisms.

The oxygen essential to life as we know it did not start to accumulate in the atmosphere until organisms that were capable of photosynthesis evolved. Photosynthesis is the process that some algae and all plants use to convert chemically the Sun's light into food. This process uses carbon dioxide and water to make energy-packed glucose, and it gives off oxygen as a by-product. These very first photosynthesizers were a blue-green algae called cyanobacteria (pronounced SIGH-uh-no-bak-teer-eea) that live in water. Eventually, these organisms produced so much oxygen that they put the older anaerobic bacteria out of business. As a result, the only place that anaerobic bacteria could survive was on the deep-sea floor (as well as in heavily water-logged soil and in our own intestines). Love-lock's basic point was that the existence of life (bacteria) eventually made Earth a very different place by giving it an atmosphere.

Lovelock eventually went beyond the notion that life can change the environment and proposed the controversial Gaia hypothesis. He said that Gaia is the "Living Earth" and that Earth itself should be viewed as being alive. Like any living thing, it always strives to maintain constant or stable conditions for itself, called homeostasis (pronounced hoe-mee-o-STAY-sis). In the Gaia hypothesis, it is the presence and activities of life that keep Earth in homeostasis and allow it to regulate its systems and maintain steady-state conditions.

Cooperation over competition

Lovelock was supported in his hypothesis by American microbiologist Lynn Margulis (1918 ) who became his principal collaborator. Margulis not only provided support, but she brought her own scientific ability and achievements to the Gaia hypothesis. In her 1981 book, Symbiosis in Cell Evolution, Margulis had put forth the then-unheard of theory that life as we know it today evolved more from cooperation than from competition. She argued that the cellular ancestors of today's plants and animals were groups of primitive, formless bacteria cells called prokaryotes (pronounced pro-KAR-ee-oats). She stated that these simplest of bacteria formed symbiotic relationshipsrelationships that benefitted both organismswhich eventually led to the evolution of new lifeforms. Her theory is called endosymbiosis (pronounced en-doe-sim-bye-O-sis) and is based on the fact that bacteria routinely take and transfer bits of genetic material from each other.

Margulis then argued that simple bacteria eventually evolved into more complex eukaryotic (pronounced you-kar-ee-AH-tik) cells or cells with a nucleus. These types of cells form the basic structure of plants and animals. Her then-radical but now-accepted idea was that life evolved more out of cooperation (which is what symbiosis is all about) than it did out of competition (in which only the strong survive and reproduce). The simple prokaryotes did this by getting together and forming symbiotic groups or systems that increased their chances of survival. According to Margulis then, symbiosis, or the way different organisms adapt to living together to the benefit of each, was the major mechanism for change on Earth.

Most scientists now agree with her thesis that oxygen-using bacteria joined together with fermenting bacteria to form the basis of a type of new cell that eventually evolved into complex eukaryotes. For the Gaia hypothesis, the Margulis concept of symbiosis has proven to be a useful explanatory tool. Since it explains the origin and the evolution of life on Earth (by stating that symbiosis is the mechanism of change), it applies also to what continues to happen as the process of evolution goes on and on.

Gaia explained

The main idea behind the Gaia hypothesis can be both simple and complex. Often, several similar examples or analogies concerning the bodies of living organisms are used to make the Gaia concept easier to understand. One of these states that we could visualize Earth's rain forests as the lungs of the planet since they exchange oxygen and carbon dioxide. Earth's atmosphere could be thought of as its respiratory system, and its streams of moving water and larger rivers like its circulatory system, since they bring in clean water and flush out the system. Some say that the planet actually "breathes" because it contracts and expands with the Moon's gravitational pull, and the seasonal changes we all experience are said to reflect our own rhythmic bodily cycles.

Many of these analogies are useful in trying to explain the general idea behind the Gaia hypothesis, although they should not be taken literally. Lovelock, however, has stated that Earth is very much like the human body in that both can be viewed as a system of interacting components. He argues that just as our bodies are made up of billions of cells working together as a single living being, so too are the billions of different lifeforms on Earth working together (although unconsciously) to form a single, living "superorganism." Further, just as the processes or physiology of our bodies has its major systems (such as the nervous system, circulatory system, respiratory system, etc.), so, says Lovelock, Earth has its own "geophysiology." This geophysiology is made up of four main components: atmosphere (air), biosphere (all lifeforms), geosphere (soil and rock), and hydrosphere (water). Finally, just as our own physiological health depends on all of our systems being in good working condition and, above all, working together well, so, too, does Earth's geophysiology depend on its systems working in harmony.

Life is the regulating mechanism

Lovelock claims that all of the living things on Earth provide it with this necessary harmony. He states that these living things, altogether, control the physical and chemical conditions of the environment, and therefore it is life itself that provides the feedback that is so necessary to regulating something. Feedback mechanisms can detect and reverse any unwanted changes. A typical example of feedback is the thermostat in most homes. We set it to maintain a comfortable indoor temperature, usually somewhere in the range between 65°F (18°C) and 70°F (21°C). The thermostat is designed so that when the temperature falls below a certain setting, the furnace is turned on and begins to heat the house. When that temperature is reached and the thermostat senses it, the furnace is switched off. Our own bodies have several of these feedback mechanisms, all of which are geared to maintaining conditions within a certain proper and balanced range.

For Earth's critical balance, Lovelock says that it is the biosphere, or all of life on Earth, that functions as our thermostat or regulator. He says that the atmosphere, the oceans, the climate, and even the crust of Earth are regulated at a state that is comfortable for life because of the behavior of living organisms. This is the revolutionary lesson that the Gaia hypothesis wants to teach. It says that all of Earth's major components, such as the amount of oxygen and carbon dioxide in the atmosphere, the

saltiness of the oceans, and the temperature of our surface is regulated or kept in proper balance by the activities of the life it supports. He also states that this feedback system is self-regulating and that it happens automatically. As evidence that, if left alone, Earth can regulate itself, he asserts that it is the activity of living organisms that maintain the delicate balance between atmospheric carbon dioxide and oxygen. In a way, Love-lock argues that it is life itself that maintains the conditions favorable for the continuation of life. For example, he contends that it is no accident that the level of oxygen is kept remarkably constant in the atmosphere at 21 percent. Lovelock further offers several examples of cycles in the environment that work to keep things on an even keel.

Lovelock also warns that since Earth has the natural capacity to keep things in a stable range, human tampering with Earth's environmental balancing mechanisms places everyone at great risk. While environmentalists insist that human activity (such as industrial policies that result in harming Earth's ozone layer) is upsetting Earth's ability to regulate itself, others who feel differently argue that Earth can continue to survive very well no matter what humans do exactly because of its built-in adaptability.

Earth as seen from space

An important aspect about the Gaia hypothesis is that it offers scientists a new model to consider. Most agree that such a different type of model was probably not possible to consider seriously until humans went into space. However, once people could travel beyond the atmosphere of Earth and put enough distance between them and their planet, then they could view their home from an extra-terrestrial viewpoint. No doubt that the 1960s photographs of the blue, green, and white ball of life floating in the total darkness of outer space made both scientists and the public think of their home planet a little differently than they ever had before. These pictures of Earth must have brought to mind the notion that it resembled a single organism.

Although the Gaia hypothesis is still very controversial and has not been established scientifically (by being tested and proven quantitatively), it has already shown us the valuable notion of just how interdependent everything is on Earth. We now recognize that Earth's biological, physical, and chemical components or major parts regularly interact with and mutually affect one another, whether by accident or on purpose. Finally, it places great emphasis on what promises to be the planet's greatest future problemthe quality of Earth's environment and the role humans will play in Earth's destiny.

[See also Biosphere; Ecosystem ]

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Gaia Hypothesis

Gaia hypothesis

The Gaia hypothesis is a recent and controversial theory that views Earth as an integrated, pseudo-organismic entity, and not as a mere physical object in space . Gaia, Earth, was believed by the ancient Greeks to be a living, fertile ancestor of many of their important gods. The Gaia hypothesis suggests that organisms and ecosystems on Earth cause substantial changes to occur in the physical and chemical nature of the environment, in a manner that improves the living conditions on the planet. In other words, it is suggested that Earth is an organismic planet, with homeostatic mechanisms that help to maintain its own environments within the ranges of extremes that can be tolerated by life. According to the Gaian hypothesis, evolution is the result of cooperative, not competitive processes. The Gaian hypothesis holds that evolution of life on Earth was enhanced by two processes: sexual reproduction, which introduced enormous variety in the gene pool, and the development of consciousness, which enabled genetic methods of evolution to be replaced with more efficient social mechanisms.

Earth is the only planet in the universe that is known to support life. This is one of the reasons why the Gaia hypothesis cannot be tested by rigorous, scientific experimentationthere is only one known replicate in the great, universal experiment. However, some supporting evidence for the Gaia hypothesis can be marshaled from certain observations of the structure and functioning of the planetary ecosystem.

One supporting line of reasoning for the Gaia hypothesis concerns the presence of oxygen in Earth's atmosphere. Scientists believe that the primordial atmosphere of Earth did not contain oxygen. The appearance of this gas required the evolution of photosynthetic life forms, which were initially blue-green bacteria and, somewhat later, single-celled algae. Molecular oxygen is a waste product of photosynthesis, and its present atmospheric concentration of about 21% has entirely originated with this biochemical process (which is also the basis of all biologically fixed energy in ecosystems). Of course, the availability of atmospheric oxygen is a critically important environmental factor for most of Earth's species and for many ecological processes. In addition, it appears that the concentration of oxygen in the atmosphere has been relatively stable for an extremely long period of time, perhaps several billions of years. This suggests the existence of a long-term equilibrium between the production of this gas by green plants, and its consumption by biological and non-living processes. If the atmospheric concentration of oxygen were much larger than it actually is, say about 25% instead of the actual 21%, then biomass would be much more readily combustible. These conditions could lead to much more frequent and more extensive forest fires. Such conflagrations would be severely damaging to Earth's ecosystems and species.

Some proponents of the Gaia hypothesis interpret the above information to suggest that there is a planetary, homeostatic control of the concentration of molecular oxygen in the atmosphere. This control is intended to strike a balance between the concentrations of oxygen required to sustain the metabolism of organisms, and the larger concentrations that could result in extremely destructive, uncontrolled wildfires.

Another line of evidence in support of the Gaian theory concerns carbon dioxide in Earth's atmosphere. To a substantial degree, the concentration of this gas is regulated by complex biological and physical processes by which carbon dioxide is emitted and absorbed. This gas is well known to be important in the planet's greenhouse effect , which is critical to maintaining the average temperature of the surface within a range that organisms can tolerate. It has been estimated that in the absence of this greenhouse effect, Earth's average surface temperature would be about 176°F (116°C), much too cold for organisms and ecosystems to tolerate over the longer term. Instead, the existing greenhouse effect, caused in large part by atmospheric carbon dioxide, helps to maintain an average surface temperature of about 59°F (15°C). This is within the range of temperature that life can tolerate.

Again, advocates of the Gaia hypothesis interpret these observations to suggest that there is a homeostatic system for control of atmospheric carbon dioxide, and of climate. This system helps to maintain conditions within a range that is satisfactory for life.

All scientists agree that there is clear evidence that the non-living environment has an important influence on organisms, and that organisms can cause substantial changes in their environment. However, there appears to be little widespread support within the scientific community for the notion that Earth's organisms and ecosystems have somehow integrated in a mutually benevolent symbiosis (or mutualism), aimed at maintaining environmental conditions within a comfortable range.

Still, the Gaia hypothesis is a useful concept, because it emphasizes the diverse connections of ecosystems, and the consequences of human activities that result in environmental and ecological changes. Today, and into the foreseeable future, humans are rapidly becoming a dominant force that is causing large, often degradative changes to Earth's environments and ecosystems. Hopefully, the changes wrought by humans will not exceed the limits of homeostatic tolerance and repair of the planet and its ecological components. If these possibly Gaian limits of tolerance are exceeded, some scientists assert the consequences could be catastrophic for life on Earth.

See also Earth (planet); Evolutionary mechanisms; Evolution, evidence of

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Gaia Hypothesis

Gaia Hypothesis


Gaia is the name of the Greek goddess of the Earth. The Gaia hypothesis is that the Earth is more worthy of the respect and reverence once shown to Gaia than modern people have supposed. According to this hypothesis, the Earth is a self-regulating system, of which humans are an unruly part. In particular, the organisms on the Earth's surface play a major role in determining the composition of the atmosphere to ensure that it is favorable to life. Some proponents judge from the scientific evidence that the Earth has its own intelligence and depict it in almost personal, quasi-divine, terms. This provides religious support for concern about particular features of the global ecosystem.


See also Animal Rights; Biological Diversity; Deep Ecology; Ecofeminism; Ecology; Ecology, Ethics of; Ecology, Religious and Philosophical Aspects; Ecology, Science of; Ecotheology; Sacramental Universe


Bibliography

lovelock, james e. gaia: a new look at life on earth. oxford: oxford university press, 1979.


john cobb

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Gaia hypothesis

Gaia hypothesis The theory, based on an idea put forward by the British scientist James Ephraim Lovelock (1919– ), that the whole earth, including both its biotic (living) and abiotic (nonliving) components, functions as a single self-regulating system. Named after the Greek earth goddess, it proposes that the responses of living organisms to environmental conditions ultimately bring about changes that make the earth better adapted to support life; the system would rid itself of any species that adversely affects the environment. The theory has found favour with many conservationists.

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Gaian hypothesis

Gaian hypothesis A hypothesis, formulated by James E.Lovelock and Lynn Margulis and first advanced by Lovelock in 1968. It holds that the presence of living organisms on a planet leads to major modifications of the physical and chemical conditions pertaining on the planet, and that subsequent to the establishment of life the climate and major biogeochemical cycles are mediated by living organisms themselves.

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Gaian hypothesis

Gaian hypothesis Hypothesis, formulated by James E. Lovelock and Lynn Margulis, that the presence of living organisms on a planet leads to major modifications of the physical and chemical conditions pertaining on the planet, and that subsequent to the establishment of life the climate and major biogeochemical cycles are mediated by the living organisms themselves.

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Gaian hypothesis

Gaian hypothesis A hypothesis, formulated by James E. Lovelock and Lynn Margulis, that the presence of living organisms on a planet leads to major modifications of the physical and chemical conditions pertaining on the planet, and that, subsequent to the establishment of life, the climate and major biogeochemical cycles are mediated by living organisms themselves.

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Gaia hypothesis

Gaia hypothesis The hypothesis, formulated by James E. Lovelock and Lynn Margulis, that the presence of living organisms on a planet leads to major modifications of the physical and chemical conditions pertaining on the planet, and that subsequent to the establishment of life the climate and major biogeochemical cycles are mediated by living organisms themselves.

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Gaia hypothesis

Gaia hypothesis Scientific theory interrelating the Earth's many and varied processes – chemical, physical, and biological. Popular in the 1970s, when it was proposed by James Lovelock, it showed the Earth as a single, living organism.

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