by
M. Alan Kazlev
The Gaia Hypothesis
"The entire range of living matter on Earth from whales to viruses
and from oaks to algae could be regarded as constituting a single
living entity capable of maintaining the Earth’s atmosphere to suit
its overall needs and endowed with faculties and powers far beyond
those of its constituent parts...[Gaia can be defined] as a complex
entity involving the Earth’s biosphere, atmosphere, oceans, and
soil; the totality constituting a feedback of cybernetic systems
which seeks an optimal physical and chemical environment for life on
this planet."
Dr James Lovelock
Gaia - A New Look at Life on Earth
The Gaia Hypothesis is the theory that living organisms and
inorganic material are part of a dynamic system that shape Earth’s
biosphere, in Lynn Margulis’s words, a "super organismic system" The
earth is a self-regulating environment; a single, unified,
cooperating and living system - a superorganism that regulates
physical conditions to keep the environment hospitable for life
Evolution therefore is the result of cooperative not competitive
processes.
The Origin of the Gaia Hypothesis
It is an ironic fact that a theory about life on Earth should begin
from an exploration of outer space.
In the mid-1960’s, Dr James Lovelock was approached by NASA, who
asked him for help in searching for life on Mars. In 1965,
Lovelock
proposed some physical tests for determining whether Mars held life
or not. He proposed that a top-down view of the entire planet be
employed. The test would analyze the composition of the planet’s
atmosphere. If it held no life, the planet should have an atmosphere
close to the chemical equilibrium state, as determined by chemistry
and physics. If the planet held life, the metabolic activities of
life-forms would result in an atmosphere far from the equilibrium
state.
Together with scientist Dian Hitchcock, Lovelock examined the
atmospheric data for the Martian atmosphere and found it to be in a
state of stable chemical equilibrium, while the Earth was shown to
be in a state of extreme chemical disequilibrium. The two scientists
concluded that Mars was probably lifeless; almost a decade later the
Viking 1 and 2 landings conformed their conclusion.
In that same year, Lovelock began to think that such an unlikely
combination of gases such as the Earth had, indicated a homeostatic
of the Earth biosphere to maintain environmental conditions
conducive for life, in a sort of cybernetic feedback loop, an active
(but non-teleological) control system. By the end of the 1960’s,
Lovelock had definitively organized his theory. The novelist
William Golding, Lovelock’s neighbor, suggested he call the control system
Gaia, after the ancient Greek Earth Goddess. First on his own in
1972, and then later in 1973 with American microbiologist Lynn Margulis,
Lovelock formally proposed the idea of Gaia as a control
system. The name for the complex system of climate control has
remained "Gaia" since then, and in 1979 his book, Gaia - a new look
at life on Earth first presented the Gaia hypothesis to the wider
public. Gaia has has become a very potentmeme in the
humannoosphere
The nature of Gaia
"The name of the living planet,
Gaia, is not a synonym for the
biosphere. The biosphere is defined as that part of the Earth where
living things normally exist. Still less is Gaia the same as the
biota, which is simply the collection of all individual living
organisms. The biota and the biosphere taken together
form part but
not all of Gaia. Just as the shell is part of a snail, so the rocks,
the air, and the oceans are part of Gaia. Gaia... has continuity with
the past back to the origins of life, and extends into the future as
long as life persists. Gaia, as a total planetary being, has
properties that are not necessarily discernible by just knowing
individual species or populations of organisms living together.
The Gaia hypothesis... suppose(s) that the atmosphere, the oceans,
the climate, and the crust of the Earth are regulated at a state
comfortable for life because of the behavior of living organisms.
Specifically, the Gaia hypothesis said that the temperature,
oxidation state, acidity and certain aspects of the rocks and waters
are at any time kept constant, and that this homeostasis is
maintained by active feedback processes operated automatically and
unconsciously the biota. Solar energy sustains comfortable
conditions for life. The conditions are only constant in the short
term and evolve in synchrony with the changing needs of the biota as
it evolves. Life and its environment are so closely coupled that
evolution concerns Gala, not the organisms or the environment taken
separately."
James Lovelock
The Ages of Gaia, p.19
Examples of Gaian Processes
Oxygen Dr Lovelock suggests that
Gaia is at work to keep the oxygen content
of the atmosphere high and within the range that all
oxygen-breathing animals require. The atmospheres of our two nearest
neighbors, Venus and Mars, contain 0.00 percent and 0.13 percent
respectively, of free oxygen.
Temperature The
Gaia hypothesis sees life regulating the surface temperature of
Earth. The average surface temperature of Earth has remained within
a narrow range - between 10 and 20 C - for over three billion years.
During that time the sun’s output has increased by thirty or forty
percent. Even ignoring the long-term trend of the sun, the
temperature would vary far more, as it does for example every day on
the surface of Mars
Carbon Dioxide This stability of
Earth’s temperature is maintained by varying the
amount of carbon dioxide (a notorious greenhouse gas) in the
atmosphere. The drop in the atmosphere’s ability to absorb solar
radiation is due to a global decline in carbon dioxide levels over
that time. The biosphere would have attempted to fix
carbon dioxide
in the form of the calcium carbonate of marine shells. - The Carbon
Cycle
Dimethyl Sulfide Production Another form of temperature control is
Dimethyl Sulfide Production.
Phytoplankton may have part of the control in that they produce
dimethyl sulfide. They release this dimethyl sulfide into the air,
which is then converted into drops sulfuric acid, which in turn
become nuclei for cloud condensation. These nuclei help to produce
thicker clouds, blocking more of the sun, and cooling the oceans.
Oceanic Salinity Natural geological weathering
releases salts into the oceans too
fast for life to adapt at the same rate. At the same time,
geological evidence indicates that the oceans have remained at a
constant salinity of 10% saturation for millions of years. Salt
flats, which are hosts to dense patches of bacteria, may be removing
the salt from the oceans. The bacteria, surviving in water too salty
for any other life, trap salts and other minerals to form a sheath
within which the bacterial colonies live
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