Gaia:
The name of Earth goddess used by Greeks.

Gaia Hypothesis:
Earth is a superorganism , actively self-regulating its environment and maintaining its environmental homeostasis.

Lovelock stated (1988):

Gaia, is the superorganism, a planet sized entity, has properties that are not necessarily discernible by just knowing individual species or populations of organisms living together. The essence of Gaia is the "emergent property " between the material Earth and the living organisms, which possesses the ability of self-regulation to its homeostasis .

The main evidence was mostly drawn from the atmospheric composition of Earth and its state of chemical disequilibrium
 

The atmospheric compositions of Mars, present Earth and Venus, and hypothetical abiological Earth (Lovelock 1979)

GAS	Venus	Earth without life	Mars	Earth today
Carbon Dioxide	98%	98%	95%	0.036%
Nitrogen	1.9%	1.9%	2.7%	78%
Oxygen	trace	trace	0.13%	21%
Argon	0.1%	0.1%	2%	1%
Surface temperature (Celsius)	477	290	-53	13
Total pressure (bars)	90	60	0.0064	1.0

The increase of oxygen and ozone in the atmosphere forms key positive feedback mechanisms for a changing biosphere.

What is NEGATIVE FEEDBACK ?

As recorded in documents, the idea of Earth as a superorganism was first coined by Scottish scientist, James Hutton, in 1785 at a meeting of Royal Society of Edinburgh.

The concept of biosphere was first introduced by Vladimir I. Vernadsky in 1911.
 

Gaia hypothesis offers a different way of viewing Earth:

1. A holistic way, instead of a reductionistic way.
2. A view of mutualism, not separationism
3. Amazing ability of maintaining its homeostasis (30% increase in solar radiation, but the same temperature about 15C)
4. Gaia does go evolution
5. View of human beings as the weed of mammals? The cancer of Gaia

The Emergent Property Principle

1. The whole is more than the sum of its parts
2. The forest is more than a collection of trees

As components, or subsets, are combined to form larger functional wholes, new properties emerge that were not present ot not evident at the level below.  These new properties at the level of the whole are called emergent properties . This is often a consequence of hierarchical organization . (from E. P. Odum 1993)

Example 1: electrons + protons + neutrons  --> elements
Example 2: O2 + H2 --> H2O
Example 3: fungus + alga (or cyanobacterium) --> lichen
 

Homeostasis, Homeostatic Mechanism, Equilibrium, Steady state, and stability

Homeostasis:
A state of equilibrium produced by a balance of functions.

Homeostatic mechanism:
Checks and balances (or forces and counterforces) that dampen oscillations or maintain an equilibrium (or positive feedback and negative feedback)

Equilibrium (or Dynamic stability):
A condition in which all acting factors are canceled by others, resulting in a stable, balanced or unchanging system. (such as a stable structure of physics which positive forces equals negative forces, or chemistry of forward rate equals reverse rate of reaction).

Biosphere : all of the earth's ecosystems functioning together on a global scale; portion of the earth in which organisms can live.  Biosphere merges imperceptibly into the lithosphere, the atmosphere and the hydrosphere.

 

Organizational Hierarchies:

Ecological	Taxonomic	Physiological	Military
Biosphere	Kingdom	Organism	General
Biome	Phylum	Organ system	Colonel
Landscape	Class	Organ	Major
Ecosystem	Order	Tissue	Captain
Biotic community	Family	Cell	Lieutenant
Population (species)	Genus	Organelle	Sergeant
Individual organism	Species	Molecule	Private