Gaia thory suggests that organisms interact with their environment to form a self regulatory, complex system.

1. Gaia
Hypothesis
Parto Siavosh

2. Signs of life in organisms:
• Eating
• Urination and defecation
• Motility
• Reproduction
• Ability to Response to stimulants

3. Lynn margulis

4. Is our planet alive?

5. 1- WHAT IS “GAIA”?
2- WHAT DOES THE THEORY SUGGEST?
3- CRITICISMS
Headlines

6. • Gaia= land,
mother
• Greek primalGreek primal
goddessgoddess
• Mother nature,
mother of earth

7. Gaia theory proposes that organisms interact with their
inorganic surroundings on Earth to form a self-regulating,
complex system that contributes to maintaining the
conditions for life on the planet.
Gaia posits that the Earth is a self-regulating system
involving : the biosphere, the atmosphere, the
hydrosphere and the pedosphere, tightly coupled as an
evolving system.
This system as a whole -(called Gaia)- seeks a physical
and chemical environment optimal for contemporary life.

8. The scientifically accepted form of the hypothesis :"influential
Gaia” states the biota influence certain aspects of the abiotic
world, e.g. temperature and atmosphere.
They state the evolution of life and its environment may affect
each other. e.g. how the activity of photosynthetic bacteria during
Precambrian times have completely modified the Earth
atmosphere to turn it aerobic, and as such supporting evolution
of life.

9. Evidence?
 Ocean salinity
 Volcanic activity
 Earth surface temperature
 Regulation of oxygen in the
atmosphere
 Processing of carbon dioxide
 Daisyworld model

10. criticism
 Lack of scientific evidence
 Gaia theory is a metaphor not a
mechanism
 Experiments with predictable
results
 Ice ages? High climate
instability?

11. Gaia philosophy is a broadly inclusive term for related
concepts that living organisms on a planet will affect the
nature of their environment in order to make the
environment more suitable for life. This set of theories
holds that all organisms on a life-giving planet regulate
the biosphere to the benefit of the whole. Gaia concept
draws a connection between the survivability of a
species and its usefulness to the survival of other
species.
Gaia philosophy