Physical and chemical conditions constrained what kind of life of life originated on earth, where it originated, and when.

When: As soon as conditions made it possible for spontaneous physical/chemical processes to be stable.

Where: Probably shallow, warm, saline (evaporative) pools; Possibly deepsea hydrothermal vent systems or terrestrial geothermal/volcanic regions

What: Anaerobic, chemotrophic micro-organisms, tolerant of reducing environments

Life on other planets? Probably a certainty for earthlike planets with sun-like stars and solar systems

Organisms changed earth in many ways:

1. Depleted simple energy-rich molecules (e.g. free ATP)

2. Depleted simple "nutrient" molecules.

3. Both processes intensified by natural selection favoring the forms that were most efficient at using those molecules at low concentrations; and especially by favoring forms able to use new sources of energy and nurients.

4. Photosynthesis was probably the greatest single advance in the history of life; the greatest pollution event in the history of the earth, and the cause of the greatest mass extinction in the history of the earth

• oxygen is a extremely reactive and highly toxic waste product
• caused massive precipitation of minerals as oxides, carbonates, phosphates etc.
• permanently changed composition and chemistry of air, sea, land and soils
• eventually led to an ozone layer giving protection from radiation (especially UV), which probably made it possible for large long-lived organisms to evolve
• blue sky

5. Only one lineage of DNA known to have survived oxygenation of the atmosphere

6. Conditions favoring spontaneous origination of life have gone forever from the face of the earth.

• Biological, geological, chemical and physical aspects of the environment interact all the time changing and constraining one another.
• Composition of atmosphere
• CO₂ comes mainly from volcanoes
• Volcanic activity has a 400-500 Ma periodicity driven by the tectonics of continental aggregation and breakup
• Photosynthesis reduces CO₂ when there is little tectonic or volcanic activity, leading to global cooling and glaciations.
• Many mass extinctions, major evolutionary advances and radiations seem correlated with glaciations.
• These global interactions mean that ecology and evolution are dynamic processes that shape the distributions and abundances of organisms on all scales from the global to micr0-environmental.

Biomes are terrestrial vegetation types characteristic of large areas with similar climatic regimes and often, similar soils. Adaptations of the plant species, and the general structure and appearance of the vegetation are similar wherever that climatic regime prevails, even though the species may differ from place to place. The biome concept per se does not include animals, and is not applicable to marine systems.

• GLOBAL CLIMATES = global precipitation patterns + global thermal regimes
• CLIMATE + GEOLOGY ( + organisms) produce SOILS
• CLIMATE + SOILS produce global patterns of vegetation ( = BIOMES)

 A. Along climatic gradients of increasing moisture and temperature, biomes have increasing:

B. Geographic trends among biomes:

C. Key to biome trends in text diagram: