Revolutions That Made the Earth
Tim Linton and Andrew Watson, Oxford University Press, Multco 550 L574r 2011
Like Melanie Lenart's Life In the Hothouse, this book posits a biosphere shaped by life.
Like Rare Earth, this book suggests life
Endpapers: 8 stages of evolution
- 1 Compartments
- 2 Chromosomes
- 3 Genetic code - critical step
- - Oxygenic photosynthesis - critical step
- 4 Eukaryotes - critical step
- 5 Sex
- 6 Cell differentiation in eukaryotes
- 7 Eusocial colonies
- 8 Natural language - critical step
Ch 8 - Photosynthesis
- p145 We are obligate oxygen breathers - aerobic metabolism produces 14 times as much combustion energy as anerobic (2870 kJ/mol vs 195 kJ/mol for fermenting lactic acid).
- p150 Photosystem II and photosystem I, PS2 and PS1 are a multistage process to produce oxygen by splitting water
- WSC - Water Splitting Complex, 3 Mg and a Ca surounded by proteins, 4 photons
- p152 LHC - Light Harvesting Complex, pigment molecules that gather and focus light on chlorophyll molecules in a nearby reaction center.
- One pigment molecule absorbs a photon rarely, a few Hz, to feed picosecond-scale reactions
- p154 about 100 carefully ordered proteins, a huge number of genes, difficult and slow to arrange by evolution
- p155 fusion of two anaerobics
Ch 9 - The trial of the oxygen poisoners
- p166 Fig 9.1 timeline - anerobic photosynthesis at 3.7 Gya, certainly before 3.4 Gya, oxidized paleosols after 2.2 Gya
- anaerobes can produce stomatolite mats and other carbon deposits, resemblance to cyanobacteria fossils does not prove oxygenic photosynthesis
My take - the earth formed 4.56 Gya, complex anerobic organisms formed over 0.8 Gy, oxygen photosynthesis needed 1.5 Gy to develop - once. Humans evolved only 0.1 Gy before it will become too hot to do so. Perhaps a G3 or colder star might last longer than our G2, and a planet at Venus's position would offer a wider window for the production of us.