WEDNESDAY, JUNE 15, 2016

Bio 101

Pathway to Humans

Eric Lee, A-SOCIATED PRESS

TOPICS: FROM SCIENTISTS, FROM THE WIRES, FUTURE ISSUES

TUCSON (A-P) — In short:

  • Abiotic organic resources left over from solar system formation serve as potential energy source.
  • Via unknown pathway, chemical entities catabolise organic matter for energy and become self-replicating.
  • Biotic entities evolve into diverse anaerobes able to use iron, sulfur and other elements and compounds as electron acceptors for energy.
  • Photons are consumed by cyanobateria for energy, with oxygen as a waste product leading to Mass Extinction Event I where anaerobes die off in oxygenated areas such as oceans.
  • Aerobes evolve to use oxygen as energy source.
  • Prokaryotes evolve into a community of mutualists living within a cell membrane to become eukaryotes having a nucleus.
  • Eukaryotes evolve into multicellular organisms; some reproduce sexually.
  • Kingdom Animalia emerges, and some survive the Ediacaran Mass Extinction Event II, possibly associated with meteorite impacts and oxygen drop.
  • Cambrian explosion in diversity, carbon dioxide levels drop causing global cooling and late Cambrian Mass Extinction Event III; some chordates survive.
  • Some vertebrates survive the Ordovician Mass Extinction Event IV caused by global cooling and glaciation possibly associated with the uplifting Appalachian Mountains where weathering caused a significant and rapid draw down of CO2.
  • Some tetrapods survive the Devonian Mass Extinction Event V, possibly related to the expansion of terrestrial plants that used and sequester carbon dioxide decreasing the amount in the atmosphere.
  • Some terrestrial tetrapods survive the Permian Mass Extinction Event VI, likely caused by volcanic eruptions increasing carbon dioxide levels causing global warming.
  • Some early mammals survive the Triassic Mass Extinction Event VII, likely caused by another bout of volcanic activity and global warming.
  • Some early primates survive the late Cretaceous Mass Extinction Event VIII, following meteor impact.
  • Some humans may survive the Anthropocene Mass Extinction Event IX caused by planetary life-support system degradation secondary to consumptive growth of fossil-fueled technoindustrial society.
  • Current rate of extinction is about 1,000 times greater than before Neolithic and rate is increasing. The pace of planetary destruction, the biosphere anyway, has not slowed. Act. Better late than too late.

For details: Human Origins in Deep Time.


 

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