3 Minute Speaker

3 Minute Speaker  Neil Heron
Earth’s Big History – The Life Chapter
 
The Science curriculum at many schools now includes a topic that covers how the Earth was formed and has changed over time to explain where we are today. I thought I might use the story of life as an example.
A simple time line of Earth’s History based on the sequence of life formation and its impact on atmospheric conditions.
  • 4.5 Billion Years Ago  - Earth as a rocky planet is stable with oceans and an atmosphere of  30% Nitrogen & 70% Carbon dioxide.
  • 3.8 BYO – life forms around oceanic geothermal vents -  water, minerals, CO2 and energy
  • 1.8 BYO – competition and evolution – first cells to develop photosynthesis so life  moves way from vents to ocean surface and sunlight  - O­2 is a byproduct
  • 1BYO – first animal type cells form as the O­2 (now 1%) builds up in the sea CO2 (now 50%) starts to be stored as coral and limestone
  • 700MYO – first land plants  CO2  30%  O2 12%
  • 600 MYO – first multi cell organisms
  • 428 MYO – first true animals – enough oxygen now 21%
  • 300 MYO – Devonian  Period – fish rule the seas and some adapt to live on land. Insects common CO2  (0.35%)  O2  30%.  Limestone now stores the bulk of the original CO2 in the atmosphere.
  • 360 MYO Carboniferous Period  - Plants Dominate coal deposits form as plants thrive. . Huge amounts of CO2 (2.5% dropping to 0.3% as carbon stored as coal) stored as coal now  2.5%. O2 peaks at 35% as plants grow and thrive. Animals and insects can use this to grow large.
  • 200 - 65 MYO – Dinosaur period ends. Oil deposits formed. O2 levels are dropping but stabilized at around 19% where they have stayed. CO2 are (around 3% and dropping). Earth is warmer. Great plant conditions.
  • 20 MYO Oxygen and Carbon dioxide stabilise at present levels
  • 1850 AD: Atmosphere C02 levels at O.28 %, O2% stable at 20%
  • Present day: Atmosphere C02 levels at 0.38 %
As I see it:  The changes in our atmosphere have since earth’s creation due to life evolving and adapting. This has caused enormous changes on the planet. However, these changes have taken 100s of millions of years to occur. The changes happening now in the atmosphere (caused by us) are occurring too quickly. Too quickly for most life forms, even plants, to adapt and maintain balance.