Origin of Life on Earth

1
Origin of Life on Earth

• The pre-Biotic Earth
• Synthesis of Organic Compounds

2
The Origin of Land

• 4.6 and 4.5 bya- The outer region of the cloud
  from which our solar system evolved, cooled
  gradually forming planets
• Approx. 4 bya- The Earth was forming much of the
  inner rocky material melted due probably to
  internal compression, huge asteroid impact, and
  radioactive decay of minerals
• As rocks melted, nickel, iron, and other heavy
  metals moved to the interior and lighter ones
  floated to the surface

3
The First Atmosphere

• When the first patches of crust were forming, hot
  gases blanketed the Earth.
• This first atmosphere was probably a mix of
  gases H2, N2, and CO, CO2
• Water and O2 were probably absent
• Rock release O2 during volcanic eruptions but
  this O2 would have reacted immediately with other
  elements

4
Formation of Seas

• When the crust cooled and solidified H2O
  condensed into clouds and rains began
• For millions of years, runoff from rains stripped
  mineral salts and other compounds from rocks.
  Salt waters collected in crustal depressions
  forming early seas

5
Origins of Life on Earth

• 200 mya life originated on the Earths surface
• Classwork
• Outline the experiments of Miller and Urey into
  the origin of organic compounds
• Discuss the hypothesis that the first catalysts
  responsible for the polymerization reactions were
  clay minerals

6
Synthesis of Organic Molecules

• Rocks collected from Mars, meteorites, the
  Earths moon,contain precursor of biological
  molecules (small atoms or molecules).
• Mars, Earth,s moon, meteorites and the Earth
  developed from the same cosmic cloud
• The energy from sunlight, lighting, o even heat
  escaping from the crust could have produced the
  combination of precursors into organic molecules

7
Stanley Miller and Harold Ureys experiments

• Miller mixed Hydrogen, CH4, NH3 and H2O in a
  reaction chamber. The mixture was recirculated
  and bombarded with a spark discharge to simulate
  lighting.
• Amino acids and other small organic molecules
  formed in less than a week

8
Other Experiments

• In other experiments that simulated conditions of
  the early Earth
• glucose, ribose, deoxiribose and other sugars
  formed from formaldehyde
• Adenine formed from hydrogen cyanide