Transcript History of Life on Earth - Woodstown

Earth’s Early History
Mystery of Life’s Origins
 Using radiometric dating, scientists believe
the Earth to be between 4.2 and 4.6 Billion
Years Old.
 Earth’s early atmosphere contained little or
no oxygen.

Made up of mostly: CO2, water vapor, and
nitrogen
How did Life Begin?

3 ideas of how life may have gotten on
Earth
1.
2.
3.
Divine Creation – a higher being put us
here on Earth
Extraterrestrial Origin – life may have
come to Earth via an asteroid or meteorite.
Spontaneous Origin – process through
which life is thought to have developed when
molecules of non-living matter reacted
chemically during the 1st billion years.
Spontaneous Origin
 1920’s A.I. Oparin – Primordial Soup Model
 Oceans were a big soup bowl with large
amounts of organic molecules
 Chemical reactions spontaneously occurred in
soup with energy from lightning/volcanoes
 Proposed that Earth’s early atmosphere
lacked oxygen, yet had plenty of nitrogen,
hydrogen, water vapor (earth was hot),
methane and ammonia.
Stanley Miller
 1953, tested Oparin’s hypothesis
 Placed gases in apparatus, zapped it, and
found some basic chemicals could have
formed spontaneously
 2 problems


Too slow
Not sure methane and ammonia was available,
and if it was, UV would destroy it
Louis Lerman
 1986 – Bubble Model
 Chemical reactions took place in the bubbles
of the ocean


Reactions would take place faster in bubbles
Inside bubbles, methane and ammonia
protected from UV rays
 Leading hypothesis accepted to date
Origins of Eukaryotic Cells
 Endosymbiotic Theory – proposes that a
symbiotic relationship evolved over time,
between primitive eukaryotic cells and the
prokaryotic cells within them.
 Ex. Mitochondria and Chloroplasts are
thought to have been ancient prokaryotes

Both have their own DNA, ribosomes and both
reproduce by binary fission like bacteria cells