Let’s gage these organisms against the gage of evolution. I won’t go into religious views at this
•Earth is approximately 4.6 billion years old and all the evidence we have about its origin
supports this date.
•The universe is 11.5 billion up to 14 billion years old.
About 1/3 of the time earth has been around as a planet. In the early days of the life of the planet
but not of organisms things were tough. This is the Hadean eon. Remember how to break down
the periods of time in geologic history? One term is eon (s) and another term is era (s). We also
refer to periods. Know these 3 terms. In the Hadean period we have 4.6 to 3.8 billion years
ago and it was a harsh time on planet earth. Meteorite fluxes, gamma rays and it was bombarded
with matter that kept hitting it. The entire solar system was very young and the planets and
moons were just forming. There was a lot of ‘traffic’ of matter in our solar system. We have
documentation of the early days on earth, the 1st 1.2 billion years ago. There are wounds and
damage on what was the surface.
S: Where did the gamma rays come from?
P: The sun was hotter and more powerful and that is where they came from.
There was little atmosphere protecting the earth at this time. It would have been impossible for
the extremeophiles to exist on the planet and everyone agrees with that.
Next was the Achean period. This is reverse to archae which is the name of the bacteria that is
from the extremeophiles that we talked about. The names are just coincidence. We don’t know
what the earliest days were but there is a time window (signified by the arrow – on overhead).
The Proterozoic period is where life began on the planet. We don’t know where they began but
the professor from Germany believed it was in the ocean vents (in the black smokers). Most
biologists think it was not in the ocean but on the surface of the earth. We are not really sure
about the timeline. 3.8 billion to about 2 ½ billion we think is the window of life. The textbook
evidence for the earliest fossils came from Australia. They were supposed to be fossils of
cyanobacteria type formations but this has been debunked successfully (by Dr. Brazier from
Oxford). Everyone wants to know the oldest fossils of life on earth. Discoveries were made in
Greenland and Africa as well that were in that bracket (3.8 billion maybe) but none we can say
for sure are fossils that represented life. The branching patterns couldn’t have been the footprints
of the early forms of life but explained by intrusions of lava flows into rocks at that time.
We know for sure that at 2 ½ billion years when proterozoic time occurred life began to
expand at a high rate. This is when photosynthesis can be documented on the planet as
well (troposphere). So photosynthesis might have evolved very quickly. The first life forms
were chemosynthetic and they are in the world’s trenches. This is where oxygen begins to rise,
prior and before we only had trace amounts of O2 on earth. All experts agree that the splitting of
the molecule was invented by using oxygen. Then you use electrons and energy out of the water
splitting to fix CO2 which was on the planet from the early days. It is also on Mars and Venus.
BGYC61H3F.September.22.2008 Lecture 3 2