Scientists believe that the Earth was first formed as a molten mass about 45 billion years ago As the Earths crust cooled water vapor in the atmosphere condensed into oceans Minerals from the Earths crust started to dissolve in the water This formed the Primordial Soup ID: 760190
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Slide1
The Origin of Life
Slide2The Earth’s Beginnings
Scientists believe that the Earth was first formed as a molten mass about 4.5 billion years ago.
As the Earth’s crust cooled, water vapor in the atmosphere condensed into oceans.
Minerals from the Earth’s crust started to dissolve in the water. This formed the Primordial Soup.
The atmosphere contained H
2
, H
2
O, CH
4
, and NH
3
. NO FREE OXYGEN! The atmosphere was
reducing
.
Slide3How Life Got “Started”
Lightning, heat, and UV radiation supplied energy for random bonding to make inorganic molecules into organic molecules.
Organic molecules began to slowly build up over time.
Since the atmosphere was reducing, these molecules were very stable and they did not break down easily.
After a while, several macromolecules had been formed and covered by protective spheres.
Think about phospholipids and hydrophobic/
philic
interactions, polar molecules…
Slide4Stanley Miller’s Experiment
In 1953, he set up an experiment that used the gases from Earth’s early atmosphere (H
2
, H
2
O, CH
4
, and NH
3
) to model early conditions on Earth.
Miller zapped the gases with electricity to see how the energy would affect the bonds of the molecules, like lightning used to on early Earth.
He ended up with some amino acids, lactic acid, and adenine.
Slide5The Development of Life
The first prokaryotic cells emerged about a billion years after the formation of the Earth.
These cells were anaerobic
heterotrophs
(remember, no Oxygen in the atmosphere…)
Eventually, cyclic photosynthesis evolved, allowing non-cyclic photosynthesis to evolve after that.
This released Oxygen gas (O
2
) into the atmosphere, where it reacted to form the Ozone (O
3
) layer, providing protection from UV rays.
Now that the atmosphere contained Oxygen, aerobic respiration could evolve.
Slide6