 |
 |
 |
 |
 |
 |
|
|
|
 • Evolutionary Essentials
The first four billion years of Earth’s history—the Precambrian—saw a planet bombarded by meteorites and smothered by volcanic gases. Amazingly, life first evolved in this hostile environment.
Two major evolutionary highlights allowed organic life to flourish during these harsh times:
 |
The development of photosynthetic organisms—cells that could harness the sun’s energy.
|
|
The development of sexual reproduction, which led to natural selection, the mechanism that drives the process of evolution.
|
Continue to Photosynthesis Becomes Possible. >>
|
|
|
|
|
|
