leslieh04/03/09
How did photosynthesis evolve?
swartzy04/03/09
Photosynthesis evolved when the only life on Earth were microorganisms.
cyclotreker04/03/09
The first photosynthetic organisms probably appeared about 3500 million years ago.
epking04/03/09
Cyanobacteria appeared about 3000 million years ago, and began to oxygenate the atmosphere.