L'alba della Vita: i "mangiatori" di luce

In the beginning our planet was a lifeless and inhospitable place; nevertheless, a few hundred millions of years later the Earth was full of microscopic living beings. These primordial microorganisms that appeared in the “primordial soup” were similar to present-day bacteria and were the only living beings on Earth for at least two billion years. Some of them became able to utilize the light and energy from the primitive Sun to synthesize the compounds required for their survival. Later on, some microorganisms (cyanobacteria) developed oxygenic photosynthesis; in this way the molecular oxygen accumulated in the atmosphere creating the ozone layer. This allowed the first organisms to colonize the dry lands and the further appearance of more complex living forms.