How life starts on earth
Earth evolution Life Approximately three and a half years ago, microscopic single-celled organisms made of complex organic molecules appeared deep in these new oceans, when the land was still a hostile place dominated by volcanoes. These organisms were the most advanced life-forms on the planet for another three billion years until suddenly (relatively speaking that is), within the period of a few million years, bacteria in the sea began processing carbon dioxide, water and sunlight to produce oxygen. This helped the single-celled microbes in the sea begin to stick to each other and create multi-cellular organisms that grew into animals. Pre life on earth was bacteria These animals began to reproduce, to evolve and eventually, when there was enough oxygen in the atmosphere to protect against the sun's radiation, to crawl onto land. Amphibians, insects, reptiles, mammals and birds all arrived on land, more or less in that order, over the next few hundred million years. At least tha...