The fossils that provide information on the formation of an oxygen-rich atmosphere are the stromatilites from the Precambrian era. These are layered and columnar fossils consisting mainly of cyanobacteria which were the original life form back then. These bacteria took in carbon dioxide and produced oxygen by photosynthesis as early as 2.5 billion years ago (the earth is about 4.5 billion yrs old).
Pretty sure most of us know that already,so what's your question?You lost buddy?
Their blueprints are in their DNA
B the 2nd answer, <span>A large region of interconnected ecosystems.</span>
