Astronomy 2021A/B Lecture Notes - Lecture 6: Extinction Event, Heredity, Chemical Energy
5 Apr 2016
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Chapter 6: the origin and evolution of life on earth. When did life begin: study fossils to answer when did life occur, three lines of fossil evidence all point to the idea that life arose quite early in. The first line of evidence comes from this. Stromatolites rocks that are characterized by a distinctive, layered structure. In size, shape and interior structure, ancient stromatolites look identical to sections of mats formed today by colonies of microbes called living stromatolites . Living stromatolites contain layers of sediment intermixed with different types of microbes. Microbes near the top generate energy through photosynthesis; those beneath use organic compounds left as waste products by the photosynthetic microbes. Grow in size when sediments are deposited over them. Similarity in structure of ancient stromatolites and modern mats suggest a similar origin, hence fossils remnants of early life. Offer evidence for microbial colonies as far back as 3. 5 billion years ago.
