ENVS 1000 Study Guide - Midterm Guide: Stromatolite, Cyanobacteria, Half-Life
17 Nov 2017
School
Department
Course
Professor
Document Summary
Earth had cooled, and liquid water had formed, by 4. 4 b. y. a. Stromatolites the oldest known fossils rock-like structures formed by mucilage-secreting marine bacteria (prokaryotes: photo: shark bay, western australia still actively growing (~3,000 yrs old) Stromatolites form when layers fossilize: oldest known stromatolites = 3. 5 billion years. Life originated very soon after liquid water became available. Earth"s early atmosphere: contained no oxygen, did contain water vapour, ammonia (nh3), methane (ch4), hydrogen (h2), carbon dioxide (co2) and carbon monoxide (co), oldest evidence of atmospheric oxygen (o2) = 2. 7 billion-year-old sedimentary rocks containing iron oxides. Photosynthesis ability to make organic molecules from carbon dioxide, using energy from sunlight: photosynthesis originated in prokaryotes > 3 billion years ago, blue-green algae, aka cyanobacteria: probably the first photosynthetic cells. Still exist today, alongside more recently-evolved plants and algae (= eukaryotes that do photosynthesis: oxygen content of the atmosphere increased slowly from 2. 7 to 2. 2 billion years ago.
