Lecture 26 _March 14_ Bacteria _ Archaea

Lecture 26 _March 14_ Bacteria _ Archaea - Biology 171...

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3/11/11 1 Lecture 26: Monday March 14, 2011 Biology 171 What Happened in the Archaean Domain Archaea Domain Bacteria Diversity & Nutrition Ecological Roles Today’s Topics: Announcements Discussion: Cichlid Evolution & Speciation Text Reading: Chapter 28 (496-518) Archaea & Bacteria Why We Care • We are descended from an archaean ancestor • Bacteria oxygenated the earth and continue to act as significant sources of oxygenic photosynthesis • The nutrient cycles that sustain life are dependent upon bacteria & archaea • Many human pathogens are bacterial Nasty Bacteria Strep throat, meningitis Syphilis, lyme disease Staph infections, food poisoning, toxic shock syndrome, gonorrhea Universal Tree of Life based on DNA sequences for Ribosomal RNA
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3/11/11 2 The origin of life, the origin of photosynthesis, and the first oxygenic photosynthesis A Lot of Important Stuff Happened During the Archaean Earth’s Greatest Moments (Recap of Archaean) Life likely evolved quite quickly after the earth cooled (end of the Hadean, start of Archaean) We have the first unequivocal fossils (stromatolites) by 3.5 Billion YA Oxygenic photosynthesis (splitting of water and production of O 2 ) likely evolved with cyanobacteria O 2 first precipitated iron oxide in the oceans O 2 then entered the atmosphere about 2.4 billion years ago, oxidizing iron in the terrestrial environment We lived in a world of only bacteria & archaea for over 1.5 billion years after life evolved – all through the Archaean and into the Proterozoic Eukaryotes evolved around 2.1 billion YA, during the Proterozoic The origin of life, the origin of photosynthesis, and the first oxygenic photosynthesis A Lot of Important Stuff Happened During the Archaean Stromatolites are among the first fossilized organisms, and still occur in shallow salty bays Later, oxygenic photosynthesis by cyanobacteria liberated oxygen into the atmosphere, resulting in iron oxide deposits
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3/11/11 3 Fun Facts About Our Friends, The Bacteria & Archaea • Their collective biological mass (biomass) is at least ten times that of all eukaryotes • The number of bacteria in a single handful of fertile soil is greater than the number of people who have ever lived • They have been discovered in rocks 2 miles below Earth's surface So What Makes Bacteria & Archaea Different from Eukaryotes? • Bacteria & Archaea are mostly
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Lecture 26 _March 14_ Bacteria _ Archaea - Biology 171...

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