BIOL 203 NOTEBOOK PART 2

BIOL 203 NOTEBOOK PART 2 - I . T h e Hi st or y of L if e...

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I. The History of Life on Earth a. Precambrian (540 million – 4.5 billion years ago) i. General Conditions 1. Coalescence of the Earth 2. Hostile 3. Considerable Bombardment 4. Origin of Continents and Supercontinents 5. Moon close to earth – tides of 1000 ft. 6. Atmosphere a. Originally lots of Carbon Dioxide, methane and ammonia b. Later mainly nitrogen c. Only later, oxygen d. Extensive Ice Ages 7. Available compounds of Early Earth a. Methane b. Ammonia c. Water d. Hydrogen Sulfide e. Carbon Dioxide/Monoxide f. Phosphate ii. Major events in life 1. Origin of Life ~ 4 billion years ago a. Origin of simple molecules b. Origin of Macromolecules c. Origin of Membranes i. Protobionts – aggregations of abiotically produced organic compounds in a lipid bilayer d. Origin of RNA i. Catalyzes reactions and is self-replicating ii. “RNA World Hypothesis” iii. DNA derived from RNA e. Origin of Metabolic Pathways i. Chemautotrophs – Sulfur and iron oxidizing bacteria f. First Life i. Protobiont -> Prokaryote ii. Unicellular iii. Mitotic Division/Asexual Development iv. Stromatolites (2.8-3.5 billion years ago) – First known living things (from fossils) 1. Films of cyanobacteria that trap sediment
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2. Origin of Photosynthesis (2.8 billion years ago) a. Use of H 2 O as a source of electrons b. Release of O 2 into atmosphere – the first Oxygen in the atmosphere i. Oxygen is toxic to anaerobic organisms ii. The “Oxygen Catastrophe” – a massive environmental change on the planet that caused mass extinction of anaerobic organisms 3. Origin of Complex Cells (2.1 billion years ago) a. Fusion of two or more cells b. Thought to have arisen once with subsequent incorporation of additional organelles c. Organelles and Bacteria/Algae i. Have similar size and morphology ii. Bounded by double-membrane: outer membrane originates as engulfing vesicle; inner membrane originates from membrane of original organism iii. Enzymes and inner membrane transport systems are similar iv. Division is similar (binary fission) v. Circular DNA vi. Similar protein synthesis machinery including rRNA and tRNAs vii. Phylogenetic analyses suggests relationship with bacteria/algae 4. Origin of Sex (1.2 BYA) a. Thought to have originated at a single time b. Originated and persisted because of benefits of sexual reproduction i. Helps spread advantageous traits ii. Helps remove or hide disadvantageous traits 5. Origin of Multicellular Life (580 MYA) a. Red Algae – b. Sex (production of alternative gametes) may have led to origin of multicellular life (combination of gametes from different individuals) i. Symbiotic Theory – Symbiosis of several species of unicellular life ii. Colonial Theory – Colonies of the same species of unicellular life iii. Cellularization Theory – A single cell may have developed multiple nuclei and internal membranization iv. Thought to have arisen many times (ancestors of plants, fungi, animals and others) Bangiomorpha pubescens
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iii. Ediacaran Period – 635-540 MYA
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BIOL 203 NOTEBOOK PART 2 - I . T h e Hi st or y of L if e...

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