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Chapter 26: Origin of life
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Figure 26.2 Clock analogy for some key events in evolutionary history
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Unnumbered Figure (page 512) Evolutionary clock: Origin of life
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Unnumbered Figure (page 512) Evolutionary clock: Prokaryotes
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HISTORY OF LIFE Earth is 4.5 billion years old Oldest rock
Contains isotopes of carbon Oldest fossils 3.5 billion years old Stromatolites Banded domes of sedimentary rock Resemble layered mats of cyanobacteria today Probably photosynthetic but not the first life form
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Figure 26.0x Volcanic activity and lightning associated with the birth of the island of Surtsey near Iceland; terrestrial life began colonizing Surtsey soon after its birth
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Figure 26.1 Some major episodes in the history of life
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Figure 26.3 Early (left) and modern (right) prokaryotes
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Figure 26.4 Bacterial mats and stromatolites
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Figure 26.3x1 Spheroidal Gunflint Microfossils
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Figure 26.3x2 Filamentous cyanobacteria from the Bitter Springs Chert
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ONE HYPOTHESIS SCENARIO Abiotic synthesis of organic monomers
CONDITIONS ON EARTH Atmosphere had little O2 Intense Lightning Volcanic activity Meteorite bombardment UV radiation SCENARIO Abiotic synthesis of organic monomers Abiotic synthesis of polymers Formation of protobionts Origin of hereditary material
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OPARIN & HALDANE 1920s Worked independently Postulated
Conditions on primitive Earth favored abiotic synthesis of organic material Atmosphere Contained less O2 Less oxidizing than today’s More reducing than today’s
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MILLER & UREY 1953 Tested Oparin & Haldane hypothesis
Created early Earth conditions in lab Atmosphere: H2O, H2, CH4, NH3 Added spark Created organic material Other labs have created All 20 AA Some sugars & lipids Purine & pyrimidine bases ATP
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Figure 26.10 The Miller-Urey experiment
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ABIOTIC SYNTHESIS OF POLYMERS
Example: connecting amino acids (AA) together to form proteins Occurred without enzymes Evidence Synthesis of protenoids Drip of sol’n of AA on hot sand or clay AA bonded together to form protein Zn and Fe ions act as catalysts
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FORMATION OF PROTOBIONTS
Aggregates of abiotically produced molecules with an internal environment different from external First primitive “cells” Evidence Coacervates Proteinoids Microspheres Liposomes
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ORIGIN OF HEREDITY Genetic information made it possible to pass along information for making new molecules Today: DNA RNAProtein Originally: RNA protein Support RNA acts as enzyme (ribozymes) Synthesized short segments of RNA in lab; replicate short segments of RNA without enzymes
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Figure 26.11 Abiotic replication of RNA
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Figure 26.13 Hypothesis for the beginnings of molecular cooperation
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MAJOR LINEAGES OF LIFE 5 Kingdoms Monera Protista Plantae Fungi
Animalia Domains Bacteria Archaea Eukarya 5 proposed protist kingdoms!!! Kingdom Plantae Kingdom Fungi Kingdom Animalia
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Figure 26.15 Whittaker’s five-kingdom system
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Figure 26.16 Our changing view of biological diversity
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