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Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition Solomon • Berg • Martin
Chapter 20
The Origin and The Origin and Evolutionary HistoryEvolutionary History
of Lifeof Life
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Conditions on early Earth• Age of Earth is ~4.6 billion years
• Atmosphere had little free O2
–Included CO2, H2O, CO, H2, N2
–Maybe also NH3, H2S, CH4
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Requirements for chemical evolution to produce life• Absence of oxygen
• Energy
• Chemical building blocks
• Sufficient time
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Prebiotic soup hypothesis• Molecules formed near the
Earth’s surface
• Sugars, nucleotides, amino acids formed spontaneously
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Miller-Urey experiment
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Iron-sulfur world hypothesis• Organic molecules formed at
hydrothermal vents on the ocean floor
• Laboratory simulations show catalyst effects of iron and nickel sulfides
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Origin of cells• Spontaneous assembly of small
organic molecules into macromolecules
• Protobionts similar to cells–Binary fission
–Homeostasis
–Catalytic activity
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Microspheres – a type of protobiont
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Microspheres• Formed from water and
polypeptides
• Electric gradient on surface
• Selective permeability
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• RNA world• Self-replicating RNA molecules
• Function as both enzyme and substrate for replication–Ribozyme is enzymatic RNA
• First step in evolution of theDNA / RNA / protein system
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Directed evolution• Large pool of RNA molecules
with different sequences• Selected for ability to catalyze a
reaction• Amplify / mutate / repeat
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Directed evolution
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• In the RNA world, ribozymes catalyzed protein synthesis
• DNA formed from double strands of RNA
• DNA more stable than RNA
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• The first cells• Heterotrophs that feed on organic
molecules• Anaerobic fermentation process
to obtain energy
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Autotrophs• Selected after organic molecule
food stock became scarce• Photosynthetic production of
organic molecules• Cyanobacteria split water
molecules and released oxygen
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Aerobes• More efficient energy production
using oxygen respiration• Significant oxygen in the
atmosphere by 2 bya
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Formation of the ozone layer• Ultraviolet radiation forms O3 from
O2 in the upper atmosphere
• Prevents UV from reaching Earth• Decreased mutagenesis• Enabled organisms to live in
surface waters and on land
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Ozone formation
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Eukaryotes arose from prokaryotes• Endosymbiont theory
–Mitochondria and chloroplasts derived from prokaryotes
–Ingested but not digested
–Reproduced along with host cell
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Endosymbiont theory
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Geological eras• Paleozoic
–543 mya - 251 mya
• Mesozoic–251 mya - 65 mya
• Cenozoic–65 mya - present
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Using a clock to represent biological time
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Precambrian time• Before 543 mya• Bacteria• Protists• Fungi• Simple multicellular animals
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Cambrian explosion• All animal phyla established• Many new body plans• Bizarre, extinct phyla
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Ordovician period• Shallow seas covered land• Cephalopods• Coral reefs• Jawless fishes
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Silurian period• Jawed fishes• Terrestrial plants• Air-breathing animals
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Devonian period• Bony fishes• Amphibians• Wingless insects• All major plant groups except for
flowering plants established
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Carboniferous period• Swamp forests• Reptiles• Winged insects
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Carboniferous forest
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Permian period• Therapsids
–Reptilian ancestors of mammals
• Seed plants dominant• Ended the Paleozoic with the
greatest mass extinction–90% of marine species–70% of land vertebrates
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Mesozoic Era
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Triassic period• Thecodonts
–Ancestors of dinosaurs and birds
• Pleiosaurs and ichthyosaurs
• Pterodonts• First mammals
–Small insectivores
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Jurassic and Cretaceous periods• Saurischians
–Ancestors of lizards
• Ornithischians–Ancestors of birds
• Ended with mass extinction caused by a meteorite impact
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Saurischians
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Ornithischians
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
Cenozoic Era
Copyright © 2005 Brooks/Cole — Thomson Learning
Biology, Seventh Edition CHAPTER 20 The Origin and Evolutionary History of Life
• Tertiary period• Diversification of flowering plants,
birds, insects, mammals
• Quaternary period• Genus Homo
• Large mammals