Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 20
The Origin and
Evolutionary History
of 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 the
DNA / 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
Copyright © 2005 Brooks/Cole — Thomson Learning