The History of Life on Earth

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The History of Life on Earth

• AP Chapter 25

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Figure 26.0 A painting of early Earth showing
volcanic activity and photosynthetic prokaryotes
in dense mats
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Overview Lost Worlds

• Past organisms were very different from those now
  alive
• The fossil record shows macroevolutionary changes
  over large time scales including
• The emergence of terrestrial vertebrates
• The origin of photosynthesis
• Long-term impacts of mass extinctions

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Fig. 25-1
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Fig 25-UN1
Cryolophosaurus
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The Age of the Earth

• 4.6 billion years

What is the age of the universe?
13 billion years
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• How did life start on earth?
• How did organic molecules originate?

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What are the characteristics of life?

• What molecules or assemblies of molecules were
  necessary to create life?
• Where did they come from?
• How did they interact?
• When did life first emerge from inanimate matter?

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Life

• NASAs definition
• Life is a self-sustained chemical system
  capable of undergoing Darwinian Evolution.
  Gerald Joyce 1994

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Two essential properties

• Any life form has to make copies of itself
• Use chemicals in the environment to sustain its
  growth (metabolism)

Which of these two properties occurred first
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Two hypotheses

• Metabolism-First (Iron-Sulfur World Hypothesis)
• Replication First (Gene-First or RNA World
  Hypothesis

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Case Study

• Which came first metabolism or replication?
• Are hypotheses about these occurrences valid?

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First Metabolism?

• Iron, sulfur hypothesis
• Iron,sulfur catalysts found near deep
  hydrothermal vents could form catalysts to
  produce organic molecules
• Like a reverse Krebs Cycle
• Also Fe-S could form bubble-like membranes

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First replicating molecule

• RNA
• Why capable of copying itself using ribozymes
  enzyme-like RNA catalysts
• DNA would have replaced RNA as a better storage
  molecule, more stable.

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Abiotic replication of RNA
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Metabolism first problems?

• Not much experimentation about
• Takes too long
• Too high temperature for reactions to take place
• Iron catalysis of CO2 cannot produce organic
  molecules

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RNA first problems?

• Out of all the nucleotides, why just those four?
• RNA not stable
• Ribozymes can only make short polymers
• Copied RNA not exact copy since single-stranded

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Steps to enclosure

• Some type of boundary had to be established
• Lipids
• Or metals replaced by lipids
• ????????????????????????????????

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Early forms of life
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Models of early life forms
Coacervates isolated by Oparin, spherical
precells made from mixtures of carbohydrates and
proteins
It was suggested by Oparin that coacervates may
have played a significant role in the evolution
of cells.
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• Protobionts collections of abiotically produced
  organic molecules surrounded by a membrane
  (Sidney Fox)
• Liposomes evidence of this possibililty
• capable of simple metabolism and reproduction

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Fig. 25-3
Glucose-phosphate
20 µm
Glucose-phosphate
Phosphatase
Starch
Amylase
Phosphate
Maltose
(a) Simple reproduction by liposomes
Maltose
(b) Simple metabolism
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3.9 billion years agoEarth cooled, first rocks

• Oceans formed, atmosphere contained nitrogen,
  CO2, methane CH4, ammonia NH3, and water vapor
• 1920s Oparin and Haldane hypothesized that under
  those conditions, organic molecules could be
  formed
• 1953 Miller and Urey performed an experiment and
  produced organic molecules

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Miller-Urey Experiment
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Was the early earth atmosphere reducing enough?
Reducing adding electrons Methane and
ammonia are able to do this but maybe not so many
of those molecules in the early
atmosphere. Maybe other areas than the
atmosphere
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Other ideas

• Submerged volcanoes, deep-sea vents

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Carbonaeceous chondrites found in meteorites
contain C compounds
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Amino acid polymers from dripping organic
monomers onto hot sand or clay
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All of these point to the possibility of an
abiotic synthesis of life.

• Life requires
• accurate replication and metabolism

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Case Study

• Which came first metabolism or replication?
• Are hypotheses about these occurrences valid?

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First Metabolism?

• Iron, sulfur hypothesis
• Iron,sulfur catalysts found near deep
  hydrothermal vents could form catalysts to
  produce organic molecules
• Like a reverse Krebs Cycle
• Also Fe-S could form bubble-like membranes

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First replicating molecule

• RNA
• Why capable of copying itself using ribozymes
  enzyme-like RNA catalysts
• DNA would have replaced RNA as a better storage
  molecule, more stable.

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Abiotic replication of RNA
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Early forms of life
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Models of early life forms
Coacervates isolated by Oparin, spherical
precells made from mixtures of carbohydrates and
proteins
It was suggested by Oparin that coacervates may
have played a significant role in the evolution
of cells.
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• Protobionts collections of abiotically produced
  organic molecules surrounded by a membrane
  (Sidney Fox)
• Liposomes evidence of this possibililty
• capable of simple metabolism and reproduction

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Fig. 25-3
Glucose-phosphate
20 µm
Glucose-phosphate
Phosphatase
Starch
Amylase
Phosphate
Maltose
(a) Simple reproduction by liposomes
Maltose
(b) Simple metabolism
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Clock analogy for some key events in evolutionary
history
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3.5 billion yearsFirst Single-Celled Organism

• Oldest known fossils are stromatolites, rocklike
  layers of prokaryotes and sediment.

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Early (left) and modern (right) prokaryotes
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2.7 billion years agoOxygen

• Evidence of oxygen accumulation from
  cyanobacteria in banded iron formations

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2.1 billion years agoeukaryotic cells

• Fossils of eukaryotic cells
• Mitochondria and chloroplasts may have originated
  as prokaryotes engulfed by other prokaryotes in
  endosymbiosis.
• In serial endosymbiosis, mitochondria probably
  evolved first

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Evidence for Endosymbiosis

• Mitochondria and plastids
• Can replicate
• Have their own circular DNA
• Similar size
• Same type proteins

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1.5 billion years agoMulticellular organisms

• Oldest known fossils are algae
• Severe ice ages (Snowball Earth)750 580 mya
  prevented diversity of eukaryotes for awhile

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535 525 Cambrian Explosion

• Great diversity of all types of eukaryotes

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500 myaMovement onto Land

• Evolved adaptations to live on land and prevent
  dehydration
• Plants and fungi colonized land together

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250 myaFormation of Pangaea

• Continental Drift destroyed and altered
  habitats, changed climates, created geographic
  isolation

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Paleozoic Era

• Began with life in the ancient seas
• New phyla due to Cambrian Explosion
• Life moves on land, dense forests, tetrapods
• Amphibians - dominant vertebrates

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Mesozoic Era

• During this time, many modern forms of plants,
  invertebrates, and fishes evolved.  On land,
  dinosaurs were the dominant animals, while the
  oceans were populated by large marine reptiles,
  and Pterosaurs ruled the air. 

Age of the Reptiles
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The Mesozoic Era came to an end with the K-T
Cretaceous Mass Extinction
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Cenozoic Era

• The demise of the dinosaurs led to the adaptive
  radiation of the mammals.

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Mass Extinctions!

• There have at least 5 mass extinctions.

http//www.youtube.com/watch?vFlUes_NPa6M
http//www.youtube.com/watch?vnqFbgkzOhRY
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Mass Extinction Event Time Frame Types of life Affected Extinction Rate Cause
  Late Ordivician     445 mya   Invertebrate marine organisms   57 marine genera Sea-level change due to shifting plate tectonics, gamma ray bursts  
  Late Devonian   370 mya   50 marine genera  
  Late Permian     250 mya Marine organisms, many land vertebrates, insects  
  Late Triassic   Marine organisms, large amphibians, many mammal-like reptiles and land animals     Sea-level changes, volcanism, climate change, break-up of Pangea  
  End Cretaceous/Tertiary KT extinction     65 mya   50genera, 75 species  
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Mass Extinction Event Time Frame Types of life Affected Extinction Rate Cause
  Late Ordivician     445 mya   Invertebrate marine organisms   57 marine genera Sea-level change due to shifting plate tectonics, gamma ray bursts  
  Late Devonian   370 mya Shallow marine organisms, Corals, spiders, scorpions, protoamphibians   50 marine genera Sea-level changes, climate changes due to plants taking in CO2 , global cooling  
  Late Permian     250 mya Marine organisms, many land vertebrates, insects  
  Late Triassic   Marine organisms, large amphibians, many mammal-like reptiles and land animals     Sea-level changes, volcanism, climate change, break-up of Pangea  
  End Cretaceous/Tertiary KT extinction     65 mya   50genera, 75 species  
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Mass Extinction Event Time Frame Types of life Affected Extinction Rate Cause
  Late Ordivician     445 mya   Invertebrate marine organisms   57 marine genera Sea-level change due to shifting plate tectonics, gamma ray bursts  
  Late Devonian   370 mya Shallow marine organisms, Corals, spiders, scorpions, protoamphibians   50 marine genera Sea-level changes, climate changes due to plants taking in CO2 , global cooling  
  Late Permian     250 mya Marine organisms, many land vertebrates, insects   83 marine genera 70 land species The Great Dying Climate change (rising global temp), eruption of volcanoes in Siberia, Formation of Pangea, Meteors, fluctuating O2 levels in the oceans
  Late Triassic   Marine organisms, large amphibians, many mammal-like reptiles and land animals     Sea-level changes, volcanism, climate change, break-up of Pangea  
  End Cretaceous/Tertiary KT extinction     65 mya   50genera, 75 species
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Mass Extinction Event Time Frame Types of life Affected Extinction Rate Cause
  Late Ordivician     445 mya   Invertebrate marine organisms   57 marine genera Sea-level change due to shifting plate tectonics, gamma ray bursts  
  Late Devonian   370 mya Shallow marine organisms, Corals, spiders, scorpions, protoamphibians   50 marine genera Sea-level changes, climate changes due to plants taking in CO2 , global cooling  
  Late Permian     250 mya Marine organisms, many land vertebrates, insects   83 marine genera 70 land species The Great Dying Climate change (rising global temp), eruption of volcanoes in Siberia, Formation of Pangea, Meteors, fluctuating O2 levels in the oceans
  Late Triassic   200 mya Marine organisms, large amphibians, many mammal-like reptiles and land animals     48 marine genera Sea-level changes, volcanism, climate change, break-up of Pangea  
  End Cretaceous/Tertiary KT extinction     65 mya   50genera, 75 species  
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Mass Extinction Event Time Frame Types of life Affected Extinction Rate Cause
  Late Ordivician     445 mya   Invertebrate marine organisms   57 marine genera Sea-level change due to shifting plate tectonics, gamma ray bursts  
  Late Devonian   370 mya Shallow marine organisms, Corals, spiders, scorpions, protoamphibians   50 marine genera Sea-level changes, climate changes due to plants taking in CO2 , global cooling  
  Late Permian     250 mya Marine organisms, many land vertebrates, insects   83 marine genera 70 land species The Great Dying Climate change (rising global temp), eruption of volcanoes in Siberia, Formation of Pangea, Meteors, fluctuating O2 levels in the oceans
  Late Triassic   200 mya Marine organisms, large amphibians, many mammal-like reptiles and land animals     48 marine genera Sea-level changes, volcanism, climate change, break-up of Pangea  
  End Cretaceous/Tertiary KT extinction     65 mya Reptiles, non-avian dinosaurs, marine organisms, Issued in the mammals   50genera, 75 species Asteroid (Mexico), Volcanism in India, climate change  
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Two biggest ones

• Permian 250 mya, over 90 of marine and
  terrestrial species disappeared maybe due to
  volcanoes, Pangeae, glaciation
• Cretaceous 65 mya ½ marine and many
  terrestrial forms, including dinosaurs due to
  environmental changes or asteroids hitting the
  earth

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• Mass extinctions provide many habitats and
  available niches to organisms that survive which
  leads to adaptive radiation.
• For ex, mammals did not change much until the
  after 65 mya and the extinction of the dinosaurs.
• It takes 5-20 million years for the diversity of
  life to recover after a mass extinction!

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Future.
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March 5, 2014

• A 30m-wide asteroid hurtled past the Earth at
  almost 33,000mph and came even closer than the
  Moon.

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