Origins and History of Life

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Origins and History of Life
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Origin of Life

• Hypothesis of today inorganic molecules in
  Earths prebiotic oceans combined to produce
  organic molecules ? primitive cells.
• Spontaneous orgin
• Chemical evolution
• Extraterrestrial origin
• Divine Creation

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Time line

• 10 billion years sun, planets
• 4.6 bya solar system in place, earths crust
• Atmosphere formed by gravitational field
• Water vapor, nitrogen, carbon dioxide, hydrogen,
  methane, ammonia, hydrogen sulfide and carbon
  monoxide
• 3.5 bya prokaryotic cells

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A.I. Oparin, 1920s

• Russian biochemist
• Abiotic synthesis formation of simple monomers
  (AA, sugars) from inorganic molecules
• Use of energy sources (volcanoes, lightning)
• Primordial soup model

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Stanley Miller, 1953 Harold Urey

• Tested primordial soup hypothesis
• Produced organic molecules

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Polymers evolve

• Sidney Fox Protein first hypothesis
• AA polymerize when exposed to heat ?proteinoids ?
  microspheres (composed of proteins but have
  properties of a cell)
• Graham Cairns Smith Clay
• Helpful in causing polymerization of monomers to
  produce proteins and nucleic acids
• RNA-first hypothesis
• RNA can be both substrate and an enzyme, genetic
  material of viruses

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Protocell

• Before true cell
• Lipid-protein membrane (liposome), carries on
  energy metabolism
• Liposomes formed double layered bubbles when in
  water, may have provided lifes first boundary.
• Chemical evolution ? biological evolution
• Figure 19.4, p321

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History of Life

• Fossils remains and traces of past life
• Trails, footprints, bone, shell, teeth
• Paleontology discovering and studying of the
  fossil record
• Sedimentation weathering and erosion of rocks ?
  sediment ? stratum (layer in a stratigraphic
  sequence.

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Relative/absolute dating of fossils

• Relative dating strata of the same age contain
  fossils of the same organisms
• Absolute dating use radioactive dating
  techniques, gives actual date of fossil
• Uses half-life of radioactive isotope to stable
  element
• Use C14 isotope for things that contain organic
  matter

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Geological Timescale era, period, epoch Table
19.1

• Precambrian period 87 of time scale
• 4.6 bya 600 mya
• Photosynthesizing organisms, O2 in atmosphere
• 3.5 bya prokaryotes
• 2.7 ozone (oxygen enters)
• 2.2 eukaryotic
• 1.4 protists

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Paleozoic era

• 599 mya 251 mya
• Plants evolve on land all types evolve
• Invertebrates, fish, amphibians, reptiles
• 3 mass extinctions
• Carboniferous period great coal-forming forest

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Mesozoic

• Triassic, Jurassic and Cretaceous periods
• 251 mya 65.5 mya
• Flowering plants evolve
• First small mammals, Dinosaurs, birds, placental
  mammals, modern insects
• 2 mass extinctions, Dinosaurs 65 mya

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Cenozoic

• Tertiary period
• 65.5 mya 2 mya
• Flowering plants flourish
• Primates to early humans, hominids
• Mammal diversity, human evolution begins
• Quartenary period
• Present
• Modern humans, Homo sapien
• Human influence on plants

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Factors that influence evolution

• Continental drift continents are not fixed,
  their positions and positions of oceans have
  changed
• Permian period 1 land mass ? pangaea
• Divided into 2 large land masses
• Laurasia
• Gondwana
• Then split into continents we know today

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Plate tectonics

• Branch of geology
• Tectonics movement of earths crust
• Earths crust is fragmented into slab-like plates
  that float on a lower hot mantle layer

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Mass Extinctions

• Disappearance of a large number of species or
  higher taxonomic groups with an interval of just
  a few million years
• At least 5
• May be due to
• climate changes
• Continental drift
• Bolide asteroid that explodes and produces
  meteorites that fall to earth
• Found clay containing high levels of iridium,
  element found in asteroids