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Evolution of Life on Earth

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Evolution of Life on Earth. Melissa Harker. Prokaryotes-first life form. We are closer to archaea than ... 3.8 billion years ago bacteria emerged, then ... – PowerPoint PPT presentation

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Title: Evolution of Life on Earth


1
Evolution of Life on Earth
  • Melissa Harker

2
Prokaryotes-first life form
  • We are closer to archaea than prokaryota (16s
    rRNA)
  • 3.8 billion years ago bacteria emerged, then
    oxygen-producing bacteria
  • Stromatolites and cyanobacteria evolved later
  • After 2.5 bya, increase in oxygen changed life
    forms...algae, etc.

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Primitive eukaryotes
  • After protista, primitive worm-like creatures
    appeared
  • Sponges, cnidaria appreared, trilobites-first
    arthropod

6
Edicaran Fauna
  • Similar to jellyfish, no hard parts to make good
    fossils
  • 635-642 Ma

7
Cambrian explosion (540 Ma)
  • A result of the rise of oxygen?
  • Chordates (will explain later)
  • Most organisms from this period, trilobites, etc.
    died off
  • First vascular plants from algae, then ferns,
    then seed plants, gymnosperms, finally
    angiosperms
  • Ferns do not evolve into seed plantsthey are an
    evolutionary dead end!

8
Primary Chordates
  • Jawless fish-most primitive
  • Hagfish have no backbone, lampreys do
  • Lungfish actually were not well-adapted,
    advanced fish
  • The Coelacanth is not the ancestor of amphibians

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Amphibians
  • Evolved from a relative of the coelacanth
  • Key structure to life on land is the amniotic egg
    that reptiles, birds, and mammals have

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Reptiles
  • Turtles closest to crocodiles genetically
  • Birds evolved from dinosaurs

13
Mammals
  • Did not evolve from birds, even though the first
    mammals laid eggs.
  • They are a separate spin off
  • Marsupials evolved before placentals

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