Transcript Melissa`s talk on the fossil record

Evolution of Life on Earth
Melissa Harker
Prokaryotes-first life form
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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.
Primitive eukaryotes
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After protista, primitive worm-like creatures
appeared
Sponges, cnidaria appreared, trilobites-first
arthropod
Edicaran Fauna
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Similar to jellyfish, no hard parts to make
good fossils
635-642 Ma
Cambrian explosion (540 Ma)
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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 plants—they
are an evolutionary dead end!
Primary Chordates
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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
Amphibians
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Evolved from a relative of the coelacanth
Key structure to life on land is the amniotic
egg that reptiles, birds, and mammals have
Reptiles
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Turtles closest to crocodiles genetically
Birds evolved from dinosaurs
Mammals
Did not evolve from birds, even though the first
mammals laid eggs.
They are a separate spin off
Marsupials evolved before placentals