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Evolution of Life on Earth Melissa Harker Slide 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. Slide 3 Slide 4 Slide 5 Primitive eukaryotes After protista, primitive worm-like creatures appeared Sponges, cnidaria appreared, trilobites-first arthropod Slide 6 Edicaran Fauna Similar to jellyfish, no hard parts to make good fossils 635-642 Ma Slide 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! Slide 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 Slide 9 Slide 10 Slide 11 Amphibians Evolved from a relative of the coelacanth Key structure to life on land is the amniotic egg that reptiles, birds, and mammals have Slide 12 Reptiles Turtles closest to crocodiles genetically Birds evolved from dinosaurs Slide 13 Mammals Did not evolve from birds, even though the first mammals laid eggs. They are a separate spin off Marsupials evolved before placentals Slide 14