Evolution of Life on Earth

1. Melissa Harker Evolution of Life on Earth

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.

5. 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 plants—they 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

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

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

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