The History of Life

The Fossil Record Compares changes over time & different organisms Relative dating: estimate a fossil’s age compared with that of other fossils Radioactive dating: calculate age based on remaining amounts radioactive isotopes

Miller & Urey’s Experiment produced amino acids by passing sparks through a mixture of hydrogen, methane, ammonia, and water suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds present on a primitive earth.

Endosymbiotic Theory Eukaryotic cells arose from living communities formed by prokaryotic organisms. Mitochondria: prokaryotes used O2 to make ATP Chloroplasts: prokaryotes carried out photosynthesis

Evolution of Multicellular Life Precambrian: 90% of Earth’s history Simple anaerobic life photosynthetic forms - added oxygen Eukaryotes Life only existed in the seas

Evolution of Multicellular Life Paleozoic Era – diversity of marine life Devonian – vertebrates invaded land Mass Extinction – end of Paleozoic Plants & animals on land and in the sea 95% of ocean life disappeared Mesozoic Era Increasing dominance of dinosaurs Flowering plants Cenozoic Era Mammals on land, water, & air

Patterns of Evolution Extinction: 99% of all species that have ever lived are now extinct Convergent Evolution: unrelated organisms come to resemble one another Coevolution: 2 species evolve due to changes in each other over time