1 2 3 4 Geologic time is a difficult concept to grasp. 12 hours Every hour = 375 million years 9:30 – 1st living cells 10:56 – end of Precambrian 11:33 – end of Paleozoic 11:56:56 – Homo sapiens appear 3 4

PRECAMBRIAN First 4.1 billion years (90% of Earth’s History) From Earth’s formation to Paleozoic era began approx. 4.1 billion years Autotrophic prokaryotes (cyanobacteria) enriched the atmosphere with oxygen Oceans filled with soft bodied organisms, algae, sponges, worms, jellyfish Ediacaran –added to geologic time scale in 2004 First new period added to the time scale since 1891

PALEOZOIC ERA Cambrian Explosion – time of rapid diversification where most ancestral animal groups emerged Life in oceans continues to evolve Fish (first vertebrates), simple land plants (mosses in moist envirnons. ) and insects appeared during the Ordovician and Silurian periods First tetrapods appeared during the Devonian Four legged creatures Amphibians (land, but return to water) Coelacanth – living fossils, ancestor of first tetrapods

Permian – last Period of the Paleozoic Carboniferous Period Ferns and evergreens Time of fossil fuel development Giant amphibians take to land By end of carboniferous period the first reptiles were roaming the forests Permian – last Period of the Paleozoic Reptiles, amphibians, insects spreading out, filling available niches Massive extinction event 96% species lost

Triassic and Jurassic Periods Mammals and Dinosaurs first appeared in late Triassic period Birds evolved circa middle Jurassic period

Cretaceous Flowering plants appear Dinosaur population peaks Meteorite ends the time of terrible lizards approx. 65 MYA Mass extinction K-T Boundary – layer of material between rocks of Mesozoic and Cenozoic period High levels of iridium – rare on Earth, common in meteorites

CENOZOIC ERA Mammals become dominant form of life on land After mass extinction at the end of the Mesozoic era mammals of all kind began to diversify into distinct groups Ice Age in Quaternary period Loss of many charismatic megafauna of the Pleistocene (climate and/or humans) Holocene – development of human civilization Anthropocene – time of human impact