lesson 7: history of earth

• earth


  the ground
• geological timescale


  is the CALENDAR for events, eons - eras, periods, epochs and ages
• precambrian eon


  -longest and least understood

  -prokaryotes

  -oxygenation event
• phanerozoic eon

  -current geological era

  -macroscopic life forms
• paleozoic era


  age of ancient life
• cambrian period


  cambrian explosion
• ordovician period


  -marine life, development of first land plants

  -mass extinction (75.7% of marines)
• silurian period


  -land plants more widespread

  -first fish with jaws
• devonian period


  -age of fishes

  -massive extinction
• carboniferous period


  -formation of vast coal deposits

  -extensive swampy forests
• permian period


  -largest extinction event

  -continents fused to form supercontinent pangaea
• mesozoic era


  -age of reptiles

  -dinosaurs rose to dominance

  -pangaea began to break apart
• triassic period


  -first dinosaurs and mammals appeared

  -warm and dry weather

  -triassic-jurassic extinction event
• jurassic period


  -continued diversification of dinosaurs

  -weather becomes more humid

  -breakup of pangaea, more continents
• cretaceous period


  -appearances of well-known species

  -flowering plants began to dominate (anglosperms)

  -massive asteroid impact
• cenozoic era


  -age of mammals

  -evolutionary and environmental transformation
• paleogene epoch


  -climate was warm and tropical

  -rapid diversification of mammals
• eocene epoch


  mammals evolve into various forms
• oliogene epoch


  saw the emergence of grasslands and first modern families of mammals
• neogene period


  further environmental changes, shift toward cooler and drier climate
• miocene period


  -expansion of grassland

  -proliferation of apes
• pliocene epoch


  -significant implication for vegetarian and animal life

  -appearance of hominids
• quaternary period 


  -2.6M years to the present

  -emergence and evolution

  -extinction of many large vertebrates
• pleistocene epoch


  glaciation
• holocene epoch


  -characterized by warmer temperature

  -current period