Transcript 1.19.11
Learning Targets Define the Geologic Time Scale Distinguish between Eons, Eras, Periods, and Epochs Homework Ch. 21.1 L.T.s due on Thursday Syllabus due Friday Review for Quiz Friday Q.O.D. In your own words, define what the geologic time scale is Fossils and the Rock Record Geologic Time Scale Fossils are found in rocks These rocks help scientists interpret, or learn, about Earth’s history Fossils and their records are used to divide time into units All time units put together make up the GTS When was the GTS developed? GTS was established over 300 years ago It has been changed a little, but mainly remains the same The GTS and its units are based on FOSSILS and their PRESENCE IN ROCKS EONS Largest of all time units Precambrian- consists of Hadean, Archean, and Proterzoic Precambrian makes up 90% of all geologic time Earth was formed during this time Earth could support simple life Many fossils were simple, soft bodied animals 4.6 billion years ago - about 550 million years ago (formation of Earth) No life on land Fossil bacteria and algae Crust becomes solid Oxygen in atmosphere ERAS Second Largest Unit of Time Determined by LIFE/FOSSILS Named for the time period (Paleo)zoic= old life (Meso)zoic= middle life (Ceno)zoic= recent life -zoic mean life Periods Shorter than eras and eons Generally named for the region where the rocks where first observed Epochs Smallest divisions of time Rocks from the Cenozoic era are the best PRESERVED due to being the newest Fossils are less subjective to weathering and erosion Early life was very SIMPLE As time passed, life became more COMPLEX Fossils from this eon are ABUNDANT Phanerozoic means “visible life” About 550 mya - 250 mya Age of invertebrates Oceans full of different organisms Trilobites: first hard shelled life-forms Land plants appeared later, followed by animals Mass extinction- end of Paleozoic Era Largest extinction where 90% of marine organisms became extinct Broken down into 6 Periods 550 mya - 490 mya Cambrian explosion First great expansion of sea life Burgess Shale 490 mya- 440 mya Jawless fish First land plants Ends in mass extinction Hagfish 440 mya - 408 mya First jawed fish Insects like millipedes and centipedes First vascular plants on land Dunkleosteus 408 mya - 360 mya Age of Fish --> Fish and land plants become very diverse First sharks appear Non-winged insects move to land Tetrapods move to land near end Late Mass extinction 360 mya - 280 mya Can be split into Mississippian and Pennsylvanian periods First insects with wings First reptiles Cockroaches first appear Wide spread Coal Swamps 280 mya - 248 mya Age of Amphibians Continents merge into Pangea Largest ever extinction ends the Permian http://palaeo.gly.bris.ac.uk/Palaeofiles/Permian/PALIn tro.html 250 mya - 65 mya “Age of Dinosaurs” All different species thrived during this time, reptiles ruled ocean, large insects evolved Water dwelling amphibians adapted to land Mammals evolved and began to diversify Flowering plants and trees emerged 3 Time periods --> Triassic, Jurassic, Cretaceous 250 mya - 208 mya First dinosaurs, mammals, and crocodyloforms Ends with a mass extinction Extinction allows dinosaurs to fill niches and diversify 208 mya - 146 mya Lots of dinosaurs including sauropods First flowering plants 146 mya - 65 mya Dinosaurs rule the earth First crocodiles, ants, bees, snakes Feathered dinosaurs appear K/T mass extinction -no more dinosaurs 65 mya - ?????? “Age of the Mammals” Increased numbers and diversity Human ancestors appeared 2 First primates emerged in Paleocene Epoch Modern humans emerged in the Pleistocene Epoch time periods --> Tertiary and Quaternary 65 mya - 1.8 mya Mammals abound Primitive primates Horses, whales, pigs, deer Grasses common Megalodon 1.8 mya - ???? Ice Ages Large mammals like mammoths, mastadons, sabertooths, giant sloths First Homo sapiens