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Earth Systems 3209: Unit 2 Notes Part 2 Personal Time Scale 1 Earth Systems 3209: Unit 2 Notes Part 2 Geological Time Scale 4 time units Eons 1. 2. 3. 4. Hadean : Arachean: Proterozoic: Phanerozoic the first three eons are grouped together as the first era, the precambrian era the phanerozoic eon is broken into three eras Eras 1. Precambrian: 2. combines first 3 eras largest group of time main organisms some simple life forms, mostly single celled some worms and simple plant like creature Paleozoic: main organisms invertebrates (age of invertebrates) jawless fish land plants fish with lungs amphibians sharks seed plants 2 Earth Systems 3209: Unit 2 Notes Part 2 final period was called the Permian Permian - Triassic Boundary boundary between the Paleozoic and the Mesozoic eras major extinction which caused 96% of all species to become extinct this was due to "loss of habitat" and changing climate the formation of Pangaea caused oceans to close and massive elevation changes as mountains formed this is the time period when trilobites, brachiopods, and a large number of other invertebrates became extinct ocean acidification has also gained scientific support as well This is the greatest known extinction. Why is it not as publicly known as other extinction events? Eras (continued) 3. Mesozoic: first period was Triassic main organisms reptiles (age of reptiles) flowering plants birds last period was the Cretaceous which marked another major extinction Cretaceous - Tertiary Boundary boundary between the Mesozoic and the Cenozoic eras 75% of all species became extinct due to "disruption of climate" this disruption was most likely caused by meteor impact volcanic activity may have also played a factor dust and debris blocked sunlight for an extended time 3 Earth Systems 3209: Unit 2 Notes Part 2 this led to a decrease in plant numbers which in turn caused an ecosystem collapse for many species, particularly larger organisms most of our fossil record comes from this time What are two reasons that most of our fossils come from the Cretaceous - Tertiary boundary? Why is it misleading to say that an asteroid killed the dinosaurs? Eras (continued again) 4. Cenozoic: 65 MYA - now last period was Tertiary current period is Quaternary main organisms mammals (age of mammals) this era (Cenozoic) will continue until a major event occurs such as another mass extinction this period (Quaternary) could change due to a less major event such as a climate change event Evolution / Dominant Life Forms depending on conditions, different life forms can become better adapted to becoming the dominant form of life in the Precambrian era physical and chemical conditions limited the life that could exist low levels of oxygen, extreme temperatures, and UV levels limited the possibilities of life shifts in these conditions led to more complex forms in the Paleozoic era dominant forms in the Paleozoic tended to spend some or all of their lives in the water (fish, invertebrates, and amphibians) land plants also thrived on land as ocean conditions changed and oxygen levels in the atmosphere increased, more complex life developed including reptiles,birds, and flowering plants 4 Earth Systems 3209: Unit 2 Notes Part 2 mammals also developed in the Paleozoic, but were unable to develop a dominant status until larger predators removed at the beginning of the Cenozoic Fossils there are multiple types of fossils that form under slightly different conditions each type of fossilization is best suited to different types of organisms fossils are more than the preserved remains of organisms, they also include footprints burrows feces / coprolite stomach stones other less common parts (feathers, skin) in general, there are 3 conditions necessary for fossilization Types of Fossilization Petrifaction by Replacement the original material, mostly bones, of the organism are slowly replaced by minerals within groundwater depending on the fossil, petrifaction may even preserve internal details often preserves bones and trees Carbonization all of the non-carbon materials in the organism decay leaving behind a shiny black or brown carbon film in less extreme cases, a carbon shell may be created this is a common form of fossilization for plants and delicate animals Mold and Cast an organism is buried and leaves a hollow space in sediment after it decays (mold) over time, minerals fill this space forming 3D copy of the outside of the original organism Preserved Intact an organism is trapped instantly in an oxygen free environment, stopping its decay this can happen in ice, amber, or other similar conditions 5 Earth Systems 3209: Unit 2 Notes Part 2 Imprints soft tissues fossils very rare as burial has to occur almost instantly to preserve soft tissue can happen due to volcanic ash Trace fossils anything that is not an organism, but comes from the presence of the organism includes: footprints burrows coprolite eggs trace fossils can be used as indirect evidence to understand organisms 6