Download Earth Systems 3209 Unit 2 student notes part 2 File

Earth Systems 3209: Unit 2 Notes Part 2
Personal Time Scale
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Earth Systems 3209: Unit 2 Notes Part 2
Geological Time Scale
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4 time units
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Eons
1.
2.
3.
4.
Hadean :
Arachean:
Proterozoic:
Phanerozoic
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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:
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2.
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combines first 3 eras
largest group of time
main organisms
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some simple life forms, mostly single celled
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some worms and simple plant like creature
Paleozoic:
main organisms
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invertebrates (age of invertebrates)
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jawless fish
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land plants
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fish with lungs
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amphibians
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sharks
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seed plants
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Earth Systems 3209: Unit 2 Notes Part 2
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final period was called the Permian
Permian - Triassic Boundary
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boundary between the Paleozoic and the Mesozoic eras
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major extinction which caused 96% of all species to become extinct
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this was due to "loss of habitat" and changing climate
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the formation of Pangaea caused oceans to close and massive elevation changes as mountains
formed
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this is the time period when trilobites, brachiopods, and a large number of other invertebrates
became extinct
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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:
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first period was Triassic
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main organisms
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reptiles (age of reptiles)
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flowering plants
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birds
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last period was the Cretaceous which marked another
major extinction
Cretaceous - Tertiary Boundary
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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
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Earth Systems 3209: Unit 2 Notes Part 2
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this led to a decrease in plant numbers which in turn caused an ecosystem collapse for many
species, particularly larger organisms
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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
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last period was Tertiary
current period is Quaternary
main organisms
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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
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depending on conditions, different life forms can become better adapted to becoming the dominant
form of life
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in the Precambrian era physical and chemical conditions limited the life that could exist
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low levels of oxygen, extreme temperatures, and UV levels limited the possibilities of life
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shifts in these conditions led to more complex forms in the Paleozoic era
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dominant forms in the Paleozoic tended to spend some or all of their lives in the water (fish,
invertebrates, and amphibians)
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land plants also thrived on land
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as ocean conditions changed and oxygen levels in the atmosphere increased, more complex life
developed including reptiles,birds, and flowering plants
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Earth Systems 3209: Unit 2 Notes Part 2
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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
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there are multiple types of fossils that form under slightly different conditions
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each type of fossilization is best suited to different types of organisms
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fossils are more than the preserved remains of organisms, they also include
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footprints
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burrows
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feces / coprolite
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stomach stones
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other less common parts (feathers, skin)
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in general, there are 3 conditions necessary for fossilization
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Types of Fossilization
Petrifaction by Replacement
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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
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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
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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
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an organism is trapped instantly in an oxygen free environment, stopping its decay
this can happen in ice, amber, or other similar conditions
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Earth Systems 3209: Unit 2 Notes Part 2
Imprints
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soft tissues fossils
very rare as burial has to occur almost instantly to preserve soft
tissue
can happen due to volcanic ash
Trace fossils
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anything that is not an organism, but comes from the presence of
the organism
includes:
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footprints
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burrows
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coprolite
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eggs
trace fossils can be used as indirect evidence to understand organisms
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