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GEOLOGIC TIME
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Earth’s History Divided into 4 eras Era’s divided into Periods
Precambrian Paleozoic Mesozoic Cenozoic Era’s divided into Periods Periods divided into epochs
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PRECAMBRIAN ERA 4.6 BYA - 540 MYA Makes up 88% of Earth’s History
4,060,000,000 YEARS LONG! Makes up 88% of Earth’s History Longest era
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PRECAMBRIAN ERA Earth’s atmosphere contained:
Hydrogen cyanide Carbon dioxide Carbon monoxide Nitrogen Hydrogen Sulfide Water (gas) Notice: Oxygen was not a main component
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PRECAMBRIAN ERA 4 BYA Earth’s surface cooled enough for rocks to form
3.8 BYA Earth’s surface cooled even more, allowing water to remain in a liquid state Constant thunderstorms Oceans covered most of the Earth’s surface
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MILLER/UREY EXPERIMENT
Tried to answer how life first formed on Earth They simulated Earth’s atmosphere combined with lightening storms, which they found produced AMINO ACIDS! Amino acids are necessary for life Not accurate, but on the right track!
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MILLER/UREY EXPERIMENT
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PRECAMBRIAN ERA 3.5 BYA, unicellular prokaryotic organisms
Evolved in the absence of oxygen Over time, photosynthetic bacteria formed Remember oxygen is released during photosynthesis Accumulations of oxygen in the atmosphere caused it to turn blue and the ozone to form Protection from solar radiation Took several hundred million years to reach the oxygen levels we have today
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PRECAMBRIAN ERA Oxygen was a deadly poison to the first cells
With the increase of oxygen on Earth, many organisms died off, while other new ones formed. The new ones were able to process this oxygen and survive. Beginning of evolution!
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PRECAMBRIAN ERA Endosymbiotic Theory
2 BYA Prokaryotic cells began evolving internal cell membranes (early eukaryotes) Prokaryotes entered these early eukaryotes and lived inside of them! Mitochondria and chloroplasts are what used to be prokaryotic cells that could use oxygen and carry out photosynthesis who lived inside these early eukaryotes Mitochondria and chloroplasts today contain DNA similar to bacteria! EVIDENCE!
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PRECAMBRIAN ERA Sexual reproduction of eukaryotic cells occurs
Allows for genetic variation Faster than asexual reproduction by prokaryotes Multicellular eukaryotic organisms developed Simple aquatic plants Sponges Flatworms Jellyfish
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PRECAMBRIAN ERA IN A NUTSHELL
Began with no oxygen in the atmosphere, ended with oxygen in the atmosphere Life only in the oceans Anaerobic organisms formed, but many became extinct later when photosynthetic organisms evolved and produced oxygen (which was deadly to the anaerobic organisms). From this, aerobic organisms formed. Prokaryotes formed first, then eukaryotes Few fossils were found from this era Soft bodied, hard to form fossils
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PALEOZOIC ERA 540 MYA-245 MYA Made up of 7 Periods
295,000,000 YEARS LONG! Made up of 7 Periods
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PALEOZOIC ERA Lots of fossil evidence
Early in the era, there was a diversity of marine life Cambrian Explosion! Age of the Invertebrates Jellyfish, worms, sponges, brachiopods, trilobites
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PALEOZOIC ERA First vertebrates formed
Jawless fish Some arthropods moved to live on land Insects First land plants Ferns AGE OF THE FISHES-Devonian Period First amphibians, then reptiles
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PALEOZOIC ERA Ended with a mass extinction
Affected both land and sea organisms Many fish and reptiles survived Cause is unknown for the mass extinction Theory-volcanic explosions? Theory-global climate change?
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MESOZOIC ERA 245 MYA-66 MYA AGE OF THE REPTILES Made up of 3 Periods
179,000,000 YEARS LONG! AGE OF THE REPTILES Made up of 3 Periods
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MESOZOIC ERA Warm and Moist Environment Pangea formed near beginning
Drifted near the end Flowering Plants Evolved Organisms-lizards, turtles, crocodiles, snakes, birds DINOSAURS!!! Mammals first appeared
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MESOZOIC ERA Ended with another mass extinction!
½ of all the plants and animals died off ALL THE DINOSAURS BECAME EXTINCT Cause unknown Meteor?
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CENOZOIC ERA 66 MYA AGO-PRESENT Made up of 2 Periods
66,000,000 YEARS LONG AND COUNTING! Made up of 2 Periods Ice Age separates the two periods AGE OF THE MAMMALS
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CENOZOIC ERA Mammals that survived the extinction of the Mesozoic Era evolved adaptations that allowed them to live in various environments Land, water, air Organisms-dolphins, whales, cattle, deer, sheep 4.5 MYA is the earliest fossil of ancient human Ardipithecus ramidus 120,000 years ago-Homo sapiens Human Evolution took about 4,380,000 years!
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