scientists have divided geologic history into 4 main parts:
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Eras of the Geologic Time Scale Scientists have divided the Earth’s history into 4 major parts: the Geologic Time scale. Scientists have divided geologic history into 4 main parts: Precambrian Time Paleozoic Era Mesozoic Era Cenozoic Era. Precambrian Time. - PowerPoint PPT PresentationTRANSCRIPT
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ERAS OF THE GEOLOGIC TIME SCALE
SCIENTISTS HAVE DIVIDED THE EARTH’S HISTORY INTO 4 MAJOR PARTS:
THE GEOLOGIC TIME SCALE
Scientists have divided geologic history into 4 main parts:
Precambrian TimePaleozoic EraMesozoic EraCenozoic Era
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Precambrian Time 4.6 billion – 543 million years ago
Life began during this time Atmosphere made of water vapor, CO2 & N2 Volcanic eruptions,
meteorites, violent storms & intense solar radiation
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Origin of Life?• Extraterrestrial
• Life came from outside the planet(i.e. meteor)• Creation
• Divine forces created life• Non-Living Matter
• Spontaneous assembly of molecules
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4 billion years ago - Earth began to cool
Water condensed and fell as rain
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Atmosphere of early Earth Hydrogen (H2) Volcanic gas
(i.e. methane (CH4), ammonia (NH3), CO, SO2, N2, CO2)
No free oxygen or ozone
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Energy stimulated chemical reactions
=ProteinsNucleic AcidsLipidsCarbohydrates
UV+
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How Did Life Begin? In the oceans Energy from radiation
and storms caused simple chemicals in the oceans & atmosphere to react
More complex molecules were made Molecules joined to form cells Prokaryotes: single-celled organisms
(without a nucleus) that did not need O2 to survive
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Photosynthesis & Oxygen Cyanobacteria (type of prokaryotic
organism) appears over 3 bya Uses sunlight to produce food
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Photosynthesis & Oxygen Oxygen gas is released into oceans & air Oxygen molecules react to form Ozone,
which absorbs harmful radiation form the sun
Now possible for life to exist on Earth’s surface
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Photosynthesis & Oxygen VOCs
Volatile organic compounds NOx
Nitrogen-oxygen compounds
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Multicellular Organisms Eukaryotes appear in the fossil record
Organism that contain a nucleus Will evolve into organisms composed of many
cells
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Paleozoic Era (543 – 248 mya) “Old life” or “Ancient life” Large fossil record
Sponges, coral, squid, clams, trilobites, fish, sharks
Reptiles, amphibians, fish, worms, & ferns first appear
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Paleozoic Era – Life on Land
Plants, fungi, & air-breathing animals slowly colonized land Crawling insects first animals to live on land Reptiles & winged insects appear near the end
of era LARGEST Mass extinction marks end of
era 90% of species extinct Oceans completely changed
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Mesozoic Era (248 – 65 mya)
“Middle Life” or “Age of Reptiles” Dinosaurs dominate Earth for 150 million
yrs First birds appear Conifers appear Flowering plants appear late in era
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End of Mesozoic Era Mass Extinction
Dinosaurs Many other plant & animal species Meteorite hit Earth
Dust, smoke, fires Temperatures dropped
for many years
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Cenozoic Era (65 mya – today)
“Recent Life” or “Age of Mammals” Many mammals, birds, insects &
flowering plants Saber-toothed cats,
camels, small horses
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Cenozoic Era Today Era we are currently living in Climate changed many times during era
Periods of ice ages Animals migrate, adapt, or become extinct