Ch 25 - The history of life on earth (1 slide per page)-2

Abundance bias abundant widespread longer occurring

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Unformatted text preview: as - Abundant, widespread, longer occurring 20 But despite these challenges A LOT has been learned from fossils Origin of mammals Figure 25.6 (Campbell 9th ed) 21 7 Key Events in Life’s History Phanerozoic Eon 1. Origin of Earth 2. Origin of life 3. Atmospheric O2 4. Eukaryotes Hadean Eon 5. Multicellularity 6. Animal diversification 7. Colonization of land Figure 25.7 (Campbell 8th ed) 22 Key Events: 1. Origin of Earth • Planets gradually increased in size • larger size = > gravity = even larger size http://lasp.colorado.edu/education/outerplanets/solsys_planets.php http://www.physci.wsc.ma.edu/young/hgeol/geoinfo/timeline/formation/formation.html 23 23 Phanerozoic Eon 1. Origin of earth How do we know earth formed ~4.6 bya? Oldest rocks on earth Hadean Eon Figure 26.10 (Campbell 7th ed) Issua Greenland: 3.8 BYA 24 24 Phanerozoic Eon 1. Origin of earth How do we know earth formed ~4.6 bya? Oldest material on earth Zircon: mineral from Australia: 4.4 BYA Figure 26.10 (Campbell 7th ed) Dated by oxygen isotope ratios 25 Key Events: 1. Origin of Earth • Early atmosphere: • H2O vapor • Volcanic gases • CO2, N2, NH3, CH4, H2, H2S • but no O2 or ozone (O3) • Bombardment slowed • Earth’s crust cooled • H2O condensed & oceans formed 26 26 Key Events: 2. Origin of life When did life begin? Formation of the first cells ~3.5 BYA 1st cells appeared in fossil record (first record of life) But maybe earlier... 27 Prokaryotes • Single-celled organisms w/o a membranous nucleus and few or no other organelles • Comprise 2 of the 3 groupings of life (Domains) Fig...
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