Introduction THREE PARTS: • PART I: Volcanoes • PART II: Single-Celled Plants • Part III: Multi-Celled Plants
4.6 billion years ago Formation of Earth
4.5 billion years ago Accretion of Earth Formation of the Moon
Part I Volcanoes
4.2 billion years ago Early Atmosphere No Life! Volcanoes add carbon dioxide, ammonia, water vapor and methane to the atmosphere.
3.8 billion years ago Earth Cools to Below 100 deg. C Liquid Water Present Early Oceans Form
Part II Multi-Celled Plants
3.8 billion years ago Earth Cools to Below 100 deg. C First Bacteria (Prokaryotic)
3.5 billion years ago Photosynthesis Produces Oxygen! Stromatolites Carbon is locked up in sedimentary rocks.
Stromatolites Formed by colonies cyanobacteria. At least 3.5 billion years old. Carbon is stored in stromatolites. Fact: Chloroplasts are actually cyanobacteria living in plant cells!
0.5 to 3.5 billion years ago Stromatolites, colonies of cyanobacteria, are alive in Australia today. Shark Bay, Australia
2.1 billion years ago Photosynthesis Produces Oxygen! Oxygen + Ammonia = NITROGEN!
2-3 billion years ago: Little free oxygen Commonly occur in sedimentary rocks 2-3 billion years old. Alternating dark bands (containing FeO) and light bands of chert (silica and Fe2O3). Occur from the deposition of alternately dissolved FeO & chert. “Bands” occur from fluctuating densities of bacteria in an ocean. When bacteria blossoms, it creates oxygen and thus chert, which falls to the ocean floor. An oxygen depletion allows for FeO. Banded iron formation
2 billion years ago Beginning of Oxygenated Atmosphere First Pollution Crisis! Redbeds Evidence of significant free oxygen
History of Atmospheric Oxygen The presence of FeS2 and UO2 set upper limits because oxygen would have produced other oxides from U and Fe From Lunine 1999 based on Kastings (1991)
Red beds Occur earlier than 2 billion years ago. Form when iron is weathered out of rock in the presence of oxygen.
1.7 billion years ago Single-celled Eukaryotes Appear Cells get a nucleus! Still Present:
Part III Multi-Celled Plants
1.2 billion years ago Multi-celled Plants Appear Photosynthesis adds more ___???___. Decaying plants add more NITROGEN.
1.2 billion years ago Multi-celled Plants Appear Photosynthesis adds more OXYGEN. Decaying plants add more NITROGEN.
0.65 billion years ago to NOW Humans did not appear until 5 million years ago! Still Present:
Summary • PART I: Volcanoes add carbon dioxide, ammonia, methane, and water vapour to the atmosphere. • PART II: Single-celled plants begin to photosynthesize which decreases the amount of carbon dioxide and increases the amount of oxygen in the atmosphere. The oxygen reacts with ammonia from volcanoes to add nitrogen to the atmosphere. • PART III: Multi-celled plants evolved which adds even more oxygen to the atmosphere. More nitrogen is added as plants decay and are consumed by denitrifying bacteria.
Review Questions • Millions of years ago, the atmosphere contained the following gases: • Ammonia, carbon dioxide, methane, nitrogen, oxygen and water vapor. • Which of these gases has increased? • Which of these gases has decreased?
Review Questions • Does photosynthesis increase or decrease the amount of oxygen in the atmosphere? • WHY? • Does photosynthesis increase or decrease the amount of carbon dioxide in the atmosphere? • WHY?
Review Questions • How did volcanoes change the atmosphere? • How did single-celled plants change the atmosphere? • How do multi-celled plants change the atmosphere?
To think about… • How is the composition of the atmosphere changing today?
Picture Sources http://rainbow.ldeo.columbia.edu/courses/v1001/7.html http://www.geol.umd.edu/~kaufman/ppt/chapter3/sld019.htm http://www.uta.edu/geology/geol1425earth_system/images/gaia_chapter_11/ArcheanLandscape.jpg http://www.uta.edu/geology/geol1425earth_system/1425chap11.html http://www.geol.umd.edu/~kaufman/ppt/chapter3/sld019.htm http://www.exhibits.lsa.umich.edu/Exhibits/Anthropology/Diaramas/Nat.Am./Copper/Copper.html http://www.novaspace.com/LTD/TUCC/PIX/Atmo.jpeg http://www2.jpl.nasa.gov/files/images/browse/p46022bc.gif http://www.gsfc.nasa.gov/gsfc/earth/pictures/pinatubo/atmosphere%20after.jpg http://commons.wikimedia.org/wiki/Image:Air_composition_pie_chart.JPG http://www.photolib.noaa.gov/sanctuary/images/big/sanc0001.jpg
Information Sources • http://www.udayton.edu/~INSS/ThemeEvol/EvolTimeline.HSM.ppt • http://www.lpl.arizona.edu/undergrad/classes/spring2006/Griffith_102-13/LectureNotes/L36-Evolution-Life.ppt • http://thurmanscience.tripod.com • http://www.olduniverse.com/1,2.htm