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Lecture 6

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University of Toronto Scarborough
Environmental Science
Nick Eyles

EESA06- LECTURE 6 Step 1: A Very Short History of Life on Earth:  Various steps of evolution of life on earth.  First one: The earliest Bacteria: 3.8 Ga  Age of Earth: 4.56  The earliest bacteria was not here at the beginning of earth..  ^ why not?? earth had lots of magma when it was formed.. so bacteria took a while to form  Life evolved around MORs  Bacteria could live in hot areas- magma How are fossils formed? - First one in slide 26 : nice shell, next one is a fossilized tree trunk: petrified wood, & idea of having to dig through rocks & sediments. - They are formed with the process of mineralization - For example: a snail that dies, the soft parts are eaten by bacteria, but you are left with the shell & overtime sediments bury the shell & it adds pressure on the snail shell  the sediments near to the bottom of the pile LITHIFY (turn into rock) & the little snail shell is affected by hot water that comes through the rock. - Water underground has stuff inside of it: silica, iron - Overtime the minerals replace the shell  a nice model of what the creature shell - It is difficult to keep a soft body - ^ Per mineralization - One of the first philosophers talked about the age of the earth was actually looking at fossils of creatures that were living in water but their bodies were on top of the great mountains. - How can we see fossils??  Those rocks were uplifted by tectonic forces - Ammonite: an organic gemstone..fancy mineral name: aragnite - It’s coloured by the chemical editions: Iron, Aluminum - All minerals are usually colored - Some fossils are like footprints in the sand & sometimes they get preserved: trace fossils (show evidence) - Study of trace fossils: ichnology - Trace fossils; creatures doing stuff to the sediments; changing the sediment; burrowing in. - Sedimentary geologist: sometimes the creatures destroy the upper sediments so geologists have to be careful - Sediments: common in carbonate or limestone rocks in Ontario; comes from the SEA LILY: made of a long stem & mop head… they live in shallow water & storms break up the bodies.. you usually find the broken up parts not the whole stem - the fossils tell us about the environments & they tell us what kind of creatures live there - Pale ecologists: study of ancient organisms & environments. - Crinoid: fancy name for sea lily - Fossil morphology: the way your body looks; hot climate-tall, cold climate-shorter - Stratigraphy: studying layers of rock - Fossils help us give us a relative age of rocks EESA06- LECTURE 6 - Geologic range: The span of time (NOT SPACE) in which something lives ;creatures come & go - Large geographic range but small geologic range is a GREAT FOSSIL (found in many places but didn`t exist for long) - William Smith: canal engineer; one of the first to figure out that fossils came from different time - The geologic time scale: the parts in blue ; it was created using fossils - KNOW THE PARTS IN BLUE: SLIDE 31 - Relative age: I`m older than you (but you don’t know the age) - Chart: geologic range: dots connected with lines – slide 32 - Index fossils - Trilobite fossils; molted like a snake - The pre Cambrian is truncated; squished into a small section Prokaryotes: Prokaryotes: some are photosynthetic; blue green algae (they don’t have a nucleus).. microscopic & only have ONE CELL - Earliest: Archaea- probably lived at MORs – lots of warmth - 3.8-2.0 years ago- only things existing - Know Eukaryotes!!!! - Hydrothermal vents- smokers - Hypothermal fites: live in really hot water.. greater than 100 degrees C.. no light down there.. get there light from Kemosynthesis - Th - Oldest cyanobacteria- 3.5 million years ago found in AUSTRALIA - Dubious - Stromatolites; greek for stoney carpet - They are on mounts- hills, layer of sticky bacteria & fine muds come & stick onto the hills. - Cynobacteria; lots of iron around but it wasn’t rusted bcuz there wasn’t oxygen - Eventually the iron on earth began to rust; banded iron formation (BIF) - We get 90% of iron from here- steel - Iron was coming out of the MORs- mafic rocks (iron, mg) Eukaryotes: - Developed 2.8 years ago - Protists - Reproduce sexually; allowed mutations - the first multicellular; metazoans - Ediacara- multicellular - NFLD- from Newfoundland - Step 2: Cambrian Explosion: 540 Million years old EESA06- LECTURE 6  Multicellular animals with shells  3800  earliest bacteria came  Next step was much later  540 million years ago  During Cambrian times; there was an explosion of life (NEW) (good thing) ; major time of evolution  Multicellular organisms- backbones  Why is the Cambrian so special?? The supercontinent: Rodinia was breaking up, lots of new shallow shore lines for creatures to inhabit, things were able to diversify  Tectonic stability;  Active margin: subduction, collision of 2 continental  Passive margin: dull  During the Cambrian, north America was surrounded by PASSIVE margins  The Burgess Shale: in BC  You don’t preserve soft body creatures; but these guys were living on the continental slopes so they did not get decomposed  Coredate: Pikaya Step 3: Diversification by the Paleozoic  Major divisions (look in the textbook)  Before the dinosaurs  Diversification; lots of life forming  Marine- lots of new families- about 160 families & by the end there were 530 (kingdom, phylum…)  Gastrophods- snails  More diverse habitats  By the end of the Paleozoic; Pangea was forming  Almost all the fossils we find are in limestone- made in coral reefs  Occasionally-in igneous rock  Pompay- people were fossilized Step 4: Role of Meteorites - The earth did not even have an atmosphere OR oceans - Because we had no atmosphere or a magnetic field, there was n
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