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AST 301:Lecture 24 Study Guide
oxygen is very
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reactive
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four billion years ago, earth did not have
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oxygen
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three billion years ago,
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stromalite bacteria colonies began to manufacture our oxygen atmosphere
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two billion years ago,
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the origin of nucleated cells (eukaryotes) was a big step in the development of ife
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one billion years ago,
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so was the development of multicellular life
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550 million years ago,
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biological "big bang" - sudden explosion in the diversity and complexity of multicellular life
oxygen reached present levels
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235-65 million years ago,
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age of dinosaurs lasted 170 million years, well adapted
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there is now strong evidence that dinosaurs were killed off in a mass extinction caused by the
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"KT asteroid impact", 65million years ago
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KT impact
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injected huge amounts of gas/dust into air, making thick clouds, "nuclear winter", much life was directly killed but most starved to death when planets froze
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KT boundary, in rocks
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tertiary period:no more dinosaurs; mammals are ascending
gray clay:rich in iridium deposited by meteorite impact that killed the dinosaurs
cretaceous period:limestone of the age of dinosaurs
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for most of earth's history, life consisted of simple bacteria called ____ they manufactured the present oxygen into our atmosphere via photosynthesis
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stromalites
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intelligence is a very recent development
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TRUE
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mass extinction have occurred ___ times in the past 500 million years
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5
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life is ....
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self-sustained chemical system capable of reproduction and Darwinian evolution, extracts energy from surroundings to modify itself and its surroundings to create offspring, evolve
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life is made out of the most
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abundant ingredients possible (hydrogen, carbon, oxygen, nitrogen) not helium cause it can escape atmosphere
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miller-urey experiment demonstrated that
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complicated organic materials could form naturally on the primitive earth through the action of energy sources like lightning on an original atmosphere, experiment duplicated these conditions and made "primordial soup" containing amino acids
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earth's primordial atmosphere contained
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methane, water, ammonia
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for organic compounds in primordial soup to interact, ____ was necessary
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concentration
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an efficient way to concentrate organics is
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foaming
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earth's surface is enormous, lots of time available, molecular experiments are fast
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reasons why these chemicals could make life
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scientists have manufactured polio from scratch why is this important?
where do we think life started?
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the deep ocean b/c it is safe from asteroid impact
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amino acids are the
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building blocks of life
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the blue print of life on Earth, the genetic code thats tells offspring how to grow is contained in
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DNA
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protolife did not at any stage have to make a huge evolutionary leap to change from _____ ____ to ___ ___
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organic materials, living beings
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why do scientists believe life developed on many planets?
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life is made out of most abundant things in universe, organic materials common in solar system, life originated very early in earth's history (life forms easily), life is very robust (live in many diff. parts)
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