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August 27th, 2008


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08:34 am - BIO
Scientific Mehod
Origin of Life 
How did life on earth begin?
Early atmosphere
-no oxygen
How did we go from molecules o cells?
Liller-Urey experiemnt: teting: "Primordial
Generation of simple biological molecules:
-amino acids
-purines
-pyrimidines

What is nessicary to SYNTHESIZE life?
1. membrane: to keep bad molecules out, good in, cell multiply
2. genetic system: control cells functions, allow to mutate and adapt to environ

DNA
2 strandsa
nucleic acids A,C,G,T
must be transcribed then translated before proteins made
requires enzyme to catalyze reaction

History of Life on Earth
how the earth has changed over time:
1. change in atmosphere
2.change in climate
3.change in lansmass
Atmosphere
oxygen level increased as result of photosynthesis
Stromatolites are composed of oxygen-creating bacteria and are abundantly preserved in fossil records
Change in climate
climmate shift from hot/humid to cold/dry
cause of climate change: catastrophic event i.e meterors; geologic factors i.e. reflectivity of earths surface; biologic acivity i.e evolution of shelled animals; human activity i.e. CO2 production, greenhouse effect
Change in land masses
Plate tectonics
earths crust consists of plates
plates float on liquid magma
convection current move the plates
continental drift is caused by the movement of tectonic plates

Evolutionary record is major source of info  on lifes history
Fossil: any preserved remnant or impression from an organsm
Radimetric dating: absolute ages of strate are extimated using isotope decay

Geologic Time
earth formed 4.5 bya
life on earth different eras and PERIODS. Each has own life forms, climate, etc
 Three great Faunas
Cambrian explosion
most of animal phyla appreaed 542 mya
anthropods, annelids, trilobites, eocrinoids
first appearance of wide-spread mineral seletons
incread complexity of interaction, predation
Paleozoic Oceans: echinoderms, cephalopods, crinoids
Mesozoic: TRIASSIC 251 mya
insects, gastropods, birds, fish w cartilage
Cenozoic: Age of mammals 65 mya
Big Five include:
1. end ordovician
2. late devonian
3. end permian
4. end triassic
5. end cretaceous













 

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