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Life Begins

A. Biogenesis

B. Fossil Dating

C. Abiogenesis

D. Where Did Life Begin?

E. The First Life-forms

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A. Biogenesis

1. Spontaneous generation wasonce believed to be theorigin of life

2. Francesco Redi discoveredthat maggots came from

eggs (biogenesis)_

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3. Lazzaro Spallanzani

a. showed that when air waskept out, microbes didnot grow

b. Some believed that the

air contained avital force_

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4. Louis Pasteur - showed thatair did not possess a vitalforce_

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B. Fossil Dating

1. Radioactive dating has beenused to find exact ages offossils

a. an isotopes half-life isthe time it takes for

half of the isotope todecay

b. Earth is shown to be 4.6billion years old

c. Formed as debris thatcircled the suncoalesced_Click

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1. Alexander Oparin BelievedEarths primitive atmospherecontained NH3, H2, H2O, andCH4

a. As Earth cooled, lightning

and ultraviolet radiationformed organiccompounds thatprecipitated into aPrimordial Soup

b. coacervates (small lipid-

like membranes) mayhave formed_

C.Abiogenesis

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2. Stanley Miller and HaroldUrey set up an experimentto test Oparins theory

a. formation of small organicmolecules including

amino acidsb. microspheres (small

protein membranes) maythen have formed asamino acids joined_

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3. Space Debris

a. organic molecules mayhave formed elsewherein the universe

b. these compounds may

have arrived onmeteors_

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D. Where Did Life Begin?

1. Many scientists believe thatdeep-sea hydrothermalvents may have been thelocation of lifes origin

a. CO2 in the atmosphere

may have interferedwith Miller-Ureyresults_

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1. RNA was probably the firstnucleic hereditary material

a. RNA molecules canself-replicate

b. RNA is necessary to

catalyze proteinsynthesis

c. Ribozymes RNAenzymes_

E. The First Life-forms

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2. Prokaryotes

a. Early prokaryotes wouldhave been anaerobicchemoheterotrophs

b. As organic material ran low,

anaerobicchemoautotrophs wouldhave followed

c. Photoautotrophs would havecome next(cyanobacteria)

d. Aerobic chemoheterotrophswould have followed_

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3. Eukaryotes

a. the inner folding of themembrane- nucleus & ER

b. engulfing of prokaryotes-mitochondrion

& chloroplast(endosymbiosis)_

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