- Earth formed approximately 4.6 billion years ago with a harsh atmosphere of high heat, water vapor, volcanic activity, and no breathable oxygen. - Early theories on the origin of life included that it began extraterrestrially or through creationism, but the prevailing theory of chemical evolution suggests that organic compounds formed on the early Earth and combined to produce life. - The Miller-Urey experiment demonstrated that organic compounds like amino acids and nucleotides can form when basic gases like methane and ammonia are exposed to electric sparks simulating lightning, supporting chemical evolution as a viable theory for how life began.

2.  Earth is estimated to be about 4.6Earth is estimated to be about 4.6
billion years old.billion years old.
 Atmosphere was very harsh.Atmosphere was very harsh.

Very hot.Very hot.

Lot’s of water vapor in the atmosphere.Lot’s of water vapor in the atmosphere.

Volcanic activity.Volcanic activity.

No breathable oxygen gas (CarbonNo breathable oxygen gas (Carbon
dioxide, ammonia, hydrogen gas, weredioxide, ammonia, hydrogen gas, were
present).present).

3. Origin of Life…Origin of Life…
 Extraterrestrial TheoryExtraterrestrial Theory
 Creationism TheoryCreationism Theory
 Chemical EvolutionChemical Evolution
Organic CompoundsOrganic Compounds

4. The Origin of Life’s Chemicals…The Origin of Life’s Chemicals…
 All of life is composed of organicAll of life is composed of organic
compounds (nucleic acids, proteins,compounds (nucleic acids, proteins,
lipids, carbohydrates)lipids, carbohydrates)
 In order for life to form, these buildingIn order for life to form, these building
blocks had to be present.blocks had to be present.
 Charles Darwin said that life probablyCharles Darwin said that life probably
formed in a “warm little pond…”formed in a “warm little pond…”

5. The Origin of Life’s Chemicals…The Origin of Life’s Chemicals…
 Once earth began to cool, oceans beganOnce earth began to cool, oceans began
to form as water vapor condensed.to form as water vapor condensed.
 Question: Could organic compounds haveQuestion: Could organic compounds have
formed from material present on earlyformed from material present on early
earth?earth?

6. Origin of Life’s ChemicalsOrigin of Life’s Chemicals
 Miller-UreyMiller-Urey
 GoalGoal:: Recreated
atmosphere of
Early Earth
 ObjectiveObjective::
Can organic
compounds form?
 ResultsResults::
amino acids,
nucleotides, lipids,
carbohydrate
pieces

7. Fossils and Ancient LifeFossils and Ancient Life
 Paleontologists are scientists who studyPaleontologists are scientists who study
fossils.fossils.
 Fossil is any trace of an ancientFossil is any trace of an ancient
organism.organism.
 Ex) bones, feathers, footprints,Ex) bones, feathers, footprints,
impressions, etc.impressions, etc.

8. MicrofossilsMicrofossils
 Scientists had hardScientists had hard
time findingtime finding
evidence of firstevidence of first
lifelife
 Most ancient lifeMost ancient life
was microscopicwas microscopic
 StromatolitesStromatolites
 3.5 Billion years old3.5 Billion years old
 11stst
life on earthlife on earth
bacteria lived in seabacteria lived in sea

9. The Fossil RecordThe Fossil Record
 Fossils occur in a particular order.Fossils occur in a particular order.
 Certain fossils only occur in more recentCertain fossils only occur in more recent
rock.rock.

10. How do fossils form?How do fossils form?
 Not everythingNot everything
fossilizes.fossilizes.
 Certain conditions haveCertain conditions have
to be perfect forto be perfect for
fossilization to occur.fossilization to occur.
 For every organism thatFor every organism that
fossilizes, hundredsfossilizes, hundreds
more die without amore die without a
trace.trace.
 Most fossils are foundMost fossils are found
in “sedimentary” rock.in “sedimentary” rock.

11. Dating Fossils (Two methods)Dating Fossils (Two methods)
1.1. Relative DatingRelative Dating

Determining age ofDetermining age of
fossil based on howfossil based on how
deep it is buried.deep it is buried.

Placement is comparedPlacement is compared
with other fossils andwith other fossils and
age is determined.age is determined.

Oldest layers of rockOldest layers of rock
at the bottomat the bottom

Relative dating allowsRelative dating allows
you to compare ageyou to compare age
one fossil to the next,one fossil to the next,
but does not give anbut does not give an
exact age to theexact age to the
fossil.fossil.

12. Dating Fossils (two methods)Dating Fossils (two methods)
2.2. Radioactive DatingRadioactive Dating

Used to determine actual age of rockUsed to determine actual age of rock
(fossils).(fossils).

Requires knowledge of chemistry and “half-Requires knowledge of chemistry and “half-
life” of radioactive isotopes.life” of radioactive isotopes.

13. Road to Modern OrganismsRoad to Modern Organisms
 Scientists believe earliest life was foundScientists believe earliest life was found
in sea.in sea.
 11stst
life was unicellular, prokaryotic =life was unicellular, prokaryotic =
bacteriabacteria
 Photosynthesis changed Earth’sPhotosynthesis changed Earth’s
atmosphere released Oatmosphere released O22 - cyanobacteria- cyanobacteria
 Unicellular Eukaryotes – EndosymbioticUnicellular Eukaryotes – Endosymbiotic
TheoryTheory
 Multicellular organismsMulticellular organisms

14. Classification/EvolutionClassification/Evolution

15. Bacteria – unicellular,Bacteria – unicellular,
prokaryoticprokaryotic

16. Protista – eukaryoticProtista – eukaryotic

17. Fungi- multicellular, eukaryoticFungi- multicellular, eukaryotic

18. Animals- multicellular,Animals- multicellular,
eukaryoticeukaryotic

19. Plants- multicellular, eukaryoticPlants- multicellular, eukaryotic