Earth is estimated to be about 4.6 Earth 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 (Carbon No breathable oxygen gas (Carbon

dioxide, ammonia, hydrogen gas, were dioxide, ammonia, hydrogen gas, were present).present).

Vigorous lightning and thunder storms.Vigorous lightning and thunder storms.

Origin of Life…Origin of Life…

Extraterrestrial TheoryExtraterrestrial Theory Creationism TheoryCreationism Theory Chemical Evolution Chemical Evolution

Organic CompoundsOrganic Compounds

The Origin of Life’s The Origin of Life’s Chemicals…Chemicals…

All of life is composed of organic All 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 In order for life to form, these building blocks had to be present.building blocks had to be present.

Charles Darwin said that life probably Charles Darwin said that life probably formed in a “warm little pond…”formed in a “warm little pond…”

The Origin of Life’s The Origin of Life’s Chemicals…Chemicals…

Once earth began to cool, oceans Once earth began to cool, oceans began to form as water vapor began to form as water vapor condensed.condensed.

Question: Could organic compounds Question: Could organic compounds have formed from material present have formed from material present on early earth?on early earth?

Origin of Life’s Origin of Life’s ChemicalsChemicals

Miller-UreyMiller-Urey GoalGoal: : Recreated

atmosphere of Early Earth

ObjectiveObjective: : Can organic compounds form?

ResultsResults: : amino acids, nucleotides, lipids, carbohydrate pieces

Fossils and Ancient LifeFossils and Ancient Life

Paleontologists are scientists who Paleontologists are scientists who study fossils.study fossils.

Fossil is any trace of an ancient Fossil is any trace of an ancient organism.organism.

Ex) bones, feathers, footprints, Ex) bones, feathers, footprints, impressions, etc.impressions, etc.

MicrofossilsMicrofossils Scientists had hard Scientists had hard

time finding time finding evidence of first evidence of first life life

Most ancient life Most ancient life was microscopicwas microscopic

StromatolitesStromatolites 3.5 Billion years old3.5 Billion years old 11stst life on earth life on earth

bacteria lived in bacteria lived in seasea

The Fossil RecordThe Fossil Record

Fossils occur in a particular order.Fossils occur in a particular order. Certain fossils only occur in more Certain fossils only occur in more

recent rock.recent rock.

How do fossils form?How do fossils form? Not everything Not everything

fossilizes.fossilizes. Certain conditions Certain conditions

have to be perfect for have to be perfect for fossilization to occur. fossilization to occur.

For every organism For every organism that fossilizes, that fossilizes, hundreds more die hundreds more die without a trace.without a trace.

Most fossils are found Most fossils are found in “sedimentary” rock.in “sedimentary” rock.

Dating Fossils (Two Dating Fossils (Two methods)methods)

1.1. Relative DatingRelative Dating Determining age of Determining age of

fossil based on how fossil based on how deep it is buried.deep it is buried.

Placement is compared Placement is compared with other fossils and with other fossils and age is determined. age is determined.

Oldest layers of rock at Oldest layers of rock at the bottomthe bottom

Relative dating allows Relative dating allows you to compare age you to compare age one fossil to the next, one fossil to the next, but does not give an but does not give an exact age to the fossil.exact age to the fossil.

Dating Fossils (two Dating Fossils (two methods)methods)

2.2. Radioactive DatingRadioactive Dating Used to determine actual age of rock Used to determine actual age of rock

(fossils).(fossils). Requires knowledge of chemistry and Requires knowledge of chemistry and

“half-life” of radioactive isotopes. “half-life” of radioactive isotopes.

Road to Modern Road to Modern OrganismsOrganisms

Scientists believe earliest life was found Scientists believe earliest life was found in sea.in sea.

11stst life was unicellular, prokaryotic = life was unicellular, prokaryotic = bacteriabacteria

Photosynthesis changed Earth’s Photosynthesis changed Earth’s atmosphere released Oatmosphere released O2 2 - cyanobacteria - cyanobacteria

Unicellular Eukaryotes – Endosymbiotic Unicellular Eukaryotes – Endosymbiotic TheoryTheory

Multicellular organisms Multicellular organisms

Classification/EvolutionClassification/Evolution

Bacteria – unicellular, Bacteria – unicellular, prokaryoticprokaryotic

Protista – eukaryoticProtista – eukaryotic

Fungi- multicellular, eukaryoticFungi- multicellular, eukaryotic

Animals- multicellular, Animals- multicellular, eukaryoticeukaryotic

Plants- multicellular, eukaryoticPlants- multicellular, eukaryotic