Transcript The Origin Of The Earth

The Origin Of The Earth
SC.912.L.15.8
• 4.6 Billion years the earth was formed
• ~3.2 Billion years ago the introduction of Blue-green
cyanobacteria
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Oxygen is produced
Free oxygen begins to accumulate
Ozone is synthesized
Aerobic metabolism can begin
http://www-cyanosite.bio.purdue.edu/images/lgimages/bloom4.jpg
How Did Life Originate?
• Spontaneous Generation?
• Chemical Synthesis “Primordial Soup”?
Spontaneous Generation
• Spontaneous Generation
▫ Organisms arose spontaneously from
non-living matter
 Example: Maggots arose from rotting meat
▫ Disproved in 1668 by Francesco Redi, an Italian physician
 Used 3 samples of rotting flesh placed in flasks
 open to air
 sealed
 covered with gauze
 Maggots were generated in the open container, where flies had
access to meat and were able to lay their eggs
▫ Results of experiment were not conclusive enough for some
people
Spontaneous Generation-Not the
Answer!
• Louis Pasteur -1864
▫ Experiment showed that life did not
spontaneously appeared
 Meat broth was boiled in a flask to kill
microorganisms
 The neck of the flask was heated and bent into the
shape of an S
 Microorganisms could not get into broth because
they would settle in S shaped neck before contact
with broth
 No growth was in discovered in the broth
 Broth was tilted into the S component and
microorganisms contaminated broth and grew
Did Darwin have the answer??
“Some warm pond with all sorts of
Ammonia, phosphoric salts,
Heat, light, electricity etc…..”
-Charles Darwin, on the
origins
of life in tidal
pools
Miller and Urey experiment
• ATTEMPTS TO CREATE LIFE IN THE
LABORATORY
• PROVIDE A MIXTURE OF GASES SIMILAR
TO THAT IN THE EARLY ATMOSPHERE
• PROVIDE WATER TO SIMULATE OCEANS
OR POOLS
• PROVIDE A SOURCE OF ENERGY
• WAIT AND SEE WHAT HAPPENS
Chemical Synthesis
• Chemical Synthesis“Primordial Soup”
▫ Dr. Stanley Miller and Dr.
Harold Urey-1953
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ammonia (NH3)
methane (CH4)
water (H2O)
hydrogen (H2)
electricity in an elaborate flask
apparatus
 Electricity was passed
through the apparatus
 Amino Acids and
hydrocarbons were
synthesized
The Results…
MANY ORGANIC MOLECULES ARE
PRODUCED, INCLUDING:
SUGARS (INCLUDING RIBOSE)
FATS OR LIPIDS
AMINO ACIDS (50% L AND 50% D)
GENETIC BASES
NOTE: IF OXYGEN IS PRESENT, THESE
MOLECULES ARE NOT FORMED!!
(IF OXYGEN IS PRESENT, EVERYTHING  CO2
& H2O)
So, when did life begin?
• PROBABLY BETWEEN 3.9 AND 4.2 BILLION
YEARS AGO
• THIS WAS 0.4 TO 0.7 BILLION YEARS (OR
400 TO 700 MILLION YEARS) AFTER THE
EARTH FORMED.
• COMPARED TO THE CURRENT AGE OF THE
EARTH (4.6 BILLION YEARS), NOT MUCH
TIME ELAPSED BEFORE LIFE STARTED.
• LIFE GOT STARTED VERY QUICKLY AFTER
THE EARTH FORMED!
• EVIDENCE FOR EARLY LIFE:
▫ ANCIENT MICROFOSSILS
▫ STROMATOLITES
▫ ISOTOPIC ABUNDANCES OF CARBON
So, how did life begin?
• SIMPLE ORGANIC MOLECULES (MONOMERS)
WERE PRODUCED VIA CHEMICAL
REACTIONS AND/OR DELIVERED VIA
COMETARY IMPACTS.
• SIMPLE ORGANIC MOLECULES COMBINED TO
MAKE LONG POLYMERS
• SOME OF THE LONG POLYMERS MUST HAVE
BEEN SELF-REPLICATING (LIKE DNA).
• POLYMERS WERE ENCLOSED INSIDE A
“CELL” THAT WAS SEPARATED FROM ITS
ENVIRONMENT BY A MEMBRANE.
So, where did life begin?
• PROBABLY NOT ON DRY LAND
▫ UV RADIATION (NO OZONE LAYER YET), IMPACTS,
OR OTHER ENVIRONMENTAL HAZARDS WOULD
MOST LIKELY HAVE WIPED IT OUT
▫ HARD FOR MOLECULES TO REACT WITH EACH
OTHER ENOUGH TO PRODUCE LONG POLYMERS
UNLESS DISSOLVED IN A LIQUID
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• POSSIBILITIES:
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OCEANS NEAR HYDROTHERMAL VENTS
HOT SPRINGS
SMALL POOLS OF WATER (TIDEPOOLS?)
INSIDE ROCKS
Did life begin in hydrothermal vents??
• ALSO KNOWN AS BLACK SMOKERS
• LOCATED ON OCEAN FLOOR AT MIDOCEAN RIDGES WHERE TECTONIC
PLATES SPREAD APART
• VERY HIGH TEMPERATURE AND
PRESSURE
• SPEW OUT HOT WATER CONTAINING
MANY DISSOLVED MINERALS
• PROVIDE A SOURCE OF RAW
MATERIALS AND ENERGY FOR A RICH
DIVERSITY OF LIFE (EXTREMOPHILES)
Hydrothermal vents
▫ ENVIRONMENT NOT AFFECTED MUCH BY
IMPACTS (UNLESS OCEAN VAPORIZES
COMPLETELY), UV RADIATION, AND OTHER
ENVIRONMENTAL HAZARDS ON EARLY EARTH
▫ ORGANIC MOLECULES CAN INTERACT & LINK
TOGETHER TO MAKE LARGER MOLECULES
MORE EASILY IF DISSOLVED IN WATER
▫ DNA EVIDENCE IS SUGGESTIVE OF THIS
Did life begin in tide pools?
▫ ORGANIC MOLECULES CAN INTERACT & LINK TOGETHER
TO MAKE LARGER MOLECULES MORE EASILY IF
DISSOLVED IN WATER
▫ IN A SMALL BODY OF WATER, CHEMICALS CAN BECOME
MORE CONCENTRATED THAN IN A LARGE BODY OF WATER
LIKE AN OCEAN (ESPECIALLY AS POOL EVAPORATES).
▫ TIDES OCCASIONALLY BRING IN NEW MATERIALS INTO
TIDEPOOLS.
▫ SOLID SUBSTRATE AT THE BOTTOM OF THE POOL COULD
AID IN LINING UP MONOMERS TO FORM POLYMERS, AND
SELECTING ONE HANDEDNESS (ISOMER) OF MOLECULES.