The Origin Of The EarthSC.912.L.15.8

• 4.6 Billion years the earth was formed • ~3.2 Billion years ago the introduction of Blue-

green cyanobacteria▫ 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 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

▫

• POSSIBILITIES:▫ 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 MID-

OCEAN 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.