The Origin of LifeEarly and Modern Ideas

I - OLD IDEA Spontaneous generation or abiogenesis - Life could arise from non-living material.

People observed that decaying matter, for example rotting meat would have maggots after a short period of time, and concluded that maggots would be “born”

from decaying meat.

This idea was popular through

the 1800s.

About 2000

years ago,

a Roman

poet wrote

these

directions.

Van Helmont: (1600s) : He

thought he could produce

mice from wheat and a

soiled shirt.

• Francisco Redi (1600s)- JARS OF MEAT & Maggots EXPERIMENT

He used covered & uncovered jars of rotting meat. After several days, the jars of uncovered meat had maggots, while the jars with the covered meat did not. He reasoned that

flies could not lay eggs

on the meat and therefore

there were no maggots.

Therefore---flies do not

spontaneously arise

from meat.

• Lazzaro Spallanzani’s experiment

(mid 1700s) Flasks of broth experiment

showed that microorganisms will not

grow in boiled & sealed broth, but will grow

If the containers are left open.

Vital force

• John Needham stated that Spallanzani

destroyed the air’s vital force when he

boiled the broth. That is why there were

no microbes.

• Louis Pasteur – (Mid 1800s) His “curved-necked flask” experiment proved that

microorganisms could not arise spontaneously from broth. Air was able to enter the curved-neck of the specially designed flask. Yet, the broth stayed clear.

Pasteur reasoned that microorganisms

are carried to the broth from dust in the

air.

Therefore microbes come from other

microbes and not through a process of

spontaneous generation.

OPARIN’S HYPOTHESIS: Describes how complex organic

compounds may have formed on Earth.

Life beganin the primitiveoceans.

Alexander Oparin(1923-Russian biochemist)

• Elements found in organic compounds were present at Earth & Solar system’s formation.

• Inorganic & simple organic compounds present in the Earth’s primitive atmosphere included inorganic compounds such as:

• NH3 = ammonia gas, • H2O = water vapor,• H2 = hydrogen gas • and a simple organic compound CH4 = methane gas.• (also carbon monoxide, carbon dioxide, Hydrogen cyanide and nitrogen)

Probable no Free Oxygen!

• A great deal of energy was available for chemical reactions. The source of this energy came from: lightning, the sun’s UV radiation , heat from the earth’s crust, volcanic activity, radioactive isotopes etc..

Which this energy present, spontaneous interactions of the simpler molecules formed more complex organic molecules such as: amino acids, sugars, fatty acids, and nitrogenous bases.

• The earth cooled over many years and the water vapor condensed into shallow pools, lakes and then seas.

• Concentrations of the organic compounds increased to form the “primordial soup.”

MILLER –UREY Experiment

supported for Oparin’s Hypothesis

• Stanley Miller (1953) a graduated student under Harold Urey, tested Oparin’s hypothesis .

He set up an apparatus

to simulate the early

Earth conditions. It

suggested how a

mixture of organic

compounds

necessary for life

could have come

from simpler

compounds

present on the

primitive Earth.

It produced organic compounds needed for living things