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The Origins of LifeChapt 25

The Origins of Life

• Earth is probably ~4.5 billion years old

• Oldest life forms began ~3.5 bya

• How did life begin???

The Origin of Life: Early Ideas• Spontaneous Generation

– idea popular in the 1600-1700’s– living things come from the nonliving– evidence: beetles and other insect larvae arise from cow

dung; frogs emerge from mud

• In 1688, the Italian Francisco Redi In 1668, Francesco Redi, an Italian physician, did an experiment with flies and wide-mouth jars. He demonstrated that meat that was covered did not produce maggots

• This may have been the first true scientific experiment…

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Francesco Redi experiment with flies and wide-mouth jars

— Redi’s expt. contained the following elements: Observation, Questions, Hypothesis, Tests, Conclusions

http://biology.clc.uc.edu/courses/bio114/spontgen.htm

• Observation: There are flies around meat carcasses at the butcher shop.

• Question: Where do the flies come from? Does rotting meat turn into or produce the flies?

• Hypothesis: Rotten meat does not turn into flies. Only flies can make more flies.

• Prediction: If meat cannot turn into flies, rotting meat in a sealed (fly-proof) container should not produce flies or maggots.

• Testing: Wide-mouth jars each containing a piece of meat were subjected to several variations of “openness” while all other variables were kept the same.

• Conclusion: Only flies can make more flies. In the uncovered jars, flies entered and laid eggs on the meat. Maggots hatched from these eggs and grew into more adult flies. In the sealed jars, no flies, maggots, nor eggs could enter, thus none were seen in those jars. Maggots arose only where flies were able to lay eggs. This experiment disproved the idea of spontaneous generation for larger organisms.

Other Ideas: Life from a Biblical Creation?

Christian Creationism states that the world, including all life, was created about 6,000 years ago in six literal days by a God.

…But how does one accurately and fairly test for this?...What’s the observation, hypothesis, test…?

This idea does not really fit into the confines of a Science course.

Like the study of French Impressionist painters, Religion is not part of, nor adequately covered in, a Science course .

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Origin of Life:Another idea

Biogenic- looking features in ALH84001 Martian meteorite

http://ares.jsc.nasa.gov/astrobiology/biomarkers/images.html

In 1969, a meteorite (left -over bits from the origin of the solar system) landed near Allende, Mexico. The AllendeMeteorite (and others of its sort) have been analyzed and found to contain amino acids, the building blocks of proteins.

This idea of panspermia hypothesized that life originated out in space and came to earth inside a meteorite. The amino acids recovered from meteorites are in a group known as exotics: they do not occur in the chemical systems of living things. The ET theory is now discounted by most scientists, although the August 1996 discovery of the Martian meteorite and its possible fossils have revived thought of life elsewhere in the Solar System.

Anyway….This only moves the problem to elsewhere!

Extra-terrestrial Origins

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The Latest on Extra-terrestrial Origins…

The Raelians• Raelians believe that humanity

was created from the DNA of superior alien scientists

• Follow the teachings of a former French magazine sportswriter and wannabe race-car driver Claude Vorilhon, 56. He took the name "Rael" after he claimed a close encounter of the third kind….

People are the product of alien-controlled cloning experiments

• On Dec. 13, 1973, Vorilhon said he was walking in the Clermont-Ferrand volcanic mountain range in France when a UFO touched down. Humanoid creatures with pale greenish skin and almond-shaped eyes took him aboard, saying they wanted him to be their messenger to humankind.

• The aliens explained they cloned the first people 25,000 years ago. The little green people said Vorilhon was himself a clone and that they impregnated his mother in 1946 after the use of the first atomic bombs awakened them to mankind's advanced scientific knowledge.

• "When I told my mother and grandmother the true story, my grandmother was relieved because she said that she had seen UFOs lingering around the house over the years and had never told anyone," Vorilhon told the Village Voice last year (2002).

• Vorilhon, who frequently dons flowing white garments, said his mission is to spread the word that there is no God, and thatscience and our alien forefathers would set people free --physically and sexually -- and help them live forever.

• Two years after the aliens' first visit, they reappeared and took Vorilhon to another planet where he said he met Jesus, Mohammed and Buddha. All became immortal through cloning, he said.

• Ever since, he's been preaching the message of protecting the rights of the "unreborn" --

Jan. 2003: Raelians claim to clone first human baby

The Raelian religious cult claim that a company founded by its adherents has cloned the first human baby. Consider, for one moment, the objective circumstances: a crackpot cult, whose French founder says he got his marching orders from a space alien, calls a press conference in Miami to announce that a cloned child has been born to an unidentified woman in an unspecified place the day after Christmas. Proof, according to the company's CEO -- a chemist named Brigitte Boisselier --will be forthcoming in nine days --not 10, not eight, but nine.

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Origin of Life: Current Theory• Chemical Evolution• .....The idea that long ago complex

collections of chemicals formed the first cells.

• Life began in the oceans 4 bya from simple chemicals joining together in a “primordial soup”

• Complex chemicals evolved into living cells

Conditions on the Early Earth

• A hot reducing environment

• High temperatures• H2O, CO2, N2

• H2S, CH4, NH3, H2

• No O2

• Text pg. 451

Miller ExperimentIn 1950, a student, Stanley Miller, designed an experiment in which he discharged an electric spark into a mixture thought to resemble the primordial composition of the atmosphere.

From the water receptacle, designed to model an ancient ocean, Miller recovered some amino acids.

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Subsequent modifications of the atmosphere have produced representatives or precursors of all four organic macromolecular classes.

Including the molecules below:

Quiz

• What gases were believed to be present in the early earth’s atmosphere?

• What energy source may have helped create life on earth?

• What complex structures did the Miller-Ureyapparatus produce?

• Has life been recreated in this apparatus?