Transcript Chapt. 4: The Origins of Life

The Origins of Life
Chapt 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…
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
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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.
Origin of Life:
Another idea
Biogenic-looking features in
ALH84001 Martian meteorite
http://ares.jsc.nasa.gov/astrobiology/biomarkers/images.html
Extra-terrestrial Origins
In 1969, a meteorite (left-over bits from the origin of the solar
system) landed near Allende, Mexico. The Allende
Meteorite (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!
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 aliencontrolled cloning experiments
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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 that
science 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.
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 Experiment
In 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.
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-Urey
apparatus produce?
• Has life been recreated in this apparatus?