ORIGIN OF LIFE
SC.912.L.15.8
Intro
• This presentation is on benchmark
SC.912.L15.8 which covers the origin of life on
Earth.
• Origin of life research is the study of the
beginnings and early development of life.
• We will also learn about scientific
contributions from a few scientist.
Scientific explanation of the origin of life on Earth
• Science shows us that the universe evolved by
self-organization of matter towards more and
more complex structures.
• The most common hypothesis in the scientific
community, is that life began approximately 3.5
billion years ago as the result of a complex
sequence of chemical reactions that took place
spontaneously in Earth's atmosphere.
Scientific Explanations
• The earliest known life on Earth existed
between 3.9 and 3.5 billion years ago.
• In the science community there have
been many hypothesis thrown around
to figure out how did life occur.
• But we can all conclude that it all
started with a cell.
Louis Pasteur Contributions
• Prior to the 1860s, when Louis Pasteur developed his
germ theory of disease, the common consensus was that
life could spontaneously generate. Today we know new
life won't generate out of nothing, but this is due largely
to Pasteur's work. Pasteur showed us that
microorganisms, incapable of detection by human
senses, live everywhere around us. Ironically, science
has come back to explore this very concept as a
possibility once more as one of two main competing
explanations for the origin of life on Earth. No one can be
sure which one adequately explains the origin of life on
Earth, but amazingly, both have been shown to be
possible.
Alexander Oparin Contributions
• Oparin was primarily interested in how life initially began. There is no
fundamental difference between a living organism and lifeless matter.
Oparin thought that the infant Earth had possessed a strongly reducing
atmosphere, containing methane, ammonia, hydrogen, and water vapor.
In his opinion, these were the raw materials for the evolution of life. In
this process biological orderliness already comes into prominence.
Competition, speed of cell growth, survival of the fittest struggle for
existence and, finally the natural selection determined such a form of
material organization which is characteristic of living things of the
present time. Oparin outlined a way in which basic organic chemicals
might form into microscopic localized systems possible precursors of the
Cell from which primitive living things could develop. While Oparin
himself was unable to do extensive experiments to investigate any of
these ideas, scientists were later able to.
The Miller Urey Experiment
• In the 1950's, biochemists Stanley Miller and Harold Urey,
conducted an experiment which demonstrated that several
organic compounds could be formed spontaneously by
simulating the conditions of Earth's early atmosphere. They
designed an apparatus which held a mix of gases similar to
those found in Earth's early atmosphere over a pool of water,
representing Earth's early ocean. Electrodes delivered an
electric current, simulating lightning, into the gas-filled
chamber. After allowing the experiment to run for one week,
they analyzed the contents of the liquid pool. They found that
several organic amino acids had formed spontaneously from
inorganic raw materials. Their experiments, along with
considerable geological, biological, and chemical evidence,
lends support to the theory that the first life forms arose
spontaneously through naturally occuring chemical reactions.
However, there are still many skeptics of this theory who
remain unconvinced.
Lynn Margulis Contributions
• Margulis is best known for her theory on the origin
of eukaryotic organelles, and her contributions to
the endosymbiotic theory, which is now generally
accepted for how certain organelles were formed.
• While her organelle genesis ideas are widely
accepted, symbiotic relationships as a current
method of introducing genetic variation is
something of a fringe idea.
Sidney Fox Contributions
• A biochemist responsible for discoveries on the origins of life.
Fox explored the synthesis of amino acids from inorganic
molecules, the synthesis of proteinous amino acids and amino
acid polymers called "proteinoids" from inorganic molecules
and thermal energy, and created what he thought was the
world's first "protocells" out of proteinoids and water. Fox
believed in spontaneous generation of life and suggested that
his experiments possessed conditions that were similar to
those of primordial Earth. In his experiments, he demonstrated
that it is possible to create protein-like structures from
inorganic molecules and thermal energy. Dr. Fox went on to
create microspheres that he said closely resembled bacterial
cells and concluded that they could be similar to the earliest
forms of life.
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•
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As for the first, three scenarios have been proposed:
organic molecules were synthesized from inorganic compounds in the
atmosphere
rained down on earth from outer space;
were synthesized at hydrothermal vents on the ocean floor.
•
Chemical evolution: The formation of complex organic molecules from
simpler inorganic molecules through chemical reactions in the oceans
during the early history of the Earth; the first step in the development of
life on this planet. The period of chemical evolution lasted less than a
billion years.
•
A eukaryote is an organism whose cells contain complex structures
enclosed within membranes. Which takes a big part in the building blocks
of life.
•
The endosymbiotic theory postulates that several key organelles of
eukaryotes originated as symbioses between separate single-celled
organisms. According to this theory, mitochondria and plastids and
possibly other organelles--represent formerly free-living bacteria that were
taken inside another cell as an endosymbiont.
What did I review?
• You reviewed the many hypothesis and
making of the origins of life on Earth.