Download Origins of Life

Chemical
Evolution
The understanding of the origin of life was largely speculative until
the 1920s, when Oparin and Haldane, working independently,
proposed a theoretical model for "chemical evolution."
The Oparin-Haldane model suggested that under the strongly
reducing conditions (no oxygen believed to be present 4.0 billion
years ago), inorganic molecules would, with an energy source,
spontaneously form organic molecules (simple sugars and amino
acids).
Miller
Urey
In 1953, Stanley Miller and Harold Urey, tested
the Oparin-Haldane hypothesis by constructing
an apparatus that simulated the Oparin-Haldane
"early earth." When a gas mixture based on
predictions of the early atmosphere was heated
and given an electrical charge, organic
compounds were formed
water (H2O
methane (CH4)
ammonia (NH3)
and
hydrogen (H2)
but no oxygen
Thus, the Miller-Urey experiment demonstrated
how some biological molecules, such as simple
amino acids, could have arisen abiotically, that is
through non-biological processes, under
conditions thought to be similar to those of the
early earth.
Panspermia Theory
This theory suggests that life seeds came from outer space
and planets exchanged life.
Panspermia literally means seeds everywhere.
Panspermia suggests that life could have existed on another
planet and moved to Earth. Statistics have showed 7.5% of
rocks from Mars reach Earth. The rocks would travel between
less than 100 years to 16,000 years and more to get to earth.
This meteorite blasted off of
the surface of the planet Mars
since its creation some 180
million years ago. Maybe by
the impact of an asteroid on
the surface and traveled
through space to the earth,
where it landed on Antarctica.
This meteorite contained traces
of Martian atmospheric gases
and shows signs of having
reacted with Mars’
groundwater.
Evidence for Panspermia
1. Bacteria can survive harsh environment of space
a. Ultraviolet radiation
b. Protons bombardments
c. Cold
2. Evidence that meteorites contain life
a. Amino acids
b. Bacteria
c. Carbon
d. Protected inside rocks
3. Bacteria can live for a long time in sleeping state until awakened
4. Mars safer than Earth (less bombardments and less gravity)
5. Mars not as hot as Earth in early development
6. Mars had oxygen back when earth did not
GAIA THEORY
Gaia theory is a model of the
biosphere in which life fosters and
maintains suitable conditions for
itself by affecting Earth's
environment.
The first such theory was created
by the English atmospheric
scientist, James Lovelock, in 1969.
He hypothesized that the living
matter of the planet functioned like
a single organism and named this
self-regulating living system after
the Greek goddess, Gaia.
Intelligent design (ID) - is a controversial set of arguments
which assert that empirical evidence supports the conclusion that
life on Earth was deliberately designed by one or more intelligent
agents.
ID advocates argue that the standard scientific model of evolution
by natural selection is insufficient to explain the origin, complexity,
and diversity of life. More specifically, ID adherents believe that
there exist instances of irreducible complexity, which in their view
are improbable to evolve and therefore it is highly probable to have
been created by an intelligent designer or designers.
Heterotroph Hypothesis
1. Alexandar Oparin - 1936 - Stated that the earliest living
organisms on earth were simple heterotrophs (organisms that cannot
make their own food)
The strength of the heterotroph hypothesis is that it gives the first
forms of life a source of "food" that doesn't itself come from living
things: the primordial soup. This is how the rest is supposed to have
happened...
The ability to self-organize. This requires some already-formed
building blocks, from the soup, and a source of energy that would
serve to help drive them into increasingly complex forms.
Experiments in the early 1950s began to confirm that such processes
could at least begin. Those experiments used lightning, confined to a
"primordial soup bottle," to stimulate production of complex
materials. Since that time, all of the various forms of energy available
on the early earth have been tested, with varying results. The current
"leading contender" for life-organizer are Hydrothermal vents,
openings between Earth's surface plates at the bottom of the oceans.
There, water mixes with hot magma and releases a hot soup of
materials even today. They have an energy source - heat - a source of
materials - once soup, now magma - and, perhaps most importantly,
are a stable, long-lasting ecosystem and a place to "work the bugs
out" of the earliest living systems.
The ability to reproduce. As these early self-organizing molecules
grew, only those which could make and spread copies of
themselves had any real future. Life on today's Earth uses DNA
code to store all of the information it needs to make the proteins it
actually runs on, but DNA has little activity beyond that, and
proteins generally can't duplicate themselves. There are theories
that try to address those problems, but the leading current theory is
that the first really complex systems were of RNA, a hypothesis
usually called the RNA World hypothesis. RNA has DNA's coding
abilities and some protein-like activity, and it isn't difficult to see
the evolution of a DNA-coded protein system growing quickly
from an RNA ancestor.
The ability to evolve. Once you have a planetwide ocean full of selforganizing molecules able to reproduce themselves, you have a
competitive ecosystem where selection can take place. This stage of
molecular evolution would have favored those who could work most
efficiently, or best accumulate building blocks, or reproduce the
fastest, or work with other molecules in a cooperative fashion,
perhaps linking RNA or DNA codes for particularly good proteins
together to work as a unified system. And these unified systems
might work even better with some confinement and protection...
Symbiogenesis refers to the merging of two separate organisms
to form a single new organism. The idea originated with Konstantin
Mereschkowsky in his 1926 book Symbiogenesis and the Origin of
Species, who proposed that chloroplasts originated from
cyanobacteria captured by a protozoan. Today both chloroplasts
and mitochondria are believed to have such an origin; see
endosymbiotic hypothesis.