2/19/2009
Evolution
Dawkins & Darwin
Conceptualizations
Of Evolution
Richard Dawkins
• Simple to state
• Difficult to apply
• Astonishing to contemplate
• RDA
Dawkins
• 1. Survival of the stable
1941-
– Earliest form of natural selection was rejection
of unstable molecules
British biologist
Dawkins
• 2. At some point the “replicator” emerged
Researchers at the Scripps Research Institute have made important
steps toward understanding how life originated by shedding light on
the ‘RNA World’ hypothesis. The ‘RNA World’ refers to the idea that
life on Earth went through a stage where RNA was used to store
information and act as a catalyst, much like DNA and proteins are
used in organisms today.
– A molecule with the property of being able to
make copies of itself
– Over time it would become the most abundant
entity
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2/19/2009
Dawkins
A critical component of this stage would be
that RNA molecules would have to
replicate themselves. The team at Scripps
has now synthesized RNA enzymes that
can replicate themselves without the help
of additional molecules. These RNAbased, self-replicating systems could be a
model for how life on Earth first began
to operate. (1-16-2009)
• 3. No copying process is perfect, and this
fact would generate a variety of miscopies.
– Natural
N t l selection
l ti will
ill ffavor th
those miscopies
i
i
that exhibit
• A. Increased longevity
• B. High fecundity
• C. High accuracy of replication
Dawkins
• Paradox:
Dawkins
• 4. Earth is finite
• Molecular building blocks are limited
– Copying errors are necessary to introduce
variation yet natural selection favors high
variation,
copy fidelity
– Primeval soup populated by molecules that
are stable, replicate rapidly, replicate
accurately
– Competition for resources
•
•
•
•
P t
Proto-carnivores
i
Protective coats
Structural/behavioral adaptations
Organisms are survival machines for the
perpetuation of the genes
Darwin
• Evolution is the consequence of the
interaction of 5 basic phenomena:
– Inheritance
I h it
– Mutation
– Selection
– Drift
– Isolation
Darwin
• 1. Inheritance:
– Genetic materials are preserved from
generation to generation
– High copy fidelity
– The phenotype results from an interaction
between genetic materials and the
developmental environment
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Darwin
• 2. Mutation:
Darwin
• 3. Selection:
– Genetic materials do change occasionally,
and these changes
changes, in turn,
turn are heritable
heritable.
– Copying errors
– Alternative genetic lines producing alternative
phenotypes are not equally fit,
fit and the fittest
lineage will, over time, out reproduce the less
fit lineage
– Differential reproduction is the principal
driving force of evolution
Darwin
• 4. Drift:
Darwin
• 5. Isolation:
– Genetic materials are sometimes lost through
accidents
• Random and non-repetitive events
• In small populations rare traits in rare individuals
may be lost through accidental death. This mimics
changes in gene frequencies produced by
selection.
Darwin
• The theory of evolution is the proposition
that the interaction of these five
phenomena in the successions of
environments in which organisms have
lived account for all the traits, tendencies
and characteristics of all forms of life.
– Not all genetic lines are able to interbreed
freely Hence
freely.
Hence, they are unable to re
reamalgamate their differences.
Darwin
• “If it could be proved that any part of the
structure of any one species had been
formed for the exclusive good of another
species, it would annihilate my theory, for
such could not have been produced
through natural selection.”
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2/19/2009
Evolution
• All traits: morphological, physiological,
and behavioral, of all species must favor
the perpetuation of the assemblage of
genes which constitute that organism or
the theory of natural selection is
annihilated.
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