Transcript Darwinsprinciples

Darwin’s Principles
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2010-2011
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Evolution of Evolutionary Thought
 Develop time line of historical events
427-347 B.C. Plato’s divinely inspired “ideal form”
 384-322 B.C. Aristotle’s “Ladder of Nature”
 until 1700s Creationism

 Each species was created individually by God
 Earth was the center of the universe
 Man stood atop creation
 Exploration of New Lands
• Number of species was greater than expected
• Some species closely resembled one another
• Some naturalists concluded that similar
species may have developed from a common
ancestor
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Evolution of Evolutionary Thought
 1707-1788 George LeClerc
(Comte of Buffon);

creation provided a relatively small
number of founding species that
evolved through natural processes
 Idea was not accepted by science
Did not provide a mechanism for
evolution
 Earth was not old enough to allow time
for the process of evolution

 1769-1832 G. Cuvier; theory of
catastrophism (creationist w/extinction)
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Evolution of Evolutionary Thought
 1726-1797 James Hutton developed

uniformitarianism – gradual change
1797-1875 Charles Lyell’s “Old Earth
Hypothesis” supported Hutton, gave time
for gradual change

(Archbishop James Ussher calculated the date of
the creation of the Earth…9AM, Oct 23,
4004BCE…using biblical lineages.)
 1744-1829 Jean Baptiste de Lamarck inheritance of acquired characteristics

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(‘cuz if you are gonna be wrong…do it
spectacularly!’)
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Evolution of Evolutionary Thought
 1809-1882 Charles Darwin

Developed the theory of evolution
 Species evolved through natural selection;
 Adaptation to their ever-changing
environment.
 1823-1913 Alfred Wallace; supported
Darwin's theory

(worked separately, came up with same
conclusion, came in “2nd”)
 Present theory of evolution by natural
selection
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In historical context
 Other people’s ideas paved the
path for Darwin’s thinking
competition:
struggle for survival
population growth
exceeds food supply
land masses change over
immeasurable time
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Darwin’s Finches
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Ch
apt
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Darwin’s finches
 Differences in
beaks allowed
some finches to…
successfully
compete
 successfully feed
 successfully
reproduce

 pass successful
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traits onto their
offspring
Voyage: 1831-1836
November 24, 1859, Darwin published
“On the Origin of Species by Means of Natural Selection”
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Essence of Darwin’s ideas
 Natural selection
heritable variation exists in populations
 over-production of offspring

 more offspring than the environment can support

competition
 for food, mates, nesting sites, escape predators

differential survival
 successful traits = adaptations

differential reproduction
 adaptations become more
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common in population
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A Flowchart of Evolutionary Reasoning
Potential for
rapid reproduction
Relatively constant
resources and
population over
time
Competition for
survival and
reproduction
Variability in
structures and
behaviors
NATURAL SELECTION
On average, the fittest
organisms leave
the most offspring
Some variability is
inherited
(observations)
(conclusions)
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EVOLUTION:
The genetic makeup of the
population changes over time,
driven by natural selection
Where does Variation come from?
 Mutation

random changes to DNA
 errors in mitosis & meiosis
 environmental damage
 Sexual reproduction

mixing of alleles
 genetic recombination
 new arrangements of alleles in every offspring
 new combinations = new phenotypes
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Lamarckian vs. Darwinian view
 Lamarck

in reaching higher
vegetation giraffes
stretch their necks &
transmits the acquired
longer neck to offspring

 Darwin

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giraffes born with longer
necks survive better &
leave more offspring who
inherit their long necks
Stick your neck out…
Ask Questions!
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