Transcript Evolution by Natural Selection

Evolution by Natural Selection
Pre-Darwinian Ideas
• At the time, biology was not a separate
science from geology, etc… all of which were
considered ‘Natural History’. Some
interpreted natural history from a biblical
perspective as in William Peale’s Natural
Theology
• It was believed that the Earth was relatively
young (6000 years old) and that species were
fixed and unchanging.
Pre-Darwin Geology:
Catastrophism
• Georges Cuvier helped
to develop the geologic
theory of catastrophism
which stated that
geologic change results
from catastrophies like
the biblical flood, etc…
and that the Earth was
young.
• He interpreted changes
in the fossil record in
this way.
Pre-Darwin Biology:
Carl Linnaeus & Georges Buffon
• The Father of Taxonomy,
Linneaus, believed
organisms were created
and remained fixed
through time. His goal
was to determine the
underlying order to “Gods
plan”
• The French naturalist,
Buffon, was effected by
the Enlightment and took
a more secular
perspective.
Societal Change
• Most peoples position in life was static and
unchanging.
• Changes in religion (reformation),
government (American and French
revolutions), and economy (Industrial
revolution) were important societal changes
that provided a new paradigm.
• This new paradigm was associated with
individual rights and responsibility.
Changes in Geology
• Because of the
increased need for
coal and iron ore for
Industrial Revolution
geologist began to
discover the fossils
that would call into
question our view of
geology and life
Theory of Uniformity
• Charles Lyell
• Uniformity a concept
developed by James
Hutton became popular
after Lyell’s publication
of the Principles of
Geology
• Geologic change tends
to be slowly cumulative,
not catastrophic, and
caused by familiar
forces like erosion.
Change in Biology:
Charles Darwin
• A wealthy gentleman
who was educated in
medicine and theology,
before his Voyage on
the HMS Beagle.
• Used his knowledge of
selective breeding
(Artificial Selection) and
the Malthusian Doctrine
of population limits to
propose a mechanism
for evolution.
Darwin’s Voyage
• Sailed for 5 years
around the Earth on
the H.M.S. Beagle
as Captain Fitzroy’s
companion
• Became a
secondary naturalist
making observations
in the Galapagos
Islands
Darwin’s Natural Experience
• Unlike Linnaeus,
Darwin observed living
organisms within the
habitats they lived, and
concerned himself with
more than just naming.
• He noticed differences
in related species that
correlated geography.
Natural Selection
• Principle of Variation
Variations exists between individual members of a
species that are inheritable from one generation to
the next.
• Principle of Overpopulation
Species tend to produce more offspring than can
survive during any given generation.
• Principle of the Struggle for Existence
The environment may favors members of a species
having particular variations, and those favored will
pass their variations on to the next generation.
On the Origin of Species
• Alfred Wallace a
biologist studying in
Indonesia wrote to
Darwin about natural
selection
• A joint paper was
arranged and presented
before the Royal
Society of London
• Subsequently published
Origin of Species in
1859
Darwinian Deductions
• Darwinian evolution suggests that all currently living
and extinct species share a distant common ancestor
• Darwinian evolution is ‘materialistic’ in that is is based
purely on the empirical world and does not rely on the
spiritual.
• Darwinian evolution is ‘not progressive’ in that all
organism currently alive are equal in their
adaptability. We are not unique or more important
than other organisms.
• Similar to the Copernican Revolution in the physical
sciences.
Directional Selection
• Type of selection
event in which the
phenotypes at one
end of the
continuum of
variation are
selected against
Disruptive Selection
• Type of selection
event in which those
individuals with the
average phenotype
are selected against
Stabilizing Selection
• Type of selection
event in which
individuals having
the extreme
phenotypes in the
continuum of
variation are
selected against