C. Observations

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C. Observations 4. Biogeography Island Faunas
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C. Observations 4. Biogeography Island
Fauna - Fauklands species same as mainland
- Galapagos species different from mainland
a. degree of isolation correlated with uniqueness
of inhabitants..
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Voyage of the Beagle Darwin (1845) "The
natural history of these islands is eminently
curious, and well deserves attention. Most of the
organic productions are aboriginal creations,
found nowhere else
Flightless Cormorant
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there is even a difference between the
inhabitants of the different islands yet all
show a marked relationship with those of America,
though separated from that continent by an open
space of ocean, between 500 and 600 miles in
width.
Green Iguana Central and South America
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The archipelago is a little world within
itself, or rather a satellite attached to
America, whence it has derived a few stray
colonists, and has received the general character
of its indigenous productions. Considering the
small size of the islands, we feel the more
astonished at the number of their aboriginal
beings, and at their confined range.
Galapagos Land Iguana, pallid species, only on
Santa Fe island.
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Seeing every height crowned with its crater,
and the boundaries of most of the lava streams
still distinct, we are led to believe that within
a period geologically recent the unbroken ocean
was here spread out.
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Hence, both in space and time, we seem to be
brought somewhat near to that great fact -- that
mystery of mysteries -- the first appearance of
new beings on this earth. The Voyage of the
Beagle Charles Darwin
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C. Observations 4. Biogeography Island
Faunas a. Isolation correlates with uniqueness
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C. Observations 4. Biogeography Island
Faunas a. Isolation correlates with
uniqueness b. islands are dominated by
dispersive forms
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C. Observations 4. Biogeography Island
Faunas a. Isolation correlates with
uniqueness b. islands are dominated by
dispersive forms c. there is even variation
among islands
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- Finches
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"Seeing this gradation and diversity of structure
in one small, intimately related group of birds,
one might really fancy that from an original
paucity of birds in this archipelago, one species
had been taken and modified for different ends."
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- Mockingbirds
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- Mockingbirds Darwin classified four varieties
of one species
One species
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- Mockingbirds John Gould, the premiere
ornithologist of the day, classified these as
four species
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- Mockingbirds Darwin began to think could the
variation WITHIN species eventually lead to
variation BETWEEN species?
Could organisms in a species become so different
that they become different species?
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C. Observations 4. Biogeography Island
Faunas - How did these animals get here?
Everything points to migration from Americas
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C. Observations 4. Biogeography Island
Faunas - How did these animals get here?
Everything points to migration - But if
ancestors migrated from Americas,
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C. Observations 4. Biogeography Island
Faunas - How did these animals get here?
Everything points to migration - But if
ancestors migrated from Americas, then the
species must have changed over time into the
species we observe there today. Because they
are not the same.
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C. Observations 5. Argument P1 Species that
are alive today are different from those that
have lived previously. (Fossil Record)
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C. Observations 5. Argument P1 Species that
are alive today are different from those that
have lived previously. P2 Spontaneous Generation
is refuted, so organisms only come from other
organisms. (Experimentation)
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C. Observations 5. Argument P1 Species that
are alive today are different from those that
have lived previously. P2 Spontaneous Generation
is refuted, so organisms only come from other
organisms. C1 Thus, the organisms alive today
must have come from those pre-existing, yet
different, species.
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C. Observations 5. Argument P1 Species that
are alive today are different from those that
have lived previously. P2 Spontaneous Generation
is refuted, so organisms only come from other
organisms. C1 Thus, the organisms alive today
must have come from those pre-existing, yet
different, species. C2
There must have been change through time
(evolution).
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C. Observations 5. Argument P1 Species that
are alive today are different from those that
have lived previously. P2 Spontaneous Generation
is refuted, so organisms only come from other
organisms. C1 Thus, the organisms alive today
must have come from those pre-existing, yet
different, species. C2
There must have been change through time
(evolution). Corollary The fossil record,
vestigial organs, and homologies are all
explicable and logical in this context, and
inexplicable (even heritical) in some theological
contexts (imperfection).
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I. Darwins Contributions A. His Life B. Origin
of Species C. Observations D. Hypothesis How
Change Occurs
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D. Hypothesis How Change Occurs 1.
Transitional Observations a. Domesticated Animals
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D. Hypothesis How Change Occurs 1.
Transitional Observations a. Domesticated Animals
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D. Hypothesis How Change Occurs 1.
Transitional Observations a. Domesticated
Animals Humans can change the characteristics
of a species by selecting for particular
traits. This can lead to the expression of
extreme variation, well beyond the original range
of variation in the initial group. Selection can
create. There are no wolves that are as small as
Chihuahuas
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D. Hypothesis How Change Occurs 1.
Transitional Observations b. 1844 Darwin Reads
Malthus - Essay On the Principle of Population
(1798)
Thomas Malthus (1766-1834)
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D. Hypothesis How Change Occurs 1.
Transitional Observations b. 1844 Darwin Reads
Malthus - Essay On Population P1 All
populations have the capacity to over-reproduce
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D. Hypothesis How Change Occurs 1.
Transitional Observations b. 1844 Darwin Reads
Malthus - Essay On Population P1 All
populations have the capacity to
over-reproduce P2 Resources are finite
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D. Hypothesis How Change Occurs 1.
Transitional Observations b. 1844 Darwin Reads
Malthus - Essay On Population P1 All
populations have the capacity to
over-reproduce P2 Resources are finite C
There will be a struggle for existence most
offspring born will die before reaching
reproductive age.
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D. Hypothesis How Change Occurs 2. Natural
Selection P1 All populations have the
capacity to over-reproduce P2 Resources are
finite C There will be a struggle for
existence P3 Organisms in a population
vary, and some of this variation is
heritable
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D. Hypothesis How Change Occurs 2. Natural
Selection P1 All populations have the capacity
to over-reproduce P2 Resources are finite C
There will be a struggle for existence P3
Organisms in a population vary, and some of this
variation is heritable C2 Some
organisms, as a consequence of their inherited
traits, will be more likely to survive and
reproduce than others. There will be
differential reproductive success.
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D. Hypothesis How Change Occurs 2. Natural
Selection C2 Some organisms, as a consequence
of their inherited traits, will be more likely to
survive and reproduce than others. There will be
differential reproductive success. C3 So,
adaptive traits will be passed on in a population
at higher frequency than less adaptive traits.
These adaptive traits will accumulate in a
population. The population will change over
time. LINEAGE EVOLUTION.
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D. Hypothesis How Change Occurs 2. Natural
Selection C2 Some organisms, as a consequence
of their inherited traits, will be more likely to
survive and reproduce than others. There will be
differential reproductive success. C3 Over
time, adaptive traits will be passed on in a
population at higher frequency than less adaptive
traits. These adaptive traits will accumulate in
a population. The population will change over
time. LINEAGE EVOLUTION. Corollary Two
populations, adapting to different environments,
will become different from one another perhaps
so different that they are unable to mate, and
are different species RADIATIONAL EVOLUTION.
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E. Dilemmas 1. Evolution of complex traits

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E. Dilemmas 1. Evolution of complex traits

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E. Dilemmas 1. Evolution of complex traits 2.
Where are the continuous sequences of
transitional forms?
X
X
X
?
X
X
X
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• E. Dilemmas
• 1. Evolution of complex traits
• 2. Where are the continuous sequences of
  transitional forms?
• the fossil record is incomplete not all species
  leave a fossil
• Keep looking

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E. Dilemmas 1. Evolution of complex traits 2.
Where are the continuous sequences of
transitional forms? 1861 Archeopteryx
Lithographica
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E. Dilemmas 1. Evolution of complex traits 2.
Where are the continuous sequences of
transitional forms? 3. What is the source
of heritable variation???
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E. Dilemmas 1. Evolution of complex traits 2.
Where are the continuous sequences of
transitional forms? 3. What is the source
of heritable variation??? - Natural selection
should weed out poorly adapted forms over time,
making the organisms in the population more
similar (less variation). Why is there still so
much variation in natural populations?
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E. Dilemmas 1. Evolution of complex traits 2.
Where are the continuous sequences of
transitional forms? 3. What is the source
of heritable variation??? - selection should
eliminated variation - and if heredity is
governed by blending traits, then how is
variation produced generation after generation?

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E. Dilemmas 1. Evolution of complex traits 2.
Where are the continuous sequences of
transitional forms? 3. What is the source
of heritable variation??? - selection should
eliminated variation - and if heredity is
governed by blending traits, then how is
variation produced generation after generation?
- Darwins explanation - Lamarckian use and
disuse, and gemmules
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F. Darwinian Evolution 1. Darwins Model Sources
of Variation Causes of Change ????????????????
? VARIATION ? NATURAL SELECTION (use and
disuse??)