Transcript Darwin`s Finches - BioGeoWiki-4ESO

Darwin’s Finches
An example of Adaptive Radiation
The Galapagos Islands
Finch Types:
Using Darwin’s
Theory, explain how all
of these different
species evolved.
Darwin…one smart guy…
“Seeing this gradation &
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.”
Phylogenetic Trees
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Show evolutionary “relatedness”
Based on fossil record, dna evidence, structural
similarity, etc
What common ancestor do all of
These organisms share?
Darwin’s Finches…again…
What common ancestor do
the seed eating and cactus
eating finches share?
What do each of the finch
pictures on here represent?
Which 2 species are more
closely related:
a. Mangrove Finch and
Woodpecker finch
b. Small ground finch and
Bud-eating finch
Good Questions with Good Answers.
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How can new species be formed and the
old one not go extinct? Wasn’t the whole
reason a new species formed was that it
had a survival advantage?
Speciation does NOT necessarily
cause EXTINCTION!
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A NEW SPECIES’ existence just means…
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That POPULATION’S GENE POOL has been
altered so much that there are new genes in
EVERY MEMBER’S GENOTYPE
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And THESE NEW GENES make it impossible for
them to mate with members of the other
population
NOW there are TWO SPECIES
Eventually…one may go extinct, but NOT
NECESSARY!!!
Geographic Isolation…
Sometimes populations
are spit In two due to a
geographic barrier. This
can lead to reproductive
isolation. How could this
lead to speciation?
Reduction of Gene Flow…
If members of a species live far away from each other, they will have a
decreased chance of mating. This would create reduced gene flow, but not
total isolation. Speciation would probably also require different selective
pressures at the two ends.
Eventually, this could alter
gene frequencies in
groups at different ends
of the range so much that
they would not be able to
mate if they were
reunited…that’s
speciation!