Change Through Time

Evidence of change through time
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Central tenet of the Theory of Special
Creation is that species, once created,
are immutable.
ƒ Microevolution
fEvolutionary changes
on the small scale,
such as gene frequencies within a population
ƒ Macroevolution
fEvolution on the grand scale; events above
the species.
Change Through Time
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Direct observation of
change of a species
ƒ Soapberry bug
evolved a shorter
beak within 20 years
of switching host
plants
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Change Through Time
Evidence from living species
` Vestigial structures
` Can be identified at structural,
developmental, and genetic levels
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Vestigial Organs
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A functionless or rudimentary version of a
body part that has an important function in
other, closely related species
Vestigial Organs
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Change Through Time
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Evidence from fossil record
ƒ Fossils are unlike species living today
ƒ Used to think that if we looked hard enough
we would find those fossilized species alive
somewhere
ƒ Extinction eventually became known as a
fact
ƒ Special creationists asserted that extinct
species were killed by biblical flood
Change Through Time
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Evidence from fossil record
ƒ Law of Succession shows extinct species are
ancestors of living species
f Did not die
in flood leaving no descendants
Pygmy Armadillo
Fossil Glyptodont
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Irish Elk (Cuvier)
Change Through time
ƒ Transitional forms
fDarwin was concerned that no transitional
forms had been found
the first Archaeopteryx was found
fIn 1860
ƒ Environmental change
fMarine
organism fossils found in deep
deserts and on high mountains
Transitional forms
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A. Archaeopteryx (140(140-150)
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B. Sinosauropteryx
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C. Dromaeosaurid
ƒ Confusciousornis (modern(modern-looking bird)
ƒ Primitive feathers
ƒ Primitive feathers
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D. Modern feathers
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Tree Thinking
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Species not
independently created
Darwin invented
technique to illustrate
how species are
related by descent
with modification
Species form the
Tree of Life
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Relatedness of Life Forms
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Comte de Buffon,
Buffon, Erasmus Darwin, JeanJeanBaptiste Lamarck had already proposed
evolution by compiling evidence
ƒ Homology
fSimilarity due
fComparative
to common ancestry
anatomy and comparative
embryology
fStructural, developmental, genetic
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Genetic code
Pseudogenes
Functional genes = exons,
exons, introns,
introns,
promoters
` Processed Pseudogenes =non=non-functional
` Arise from reverse transcription of
mRNA
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ƒ Resulting DNA is inserted at another locus
ƒ Newly created gene lacks introns,
introns, promoter
Pseudogenes
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Relatedness of Life Forms
Homology must be caused by
relatedness
` Why else would the exact same
underlying structures exist in very
different organisms that have different
ecologies?
` Evidence that all species are derived
from each other
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Relatedness of Life Forms
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Galápagos Islands
ƒ Darwin visited on HMS Beagle
ƒ Impressed by similar but distinct species on
each of the islands
ƒ Mockingbirds
ƒ Then, finches and tortoises
ƒ A population must have arrived from South
America on one island and spread to others
fSpecies
diverged separately on each island
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Age of the Earth
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By the time of Darwin’s work, evidence was
mounting that the earth is ancient
Principle of Uniformitarianism
ƒ James Hutton and Charles Lyell
ƒ Same processes we see today have always
been acting
f Volcanoes, erosion, earthquakes,
etc.
ƒ Opposed principle of catastrophism
f Geology result of
catastrophic events
ƒ The biblical flood
Age of the Earth
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Geologists measured rockrock-forming processes
and erosion rates
Earth is unimaginably old
Used relative dating
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Constructed geological time scale
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ƒ Assume that deepest rock layers are oldest
ƒ http://www.enchantedlearning.com/subjects/Geologi
http://www.enchantedlearning.com/subjects/Geologi
ctime.html
Each division is associated with a distinct fossil
biota
` Absolute dates later added
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Radiometric Dating
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Absolute dating of rocks
Unstable isotopes decay at a constant
rate
ƒ Rate not affected by temperature or
moisture
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Know halfhalf-life of isotope and measure
amount of original and daughter isotope
in rock sample
ƒ Gives age of rock
Radiometric Dating
Radiometric Dating
Different isotopes have appropriate halfhalflives for dating different time scales
` Some can be used to date the earth
`
ƒ Because earth was molten at beginning,
measure age of meteorites or moon rocks
fBecause solar system started at
same time
ƒ Earth is 4.6 billion years old
ƒ Life is 3.7 billion years old
fFirst fossil life
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Correspondence Among Data Sets
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Data in this chapter contradict three
propositions of special creation
ƒ Species created independently
ƒ Species are immutable
ƒ Earth is young
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If several data sets agree, we have even
stronger evidence
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Correspondence Among Data Sets
Theory of Plate Tectonics
` Radiometric dating
` Magnetic field of earth
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ƒ Magnetic field frozen in rocks when they
reach the crust so we know the direction of
magnetic field at that time
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Combined with the fossil record, we have
multiple lines of evidence
Correspondence Among Data Sets
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History of marsupials
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Once lived only in North America
Spread to Central and South America
Spread to Antarctica, Europe, Africa, and
Australia
Spread to Asia
Now only occur in the Americas and,
especially, Australia
Australia lacks placental mammals
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Conclusions
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Darwin and others found evidence against
Special Creation
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Homology
Vestigial structures
Direct observation
Fossil record
Geology
Correspondence among data sets
Created phylogenetic trees using parsimony
Defeated special creation with evolution
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