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Evidence for Evolution
Professor Andrea Garrison
Biology 11
Illustrations ©2010 Pearson Education,
Inc. , unless otherwise noted
Fossil Evidence
• Fossil record
– Fossils accepted as
evidence of once-living
organisms that have
been preserved
– Give idea of types of
organisms living during
the time rock was being
deposited
– Date rocks to date fossils
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Fossil Evidence
• Give general picture of changes that have
occurred in living forms over geologic history
– Oldest fossils less complex
– Younger fossils more similar to living species
• Trends support concept of change in species
over time
• Variety of fossil types
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Fossil Evidence
• Trace fossils
– Evidence that organism
was there
– Tracks, burrows, dung
– Tracks to right (identified
as Chirotherium) are
only known from the
tracks—do not know
what dinosaur is
associated with them
Evidence for Evolution; picture
http://en.wikipedia.org/wiki/Trace_fossil
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Fossil Evidence
Mesolimulus walchi fossilized w/its tracks, (very rare to find together)
Evidence for Evolution; picture
http://en.wikipedia.org/wiki/Trace_fossil
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Fossil Evidence
Arthropod tracks from late Cambrian
Evidence for Evolution; picture
http://en.wikipedia.org/wiki/Trace_fossil
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Fossil Evidence
• Trace fossils
– Coprolite: fossil dung
• Coprolite shown is from a carnivorous dinosaur (~13 inches long)
Evidence for Evolution; picture http://en.wikipedia.org/wiki/Coprolite, source
USGS
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Fossil Evidence
• Trace fossils
– Burrows shown below are believed to have been made by
crustaceans during the middle Jurassic (145 – 200 MYA)
Evidence for Evolution; picture
http://en.wikipedia.org/wiki/File:ThalassinoidesIsrael.JPG
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Fossil Evidence
• Compression fossils
– Carbon film: Original organic material altered to a carbon
film in rock layers
Evidence for Evolution; picture
http://en.wikipedia.org/wiki/File:Priscacara_liops_Green_River_Formation.jpg
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Fossil Evidence
• Compression fossils
– Ginkgo biloba, Eocene (34-56 MYA)
Evidence for Evolution; picture
http://en.wikipedia.org/wiki/File:Ginkgo_biloba_MacAbee_BC.jpg
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Fossil Evidence
• Replacement fossils
– Original organic material replaced by another mineral
Evidence for Evolution; picture
http://en.wikipedia.org/wiki/File:PetrifiedWood.jpg
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Plate Tectonics
Evidence for Evolution; picture
http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php
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Plate Tectonics
Evidence for Evolution; picture http://en.wikipedia.org/wiki/File:Tectonic_plate_boundaries.png,
USGS
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Plate Tectonics
Evidence for Evolution; picture
http://earthquake.usgs.gov/learn/topics/plate_tectonics/rift_man.php
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Plate Tectonics
• Pangaea (225 MYA)
– Tectonic plates brought
continents together in
supercontinent
• Gradually split apart (starting
180 MYA)
– About the time mammals show
up in fossil record
– Formed current continental
patterns
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Plate Tectonics
• Australia separated very early
– Mammals here unlike those of other
plates
• Fossil records show common fossils
during periods when continents
touching
– Brazil and W. Africa show matching
reptiles
• Can watch separate evolutionary
patterns after the split
– Mammals vary between the continents
(different selective pressures due to
different environments on two sides of
ocean)
Evidence for Evolution
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Biogeography
• Fossils in given area tend to be more closely
related to living organisms only in that region,
not in other regions with same climate
• Regions with similar climates have organisms
which show similar adaptations, but are not
related to one another
– Cactus in N. America and spurge in Africa show
adaptations for desert areas, but are very different
plants
Evidence for Evolution; picture
http://earthquake.usgs.gov/learn/topics/pl
ate_tectonics/rift_man.php
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Biogeography
• Unusual mammals in Australia show the effects of
being isolated from other continents
Evidence for Evolution
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Comparative Embryology
• Early developmental stages of organisms related at
subphylum level or below have very similar
embryology
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Comparative Anatomy
• Homologous structures show common anatomical theme
– Similar body parts derived from similar embryonic structures,
even if used differently
Evidence for Evolution
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Comparative Anatomy
• Extinct whale with hind limbs (considered transitional)
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Comparative Biochemistry
• All living organisms have same types of
molecules
– Proteins, carbohydrates, fats, nucleic acids
• Universal genetic code
– All living organisms have DNA as hereditary
material
• Same 4 bases: A, T, C,G
• In almost all cases, the DNA codes for amino acids are
the same
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Comparative Biochemistry
• Comparison of DNA sequences used to
determine close relationships
– Argument assumes similar DNA implies close
relationship
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Experimental Evolution
• Basic tenet of science is that it is observable
and testable
– Should be able to observe and test evolutionary
theory
– Difficult due to length of time required
– Some success with short-lived organisms
• Indiscriminate use of pesticides → resistant insect
strains
• Indiscriminate use of antibiotics → resistant bacteria
• These are not new species, however
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Experimental Evolution
• New species of plant created in the lab
– Stebbins (1940s) induced doubling of
chromosomes in Ehrharta erecta
• Resulting plant was new species
– Unable to mate with parent plant
» Survived in environment in So. California for 40 years
» Not as successful as parent plant in the environment
• http://www.calflora.org/cgibin/species_query.cgi?where-calrecnum=2895
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Evidence of Evolution
• There does appear to be evidence for change within a
species
• Evidence points to environment as being driving force
for change
• Fossil record tells a lot
• Most of the changes we can observe are not new
species, but rather new strains
• Recent evidence indicates rate of change may vary over
time
• Natural selection still best mechanism we have to
explain what we see
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