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Chapter 15.3
Evidence of Evolution
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2006-2007
Dodo bird
Fossil Record
 The fossil record is incomplete but provides

some evidence about the history of the earth.
Fossils can show the progression of ancient,
primitive organisms to modern day forms.
Trilobite
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Leaf
 Fossil Record: The
history of life on
Earth can be partially
constructed by dating
(age) and comparing
fossils
- Relative Dating:
approximate age
based on position on
the rock layers
- Absolute Dating: Exact
age determined by
radioactive dating
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Extinct: Trilobite (crustacean)
Ammonite (mollusc)
Similar to present-day species: still around
Fish
Scallop (mollusc)
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Comparative Anatomy
A. Homologous structures: Homologous
structures develop from the same tissues, but
have different forms with different functions.
Same origin -- different form/function
 The similarity is due to having derived from the
same common ancestor.
Example: Bone structure of arms and legs in all vertebrates.
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B. Analogous Structures: Different origin but have similar
function
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Vestigial structures
 Modern animals may have structures
that serve little or no function
remnants of structures that were
functional in ancestral species
 evidence of change over time

 some snakes & whales show remains of the
pelvis & leg bones of walking ancestors
 eyes on blind
cave fish
 human tail bone
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 Hind leg bones on whale fossils
Why would whales
have pelvis & leg
bones if they were
always
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Comparative embryology
 Similar embryological development in
closely related species

all vertebrate embryos have a gill pouch
at one stage of development
 fish, frog, snake, birds, human, etc.
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Molecular record
 Comparing DNA & protein structure

universal genetic code!
 DNA & RNA

cytochrome C (respiration)
 protein structure

hemoglobin (gas exchange)
 protein structure
Evolutionary relationships among species are documented
in their DNA & proteins.
Closely related species have sequences that are more
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similar
than distantly related species.
Comparative hemoglobin structure
Human Macaque
8
Dog Bird
Frog
Lamprey
32 45
67
125
0 10 20 30 40 50 60 70 80 90 100 110 120
Number of amino acid differences between
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hemoglobin (146 aa) of vertebrate species and that of humans
Building “family” trees
Closely related species (twigs of tree) share same
line of descent until their recent divergence from a
common ancestor
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 VIEW:
http://www.pbs.org/wgbh/evolution/libr
ary/07/3/real/l_073_47.html
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What data from whole
genome sequencing can tell
us about evolution of humans
• Macroevolution – evolution on a large scale
(above population level)
How fast is evolution?
How fast do organisms change?
Gradualism
Punctuated Equilibrium
Gradualism
• Organisms go through gradual and continuous
change
Punctuated Equilibrium
• Organisms go through fast periods of change,
followed by long periods of no change (according to
fossil record)
Gradualism
Punctuated Equilibrium
Patterns of Evolution:
1. Convergent Evolution
• Convergent Evolution: When 2 or more unrelated
species become more similar due to similar
adaptations to their environment.
Convergent evolution
• Flight evolved 3 separate times
– evolving similar solutions to similar “problems”
Patterns of Evolution:
2. Divergent Evolution-Adaptive Radiation
• Divergent Evolution:
when related species
become more
different as they adapt
to different
environments
• Divergent evolution
leads to Adaptive
Radiation
Adaptive Radiation
• Process by which a
single species or
small group of
species evolved
into several
different forms
that live in
different ways
Coevolution
• Predator-prey relationships
• Parasite-host relationships
• Flowers & pollinators
Process by
which two
species
evolve in
response to
each other
over time