Evidence for Evolution
Honors Biology
What is the Evidence of Evolution?
Darwin Argued That Living Things Have Been Evolving On
Earth For Millions of Years. Evidence For This Process
Could Be Found In:
– The Fossil Record
– Biogeography (the Geographical Distribution of
Living Species)
– Homologous Structures of Living Organisms
(Comparative Anatomy)
– Embryology
1.
Homology
• a similarities in characteristic traits resulting from
common ancestry
2. Anatomical Homologies (Comparative
Anatomy)
• From a common ancestor
• Called HOMOLOGOUS STRUCTURES
• Same structure and development, but
different function
• Examples = Vertebrate limb bones, bird
feathers/mammal hair
Homologous Structures
• Homologous structures are structures (body
parts) that are anatomically similar structures
inherited from a common ancestor but
different function.
LE 22-14
Human
Cat
Whale
Bat
Comparative Anatomy
3) Analogous Structures:
• Through convergent evolution
– Convergent evolution the evolution of a
species from different ancestors toward
a similar (not the same!) form
• Structures that perform a similar job,
but are not from a common ancestor
• Example = bird wing, bat wing, and an
insect wing
4. Vestigial organs
• remains of
structures/organs that
ONCE had an importance
in organism’s ancestors
– Example: tailbones in
humans, appendix,
wings on ostrich,
wisdom teeth in
humans, nipples in
male mammals, femur
and pelvis in whales
5. Comparative Embryology
Embryology
• Embryology is a new method
of examining evidence of
evolution
– Embryo = first 9 weeks of
vertebrate development
• Embryonic structures of
different species show
significant similarities
• By studying the same
patterns of early
development across many
different animals, we can
find evolutionary links
between animals
6. Molecular Homologies
• Similar genes (DNA), RNA or amino
acid sequences
–Example
• genes shared among organisms
inherited from a common ancestor
• Ex #1: Homeobox is a DNA sequence
in genes that regular development in plants,
animals and fungi
• http://www.pbs.org/wgbh/evolution/library/03/4/l_034_04.html
LE 22-16
Species
% of Amino Acids That Are
Identical to the Amino Acids in a
Human Hemoglobin Polypeptide
Human
100%
95%
Rhesus monkey
87%
Mouse
69%
Chicken
54%
Frog
Lamprey
14%
Ex #2:
Amino
Acid/
Protein
sequenc
7. Biogeography
• the geographic distribution of species
Sugar
Glider
Marsupial
•Some similar mammals that
have adapted to similar
environments have evolved
independently from different
ancestors
Flying
Squirrel
Eutherian
(placental)
8. Genetic Changes over
time
• Bacteria becomes resistant
to antibiotics
9. Fossil Records
• Paleontologists have discovered
fossils of many transitional forms
• Shows variety on organism across
time
The Fossil Record
• Earth is BILLIONS of years old
• Fossils in different layers of rock
showed evidence of gradual
change over time
• Paleontologists have discovered
fossils of many transitional
forms
– Example- Whales have an
excellent fossil record-showing
transitional forms
The Fossil Record
• The succession of forms in the fossil record clearly
suggests that organisms change through time, and
have descended from a common ancestor
• Different groups appear in the fossil record at
different times, with a general trend toward the
simplest organisms appearing the EARLIEST
RECALL: Evidence for
Evolution
• Fossil record
• Comparative Anatomy
– Homologous structures
– Analogous structures
• Comparative Embryology
• Vestigial structures
• Molecular biology (DNA/RNA/protein amino
acid differences)
• Biogeography
• Field studies
Natural Selection vs.
Artificial Selection
• Recall Natural selection
– http://bcs.whfreeman.com/thelifewire/content/chp23/2
302001.html
• In artificial selection,
• humans modify other species over many
generations by selecting and breeding
individuals with desired traits
Key Concepts
What is the raw material necessary for
the mechanism of Natural Selection?
• Heritable variations
What is the smallest unit of evolution?
• Populations (NOT individuals)
• Darwin incorporated Lyell’s gradualism into
biological evolution combined with Malthus’
observations regarding populations
Is Evolution JUST a
THEORY??? Is it SCIENCE
based?
• A theory
• accounts for MANY observations and data
• attempts to explain and integrate a great variety
of phenomena
• http://www.pbs.org/wgbh/evolution/educators/t
eachstuds/svideos.html
• Video #1: Isn’t Evolution Just a Theory?
Cladogram
• Diagram showing how organisms are related
based on shared, derived characteristics
such as feathers, hair, or scales
copyright cmassengale
24
Outgroups vs. Ingroups
• Outgroup
– The species or group of species that is closely
related to the ingroup
– Distinguishes between shared primitive and
shared derived characteristics
– Closely related to ingroup
• Ingroup
– the various species we are studying
A Cladogram
What is the shared primitive characteristic? Notochord
Lamprey
Aminion
Placenta
Foramen magnum