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Evolution
Evidence and Theory
Biology 2009
Charles Darwin
Natural Selection
Organism best
suited to their
environment will
survive and
reproduce
Population
Interbreeding of a
single species
HMS Beagle
 Darwin was a
naturalist on the
H.M.S. Beagle
 5 year mapping and
collecting expedition
of South America
 Darwin observed
finches of Galapagos
Islands
 13 species with
different beaks but
all similar
The Origin of Species
(1859)
Book stating
Darwin’s Theory
21 years of
refining after trip
to Galapagos
Descent With Modification
Newer forms are
modified
descendents of
older forms
because of
VARIATION
Variation
Subtle differences
between
individuals
Modification with Natural
Selection
 Environment limits
population growth
because of variation
 Organisms with
more favorable traits
will survive and pass
on traits to offspring.
Unfavorable traits
will die out thus
changing the
population
Adaptation
 Adapt
 To change genetically
over generations to
be more suited to the
environment
 Adaptive Advantage
 An organism that
adapts will more likely
survive and reproduce
 Ex. giraffes
Geographic Isolation
Separation of
populations as
a result of
geographic
change or
dispersal to
isolated places
Adaptive Radiation
Evolution from
a common
ancestor that
results in
diverse species
adapted to
different
environments
Punctuated Equilibrium
Species often
diverge in
spurts of rapid
change
followed by
periods of
stability
Evidence of Evolution
Fossils
Traces of a dead
organism often
found in layers of
sedimentary rock
Mold
 Imprint in rock of
shape of
organism
Cast
 Rock-like model
of organism
More Fossil Stuff
 Law of Superposition
 Successive layers of
rock are deposited on
top of one another by
wind or water
 Stratum - Layer of
Earth
 Relative age - Use
stratum to say
whether fossil was
older or younger
 Absolute age - Age
in years depending
on layer above it
Succession Forms
Extinct
Disappearance of
a species
Mass Extinction
Brief period when
large number of
species
disappeared
Homologous Structures
Similar Features
that originated
from a common
ancestor
Beaks of finches
Forelimb of
vertebrate
animals
Vestigial Structure
 Structures that were
useful to an ancestor
but not to modern
organism
 Human tailbone
 Once a tail
 Pelvic bones in snakes
 Previous attachment
of legs
Similarities in Embryos
 Vertebrates had
common ancestors
 Ontogeny
Recapitulates
Phylogeny
 Embryo - fertilized
egg that develops into
an individual
 Develop and look
alike
Similarities in
Biochemistry
 Many species with
common ancestors
share similar
proteins, DNA, and
RNA
 Human vs Gorilla
hemoglobin protein
 Amino Acid sequence
has 1 different
Amino Acid
 Human Vs. Frog
 67 differences in
hemoglobin protein