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MODERN
EVOLUTIONARY
THEORY
WHAT HAPPENED AFTER DARWIN?
PROBLEMS WITH DARWIN’S
THEORY
1. Why is there
variation within
a species?
2. How are traits
passed from
one generation
to another?
http://4.bp.blogspot.com/EmedhzGoq4U/Tl14PpYybRI/AAAAAAAAgT0/nzHhIdibNw8/s800/101%2Bdalmatians%2Bposter.jpg
WATSON AND CRICK’S MODEL OF
DNA STRUCTURE
Central Dogma of Molecular Biology
DNA  RNA  protein
•
genes – portions of the DNA
that code for a specific
protein
•
proteins – amino acid
sequences that are
workhorses of living
systems
http://www.chemheritage.org/Images/Main-Images250x290/Discover/Themes/Biomolecules/watsoncrick1.jpg
DISCOVERY OF
THE GENETIC
CODE
series of
instructions that
shows how
proteins are made
based on DNA/RNA
http://4.bp.blogspot.com/-v3WGNk6Pps/TxgT9DFFntI/AAAAAAAAGgA/U2ZMO0Qzjc/s1600/Dna%2Bgenetic%2Bcode%2BUnseen%2BR
are.jpg
SOURCES OF
INHERITABLE
VARIATION
1. Mutation
•
any change in DNA sequence
•
due to
•
•
mistakes in DNA replication
environmental factors
http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/MUT/Mut.Mutation.html,
http://static.ddmcdn.com/gif/evolution-fly.gif
SOURCES OF
INHERITABLE
VARIATION
2. Gene shuffling
•
independent chromosome
movement during gamete
formation (223~8.4 million gene
combinations)
•
sexual reproduction causes
variation within populations
•
members of a population
interbreed and are acted on in
similar ways by the environment;
they evolve together
http://1.bp.blogspot.com/_bAYLalavZ6w/TPtJ5s9xlZI/AAAAAAAAAD0/6KPTjLGRM8g/s1
600/meiosis.gif, http://local.brookings.k12.sd.us/biology/Mitosis.htm
EVOLUTION AS
GENETIC CHANGE
Natural
selection on
single-gene
traits
http://www.brainbeau.com/cihs/Evolution/Genes_Variation_Genetic
_Change_files/slide0066_image020.jpg
Change in
allele
frequency
Evolution
EVOLUTION
AS GENETIC
CHANGE
Natural
selection on
polygenic
traits
Change in
distribution
of
phenotypes
Evolution
http://www.citruscollege.edu/lc/archive/biology/PublishingImages/0306l.jpg
EVOLUTION
AS GENETIC
CHANGE
•
Natural selection is NOT always necessary for
genetic change to occur
•
Genetic drift
•
•
when an allele becomes common in a population by chance
not all characteristics of an organism contribute to its fitness
http://biology.unm.edu/ccouncil/Biology_203/Images/PopGen/bottleneck.gif
SPECIATION
Formation of a new species
• species  group of
organisms that
interbreed and
produce fertile
offspring
• reproductive
isolation
•
•
•
behavioral isolation
geographic isolation
temporal isolation
Evolution
Reproductive
isolation
Separation
of gene
pools
Different
responses to
natural
selection
and genetic
drift
http://csmith1974.files.wordpress.com/2010/11/behavioral-isolation-1.jpg, http://bioweb.cs.earlham.edu/912/formation/IMAGES/fish.jpg, http://biology-forums.com/gallery/33_14_07_11_5_59_19.jpeg
EXPERIMENTAL EVOLUTION
Darwin’s Hypothesis
http://4.bp.blogspot.com/-KhUhy5HCFNk/TVb-KjAZtGI/AAAAAAAAAew/f4iTxy9qSE4/s1600/Galapagos-finches.jpg
EXPERIMENTAL EVOLUTION
Grant Experiment
Enough inheritable
variation in beak size and
shape
Differences in beak size and
shape  differences in
fitness
Identify and measure as
many birds as possible on
one island
Observe survival of different
birds when resources are
scarce
Many of the characteristics
appeared in bell-shaped
distributions
Birds with differently-sized
beaks had different chances
of surviving a drought
There is great variation of
inheritable traits among
finches
Big-beaked birds had higher
chances of surviving during
a drought
SPECIATION IN DARWIN’S FINCHES
Founders
arrive
Separation of
populations
on different
islands
Natural
selection 
changes in
the gene pool
Continued
evolution
Ecological
competition
Reproductive
isolation
MACROEVOLUTION
Large-scale evolutionary changes that occur over long periods of time
MASS EXTINCTIONS
• Disappearances of
huge numbers of
species
• Asteroids, geological
activity
• Disappearance of
dominant species
allowed other species
to take over
ADAPTIVE RADIATION
• A single group of
species evolved into
different forms that live
in different ways
• Produces great
diversity
http://mindblowingscience.com/science-by-numbers/the-5-major-mass-extinction-events/
MACROEVOLUTION
Large-scale evolutionary changes that occur over long periods of time
CONVERGENT
EVOLUTION
• Unrelated
organisms
resemble one
another
• Due to similar
environmental
conditions
COEVOLUTION
• When organisms
that interact closely
with one another
evolve together
http://students.washington.edu/kjbyers/coursework.html
MACROEVOLUTION
Large-scale evolutionary changes that occur over long periods of time
PUNCTUATED
EQUILIBRIUM
CHANGES IN
DEVELOPMENTAL GENES
• Rapid evolution may
occur after long stable
periods
• Usually occurs because of
genetic drift or together
with adaptive radiation
• Similar hox genes are
present in diverse
organisms
• These dictate the basic
body plan of the organism
• Major evolutionary
changes may have
occurred through these
genes
http://withfriendship.com/images/i/42351/Punctuated-equilibrium-picture.jpg, http://sciphu.files.wordpress.com/2008/02/punctuated-equilibrium.jpg