Download - Modern Evolutionary Theory
MODERN EVOLUTIONARY THEORYWHAT 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
• 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-Images-2
50x290/Discover/Themes/Biomolecules/watson-crick1.jpg
Central Dogma of Molecular Biology
DNA RNA protein
DISCOVERY OF THE GENETIC CODE
series of instructions that shows how proteins are made based on DNA/RNA
http://4.bp.blogspot.com/-v3WGNk-6Pps/TxgT9DFFntI/AAAAAAAAGgA/U2ZMO0-Qzjc/s1600/Dna%2Bgenetic%2Bcode%2BUnseen%2BRare.jpg
SOURCES OF INHERITABLE VARIATION
http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/MUT/Mut.Mutation.html, http://static.ddmcdn.com/gif/evolution-fly.gif
1. Mutation• any change in DNA sequence• due to
• mistakes in DNA replication• environmental factors
SOURCES OF INHERITABLE VARIATION
http://1.bp.blogspot.com/_bAYLalavZ6w/TPtJ5s9xlZI/AAAAAAAAAD0/6KPTjLGRM8g/s1600/meiosis.gif
, http://local.brookings.k12.sd.us/biology/Mitosis.htm
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
EVOLUTION AS GENETIC CHANGE
Natural selection on single-gene traits
Change in allele
frequencyEvolution
http://www.brainbeau.com/cihs/Evolution/Genes_Variation_Genetic_Change_files/slide0066_image020.jpg
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
SPECIATIONFormation 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/9-12/formation/IMAGES/fish.jpg, http://biology-forums.com/gallery/33_14_07_11_5_59_19.jpeg
EXPERIMENTAL EVOLUTIONDarwin’s Hypothesis
http://4.bp.blogspot.com/-KhUhy5HCFNk/TVb-KjAZtGI/AAAAAAAAAew/f4iTxy9qSE4/s1600/Galapagos-finches.jpg
EXPERIMENTAL EVOLUTIONGrant Experiment
Enough inheritable variation in beak size and
shape
Identify and measure as many birds as possible on
one island
Many of the characteristics appeared
in bell-shaped distributions
There is great variation of inheritable traits among
finches
Differences in beak size and shape differences in
fitness
Observe survival of different birds when resources are
scarce
Birds with differently-sized beaks had different
chances of surviving a drought
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
Reproductive isolation
Ecological competition
Continued evolution
MACROEVOLUTIONLarge-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/
MACROEVOLUTIONLarge-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
MACROEVOLUTIONLarge-scale evolutionary changes that occur over long periods of time
PUNCTUATED EQUILIBRIUM
• Rapid evolution may occur after long stable periods
• Usually occurs because of genetic drift or together with adaptive radiation
CHANGES IN DEVELOPMENTAL GENES• 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