Modern Evolutionary Theory What happened after darwin?

Problems with darwin’s theory Why is there variation within a species? 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-Images-250x290/Discover/Themes/Biomolecules/watson-crick1.jpg

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 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/s1600/meiosis.gif, http://local.brookings.k12.sd.us/biology/Mitosis.htm

Evolution as genetic change http://www.brainbeau.com/cihs/Evolution/Genes_Variation_Genetic_Change_files/slide0066_image020.jpg Natural selection on single-gene traits 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 Evolution Reproductive isolation Separation of gene pools Different responses to natural selection and genetic drift Speciation Formation of a new species species  group of organisms that interbreed and produce fertile offspring reproductive isolation behavioral isolation geographic isolation temporal isolation

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 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 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

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

PUNCTUATED EQUILIBRIUM CHANGES IN DEVELOPMENTAL GENES Macroevolution Large-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