1 Define evolution and make sure you understand the definitions of the terms we used in that definition Evolution process of descent with modification o descent the cumulative transmission of a population s genetic information across generations o modification the changes in the composition of the genetic information that is passed down in a population 2 What was Darwin s critical insight into the mode of operation of this natural selection idea In other words how did his conception of selection differ from the ideas about selection that were circulating in scientific circles before he proposed his idea Darwin drew on the idea of artificial selection to say there was a natural selection Natural selection association between trait variation and fitness of offspring Said selection works among individuals not based on common traits He saw what everyone else saw but thought about it differently same evidence Natural selection acts on small continuous differences among individuals within a population o Variation among individuals originates via chance novelties o No ultimate purpose or design whichever features enhance fitness are selected This process ultimately creates new species and identity by descent Came up with many of these ideas working on the Beagle as a naturalist Divergent selection a species evolves into two or more different species with different characteristics o Often due to geographic isolation followed by different selective pressures o Divergent selection and isolation split a lineage o This is why end up with different species of finches on the Galapagos o Homologies that aren t analogous shows shared pattern of decent Homologous characters in different organisms that are similar because they were inherited from a common ancestor that also had the character share common embryonic features o Ex The four limbs in birds bats mice and crocodiles o Ex Nonhomolgous the wing types of birds and bats structural dissimilarities that suggest the wings weren t inherited from a common ancestor with wings Analogous have separate evolutionary origins but are superficially similar because they evolved to serve the same function from convergent evolution organisms not closely related independently evolving similar traits o Birds and bats wings are analogous as wings have different features o BUT they are homologous as forelimbs both have 4 forelimbs o Start talking about grouping species on relatedness Same mechanism natural selection works upon both o Anagenesis change in feature of an organism across time within a lineage o Cladogenesis formation of new species from splitting of a lineage Sexual selection things that make male stand out o Put males at risk cause greater energy expenditure o For males drive to mate is so strong can overrun the drive to survive and females encourage this by choosing males with these exaggerated traits Originally thought small continuous variation were inherited but now know through mendel s work goes by o Particular inheritance segregation of discrete traits Ex Round vs wrinkled pees Segregate in 1 2 1 ratio Only large discrete differences are inherited o Limited allelic variation for any character o Selection cant push a trait beyond its original limits its average range what can cause this though is mutation 3 What do we mean when we speak of hidden genetic variation in the context of selection and evolution o Many times genetic variation is hidden the genotypes are different but this different isn t shows in phenotype could be because heterzygote vs homozygote 4 How do entirely new genes appear to arise Think about this carefully you have to be clear about what we mean by a new gene a gene whose product has a different function than the function performed by its ancestor and what steps unfold to make a gene new o Unequal recombination and gene duplication 1 Duplicate genes lined up in tandem produces series of genes that then diverge when expressed a Number of copies changes in ordered fashion 2 Deletes a sequence from one stand and replaces it with a sequence from homologous or sister strand ii Domain shuffling 1 This is the reason why groups of genes appear to include elements in common in various combinations as if some domains have been shuffled mixed and spliced together 2 Have same segment of nucleotides in common 3 Mix and match among many different genes 4 groups of genes include element in common in various combos as if domains 5 transposon mediated a transposable element small piece of DNA that inserts itself into another place in the genome i element within DNA that replicates and can dispatch or transpose the copy to another location in the genome b if it takes other chunks of DNA with it then you can have another gene form c Class I Replication via RNA intermediate i Retrotransposons 1 LINE contain coding sequences for reverse transcriptase and catalyze their own transposition 2 LTRs insertion points for retroviral infections of host DNA often seen as naked LTRs that have lost the coding sequence for viral products like capsule protein ii Retrosequences 1 SINE can amplify RNA intermediates whose DNA sequence is nearly identical with viral genes d Class II Replication via DNA intermediate i Contain specific insertion sequences inverted repeats and transposase and associated proteins sometimes coding sequences for other proteins ii Found in eukaryotic DNA variegated corn and prokaryotic DNA especially on plasmids iii Agents of many visible mutations ex Wrinkled peas iii alternative splicing 1 different genes spliced differently end up with very different products 2 results in a single gene coding for multiple proteins 3 multiple RNA generated from a single gene 4 involved splicing together of exons iv overlapping genes one genes expressible nucleotide sequence overlaps that of another gene 5 What was the significance of Darwin s observing the differences among populations of many species or closely related species e g mockingbirds tortoises etc on different islands in the Galapagos in their morphological features o Patterns in biogeography i Same species look different on different islands ii Began noticing some islands were younger than the mainland this was important because found forms of things on newer islands that weren t found on mainland iii Galapagos mocking birds may vary throughout island 1 Different mocking birds were descendants of migrants from mainland iv Insitu mutability changes on young islands 6 A critical