BIO 171 1st Edition Lecture 7Outline of Last Lecture I. Gene by Gene Interactions II. Sex Chromosomes and Sex Linked Inheritance III. Linkage Between Genes Outline of Current Lecture I. Darwin and WallaceII. Phylogenetics Current LectureDarwin and Wallace -They had the following observations that lead to the idea that species evolve from other species:oSimilarities exist between fossils of extinct animals and animals found todayoIslands that are close together have similar animals inhabiting them oSome species posses vestigial structures (which are structures that don't serve a function but are still present in different species)oIndividuals within a given species vary in small waysoPopulations are kept in check due to the number of young animals that die in each generation (due to predation, lack of resources, etc.)-Darwin hypothesized that animals have similarities because they descended with modification from a common ancestoroIn development…..-Homology= similarities in organisms due to common descendant from a shared ancestor Ex) development of arms, similarities in DNA sequence, cell structure, etc.-Analogy= similarities in organisms that result from convergent evolution (result of adaptation to their environment)Ex) Both birds and butterflies have wings, but they have evolved differently and are used for different purposes These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.-The idea that organisms produce far more offspring than can survive is what gave rise to differential survival as a key mechanism in evolution (differential reproduction, or unequal reproduction, is most important)-Darwin/Wallace two big ideas:oLife on Earth had one single origin and all organisms present today are modified descendants of this common ancestor oNatural Selection= process by which individuals with advantageous heritable traits produce more offspring than individuals with less advantageous traits -Nat. Selection results in allele frequencies of the "favored" traits to increase from generation to generation -This allows for mutations that are deleterious to be eliminated, so they don't have a long-term evolutionary effect-Nat. Selection acts to increase the overall fitness of a population Fitness= a measure of the extent to which the individual's genotype is represented in the next generation-Conditions for Natural Selection:Must be variation within the population (something must be "selected")A selective pressure (or predator) must be present-favoring one variation over another (this leads to differential reproduction because only one, or few, variations are left to reproduce)Biological evolution= proportion of "favored" alleles increases in the population-Natural Selection is the only process that can result in adaptations, which are heritable traits that increase survival and/or reproductive success Phylogenetics -Phylogenetics aims to discover the pattern of evolutionary relatedness among groups of species or other groups, depicted as a phylogenetic tree-A phylogeny is a hypothesis about the evolutionary history of a group of organisms -Two species or groups are considered to be closest relatives if they share a common ancestor not shared by any other species or group (these are called sister groups) -Speciation (or the formation of new species through the course of evolution) begins with the cessation of gene flow between populations oIf species' are given a long enough period of isolation (due to separation of some sort), they will no longer be able to interbreed, so the result will be two different species -Different alleles will increase more or less in frequency in the different areas thathave been separated, meaning different traits are favored leading to different species -Phylogenetic trees are inferred by comparison of character states shared among different groupsof organismsoA monophyletic group on a phylogenetic tree includes a common ancestor and all of its descendants-Only monophyletic groups reflect evolutionary relationships because only they include all of the descendants of a C.A.oThe nodes, or places here the different branches connect in different places, represent a common ancestor or a speciation event occurring oExtinct species are represented on the tree by the early termination of a branchoThe outgroup= a species closely related to the species whose phylogeny is being constructed, but not related.-Any traits shared between the outgroup and the other members of the phylogeny are called ancestral traits-Any traits that are found in all other members other than the outgroup are called shared derived traitsShared derived traits are most useful in constructing phylogenetic trees because they show the differences among