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UT BIO 311D - The Origin of Species (Part II)
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Lecture 9 BIO 311D 1st EditionOutline of Last Lecture I. Frequency-Dependent SelectionII. Why natural selection cannot fashion perfect organismsIII. Reproductive IsolationIV. SpeciationOutline of Current Lecture I. Sympatric SpeciationII. Habitat DifferentiationIII. Sexual selectionIV. PhylogenyV. Hierarchal ClassificationVI. Homology and Analogy DifferencesToday’s LectureSympatric (same country) Speciation:- Speciation takes place in geographically overlapping populations- Polyploidy is the presence of extra sets of chromosomes due to accidents during cell division- Polyploidy is much more common in plants than in animals- An autopolyploid is an individual with more than two chromosome sets, derived from one species- An allopolyploid is a species with multiple sets of chromosomes derived from different speciesHabitat Differentiation:- Sympatric speciation can also result from the appearance of new ecological niches- For example, the North American maggot fly can live on native hawthorn trees as well asmore recently introduced apple treesSexual Selection:• Sexual selection can drive sympatric speciation• Sexual selection for mates of different colors has likely contributed to speciation in cichlid fish in Lake VictoriaPhylogeny:- Evolutionary history of a species or group of related species- Can’t tell time differences, but we can tell the amount of divergence - Systematists use fossil, molecular, and genetic data to infer evolutionary relationships- Shows evolutionary relationships- Taxonomy is the ordered division and naming of organisms- Binomial nomenclatureo The first part of the name is the genuso The second part is unique for each species within the genus (called the specific epithet)o The first letter is capitalized and italicizedo The second letter is not capitalizedWhich is the correct way to write the Latin binomial for human beings?A. Homo sapiensB. Homo SapiensC. Homo sapiensD. Homo SapiensHierarchical Classification:- From most broad to narrow is:o Domaino Kingdomo Phylumo Classo Ordero Familyo Genuso Species- The broader taxa are not comparable between lineages What we can and cannot learn from phylogenetic trees:• Phylogenetic trees show patterns of descent, not phenotypic similarity• Phylogenetic trees do not indicate when species evolved or how much change occurred in a lineage• It should not be assumed that a taxon evolved from the taxon next to it• Phylogeny provides important information about similar characteristics in closely relatedspecies• A phylogeny was used to identify the species of whale from which “whale meat” originatedSorting Homology from Analogy:- Homology: similarity between siblings due to inheritance from genetic make up- Analogy: Similarities due to some other factor like an environmental factor or convergent evolutiono Convergent evolution occurs when similar environmental pressures and natural selection produce similar adaptations in organisms from different evolutionary lineages- Bat and bird wings are homologous as forelimbs, but analogous as functional wings- Analogous structures or molecular sequences that evolved independently are also calledhomoplasies- Homology can be distinguished from analogy by comparing fossil evidence and the degree of complexity- The more complex two similar structures are, the more likely it is that they are homologous- Systematists use computer programs and mathematical tools when analyzing comparable DNA segments from different


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UT BIO 311D - The Origin of Species (Part II)

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