Lecture 9 BIO 311D 1st Edition Outline of Last Lecture I Frequency Dependent Selection II Why natural selection cannot fashion perfect organisms III Reproductive Isolation IV Speciation Outline of Current Lecture I Sympatric Speciation II Habitat Differentiation III Sexual selection IV Phylogeny V Hierarchal Classification VI Homology and Analogy Differences Today s Lecture Sympatric 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 species Habitat 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 as more recently introduced apple trees Sexual Selection Sexual selection can drive sympatric speciation Sexual selection for mates of different colors has likely contributed to speciation in cichlid fish in Lake Victoria Phylogeny 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 nomenclature o The first part of the name is the genus o The second part is unique for each species within the genus called the specific epithet o The first letter is capitalized and italicized o The second letter is not capitalized Which is the correct way to write the Latin binomial for human beings A Homo sapiens B Homo Sapiens C Homo sapiens D Homo Sapiens Hierarchical Classification From most broad to narrow is o Domain o Kingdom o Phylum o Class o Order o Family o Genus o 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 related species A phylogeny was used to identify the species of whale from which whale meat originated Sorting 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 evolution o 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 called homoplasies 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 organisms
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