BIOL 112 1st Edition Lecture 9 Outline of Last Lecture I Observed Speciation II Questions III Shift in Host Availability IV Divergence of Fly Populations V Speciation in Action VI Classification and Diversity VII Naming Organisms VIII Carl von Linn IX Systema Naturae X Binominal System of Nomenclature XI Genus Name XII Specific Epithet Descriptor XIII Proper Use of Binominal XIV What is a Species XV Ways of Defining XVI Larger Linnaean Categories Outline of Current Lecture XVII Goal of Systematics XVIII Systematics Approaches XIX Cladistics XX Phylogenetic Trees 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 XXI Problems with Techniques XXII Hypothesis Formation XXIII How many Kingdoms XXIV Domains Current Lecture I Goal of Systematics Develop a scheme of organization which reflects the phylogeny evolutionary family tree of organisms Value judgments similarities and differences among organisms as basis of systematic schemes Birds and Mosquitos both fly should they be in the same category No Traits being compared for such a scheme should reflect a shared common ancestry Birds and mosquitos do not Traits important to categories should be homologous common origin Consequences of Goal Create monophyletic categories All organisms in category taxon have immediate common evolutionary ancestry including ancestors Avoid polyphyletic or paraphyletic taxa Paraphyletic leave creatures out of the taxa that make the data invalid Polyphyletic include other taxa that isn t homologous with the data has a different lineage II Systematics Approaches Classical Evolutionary Systematics Combines fossil records and fundamental homologies tried to create a balanced scheme of evolution and obvious characters of living groups not widely used these days because it s obsolete Phenetics Ignored or missing fossil record Analysis based upon characteristics of living organisms Didn t attempt to sort out homologies or analogies Scored hundreds or thousands of characters Used computers to develop categories based on numbers of common characters between organisms Closer related organisms will share more traits and analogies were regarded as random noise that would cancel itself out in the analyses Pioneered computer use in systematics Obsolete Cladistics major modern systematics approach Concentrates upon evolutionary developments Evolutionary innovations are critical to develop nested sets of categories clades III Cladistics Objective approach to evaluating data in the construction of degrees of relatedness Product is a diagram called a cladogram discussed in labs a lot a series of branch points that represent evolutionary divergence of two species from a common ancestor and nested categories called clades Clade contains ancestral species and all its descendants The lower the branch on the cladogram the more ancient the divergence so the structure of a cladogram can represent a historical evolutionary sequence Criteria Identify similar characteristics that would have taxonomic value Separate homologous characteristics discard analogous characters Identify shared primitive characters plesiomorphies every organism in the group has these so they have no value in our analysis Identify shared derived characters apomorphves evolutionary novelties that allow us to distinguish history of emergence of clades in the group Go to http evolution berkeley edu evolibrary article phylogenetics 01 for a demonstration on developing and using cladograms Molecular Cladistics Compares sequences for particular selected genes of evolutionary significance 16S rRNA sequences for example Or some genes common to all creatures in group being analyzed Computer programs set to construct clades and cladograms based on reconstruction of sequence changes necessary to produce the range of sequences in the group being studied IV Phylogenetic Trees Product of cladistics cladogram is not necessarily a phylogenetic tree a reconstruction of evolutionary history of group Need evolutionary history data fossils and or DNA sequence change information Cladogram can be a hypothesis of evolutionary sequence but extensive data needed to give historical information to reconstruct evolution in phylogenetic tree V Problems with Techniques Simplest cladistic trees can produce erroneous relationships in cladograms Groups formed might not correspond to known evolutionary relationships Requires careful application of cladistic methods to avoid these errors principle of maximum likelihood VI Hypothesis Formation Cladograms and phylogenetic trees can be the basis for development of testable evolutionary hypotheses VII How many Kingdoms Oldest scheme Linnaeus Two Kingdoms Plantae and Animal Intuitive categories but fitting organisms in was difficult by mid 19th Century Whittaker Margulis scheme Five Kingdoms Monera Protista Plantae Animalia Fungi New schemes based on emerging molecular information 9 to 16 or more kingdoms now up to 100 VIII Domains Recent work using molecular data has indicated the need for a taxon larger than Kingdom and for a radical reorganization of the larger categories Domains reflect major structural biochemical and molecular DNA sequences categories of life D Bacteria Prokaryotic familiar biochemistry D Archaea Prokaryotic less familiar biochemistry D Eukarya Eukaryotic forms Archaeans closer in many features to eukaryans than than they are to bacteria LUCA last universal common ancestor