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Morphological traits: fossil record and living organismsBiochemical/physiological traits: living organisms, chemical processes, molecules producedMolecular systematics: comparing DNA/RNA sequences in living organismsTaxonomy: based on Linnean system (Carolus Linnaeus, 1700’s)Classified all plants and animals knowns at the timeBased on morphological similarities/differences (not evolutionary relationshipsHierarchical (species grouped into increasingly broad categories)Ex: Leopard (Panthera pardus), genus Panthera includes African lion (Panthera leo) and tiger (panther pardus)Taxonomy and systematics are linkedHistory of morphological characters (fossil record + age of rocks)Additional clues about evolutionary history: morphological, physiological and molecular (DNA/RNA) information about living organismsConstruct branching, hierarchical diagrams about relationships among groups of organisms (phylogeny = hypotheses)Phylogeny: the evolutionary history of a group of organisms; A summary of relatedness among groupsPhylogenetic Tree: A graphical summary of relatedness that describes the pattern (and sometimes timing) of branching (relatedness) among lineagesClade: A group of taxa derived from a common ancestorTaxon: A group of genetically related organisms, such as populations, species, genera, families, etc.e.g., Humans, great apes, mammals, vertebratesSpeciation events = so divergent that speciation doesn’t occur anymorePolytomy something you want to try and avoid
What Characteristics should be used to construct a phylogeny?3 major factors (or considerations)1.They must be homologous a.Homologous Trait: Shared trait found in common ancestor and descendentsi.Ex: ARM of monkey and wing of bird is ok because morpholcially similarii.Ex: LEG of “ “ is NOT ok due to morphological differences2.They must minimize homoplasya.Homoplasy: shared trait NOT found in common ancestor; phenotypic similarity among distantly related taxa (convergence) or phenotypic dissimilarity among closely related taxa (divergence)i.Ex: fur color is NOT a good trait, but presence of feathers IS a good trait because feathers is a homologous trait for all birdsii.Convergence: unrelated groups evolve similar phenotypes independently (Ex. Flippers in penguins and dolphins is example of homoplasy flippers is an advantage in the environment in which they live)iii.Reversals: Related taxa no longer share a homologous trait found in a common ancestor (lost in one or both taxa) (Ex. porpoises & fish lack fur and cattle have fur cattle and porpoises are more closely related than porpoises and fish (No hair was an adaptation for porpoises))3.Many independently evolving characters to help counter the “noise” of homoplasya.2 major types of charactersi.Molecular Data: usually DNA, RNA or Protein sequences)ii.Gross Phenotypic Data: bones, teeth, behavior, etc.)iii.EX: Birds, lizards, and crocodiles crocodiles and birds have gizzards, lizards do not even though lizard and crocodile look similarCladistic Method: Identifies monophyletic groups (i.e. those derived from a common ancestor = clades)