Morphological traits fossil record and living organisms

Morphological traits fossil record and living

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Morphological traits: fossil record and living organisms Biochemical/physiological traits: living organisms, chemical processes, molecules produced Molecular systematics: comparing DNA/RNA sequences in living organisms Taxonomy : based on Linnean system (Carolus Linnaeus, 1700’s) Classified all plants and animals knowns at the time Based on morphological similarities/differences (not evolutionary relationships Hierarchical (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 linked History of morphological characters (fossil record + age of rocks) Additional clues about evolutionary history: morphological, physiological and molecular (DNA/RNA) information about living organisms Construct 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 groups Phylogenetic Tree: A graphical summary of relatedness that describes the pattern (and sometimes timing) of branching (relatedness) among lineages Clade: A group of taxa derived from a common ancestor Taxon: A group of genetically related organisms, such as populations, species, genera, families, etc. e.g., Humans, great apes, mammals, vertebrates Speciation events = so divergent that speciation doesn’t occur anymore Polytomy 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 descendents i. Ex: ARM of monkey and wing of bird is ok because morpholcially similar ii. Ex: LEG of “ “ is NOT ok due to morphological differences 2. They must minimize homoplasy a. 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 birds ii. 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 homoplasy a. 2 major types of characters i. 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 similar Cladistic Method : Identifies monophyletic groups (i.e. those derived from a common ancestor = clades)

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