BI111 Lecture Notes - Lecture 11: Recapitulation Theory, Quills, Natural Selection
Document Summary
Twin goals of systematics: reconstruction of evolutionary history and classification of species. Phylogenetic trees come about through successive events of speciation (branching), in which one species gives rise to two (or more!)) Reconstructing these trees requires comparison of traits (with shared genetic ancestry) Binary nomenclature: genus and species (reflect the nested hierarchy of life) Name: what group does it belong to. Rank: where does it fit into phylogeny. All have similar homologous traits due to recent common ancestor. Resemblance due to similar selective pressures to fill niche (homoplasties) E. g. bones that support wings of bats, birds, and pterosaur all look like modifications of pentadactyl limb. When no homologies exist, traits are said to analogous. Often development of an individual "recreates" its evolutionary history: "ontogeny recapitulates phylogeny" Insect pit-fall trap pitcher structures developed in response to low soil nitrogen. Old world porcupine vs. new world porcupine vs. hedgehogs. Regulatory sites of transcription factors switch on or off downstream genes.
