BI111 Lecture Notes - Lecture 4: Double Fertilization, Tracheid, Rhynia
Document Summary
Twin goals: reconstruction of evolutionary history and classification of species. Phylogenetic trees come through successive events of speciation (branching), in which one species gives rise to 2+ Reconstructing these trees requires comparison of traits (with shared genetic ancestry) in multiple species: homologies are good, analogies are not. Name: what group does it belong to. Homologous structures reflect underlying genetic similarities: e. g. bones that support wings of bats, birds, & pterosaur all look like modifications of pentadactyl limb, develop from comparable embryonic structures. When no homologies exist, traits are said to be analogous: wings of insects are distinct. Insect pit-fall trap pitcher structures developed in response to low soil nitrogen. Regulatory sites of transcription factors switch on or off downstream genes: small changes in regulation produce large changes in morphology. Natural selection still determines success of regulatory genes. Principle of parsinomy: simplest explanation most likely to be correct, all phylogenetic trees are hypotheses that attempt to accurately reflect historical events.
