BI111 Lecture Notes - Lecture 3: Dactyly, Pterosaur, Cladistics
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 tree requires comparison of traits (with shared genetic ancestry) in multiple species. Binary nomenclature: genus and species (reflect the nested hierarchy of life) Homoplasties: resemblance due to similar selective pressures to fill niches. Ex- bones that support wings of bats, birds and pterosaur all look like modifications of a pentadactyl limb. When no homologies exist, traits are said to be analogous. 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. All groups in a clade includes a common ancestor and all of its descendants. Simplest explanation is most likely to be correct.
