Biology 1001A Lecture Notes - Lecture 21: Convergent Evolution, Divergent Evolution, Ingroups And Outgroups
12 Dec 2017
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Butterflies and their close relatives: using this logic, 6 legs is the ancestral trait, and translates to 4 legs is the derived trait; the derived trait is not always the most complex trait. Is this trait ancestral or derived: present in outgroup and all of ingroup, this is an ancestral trait. Outgroup comparison relies on parsimony: simplest explanation is the best: whichever tree requires the fewest evolutionary changes (gains or losses of a trait) is probably correct. Using parsimony to evaluate candidate trees: outgroup: shark, no lactation, no wings, no fur, no beak. No beak: beaks are not shared, tree a is more parsimonious. Similarity versus relatedness: homology similarity that reflects recent common ancestry, two taxa has the same trait: inherited from their ancestor, unfortunately, not all similarities are homologies. Homoplasy: misleading similarity or dissimilarity: convergent evolution, divergent evolution: misleading differences between taxa that are closely related to each other, rapidly evolving to selection pressures, type of homoplasy too.
