Sept 8 - Animals Lecture #1

G independent evolution of image forming eyes by

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E.g. independent evolution of image-forming eyes by cephalopod mollusks and by vertebrates illustrates homosplasy but the most recent common ancestor of mollusks did not have such eyes Similarity due to convergent evolution, but independent origins. For instance, take the fin and the caudal fin of tuna and of dolphin; they are similar but have independent histories, and their similarity comes from adaptation to similar environments and functions Evolutionary convergence of fusiform shape an example of Homoplasy Modern Phylogenetic systematics cladistics analysis How do we use character variation to reconstruct phylogeny? Cladistics – evaluation of information for tree building and classification Cladogram – phylogenetic diagram based on cladisistic analysis o a nested hierarchy of clades presented as a branching diagram (see outgroup pic)
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o branches on a cladogram are formal device for indicating a nested hierarchy of clades within clades o difference between phylogenetic tree: to obtain phylo tree, one must add to a cladogram information concerning ancestors, duration of evolutionary linages, or amounts of evolutionary change that occurred on lineages Simplest Cladogram – a tree with dichotomies, two-way branch points Branch represents divergence of two species from a common ancestor
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