1BIS2C Winter 2012 (Ward)Lecture 2. Fun with trees (cont’d)Today’s second lecture (9 Jan)•more tree terminology and concepts•phylogeny and classificationWednesday (11 Jan)•methods for building treesterminal taxauvxyzroot, root nodeinternal nodesinternal brancheswInternal nodes represent hypothetical ancestral taxatSo far we have been discussingbifurcating trees.These are trees inwhich each internal node gives rise totwodescendant branches.Sometimes we draw trees in which some nodes havethree or moredescendant branches. Such nodes are calledpolytomiesand theyusually reflectuncertaintyabout phylogenetic relationships.polytomyAn extreme case of ignorance: a completely unresolved bushpolytomy
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