BIOL 150 Lecture Notes - Lecture 2: Polyphyly, Paraphyly, Synapomorphy
Document Summary
Phylogeny evolutionary history of a group of organism. Shows ancestor-descendent relationships among populations, species, higher taxa. Root most ancestral branch in the tree. Node point where branch splits into two branches. Tip represents a living or extinct group (is most recent) Monophyletic groups (also called clades or lineages) Evolutionary unit that includes an ancestral group and all descendents but no others. Molecular clocks - rates of molecular change (i. e. mutations) are fairly constant and can give the timeline of a phylogentic tree. Horizontal distance on a branch indicates time. Phylogenies depends upon best available data - is why they are hypotheses : fossils and morphology, dna sequences. A tree constructed with four taxa produces 15 possible trees. A tree constructed with 15 taxa produces over 100,000 possible trees. It is assumed that independent evolution of derived traits would be rare compared to similarity due to shared descent .
