Polarization Examples Ax Bx C x Ax Bx x C x x x Synapomorphy homology Symplesiomorphy Bx Ax C x x Dx x Ax Bx C x Ingroup Node Ancestor Outgroup Node x Ex This tree pictures the trait x as a symplesiomorphy C E x Ax Bx C x Ingroup Node Ancestor Outgroup Node x This allows for D x x Ax Bx C x Phylogenetic Systemacists only use synapomorphies to build their trees D x x D x Ax Bx C Ex The information between Species E and Species D is unknown of what happened with trait x meaning x cannot be polarized In this case you would you other traits that have more complete information and then try to plot x Ax Bx C x x x Ex F x x is the best guess and allows for Ax and Bx to be group together The presence of x is convergent is a data conflict or no data x Ax Bx C x x x x is a synapomorphy D x Ex F x Gx H x x x But how do we know outgroup relationship o This presumes prior knowledge We should view prior knowledge as a working hypothesis as our views can change with time However this assumption of prior knowledge is testable using more global taxonomically more inclusive phylogenetic analysis
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