BIOLOGY 1M03 Chapter 25: 25 Phylogeny
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Phylogeny is the evolutionary history of a group of organisms. Based on the idea that organisms are related by evolution. Understanding these relationships is critical to both evolution and how biological processes work. A phylogenetic tree is a model of how group of organisms descended from a common ancestor. Model consists of nodes, where groups split, branches where evolution occurs and tips representing observed taxa which are the endpoints of the process we are trying to model. A point where more than two branches diverge is called a polytomy. Polytomies mean we do not know which event happened first. A monophyletic group is a group defined by a single common ancestor. All descendants of the ancestor must be in the group. Monophyletic groups can also be called clades or taxa. Sister taxa can be a useful way of thinking about trees. Two taxa that share a common node. Ex. sisters of : homo sapiens; homo erectus; humans.