18 2 Modern Systematics I Traditional A Scientists

18. 2 Modern Systematics I. Traditional _______ A. Scientists use similarities in ______ & ______ to group organisms. 1. this approach is ______. 2. Some groups look ______ but turn out to be _______ related. 3. Other groups look _____ but turn out to be ________ related. 1

II. Phylogenetics A. Def – The study of the ______ relationships between _____. B. It’s like trying to draw a huge family ____ over millions of ________. C. Not all similar ______ are inherited from a common _______. 1. Ex. -_______ of an insect & the _______ of a bird. D. _______ evolution = similarities in groups that are _____ closely related. 2

2. ______ characters = Similarities that arise through _______evolution. E. This family tree, or _____ tree, represents a hypothesis of the relationships between ______ groups. III. ________ A. Objective method that unites _______ with ________. 1. Focuses on finding _______ that are shared between ______ groups because of shared ________. 3

2. Ancestral character is defined as having evolved in a common ____ of _____ groups. 3. ______ character = one that evolved in ____ group but ______ the other. C. Constructing a Cladogram 1. A _____ is a phylogenetic tree that is drawn in a ______ way. 2. A ______ is a set of groups that are related by descent from a single ancestral ______. 3. Outgroup = group that lacks some of the shared __________. 4

5

IV. Inferring Evolutionary Relatedness A. ________ 1. refers to the ______ structure or ______ of organisms. 2. Organisms that share ancestral genes often show similarities during ________. B. Molecular Evidence 1. Scientists now use _____ info. to infer phylogenies. 2. DNA _______ in a _______ is determined for several species 3. Then, each letter at each position is ______. 6

7

C. Evidence of Order and Time 1. Cladistics can determine only the relative _______ of divergence, or ______, in a phylogenetic tree. 2. The ____ record can often be used to infer the actual _______ when a group may have begun to “branch off. ” D. Inference Using _______ 1. This principle holds that the _____ explanation for something is the most ______, unless strong evidence exists _____ that explanation. 2. Given two possible cladograms, the one that implies the _____ character changes between _____ is preferred 8