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Canada (158,187)
Biology (379)
BI111 (118)
Chapter 19

Chapter 19 Textbook Notes.docx

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Wilfrid Laurier University
Tristan Long

CHAPTER 19192The science of systematics has two goals The first is to reconstruct the phylogeny or evolutionary history of a group of organisms Phylogenies are presented as phylogenetic trees which are formal hypotheses identifying likely relationships among species These are essential to the comparative method that is used to analyze evolutionary processes The second goal is taxonomy the identification and naming of species and their placement in classification A classification is an arrangement of organisms into hierarchical groups that reflect their relatedness193A family is a group of genera that closely resemble one another Similar families are grouped into orders similar orders into classes similar classes into phyla similar phyla into kingdoms and lastly all life on earth is classified into three domains Each category is called a taxon195Useful systematic characteristics must be genetically independent reflecting different parts of organisms genomes Systematic analyses rely on the comparison of homologous characters as indicators of common ancestry and genetic relatednessAnalogous characters are homoplasious phenotypic similarities that evolved independently in different lineages By definition analogous characters serve a similar function in different species Systematists exclude homoplasies from their analyses because homoplasies provide no information about shared ancestry Homologous characters emerge from comparable embryonic structures
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