02_Evolution and Systematics

02_Evolution and Systematics - EVOLUTION AND SYSTEMATICS...

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Unformatted text preview: EVOLUTION AND SYSTEMATICS Reading: Chapter 26 A. HOW TO UNDERSTAND PHYLOGENETIC TREES 1. The tree shows evolutionary divergence through time. 2. A branch point (node) represents the most recent common ancestor. 3. The most recent common ancestor did not necessarily resemble any of its living descendants. 4. Branches in phylogenetic trees (lineages in evolution), once separated, can come back together by two important processes. Fig. 26.5 In some trees the past is at the left and the present is at the right, as here; in others, the past is at the bottom and the present is at the top. Evolution and Systematics - 2 5. A phylogenetic tree does not imply any goal-directedness of evolution and does not enable you to predict the future of evolutionary change. B. SYSTEMATICS 1. Systematics is the study of biological diversity and its relationship to evolution. Systematics encompasses taxonomy, the naming and classification of organisms. 2. Two similar but distinct terms taxonomic category taxon ( pl. taxa) 3. Taxonomic categories Domain Kingdom Phylum (Division) Class Order Family Genus Species C. MONOPHYLETIC TAXA 1. A monophyletic taxon is a named group of organisms that includes a common ancestor and all of its descendants. A monophyletic group is called a clade . Evolution and Systematics - 3 2. Biologists are seeking to make all taxa monophyletic. This requires a knowledge of correct evolutionary relationships, and there has been much change in taxonomy in the last few years because of our improved understanding of evolutionary history. 3. There is a movement in systematics to dispense with taxonomic categories and simply refer to named clades. D. HOW EVOLUTIONARY RELATIONSHIPS ARE DETERMINED 1. Because taxa are constructed on the basis of evolutionary relatedness, we must have a reliable way to determine this relatedness....
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02_Evolution and Systematics - EVOLUTION AND SYSTEMATICS...

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