Evolution and Biodiversity Laboratory Systematics and Taxonomy I ...

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Figure ST-1a. Phylogeny of primates. The nodes from which branches emergerepresent the hypothetical common ancestor of all taxa above that node on thetree. The endpoints of the branches represent the descendants of that ancestor.Some phylogenetic trees include both extinct and extant (still living) taxa. Inmodern systematics, extinct taxa (represented by fossils) are treated the sameway as extant taxa, and are not considered ancestral to extant taxa.Figure ST-1b. Phylogeny of primates demonstrating a rotation of the node atAncestor G, relative to the original drawing shown in Figure ST-1a. Rotating thenode in this manner does not change the phylogenetic information.systematics-12
Rule #3: There is no such thing as a “most highly evolved species”. All extantspecies are descended from successful ancestors, and are evolved to survive andreproduce in the context of their specific environment. Evolution is a process. It hasneither a goal nor a subjective value system.Rule #4. No extant taxon is ancestral to any other extant taxon. When anancestral lineage diverges to become two separate taxa, the ancestral lineage isconsidered extinct. This should be remembered when one hears the oft-repeated, butincorrect statement “humans evolved from monkeys”. They did not. Humans andmonkeys share a common ancestor. That’s not the same thing.Figure ST-2. Representative vertebrate taxa are grouped in monophletic (a), paraphyletic(b) and polyphyletic (c) assemblages, shown by blue shading. Note that the paraphyletictree (b) shows the traditional, evolutionary system for classifying Reptilia (turtles,crocodilians, snakes, and lizards), which does not reflect actual evolutionaryrelationships. Reptilia can be made monophyletic by including Aves (birds). Thepolyphyletic tree (c) illustrates what can happen when organisms are classified on thebasis of superficial similarity, such as “warm bloodedness” or “four-chambered heart”.These characters most likely evolved independently in mammals and in birds.A phylogenetic tree is not constructed randomly. The systematist uses data onmorphology, homology of nucleic acids, congruence of similar proteins, etc. todetermine recency of common descent.systematics-13
Page 1 and 2: Evolution and Biodiversity Laborato
Page 3 and 4: Organisms are not randomly classifi
Page 5 and 6: A Key to the Hardware of Southern F
Page 7 and 8: To classify an unknown organism mor
Page 9 and 10: List five homologous characters you
Page 11: determined by identification of syn
Page 15 and 16: The hypothetical animals used in th
Page 17 and 18: common ancestry among these three O
Page 19 and 20: Exercise: Constructing a Cladogram

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