2011-03_Syst - EVOLUTION(11:704-486 SYSTEMATICS SMOUSE SPRING 2011 EVOLUTIONARY SYSTEMATICS Linnaean Classification No one really knows how many

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EVOLUTION (11:704-486) SYSTEMATICS S MOUSE – SPRING 2011 1 E VOLUTIONARY S YSTEMATICS Linnaean Classification: No one really knows how many species there are. No one has even really collected the numbers already named, but there are probably ~1.5 million already named. If you include the those we are pretty sure are “out there” but which we have not yet named, perhaps not yet even seen, there may be as many as 3-5 million. Some people think 30 M. By the early 1700s, several classification systems had cropped up, all cumbersome. In 1735, Linnaeus published his Systema Naturae . Linnaeus introduced binomial nomenclature, in Latin, of course, indicating the Genus and species: Homo sapiens , Equus caballus , Canis lupus , Pinus rigida , Quercus alba . It was an instant hit - basically wiped out the competition. Category – Linnaeus also used a series of nested categories , each more inclusive as one moved up the ladder, species genus family order class phylum kingdom . As an organizing scheme, it could not be beat; we’re still using it. Linnaeus did not understand why it worked (in other than religious terms), but the fact is that it “felt right.” It still does, today. Taxon – A particular species, say Betula lenta , is a taxon . A particular genus, say Pinus , is also a taxon (a more inclusive taxon). We use the term taxon to mean “a unit”, the name for which is secondary, but whose existence is definite. The plural of taxon is taxa . A particular family is also a taxon, a higher (more inclusive) taxon, and so on. The members within any given taxon were understood to be related, by which Linnaeus and his contemporaries meant, “created on the same general plan by God”, small (or large) variations on a single theme. Small variations for species within a genus, larger variations for genera within a family, and so on, but all ordered in a convenient way that we had only to discover. Evolutionary Classification: Of course, once the idea of evolution took hold, the meaning of ‘related’ and the relevance of categories changed forever. Darwin held that the close relationship of different species in the same genus was due to their recent descent from a common ancestor. Genera were more different, because that common ancestor was further back in time. Phlogenetic Trees – He viewed all organisms as having sprung from a vast tree of life . The idea of a tree had real appeal, because people could visualize a tree, and could understand how it grew. Darwin plays the tree theme to the hilt. He added the important realization that Linnaean classification represented the actual historical (evolutionary) record. Cladogenesis vs Anagenesis – Darwin’s hypothesis had two major features, cladogenesis (the splitting of one lineage into two or more descendent lines), and anagenesis (the evolutionary change of various characters within each of the descendents). The idea of post-Darwinian systematics is to place all taxa within higher taxa that are internally
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This note was uploaded on 08/18/2011 for the course ECOLOGY 301 taught by Professor Staff during the Spring '11 term at Rutgers.

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2011-03_Syst - EVOLUTION(11:704-486 SYSTEMATICS SMOUSE SPRING 2011 EVOLUTIONARY SYSTEMATICS Linnaean Classification No one really knows how many

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