Lecture_2,_2008 - Bio 187 Fall 2008 Lecture 2 Sept 2...

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Bio 187, Fall 2008 Lecture 2, Sept 2 BIODIVERSITY AND THE CLASSIFICATION OF ORGANISMS Understanding the historical pathways that produced earth’s biodiversity. Associated text readings: Ch 25: all CH 24: 524-527,530-531, 537 (understanding that mutation rates can be measured and gene sequence divergence applied to systematics) Other readings as mentioned in notes Current estimates of global biodiversity put the number of named species at close to 2 million, but scientists estimate there could easily over 10 million unidentified species of insects alone. The key questions in this section are: 1. How can we usefully categorize and understand the diversity of living things? 2. How did the diverse living things on earth get here? Key concepts: 1. To understand the processes underlying biodiversity we must place them in an evolutionary perspective. 2. All living things are connected through an evolutionary history (the “Tree of Life” hypothesis) 3. All organisms can be traced back to common ancestors 4. The fields of Systematics and Phylogenetics reconstruct these pathways and categorize organisms accordingly. Taxonomy and Linnaeus: The beginning of organized categorization Taxonomy is the systematic categorization of living things, based on shared characteristics. Some Background : Humans have been categorizing life on earth likely since before written records. We have records from Aristotle identifying different types of organisms. But classification systems weren’t standardized until… In the mid 1700’s Karl von Linne developed a standardized system, where species were identified by a two-name system = binomial nomenclature . The names are in Latin. The first word identifies the species to a group of similar species —the genus. The second identifies that species uniquely.
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Linne liked Latin so much he changed his own name to Carolus Linnaeus, thus, the Linnaen system. Linnaeus devoted his life to the classification of living things, and trained a large number of apprentices who continued his work. Linnaeus produced a volume with standardized classifications: the Systema Natura . Linnaeus’ system moved from a designation of organisms that are clearly distinct from all others (species), to higher and more inclusive divisions or taxa. His basic system is still in place today. It consists of: Species : groups of organisms that are clearly distinct from all others (and which breed only amongst themselves). A species example: Canis familiaris -the domestic dog Genus : groups of very similar organisms, but which do not interbreed. Canis lupus , the gray wolf, is in the same genus, Canis , as the domestic dog. Note: Species names include the genus. Genus and species are always either underlined or italicized in writing. Family
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Lecture_2,_2008 - Bio 187 Fall 2008 Lecture 2 Sept 2...

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