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Published byPhebe Harper Modified over 9 years ago
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Why do we classify things? Finding Order in Diversity Classification provides scientists and students a way to sort and group organisms for easier study. Taxonomy – branch of biology that deals with the classification and naming of living things There are millions of organisms on the earth! (approximately 1.5 million have been already named)
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Classifying and Naming Organisms 1.Grouping organisms based on comparing characteristics makes it easer to study the diversity of live. 2.Binomial Nomenclature – 2 word system of identifying each kind of organism; avoids confusion A. Carolus Linnaeus – founder of modern taxonomy; used structural similarities as a basis for his classification system
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Carolus Linnaeus Why do biologists consider Linnaeus’s system an improvement over earlier systems?
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Classifying and Naming Organisms 1.Binomial Nomenclature (cont.) B. Scientific Name – both names together i. 1 st name – genus (always capitalized) ii. 2 nd name – identifies species within the genus (lower case) ii. 2 nd name – identifies species within the genus (lower case) iii. Name is written in italics or underlined iii. Name is written in italics or underlined
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Linnaeus’s Classification System – hierarchical system from most inclusive to least inclusive are:
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This illustration shows how a grizzly bear, Ursus arctos, is grouped within each taxonomic category.
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Go to Fig. 18-4 What do the scientific names of the polar and grizzly bears tell you about their similarity to each other?
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Linnaeus’s system was limited because similarities and differences were mainly visible What was invented that helped to change the way scientists classify organisms?
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Evolutionary classification based on Darwin’s Theory of Evolution – Decent with Modification Species gradually change, or evolve, over time from pre-existing species
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Classifying species based on easily observed adult traits can pose problems. Which of these organisms seem most alike?
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Cladograms – a diagram that shows evolutionary relationships among organisms based on shared derived characters (Fig. 18-7)
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Structural – ex. Skeletal structure, leaf anatomy
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Behavioral – similar behaviors may indicate a close relationship – Fig. 18-8 American and African vultures look very much alike and were once classified together. American vultures have a peculiar behavior: When they get overheated, they urinate on their legs to cool down. The stork is the only other bird known to behave this way.
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Biochemical – information about DNA, RNA & proteins can be used to help determine relationships and can be used to estimate how long different species have been separated African Vulture American VultureWood Stork
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Cytological – cellular structure – ex. Prokaryotic vs. eukaryotic, plant cell vs. animal cell
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Embryological – early stages of development may show shared characteristics that are absent at the adult stages (Fig. 15-17 pg. 385)
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Fossil Formation – establish relationships between modern-day species & those that lived years ago
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http://www.pbs.org/wgbh/nova/tech/radiocarbon- dating.html?elq=c91efd4570264eeb936ce73b956e a24e&elqCampaignId=155 http://www.pbs.org/wgbh/nova/tech/radiocarbon- dating.html?elq=c91efd4570264eeb936ce73b956e a24e&elqCampaignId=155
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Arranging the diversity of life into the highest taxa is a work in progress. What is important to understand is that new information has reopened issues concerning biological diversity. Fig. 18-11
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Domains – the most inclusive categories, assigns more significance to the ancient evolutionary split between bacteria and archaea
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Bacteria unicellular, prokaryotic, cell wall contains peptidoglycan, ecologically diverse (free living or parasitic; autotroph or heterotroph; anaerobic or aerobic)
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Archaea – unicellular, prokaryotic, cell wall lacks peptidoglycan, most live in very extreme habitats that are devoid of oxygen
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Eukarya – consists of all organisms that are eukaryotic; Kingdoms of this domain include a.Protista b.Fungi c.Plantae d.Animalia
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Fungi – Eukaryote, Cell walls of chitin, Most multicellular; some unicellular; Heterotroph
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Protista – Eukaryote, cell walls of cellulose in some; some have chloroplasts; most unicellular, some colonial, some multicellular
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Plantae – Eukaryote, cell walls of cellulose; chloroplasts, multicellular, autotroph
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Animalia – Eukaryote, no cell walls or chloroplasts, multicellular, heterotroph
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