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Why classify organisms?1. Order and organization
2. Common names confusing• Ex. Jellyfish, starfish, etc.
3. Common names vary from place to place• Ex. Cougar, puma, mountain lion
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Aristotle divided organisms into two groups:
Plants Animals1.)herbs 1.)air2.)shrubs 2.)sea3.)trees 3.)land
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Linneaus: founder of modern taxonomy• Classified organisms based on
structural features• Binomial Nomenclature: each species
is given a two-word Latin name1st word = genus
2nd word = species
Ex: canis familiarisfelis domesticus homo sapiens
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The Linnaean Hierarchy Taxa are based on shared characteristics
-Domain (most shared)
-Kingdom
-Phylum
-Class
-Order
-Family
-Genus
-Species (least shared)
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Classification of Organisms
Taxonomy: the science of classifying living things
-A classification level is called a taxon
- taxonomic key: used to identify species, by following a series of choices between characteristics
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Grouping Organisms
3 domains:
-Bacteria
-Archaea
-Eukarya
Archaea and Eukarya are more closely related to each other than to bacteria
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Domain: Bacteriakingdom: Eubacteria
• Unicellular
• Prokaryotic, Cell walls with peptidoglycan
• Some heterotrophic, some autotrophic
• Most abundant organisms on Earth
• Ex: E. coli, Streptococcus, many diseases
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Domain: Archaeakingdom: archaebacteria
• Unicellular
• Prokaryotic, Cell walls lack peptidoglycan
• Most heterotrophic, some autotrophs
• Includes methanogens, extremophiles
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Eukarya
• Eukaryotes appeared about 2.5 BYA
• Key characteristics:– Complex cell organization– Multicellular– Sexual reproduction
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Mitochondria and chloroplasts most likely gained entry by endosymbiosis
-Mitochondria were derived from purple nonsulfur bacteria
-Chloroplasts from cyanobacteria
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Eukaryote Kingdoms
1. Protista• Unicellular (some multi)• Most are heterotrophic• Ex: simple algae, giant kelp,
amoeba, paramecium(Catchall for eukaryotes that
are not plant, fungus or animal)
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2. Fungi• Multicellular (some uni)• Heterotrophic by absorption• Ex: yeast, mold, mushrooms,
athlete’s foot
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