Taxonomy - the science of classifying organisms
Common Names
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spider monkey | 
sea monkey | 
sea horse | 
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gray wolf | 
Firefly | 
Crayfish | 
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mud puppy | 
horned toad | 
Ringworm | 
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black bear | 
Jellyfish | 
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*Common names can be confusing and names can vary by region.
Why Classify?
About 1.5 million species named
2-100 million species yet to be discovered
Taxonomy =science of classifying organisms
--groups similar organisms together
--assigns each a name
Naming Organisms:
Organisms have common & scientific name -all organisms have only 1 scientific name
-usually Latin or Greek
-developed by Carolus Linnaeus
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The scientific name is always italicized or underlined. Genus is capitalized. Species is not. Scientific names can be abbreviated by using the capital letter of the genus and a period: Example.P. leo (lion) 
 
 
Members of the same genus are closely related. Only members of the same species can interbreed (under natural conditions)
 Some hybrids do occur under unnatural conditions: Ligers are crosses between tigers and lions.
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This two-word naming system is called 
Binomial Nomenclature
-written in italics (or underlined)
-1st word is Capitalized --Genus
-2nd word is lowercase ---species
Examples: Felis concolor, Ursus arctos, Homo sapiens,Panthera leo , Panthera tigris 
Linneaus - devised the current system of classification, which uses the following schema
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Kingdom |  |  |  |  |  |  | 
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Phylum/Division |  |  |  |  |  | 
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Class |  |  |  |  | 
|  |  |  | 
Order |  |  |  | 
|  |  |  |  | 
Family |  |  | 
|  |  |  |  |  | 
Genus |  | 
|  |  |  |  |  |  | 
Species | 
 
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Human | 
Cougar | 
Tiger | 
Pintail Duck | 
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Kingdom | 
Animalia | 
Animalia | 
Animalia | 
Animalia | 
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Phylum/Division | 
Chordata | 
Chordata | 
Chordata | 
Chordata | 
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Class | 
Mammalia | 
Mammalia | 
Mammalia | 
Aves | 
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Order | 
Primate | 
Carnivora | 
Carnivora | 
Anseriformes | 
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Family | 
Homindae | 
Felidae | 
Felidae | 
Anatidae | 
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Genus | 
Homo | 
Felis | 
Panthera | 
Anas | 
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Species | 
sapiens | 
concolor | 
tigris | 
Acuta | 
 
18-2 Modern Evolutionary Classification
- Linnaeus grouped species mainly on visible similarities & differences
- Today, taxonomists group organisms into categories that represent lines of evolutionary descent (phylogeny)
- Evolutionary relationships among a group of organisms can be shown on a cladogram 
Similarities in DNA and RNA
- DNA & RNA is similar across all life forms
- Genes of many organisms show important similarities at the molecular level
- DNA shows evolutionary relationships & helps classify organisms
The Six Kingdoms and Domains
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number of Cells | 
Energy | 
cell type | 
Examples | 
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archaebacteria | 
Unicellular | 
some autotrophic, most chemotrophic | 
Prokaryote | 
"extremophiles" | 
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Eubacteria | 
Unicellular | 
autotrophic and heterotrophic | 
Prokaryote | 
bacteria, E. coli | 
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Fungae | 
most multicellular | 
Heterotrophic | 
Eukaryote | 
mushrooms, yeast | 
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Plantae | 
Multicellular | 
Autotrophic | 
Eukaryote | 
trees, grass | 
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Animalia | 
Multicellular | 
Heterotrophic | 
Eukaryote | 
humans, insects, worms | 
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Protista | 
most unicellular | 
heterotrophic or autotrophic | 
Eukaryote | 
ameba, paramecium, algae | 
Using Dichotomous Keys
A dichotomous key is a written set of choices that leads to the name of an organism. Scientists use these to identify unknown organisms.
Consider the following animals. They are all related, but each is a separate species. Use the dichotomous key below to determine the species of each.
 
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1. | 
Has green colored body ......go to 2 | 
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Has purple colored body ..... go to 4 | 
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2. | 
Has 4 legs .....go to 3 | 
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Has 8 legs .......... Deerus octagis | 
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3. | 
Has a tail ........ Deerus pestis | 
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Does not have a tail ..... Deerus magnus | 
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4. | 
Has a pointy hump ...... Deerus humpis | 
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Does not have a pointy hump.....go to 5 | 
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5. | 
Has ears .........Deerus purplinis | 
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Does not have ears ......Deerus deafus | 
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