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ClassificationChapter 9

Sorting It All Outsection 1

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Why Classify?Classification

Is the division of organisms into groupsor classes based on common characteristics

For thousands of years, humans haveclassified living organisms based on useful­ness

Some biologists classify living and extinct organisms

Scientists classify organisms to help make sense andorder of the living things in the world

Biologists use a system to classify living thingsgroups according to characteristics shared

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Classifying things makes it easier to answer questions about:

How many known species are there?What are the defining characteristics?What are the relationships between the species?

How Do Scientists Classify Organism?Before 1600's, scientists divided organisms into 2 groups

plantsanimal

As more organisms were discovered, they didn't fit into these categories

In the 1700's, a Swedish scientist named Carolus Linnaeus founded modern taxonomy

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Taxonomy is the science of describing, classifying and naming living things

Linnaeus tried to classify living things based on their shape and structure

described a 7 level system of classificationstill used today

Classification TodayTaxonomists use the 8 level system to classifyliving things based on shared characteristics

Scientists also use these characteristics to alsohypothesize how closely organisms are related

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Branching DiagramsIn branching diagrams, several characteristicsare listed along a line

Characteristics are shared by the animals to the right of it

ability to purr

retractable claws

give birth to live young

hair and mammary glands

platypus

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Levels of ClassificationEvery living thing is classified into one of 6

kingdomsDomains largest, most general groupKingdoms ­ domains are sorted in kingdomsAll living things in a kingdom are sorted intoPhyla ( phylum)

members in one phylum are alike and different from the other phylums

Phylum are sorted into classesClasses are separated into ordersOrders are separated into familiesFamilies are broken into genera (genus)Genus is broken into species

A species is a group of organisms that are closely related and can mate to produce fertile offspring

ex. house cat (pg. 225)

KingdomPhylumClassOrderFamilyGenusSpecies

KingPhillipCameOver ForGreat Spaghetti

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Scientific NamesBy classifying organisms, biologists are able

to give organisms scientific names

A scientific name is always the same regardless of what the common name may be

Before Linnaeus, names were 12 words long and were often different among scientists

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Two­ Part NamesLinnaeus simplified the naming of living

things by giving each species a two­part scientific name

First part is the genusSecond part is the species

example; Asian elephantElephas maximus

No other species has both genus and speciesNaming rules help scientists communicate

clearly about living things

All scientific names :genus names begin with a capital letterspecies names are lowercaseboth words are underlined or italicizedusually in Latin or Greekmay contain information about the organism

ex Tyrannosaurus rex"Tyrannosaurus" two Greek words

meaning tyrant lizard"rex" in Latin means king

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Dichotomous KeyTaxonomists have developed special guides tohelp scientists identify organisms

dichotomous keyis an identification aid that uses sequential pairs of descriptive statements

there are only 2 alternative responsesperson trying to identify chooses the

correct oneit either identifies the organism or

leads to another statementby working through the statements,

an organism can be identified

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A Growing SystemPeople are still discovering and classifying new organisms

some will fit into existing catergoriessometimes new evidence doesn't fit and a new

category is madeexample: Symbion pandora

found on lobster's lipsdidn't fit an known groupscientists made a new phylum