This document discusses biological classification and taxonomy. It begins by explaining why biologists classify organisms and provides a brief history of classification from Aristotle to Linnaeus establishing the modern 7-level system. The 7 levels are kingdom, phylum, class, order, family, genus, and species. An example classification of a housecat is given from kingdom to species. Scientific names are introduced as the standardized naming system. The document concludes by mentioning dichotomous keys which help identify organisms based on distinguishing characteristics.

1. Sorting It All OutSorting It All Out
CLASSIFICATION!

2. Why Classify?Why Classify?
 Classification: the division of organismsClassification: the division of organisms
into groups, orinto groups, or classesclasses, based on specific, based on specific
characteristicscharacteristics
 For thousands of years, humans haveFor thousands of years, humans have
classified things based onclassified things based on usefulnessusefulness
 Biologists use a system to classify thingsBiologists use a system to classify things
—this system groups organisms according—this system groups organisms according
to theirto their sharedshared characteristicscharacteristics

3.  Classification of living thingsClassification of living things
makes it easier for biologists tomakes it easier for biologists to
answer many importantanswer many important
questions, such as:questions, such as:
How many knownHow many known
species are there?species are there?
What are the definingWhat are the defining
characteristics of eachcharacteristics of each
species?species?
What are theWhat are the
relationshipsrelationships betweenbetween
these species?these species?

4. How Do Scientists ClassifyHow Do Scientists Classify
Organisms?Organisms?
 Great GreekGreat Greek
philosopher andphilosopher and
scientistscientist AristotleAristotle
(384-322 BCE)(384-322 BCE)
began classifyingbegan classifying
animalsanimals intointo
logical groupingslogical groupings
more thanmore than 20002000
years agoyears ago

5. – He arranged all livingHe arranged all living
things in an ascendingthings in an ascending
ladder withladder with humanshumans atat
the topthe top
– Animals wereAnimals were
separated intoseparated into twotwo
major groups—thosemajor groups—those
with red blood andwith red blood and
those without red bloodthose without red blood
(very similar to our(very similar to our
modern classification ofmodern classification of
invertebrates andinvertebrates and
vertebratesvertebrates ))

6.  In 1700s, SwedishIn 1700s, Swedish
scientist Carolusscientist Carolus
Linnaeus foundedLinnaeus founded
modern taxonomymodern taxonomy
 TaxonomyTaxonomy:: thethe
science of describing,science of describing,
naming, andnaming, and
classifying organismsclassifying organisms
 Linnaeus tried toLinnaeus tried to
classify all living thingsclassify all living things
based on theirbased on their shapeshape
and structureand structure

7. – Species were givenSpecies were given
distinctivedistinctive two-wordtwo-word
namesnames
 Described aDescribed a sevenseven--
level system oflevel system of
classification, which isclassification, which is
still used today,still used today,
although it has gonealthough it has gone
through manythrough many
changes.changes.

9. Classification TodayClassification Today
 Taxonomists use the 7-level system toTaxonomists use the 7-level system to
classifyclassify living things based on sharedliving things based on shared
characteristicscharacteristics
 Also useAlso use sharedshared characteristics tocharacteristics to
hypothesize how closely related livinghypothesize how closely related living
things arethings are
 The more characteristics they share, moreThe more characteristics they share, more
closely related the organisms areclosely related the organisms are

10. Example: platypus, brown bear, lion, and house cat are
thought to be related because they share many
characteristics. These animals have hair and mammary
glands, so they are grouped together as mammals.
They can be further classified into more-specific
groups.

11. Branching DiagramsBranching Diagrams
 Each characteristic on theEach characteristic on the lineslines of the branch areof the branch are
shared by the animals to the right of itshared by the animals to the right of it
 As you moveAs you move upup the line, the animals are morethe line, the animals are more
closely related to each otherclosely related to each other

12. 7 Levels of Classification7 Levels of Classification
 Every living thing is classified into one of sixEvery living thing is classified into one of six
kingdomskingdoms::
1.1. 1. KINGDOM1. KINGDOM: largest, most: largest, most generalgeneral groupgroup
2.2. 2. PHYLUM2. PHYLUM: sorted from the kingdom: sorted from the kingdom
3.3. 3. CLASS3. CLASS: all living things in a phylum are 4.: all living things in a phylum are 4.
sorted into classessorted into classes
4.4. ORDERORDER: each class includes one or more: each class includes one or more
ordersorders
5.5. FAMILYFAMILY: one or more orders: one or more orders
6.6. GENUSGENUS: families are broken into genera: families are broken into genera
7.7. SpeciesSpecies: organisms able to mate and: organisms able to mate and
reproduce fertile offspring together

13.  Genera are sorted intoGenera are sorted into
speciesspecies
 A species is a group ofA species is a group of
organisms that areorganisms that are
closely related and canclosely related and can
mate to produce fertilemate to produce fertile
offspringoffspring
 Let’s see theLet’s see the
classification of aclassification of a
housecat from kingdomhousecat from kingdom
Animalia to genus andAnimalia to genus and
species,species, Felis domesticusFelis domesticus

14. Kingdom AnimaliaKingdom Animalia
All animals are in theAll animals are in the kingdom animaliakingdom animalia

15. Phylum ChordataPhylum Chordata
All animals in theAll animals in the phylum Chordataphylum Chordata have ahave a
hollow nerve cord. Most have a backbone.hollow nerve cord. Most have a backbone.

16. Class MammaliaClass Mammalia
Animals in theAnimals in the class Mammaliaclass Mammalia have ahave a
backbone. They also nurse their young.backbone. They also nurse their young.

17. Order CarnivoraOrder Carnivora
Animals in theAnimals in the order Carnivoraorder Carnivora have ahave a
backbone and nurse their young. They also havebackbone and nurse their young. They also have
special teeth for tearing meat.special teeth for tearing meat.

18. Family FelidaeFamily Felidae
Animals in theAnimals in the family Felidaefamily Felidae are cats. They have aare cats. They have a
backbone, nurse their young and have special teeth forbackbone, nurse their young and have special teeth for
tearing meat. The Felidae have five toes on the front feet,tearing meat. The Felidae have five toes on the front feet,
four on the hind ones, all armed with strong "retractilefour on the hind ones, all armed with strong "retractile
claws”.claws”.

19. GenusGenus FelisFelis
Animals in theAnimals in the genusgenus FelisFelis have traits ofhave traits of
other animals in the same family. However,other animals in the same family. However,
these cats cannot roar; they can only purr.these cats cannot roar; they can only purr.

20. SpeciesSpecies Felis domesticusFelis domesticus
the speciesthe species Felis domesticusFelis domesticus is theis the
common house cat. The house cat sharescommon house cat. The house cat shares
traits with all of the organisms in the levelstraits with all of the organisms in the levels
above the species level, but it also hasabove the species level, but it also has
unique traits.unique traits.

21. Scientific NamesScientific Names
 A scientific name is always the same for aA scientific name is always the same for a
specificspecific kind of organism no matter howkind of organism no matter how
many common names there might bemany common names there might be
 Before Linnaeus, different scientistsBefore Linnaeus, different scientists
named organisms differently, so annamed organisms differently, so an
organism could haveorganism could have moremore than one namethan one name
Example on next slide…

22. Example:Example:
What do the mountain lion, cougar, and puma all
have in common? They are ONE ANIMAL with
several common names! The scientific name for
all three common names is Felis concolor, no
matter where you go in the world!

23. Two-Part NamesTwo-Part Names
 Linnaeus simplified the naming ofLinnaeus simplified the naming of
living things by giving each speciesliving things by giving each species
a two-parta two-part scientificscientific namename
 For example, the scientific name forFor example, the scientific name for
the Asian elephant isthe Asian elephant is ElephasElephas
maximusmaximus. First part of name. First part of name
ElephasElephas is genus name. Secondis genus name. Second
part,part, maximusmaximus, is species name., is species name.
 No other species has both thisNo other species has both this
genus name and species name.genus name and species name.

24.  All genus names begin with aAll genus names begin with a
capitalcapital letterletter
 All species names begin with aAll species names begin with a
lowercaselowercase letterletter
 Usually, both words areUsually, both words are
underlinedunderlined oror italicizeditalicized
 Scientific names are usually inScientific names are usually in
GreekGreek or Latin, and containor Latin, and contain
information about the organisminformation about the organism
Equus caballusEquus caballus

25. Dichotomous KeysDichotomous Keys
 Dichotomous keyDichotomous key: an aid that is used to: an aid that is used to
identifyidentify organisms and that consists of theorganisms and that consists of the
answers to a series ofanswers to a series of statementsstatements
 There are only 2 alternative responses toThere are only 2 alternative responses to
each statementeach statement
 Either the chosen statement identifies theEither the chosen statement identifies the
organism or the person is directed toorganism or the person is directed to
another pair of statementsanother pair of statements

26.  By working throughBy working through
the statements in thethe statements in the
key inkey in orderorder, the, the
person can eventuallyperson can eventually
identify the organismidentify the organism
Dichotomous Key for Identifying Candy

28. A Growing SystemA Growing System
 People are still discovering and classifyingPeople are still discovering and classifying
organismsorganisms
 Some newly discovered organisms fit intoSome newly discovered organisms fit into
existing categoriesexisting categories
 Sometimes, someone discovers newSometimes, someone discovers new
evidenceevidence or an organism is so differentor an organism is so different
from other organisms that it doesn’t fit intofrom other organisms that it doesn’t fit into
a category.a category.