Classifying Organisms
7th Grade Science
Objectives:
1. You will be able to explain why
classification systems are
important.
2.You will be able to demonstrate
your understanding with a
dichotomous key.
Why do Scientists Classify?
 Why?
 Easier to study
 Less confusion
 Easier to see connections
 How?
 Physical characteristics
 DNA
Types of Cells




Prokaryotes
No Nucleus
Very small
Bacteria
Domains: Bacteria and Archaea
Eukaryotes
 Cells contain a nucleus
 Larger than prokaryotes
 Domain Eukarya
Scientific Naming
 Why?
 Reduces confusion
 Binomial Nomenclature
 Two words for every name
 Greek or Latin
 Genus species (ex. Canis lupis)
 General Rules
 Always use italics or underline
when written
 Capitalize genus
 Lowercase for species
Canis lupis
Taxonomy
 Taxonomy:
 Classification of organisms
based on characteristics
 8 levels
 Each level has fewer
organisms
 Which organisms are more
similar?
 Same genus
 Same family
3.1 Classifying life
 Taxonomy is the process of identifying and classifying living
things.
 A Swedish scientist and explorer named Carolus Linnaeus
(1707–1778) developed a system of classification in the 1700s.
 There are currently seven levels of classification.
3.1 Levels of classification
 For animals, the levels of classification are: kingdom, phylum,
class, order, family, genus, and species.
•At what level are these two animals classified differently?
Kingdoms of Life
 Separated by common
characteristics
 6 kingdoms
 Archaebacteria
 Eubacteria
 Protista
 Fungi
 Plantae
 Animalia
Topic: Classification Tools
 What tools can scientist use
to classify organisms?
Classification Tools
 Suppose you to fishing and
catch a fish you don’t
recognize. How could you
figure out what type of fish
you have caught?
Is a series of descriptions arranged
in pairs that lead the user to
identification.
1.Divides a larger group in smaller
groups
2.Typically, it may separate objects
into groups that “have it” and those
that “don’t have it”
1.Divides a larger group in smaller
groups
2.Typically, it may separate objects
into groups that “have it” and those
that “don’t have it”
3.2 Dichotomous Keys
 A dichotomous key turns questions into paired statements.
Classification Today
 Scientists use shared characteristics to hypothesize how closely related
living things are
 The more shared characteristics organisms have, the more closely related
they are
 Cladograms: branching diagrams showing the similarities and
differences between organisms
3.2 Dichotomous Keys
 Most dichotomous keys are designed to identify small
groups like trees, butterflies, and song birds.
Can you
suggest a way
to tell these
arthropod
classes apart?
Dichotomous Key of Transportation Vehicles
Vehicles with wheels:
Dichotomous Key of Transportation
Vehicles
Vehicles with wheels:
Unicycle, skates,
a/p, bike, train, car,
bus
Canoe, boat,
sailboat,
Dichotomous Key of Transportation
Vehicles
Vehicles with wheels:
Unicycle, skates,
ap, bike, train, car,
bus
Wheels made of
rubber/plastic:
Canoe, boat,
sailboat,
Dichotomous Key of Transportation
Vehicles
Vehicles with wheels:
Unicycle, skates,
ap, bike, train, car,
bus
Wheels made of
rubber/plastic:
Unicycle, skates,
ap bike, car, bus
Canoe, boat,
sailboat,
train
Dichotomous Key of Transportation
Vehicles
Vehicles with wheels:
Unicycle, skates,
ap bike, train, car,
bus
Wheels made of
rubber/plastic:
Unicycle, skates,
Canoe, boat,
sailboat,
train
ap bike, car, bus
Carries over 10 people:
Dichotomous Key of Transportation
Vehicles
Vehicles with wheels:
Unicycle, skates,
bike, train, car,
bus
Canoe, boat,
sailboat,
Wheels made of rubber/plastic:
Unicycle, skates,
bike, car, bus
train
Carries over 10 people:
Bus, ap
Unicycle, skates
bike, car
Dichotomous Key of Animals
Animals with 4 legs
Dichotomous Key of Animals
Animals with 4 legs:
Horse, gorilla,
cow
Ostrich, worm,
shark, man,
rooster
Dichotomous Key of Animals
Animals with 4 legs :
Horse, gorilla,
cow
Animals with tail:
Ostrich, worm,
shark, man,
rooster
Dichotomous Key of Animals
Animals with 4 legs:
Horse, gorilla,
cow
Ostrich, worm,
shark, man,
rooster
Animals with tail:
Horse, cow
gorilla
Dichotomous Key of Animals
Animals with 4 legs:
Horse, gorilla,
cow
Ostrich, worm,
shark, man,
rooster
Animals with a tail:
Horse, cow
Animals with utters:
gorilla
Dichotomous Key of Animals
Animals with 4 legs:
Horse, gorilla,
cow
Ostrich, worm,
shark, man, rooster
Animals with a tail:
Horse, cow
gorilla
Animals with utters:
cow
horse
Tips for Classifying
 Carefully observe objects to “notice”
similarities and differences
 Place objects into either one group or
another – not both groups
 Examine each group you create – to see if it
can be further subdivided
Class Activity
Fish Classification
Levels of Classification
8 Levels
 Domain
 Kingdom
 Phylum
 Class
 Order
 Family
 Genus
 Species
Mnemonic Device?
Domains
 Major Groups
 Three domains
 Bacteria
 Archaea
 Eukarya
Review
 Naming: Binomial
Nomenclature
 Levels of Classification
 3 domains
 Types of Cells
 Kingdoms of Life