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Organizing Life’s
Diversity
Unit 5
Chapter 17
What is classification?
 the grouping of objects or information based
on similarities
 This helps biologists understand how
organisms are related to each other.
 This is useful in agriculture, forestry,
biochemistry, and medicine (to name a few
fields).
Taxonomists study taxonomy.
 the branch of
biology that
groups and
names
organisms
based on
studies of
their different
characteristics
Click on image to play video.
Aristotelian classification
Life
Plant
Herb Shrub
Animal
Tree Aristotle grouped
organisms based
on appearance
and abilities.
Carolus Linnaeus: 1707-1778
 Swedish botanist
 Created modern
classification system
based on physical
and structural
similarities
 Modern taxonomists
have altered the
Linnaean system to
reflect evolutionary
relationships.
Binomial nomenclature
 two-word naming system to identify organism
 Genus: group of related species

always capitalized
 Specific epithetic: particular characteristic

always lower case
 Ex: Homo sapiens
Genus
When writing the scientific name
which is Latin, one must italicize
when typing or underline when
handwriting.
specific epithet
Common names
 Many people refer to
organisms by common
names rather than scientific
names.
 Be careful that common
names do not always reflect
the biology of the organism.
 Scientific name: Fragaria
ananassa
 Common name: strawberry
Dichotomous key: system to identify
organisms and their scientific names
 A key is made up of sets of numbered
statements.
 Each set deals with a single characteristic of
an organism, such as leaf shape or
arrangement.
How living things are classified
 Taxon: a group of organisms (taxa, pl.)
 These groups (taxa) can be very broad or
very specific.
 The taxonomic levels from most broad to
most specific: kingdom, phylum, class,
order, family, genus, species
Taxonomic levels
Domain
Eukarya
Kingdom
Animalia
Chordata
Phylum
Class
Mammalia
Carnivora
Order
Family
Genus
Felidae
Lynx
Species Lynx Lynx
rufus canadensis
Bobcat Lynx
Comparing related animals
Lynx
Bobcat
 Lynx rufus, lynx
 Panthera concolor,
mountain lion
Mountain
lion
 Lynx canadensis, bobcat
 Which two are more
related? How do you know?
What determines evolutionary
relationship?
 Anatomy and physiology

Common structures imply a common ancestor.
 Breeding and behavior patterns
 Geographic distribution
 DNA and biochemistry
DNA comparisons between these plants show almost no difference.
Phylogeny: Studying the evolutionary
histories and relationships of organisms
 Cladistics: a phylogenic study that assumes
probabl groups of organisms diverged and
evolvedAllosaurus
Velociraptor
Archaeopteryx
Sinornis
Theropods
Light bones
Feathers with Flight feathers;
3-toed foot; Down
arms as long
shaft, veins,
wishbone feathers
as legs
and barbs
Fan model to indicate phylogeny
Modern six-kingdom classification
 Archaebacteria: prokaryotic
 Eubacteria: prokaryotic
 Protists: eukaryotic
 Fungi: eukaryotic
 Plants: eukaryotic
 Animals: eukaryotic
Archaebacteria overview
 Most live in extreme
environments such as
swamps, deep-ocean
hydrothermal vents, and
seawater evaporating
ponds.
 Most do not use oxygen
to respire.
Eubacteria overview
 very strong cell
walls
 a less complex
genetic makeup
than found in
archaebacteria or
eukaryotes
 diverse habitat
A Paramecium
Protists: A diverse group
Anal
pore
Cilia
• Kingdom Protista contains
diverse species that share
some characteristics.
• A protist is a eukaryote
that.
Oral
groove
Gullet
Contractile
vacuole
Micronucleus and
macronucleus
Protist overview
 lacks complex organ
systems
 lives in moist environments
 diverse metabolism
Fungi overview
 Decomposes matter by
absorbing materials
 Multicellular or
unicellular
Plant overview
 Multicellular
 Photosynthetic:
produce oxygen
 Immobile
 Cell walls
Animal overview
 Multicellular
 Mostly mobile
 Lack cell walls
 Diverse habitats