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Classification
Biology 11
A. Allen
Classification
There are many everyday situations in which you need to find
objects or information;
• Books in a library.
• An organized dresser drawer.
• How do you organize your hard drive?
Grouping and naming items is called “classification”.
Why classify?
• Developed by scientists to bring order to the great diversity of life
forms.
• Provides a logical naming system.
• Newly discovered organisms may be grouped.
• Identify organisms
• represent relationships among organisms.
Early Classification Systems
• Aristotle, a Greek philosopher (384-322 BC.) observed
and grouped over 500 different animals. He grouped
them according to where they lived;
Animals...
Land dwellers air dwellers
water dwellers
• What are some problems with this system?
• (Bats, birds and dragonflies are both ‘air dwellers’, yet
they are not related. They are mammals, avians and
insects respectively.)
• Today, we know that hawks, ostriches and penguins are
all birds, but Aristotle classified them as land, water and
air dwellers.
...Early Classification Systems
• Theophrastus (also from the 4th century BC.) grouped over
500 plants:
Plants...
herbs
shrubs
trees
• The invention of the microscope and increased world travel
led to the need for a more effective classification system.
Classify the following!
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Hawk
Earthworm
Whale
Leech
Fire ant
Black widow spider
Bat
Seagull
Hippo
scorpion
Binomial Nomenclature...a better method of classification
• Carolus Linnaeus (1707-1778) developed a classification
system based only on structural characteristics. He is the
father of modern taxonomy.
• Linnaeus used structural characteristics. He recognized
that the more features that an organism has in common,
the closer their relationship. Without realizing it, Linnaeus
was also grouping organisms according to their
evolutionary history or phylogeny. (Linnaeus incorrectly
viewed species as unchanging.)
...Binomial Nomenclature
• Linnaeus used a two name system for assigning names to
organisms. This is known as binomial nomenclature.
– Two word Latin name. Latin is a dead language
(unchanging)
– The first name is the genus (a noun)
– Second name is the species (an adjective) within the
genus.
– Genus and species are given together to constitute the
species name of an organism. Genus may be
indicated with first initial, but only if it is understood.
• Examples:
– Canis familiaris
(dog)
– C. lupus
(wolf)
– C latrans
(coyote)
• Note that this system shows a connection between dogs,
wolves, and coyotes.
• Genus is capitalized. Species is lower case.
...Binomial Nomenclature
Advantages of Binomial Nomenclature:
• Common names can be confusing...
A starfish is not a fish, ringworm is not a worm, panda bears
and koala bears are not considered true bears.
• Many names for one organism (puma = mountain lion =
cougar)
Relationships Among Organisms
• Organisms are classified according to evolutionary
relationships (ancestry). Various forms of evidence
are used…
• Structure: Organisms that have similar structures
may be related. Homologous structures, and vestigial
body parts are examined.
…Relationships Among Organisms
Homologous Structures are similar in appearance or structure, but not
necessarily in function. They may indicate a relationship between two
organisms.
…Relationships Among Organisms
Homologous Structures are similar in appearance or structure, but not
necessarily in function. They may indicate a relationship between two
organisms.
…Relationships Among Organisms
• Analogous Structures are used for similar function but
are not necessarily similar in structure. They do not
suggest a relationship between two organisms.
…Relationships Among Organisms
• Vestigial Structures are reduced and functionless anatomical
features. They can be used to determine relationships.
…Relationships Among Organisms
• Development. Relationships between various organisms is
revealed by comparative embryology
• Embryology
Recapitulates
Phylogeny…
Huh? Look …and
think…
Definitions
Recapitulate: to summarize
briefly
Phylogeny: The evolutionary
history of a species
…Relationships Among Organisms
• What are humans more closely related to? Starfish or crabs?...
(body cavity)
…Relationships Among Organisms
• What is this organism more closely related to… a crab or a
tarantula?
• This ‘horseshoe crab’ is more
closely related to spiders!
• Biochemistry: Biochemistry is another method scientists can use to
determine relationships. The horseshoe crab’s biochemistry more
closely resembles that of a spider than a crab.
…Relationships Among Organisms
• Molecular Studies: DNA and proteins can be used to determine
relationships. The more DNA two organisms have in common, the closer the
relationship.
• Mitochondrial DNA mutates at predictable rates. This allows scientists to
determine how long ago two related species have been diverging from one
another in their evolution.
Hey man, did
you know that we
have more than
98% of our DNA
in common?
…Relationships Among Organisms
• Fossil evidence: fossil records
can help scientists determine
changes in species as they
evolved to determine common
ancestors of today’s organisms.
Breeding capabilities
• Species:a group of organisms that is reproductively
isolated from all other groups of organisms; one species
can't breed with another species. There are exceptions; the
horse and donkey, for example, produce a mule-which is
sterile- when bred together.
• (There are exceptions where the rule breaks down,
especially in the Plant Kingdom. However, in the
majority of cases, interbreeding of species does not
produce fertile offspring.)
• Horse
+
donkey
=
mule
Classification of Sample Animals
Six Kingdom Classification System
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Eubacteria
Archaebacteria
Protista
Fungi
Plantae
Animalia
Three Kingdom Classification System
Archaebacteria
• single-celled organisms lacking nucleus and are therefore,
prokaryotes
• Many live in extreme environments geysers, acidic conditions,
hypersaline, guts of animals (cause flatulence)
• Usually harmless to humans
• ocean vents
• Cell wall does not contain peptidoglycan a polymer consisting
of sugars and amino acids that forms a mesh-like layer
…Archaebacteria
Bacteria Of Boiling Hot Springs In Yellowstone National Park
• Cell wall contains
peptidoglycan
• Prokaryotic
• Heterotrophs or
autotrophs
Eubacteria
Protista
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first eukaryotes
“garbage can” kingdom
not fungi, plants or animals
multicellular or single cell
parasitic or free-living
motile or sessile
sexual or asexual
Fungi
• more closely related
to animals than to
plants
• heterotrophs
• digest, then ingest
(decomposers)
• not limited by light can grow anywhere!
• often parasitic /
pathogenic
• important in symbiosis
• photoautotrophs
• colonized land,
produced O2
• adapted to “life in
air”
• pollination: coevolved with
animals
• massive carbon
sink
• enormous effect
on climate
Plantae
Animalia
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heterotrophs
invaded all habitats
(restricted by O2)
most animals are insects
most insects are beetles!
(~ 350,000 species - 1/5th
of all known organisms!
How many species of
organisms are known?
~ 1.5 million
How many species of
organisms might there be?
conservatively: ~ 12.5
million
Consider: oceans = 70%
of earth’s surface
< 1% has been explored
12 people have walked on
the moon; 2 have seen
deep ocean floor!
…Animalia
Okay, this has nothing to do with
anything. I just thought it was
cool…