Taxonomic
Classification
Objectives
Outline the binomial system of nomenclature.
List seven levels in the hierarchy of taxonomy – kingdom, phylum,
class, order, family, genus, and species – using an example from
two different kingdoms for each level.
Design and apply a key to distinguish a group of up to eight
organisms.
Naming things
Taxonomy: the science of classifying living things (from Greek taxon
meaning group (plural = taxa)
Organisms are classified by similarity.
Many attempts from Greek times.
Ex: is something animal, mineral,
or vegetable?
The idea of a 2-word description
for every living thing was developed around 1750 by Carrolus
(Carl) Linnaeus of Sweden.
The Linnaean system is called
binomial nomenclature (twoname naming system); uses Latin.
Naming things
Binomial nomenclature
Linnaeus preceded Darwin & didn’t know evolution, but classification by
similarity supports this theory.
Homologous structures: bird & bat wings - same bone structure so there
was a common ancestor.
But, must also consider analogous structures: Bats and butterflies both
have wings, but are unrelated.
DNA similarities support classifications.
DNA mutates at a known rate; the more similar the sequences of DNA –
the more closely related the creatures will be.
Mutations pinpoint where creatures broke from some common ancestor.
Naming things
Why name organisms?
Human need (for communication);
beginning with the Book of
Genesis 2:20. →→
So scientists can communicate without
misunderstandings.
For example, the words inu (Japanese),
chien (French), perro (Spanish), and
dog (English) all represent the same
4-legged barking animal.
Adam naming the animals
But Canis lupis familiaris (Latin)
is recognized by any scientist anywhere.
Naming things
Why name organisms?
The same word can be
used differently even
in English-speaking
countries.
Ex. American wheat is called “corn” in England.
Even in America, things have
different names among various
regions or even age groups.
Ex. Roly-poly, pillbug, or
wood louse = Porcellio scaber
Naming things
Why choose Latin for naming things?
Throughout the middle
ages, Catholic monks
kept Roman & Greek
wisdom alive copying
texts in monasteries.
The Catholic church
spoke & wrote in Latin.
Scientists had
religious
educations.
Binomial nomenclature
The Linnean system has two main characteristics.
1) Each kind of organism has 2-part name, a binomial.
1st part, the genus; 2nd part, the species - in Latin.
1st letter of the genus is capitalized, & both names are italicized (or
underlined) and latinized.
Ex: Linnaeus assigned to
humans the scientific
name Homo sapiens,
meaning “wise man”.
Taxonomic hierarchies
The Linnean system has two main characteristics.
2) Species are organized hierarchically
into broader and
broader groups of
organisms.
Closely-related
species are grouped
into the same genus.
Ex: the leopard,
belongs to a genus
that includes the
lion (P. leo) & the
tiger (P. tigris).
Hierarchy
example #1,
the panther
Taxonomic hierarchies
The Linnean system has two main characteristics.
The genus is one part
of a family – the cat
family (Felidae), along
with house cats, etc.
Families combine to form
an order – Carnivora, the
meat eaters, including dogs.
Orders form a class – Mammalia, whose creatures all
have fur and produce milk.
Classes form a phylum, in
this case the Chordates, all
having a spinal column.
Hierarchy
example #1,
the panther
Taxonomic hierarchies
The Linnean system has two main characteristics.
Several phyla – chordates,
arthropods, different worms,
sponges, etc. – form a kingdom, in this case Animalia,
which are heterotrophic and
whose cells lack a cell wall.
The plant kingdom has
cells that are autotrophic;
the cell wall is of cellulose.
The kingdoms of Animalia,
Plantae, Fungi, etc. form a
domain, in this case Eukarya
– all the creatures whose
cells contain a nucleus.
Hierarchy
example #1,
the panther
Taxonomic hierarchies
The taxonomy of Mankind
Domain= Eukarya
Kingdom = Animalia
Phylum = Chordata
Class = Mammalia
(up to this point we are
united with felines)
Order = Primates
Family = Hominidae
Genus = Homo
Species = sapiens
Hierarchy
example #2,
the human
Taxonomic hierarchies
Branches on the tree of
life represent major
changes in the way
creatures develop as
a result of evolution.
Mutations happen,
& the environment
changes.
Taxonomic hierarchies
Mutations led to changes in the animal kingdom
Dichotomous keys
A dichotomous key is a method for identifying and classifying objects, where each
feature selected to help identification requires a choice between two alternatives.
A substitute teacher asks, “Which boy is James?”
Proceed step-bystep to find him,
always making
one of two choices.
1, 2, 4, 8
Dichotomous =
“two branches”.
Go to #:
Go to #:
Dichotomous keys
What should you
ask here?
Dichotomous keys
What should you
ask here?
Taxonomic Classification (part 2)
Taxonomic hierarchies
Branches on the tree of
life represent major
changes in the way
creatures develop as
a result of evolution.
Mutations happen,
& the environment
changes.
Three Domains with Six Kingdoms of Life
Note characteristics!
Remember: viruses are not alive;
they have no kingdom.
Six Kingdoms of Life
2 kingdoms for prokaryotes (all unicellular with a cell wall) are distinguished
by habitat.
Archaebacteria (archae = ancient)
Domain Archaea
Live in extreme environments
similar to early earth: hot springs,
salty seas; oxygen is poisonous.
Autotrophic (chemoautotrophic).
Eubacteria
Domain Bacteria
Live all around us: on the floor,
in our mouths, on our skin, etc.
Auto- or heterotrophic.
Six Kingdoms of Life
Domain Eukarya: Cells with a nucleus; 4 kingdoms are distinguished by
cellularity and nutrition.
Plants are multicellular autotrophs (photosynthetic).
Fungi are heterotrophic decomposers with extracellular digestion (most are multicellular; yeast are unicellular).
Animals are multicellular
heterotrophs; most digest
their food within specialized cavities. No cell wall.
Protists are either autotrophs (algae) or heterotrophs (like amoebas).
All but seaweeds are
unicellular.
Dichotomous keys (Review)
To set up a dichotomous key, choose questions that differentiate the subjects.
Does it have:
1) a backbone?
2) a jaw?
3) legs?
4) an amniotic egg?
5) hair ?
No. It’s a lancelet.
Yes. Go to #2.
No. It’s a lamprey.
Yes. Go to #3.
No. It’s a tuna.
Yes. Go to #4.
No. It’s a salamander.
Yes. Go to #5.
No. It’s a turtle.
Yes. It’s a leopard.
Cladograms
A cladogram is a diagram that links groups of organisms by showing
evolutionary linkages branched off from common ancestors.
Can be based upon
physical characteristics.
Cladograms
A clade is a group of species that includes a single common ancestor.
Cladograms
Cladograms can be formed using similarities in the genetic code – the DNA –
which translates into proteins. This is evidence for evolution.
Cladograms
A key for several
animal phyla.
Based on:
Presence of tissues
Symmetry
Body cavity
Fetal development
animal
Changes in classification
The classification system has changed over the years.
Linnaeus only recognized two kingdoms: plants and animals.
Today there are six kingdoms. Protista may be sub-divided one day into
three or more new kingdoms.